Admittedly this essay is a rabbit-hole in the exploration of CLL biology for which you might want to read in parts or when relevant questions arise on your own journey. With the explosion of novel drugs for CLL comes the promise of better and longer responses, maybe even cures in a foreseeable future. With expanding choices and no cures for the present, anxiety can be a patient reality when needing treatment. I did this article to better learn how to guide my own journey and hope it might be of some use to you. Jump in with me on this trip to the Land-of-NOTCH where you are likely to meet the Red Queen and Cheshire Cat, if not the Mad Hatter.
We are focusing on another marker less familiar for most patients, but none the less important and fascinating for how it can affect CLL biology. If you are a first time reader to The CLL Tribune and missed my previous essay “Part I – ZAP-70” I should repeat that the term “markers” refers in general to proteins/enzymes/genes most often interchangeably recognized by our treating physicians and researchers as significant molecular entities that influence how our CLL might behave and predict what is likely to be a response to various therapies that target them.
As patients we tend to focus on only a very few, well-known markers to shape our impressions regarding prognosis and therapy choice involving the important considerations for TTT (Time To Treatment) and OS (Overall Survival). In and among our outcome concerns is the hidden fear for transformation or development of DLBCL (Diffuse Large B-Cell Lymphoma) that comes in 3 flavors commonly referred to as either RS or RT (Richter’s Syndrome or Richter’s Transformation), respectively. I will be using RT for both throughout the essay. The fear of RT has been largely associated with a subset of CLL patients positive for NOTCH1-mutated +12 (Trisomy 12).
It is part of this essay’s purpose to throw doubt on the current narrow perspective for the role of NOTCH signaling in CLL and to reveal an expanding concern for NOTCH signaling and accompanying development of therapeutic interventions.
NOTCH1 has been a fairly recent marker finding among 5 novel genetic markers for CLL. In one study published in “Leukemia” [https://www.nature.com/articles/leu2013263 S. Jeromin et al.], found NOTCH1mutations in 12.3% of 1160 untreated CLL patients with the highest association among patients with +12 (Trisomy 12) CLL through FISH (Fluorescence In-Situ Hybridization) testing. Similar to this journal “Haematologica” article [www.haematologica.org/content/early/2011/12/16/haematol.2011.060129 Ilaria Del Giudice et al.], NOTCH1 mutations are regarded as independent markers when associated with unmutated IGHV genes in +12 for an “unfavorable outcome” that refines the generally accepted “Intermediate” prognosis attached to +12 CLL. Unique attributes for NOTCH1 in +12 CLL are high occurrence of IgM and is “… not associated with TP53 disruption and 11q deletion,” “… often clustering with cases harboring +12 as a sole genetic abnormality;” The worry for CLL patients with NOTCH1 mutations is most notable in +12 cases as described in a paper titled “Mutations in chronic lymphocytic leukemia and how they affect therapy choice: …” Clive S. Zent et al., http://asheducationbook.hematologylibrary.org/content/2014/1/119.short stating: “Activating mutations of NOTCH1 are observed at low frequency in CLL patients at diagnosis (∼10%), but at a considerably higher frequency in patients with chemotherapy-refractory CLL (20%) and patients who have transformation of their CLL to diffuse large B-cell lymphoma (∼30%).” & “In CLL patients, NOTCH1 mutations are associated with a marked increase (∼20-fold) in the risk of transformation to DLBCL.” (Diffuse Large B-Cell Lymphoma)
The above has been a currently held view for impact of mutated NOTCH1 (NOTCH1-m) and although NOTCH1 can be a player in other CLL FISH profiles it is in the +12 patients that the concern is currently prominent so if you are not a +12 patient is there reason to pursue an interest in the NOTCH marker?
I would cite the following reasons not the least of which is that you would be missing out on acquiring some cool new scrabble words for your efforts😉. The focus on NOTCH signaling is a window into a microcosm of biological complexity that is both fascinating and worth paying attention for its own sake. Biological complexity is often in the way of comprehending CLL in the context of choosing among a growing number of drugs that target critical defective signaling proteins that keep CLL cells alive and reproducing. Knowledge for how CLL behaves at the molecular level and how novel drugs work will increase the appreciation for the efforts being made on our behalf by researchers and our treating physicians. Foremost in my journey, at this moment in time, is my quest to understand how markers (dots of data) are connected, how they interact and what my flavor of CLL needs to keep me in remission or whether I might need to switch therapy in case of relapse or intolerable side effects. Staying ahead of novel agents that are now targeting markers such as NOTCH1 signaling proteins might give us the Casino’s edge in the task of choosing the best available therapies and providing cautions when considering the use of such drugs. Some patients prefer the Devil one knows or the Devil one THINKS one knows to the Devil one does not know when it comes to therapy choice. A refined view of NOTCH signaling in CLL may alter your view for therapy choice.
It is very important for patients to know that in a clinical setting not even CLL specialists will all agree. Contrast these two short CLL specialist videos: https://www.youtube.com/watch?v=AzOCIaFxGvY & https://www.youtube.com/watch?v=t9jyXf8jCls. If you are the patient who is being recommended FCR or BR because you do not have 17p deletion and are young and fit, BUT your doctor does not know whether or not you have a NOTCH signaling dysfunction, how good is that recommendation? There is much more to this dilemma as you read on.
Ranking of Marker importance is an ongoing pursuit for researchers to translate significant findings from bench to a clinical application. Even though NOTCH1 is not currently designated as a priority marker in CLL, as argued in the 1st video above, recent evidence challenges that perspective. No matter what marker one chooses, that marker is not a lone actor and must be evaluated in the context of how it is networking with other proteins and so it is with NOTCH1.
Let’s step back to get a feel for what NOTCH1 is, who it works with and how it functions. A brief historical note to contextualize the enormity in figuring out how NOTCH signaling works is the >7 year effort by Yale researchers to map NOTCH family proteins resulting in the correlation of NOTCH signaling to ~10,000 genetically interactive proteins. Youtube link https://www.youtube.com/watch?v=BnwwajS76Pk (long video – nerds only).
Concept/word alert emphasized in bold:
The behavior of NOTCH protein expression is unique when compared to more familiar CLL markers in that it needs a close neighbor cell to interact with. There must be a sending cell and a receiving cell in which the determination of who is the sender and who is the receiver depends on ligand imbalance https://en.wikipedia.org/wiki/Ligand_(biochemistry). The cell with more ligand is the sender and the receiver cell expresses more NOTCH receptor. Alteration and function of the receiving cell’s NOTCH1 receptor is produced by the signal action of ligand binding which is reversible and has implications in the design of therapeutic drugs to be discussed later.
Fairly short cool videos depicting how NOTCH signaling works: https://www.youtube.com/watch?v=Pm35bSqlh6c Better graphic on next one for understanding where drugs are designed to intervene and inhibit aberrant NOTCH signaling. https://www.youtube.com/watch?v=lVmF9aGxqDw&t=135s.
NOTCH signaling is carried out by 4 protein complexes NOTCH1, NOTCH2, NOTCH3 & NOTCH4 and is labeled a ‘transmembrane receptor’ referring to parts of the NOTCH protein complex being inside the cell and part expressed on the outside of the cell membrane. The numbers 1-4 refer to the receptors. NOTCH Receptors are engaged by other NOTCH proteins called Ligands. https://en.wikipedia.org/wiki/Notch_signaling_pathway. NOTCH Ligands are signal producing substances that actively bind to an adjacent cell’s NOTCH receptors causing a conformational physiological change in the targeted protein of the receptor cell.
NOTCH signaling pathway is highly conserved. When you read that a gene/pathway is “Highly Conserved” it elevates its importance as that gene/pathway has remained expressed in most all multi-cellular organisms over eons of evolutionary time. So, What does this pathway do? NOTCH signaling is involved in cellular differentiation, proliferation, apoptosis (programed cell death) and homeostasis (maintenance of internal cellular stability). I think of CLL biology generally and NOTCH1 in particular in terms of a puzzle that has been dumped out on the table where we are finding and recognizing important pieces, attempting to place them in the appropriate areas of the incomplete picture. NOTCH1 is an important puzzle piece but we are not quite sure where NOTCH1 always fits or just how other pieces of that puzzle are related to it.
NOTCH proteins are highly pleiotropic. Pleiotropy refers to the dramatically opposite ways in which our focus gene, NOTCH1, might be mutated or expressed for determining its function as a tumor suppressor or tumor promoter. Short MDA video https://www.youtube.com/watch?v=H5bdY434xgY. Since this example of NOTCH1 pleiotropy is in neck and head cancer you might rightfully ask if the tumor suppressor side of pleiotropic NOTCH signaling is relevant to CLL? The answer is I do not know. Most all that we patients have been made aware of is the finding of mutations in NOTCH1 (NOTCH1-m) as tumor driver and possible agent for transformation to DLBCL.
Importantly through recent research the role of NOTCH signaling is being expanded to include not only NOTCH-m CLL, but NOTCH-activated CLL defined as ICN+ (Intra-Cellular Domain +). In the 2018 Journal PNAS Titled “Common non-mutational NOTCH1 activation in chronic lymphocytic leukemia” G. Fabbri et al., we learn about a newly discovered finding for NOTCH signaling in CLL that is NOT dependent on mutations of the NOTCH proteins involved. NOTCH-mutated CLL comprises ~10% of newly diagnosis patients. This paper reveals: “Our results now indicate that ∼50% of CLL cases devoid of mutations express the active form of NOTCH1 ICN1 (intracellular portion of NOTCH1), thus implicating a much broader role of this transcription factor in the disease. ICN1+ CLL cases display equivalent NOTCH1-dependent transcriptional responses regardless of the gene mutation status, indicating that the detection of ICN1 represents a reliable biomarker of NOTCH1 activation for diagnostic and therapeutic targeting” For the visually-oriented, see this video explanation of NOTCH transmembrane activity. https://www.youtube.com/watch?v=Pm35bSqlh6c&t=193s. Be aware that NOTCH1 (some report also NOTCH2 & NOTCH4) are being studied in context of mutated (NOTCH1-m) and wild type (wt) activated or unmutated forms of CLL/DLBCL. Note: ICN1 is not the whole NOTCH protein but the intracellular domain where part of the NOTCH protein receptor is active in the cell nucleus.
While there is strong evidence for a correlation of NOTCH1-m CLL to poorer prognosis, nothing I could find to corroborate support for NOTCH signaling as an operative tumor suppressor in CLL. There is one intriguing case close to our Community in the founder of CLL Society, Dr. Brian Koffman. Prior to his recent CAR-T therapy he had an 11q- ATM CLL with TP53 and NOTCH1. To prepare for CAR-T he had tumor reduction protocol with FC that returned this report from a BMB (Bone Marrow Biopsy) “… no evidence of prior 17p deletion on the BMB. No evidence of p53, ATM, or MYB.“ It would be highly speculative to attribute the mysterious disappearance of these markers to one thing like NOTCH function but does make one wonder what mechanisms to include NOTCH signaling might have been at play in his case.
We, as patients, tend to think in terms of markers as isolated entities when it should be clear that how a marker networks with other proteins can be a critical factor in how indolent or aggressive our CLL will be and to what degree therapy response will be achieved in depth, duration, likelihood of resistance or transformation to an aggressive lymphoma.
In a comprehensive overview of Notch signaling in hematological malignancies a 2016 Oncotarget Journal article https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5045435/ has a section devoted to CLL that should raise interest for the entire CLL Community.
Y. Gu et al., implicates 3 of the 4 NOTCH proteins (1,2 & 4) as involved in CLL.
In addition, studies are investigating whether NOTCH1 mutations are implicated in CLL transforming to Hodgkin Lymphoma (HL). Abstract https://www.tandfonline.com/doi/abs/10.1080/10428194.2016.1211278
Let’s take look at some of the co-marker players of NOTCH1 and see what research has to say about what these players imply.
MYC (Often seen as c-MYC is one in a family of 3 human genes that is an aggressive driver in CLL and other cancers.)
In an article investigating the relationship between MYC and NOTCH1 F. Pozzo et al., Concludes: “NOTCH1 mutations in CLL are associated with the over-expression of MYC and MYC‐related genes involved in protein biosynthesis including NPM1, which are allegedly responsible for cell growth and/or proliferation advantages of NOTCH1‐m CLL.”
In the Journal “Leukemia” an article titled “Integrating genomic alterations in diffuse large B-cell lymphoma identifies new relevant pathways and potential therapeutic targets” https://www.nature.com/articles/leu2017251. K. Karube et al., finds: “A total of 761 potential driver mutations were identified in 89 out of the 106 genes with a similar number in GCB and ABC-DLBCL”. NOTCH1 & NOTCH2 are identified as part of the constellation of potential markers, but you will not see a reference to MYC. The reason I bring attention to this study is to hold in your mind the question of how do we know the relative importance of NOTCH genes or MYC?
MYC is featured in another study in the Journal CellCycle entitled “c-MYC—miRNA circuitry” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3906236/ Jiangchuan Tao et al., “MYC (c-Myc) deregulation has been frequently associated with aggressive lymphomas and adverse clinical outcome in B-cell malignancies. MYC has been implicated in controlling the expression of miRNAs, and MYC-regulated miRNAs affect virtually all aspects of the hallmarks of MYC-driven lymphomas.” “MYC has been detected in 9–14% of diffuse large B-cell lymphomas” We know MYC is a badass oncogene to have but where is the understanding for how any markers come to dominate the course of our CLL or transformed lymphomas? Noteworthy that this paper has no references to NOTCH proteins. Having the “DOTS” of the puzzle are not enough.
NF-kB (Nuclear Factor-kappa B) https://en.wikipedia.org/wiki/NF-%CE%BAB
NF-kB is another important protein complex in which “Incorrect regulation of NF-κB has been linked to cancer, inflammatory and autoimmune diseases, septic shock, viral infection, and improper immune development.” Wiki-quote
In the following is research linking NOTCH2 to not only DLBCL but other B-cell cancers closely related to CLL.
In this PlosOne Journal article: “The Truncate Mutation of Notch2 Enhances Cell Proliferation through Activating the NF-κB Signal Pathway in the Diffuse Large B-Cell Lymphomas http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0108747. Xinxia Zhang et al., states finding in a study of 69 DLBCL patients over 4% had had a truncate NOTCH2 mutation that activated NF-kB [Nuclear Factor-kappa B] and NOTCH2 signaling enhancing B-cell proliferation. “NOTCH2 mutations have been detected in some B-cell non-Hodgkin’s lymphomas (B-NHLs) subtypes, such as DLBCLs and marginal zone lymphomas (MZLs), especially splenic marginal zone lymphomas (SMZLs, one subtype of MZLs)” “The question remains whether oncogenes such as NOTCH2 are a primary or secondary event.”
Note: DLBCL is a collective term for 3 flavors of Diffuse Large B Cell Lymphomas, GCB (Germinal Center B-cell like), ABC (Activated B-cell like) and PMLBCL (Primary Mediastinal Large B-Cell Lymphomas).
CD49d In the Journal Blood A. Zucchetto et al., http://www.bloodjournal.org/content/122/19/3317?sso-checked=true finds “CD49d is almost universally expressed by trisomy 12 CLL“ It is also acknowledged by authors that NOTCH1 is significantly over-expressed in the context of other markers makes the importance of NOTCH1 uncertain. “In CLL, the close dependency of CD49d expression on DNA methylation, as demonstrated here also outside the trisomy 12 subset, was similar to that reported for other CLL bad prognosticators and key regulators of CLL cells, such as ZAP-70, lipoprotein lipase, CLLU1, and NOTCH1.“
bax/bcl-2 ratio bax and bcl-2 are protein members of the Bcl-2 family of proteins in which bax promotes apoptosis and bcl-2 promotes cell survival. For more on this click: https://cllsociety.org/2016/03/look-treatment-toolkit-bcl-2-antagonists/. Cancer cells often hijack and promote pro-survival proteins and suppress apoptosis promoting proteins. Healthy cells need both in balance – think Homeostasis
NOTCH1 MUTATIONS ARE AN INDEPENDENT PROGNOSTIC FACTOR IN IBRUTINIB- TREATED CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) PATIENTS by Giovanni Del Poeta et al. https://learningcenter.ehaweb.org/eha/2018/stockholm/215407/giovanni.del.poeta.notch1.mutations%20are.an.independent.prognostic.factor.in.html?f=menu=6*ce_id=1346*ot_id=19041*media=3*marker=167
“All 6 patients who underwent Richter’s syndrome had bax/bcl-2 <1.5 (p=0.030). NOTCH1 M were strongly correlated with trisomy 12 (10/18; p=0.00002) and with CD49d >30% (16/18; p=0.024). There was no significant correlation between NOTCH1 M and bax/bcl-2 as well as between bax/bcl-2 and del(17)p/TP53 M. With regard to clinical outcome, lack of response/progression was significantly correlated both with NOTCH1 M (p=0.009) and bax/bcl-2<1.5 (p=0.017), but not with del(17)p/TP53 M (p=0.09). Significant shorter PFS was observed in NOTCH1 M patients (42% vs 76% at 24 months, p=0.002, Figure) and in bax/bcl-2 ratio<1.5 cases (55% vs 91% at 24 months, p=0.006, Figure). On the contrary, del(17)p/TP5 M patients did not show significant worse PFS (p=0.26). Moreover, patients with lower bax/bl-2 showed significant shorter OS (63% vs 91% at 24 months, p=0.020). Interestingly, NOTCH1 M and bax/bcl-2 showed synergistic prognostic properties, since NOTCH1 M and bax/bcl-2<1.5 identified a subset at worse prognosis with regard to PFS (43% vs 86% at 24 months, p=0.001,…”. See Kaplan Meier curves within the article.
Mcl1 is a cell survival protein and another marker that interacts with NOTCH1 signaling. In the Journal “Oncotarget” a study titled “Notch signaling sustains the expression of Mcl-1 and the activity of eIF4E to promote cell survival in CLL” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4599289/ F. Falco et al., states: “In chronic lymphocytic leukemia (CLL), Notch1 and Notch2 signaling is constitutively activated and contributes to apoptosis resistance.” The study revealed inhibition of NOTCH1 or NOTCH2 through small-interfering RNA both increases CLL cell apoptosis and decreases Mcl-1. This study also identifies yet another co-marker (eIF4E) at play in the context of activated NOTCH signaling pathology of CLL. Another very important finding and implication for therapeutic intervention is that a combined targeting of not only NOTCH1 but NOTCH2 as well, will improve decreased CLL cell viability and do a better job of degrading Mcl-1. While this is good information, it is well to remember that activated NOTCH signaling elevating Mcl-1 is not the only mechanism of CLL cell survival for the study warns: “… these data indicate that apoptosis of CLL cells induced by Notch silencing involves down-regulation of Mcl-1 but not Bcl-2 expression.” Bcl-2 is another extremely important and over-expressed survival protein for cancer cells.
This paper raises some fundamental questions.
- Which is a better strategy; to target the NOTCH signaling proteins that produce over-expression of Mcl-1 or if Mcl-1 is the dominate culprit in cell survival for your flavor of CLL then target just Mcl-1?
- Between the targeting choice of NOTCH signaling proteins and Mcl-1, which therapeutic will likely produce the least negative side effects?
- By targeting NOTCH proteins inhibiting pathological signaling implicated in transformation to Richter’s (DLBCL), can we kill two “Bears” with one stone?
- How important is it to you as a patient to have access to deep sequencing, knowing that very successful therapies like Venetoclax producing MRD negative results for a large segment of the CLL population, but will not be effective in Mcl-1 dominated CLL resistance?
- If you opt for a NOTCH protein inhibiting therapy, what assurances will we need that it will be confined to the NOTCH proteins just affecting our CLL and not interfering with normal NOTCH signaling functions?
Keeping in mind that as a Patient you might not have some potentially targeted markers, such as Mcl-1 to worry about so defining the complete puzzle that accurately represents your flavor of CLL through deep sequencing technology will become critical to conserving resources and maximizing efficacy.
IGF1R (Insulin Growth Factor 1 Receptor) is a co-marker associated with NOTCH1 mutation, +12 and aggressive disease course. In the Journal PLOS One F. Maura et al., http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0118801#pone-0118801-t001 found IGF1R was significantly higher in NOTCH1-mutated patients either with or without Trisomy 12 (+12) further emphasizing my earlier point that NOTCH1-m in CLL is a narrower context for judging a wider risk in all CLL that needs to include a host of co-markers and knowledge for how they interact or not with NOTCH signaling. The research goes on to state “we report the strong association of IGF1R with unfavorable/intermediate cytogenetic aberrations, mainly trisomy 12. This association seemed independent of IGHV-UM, NOTCH1 mutation or cMBL status. Based on this data, IGF1R could represent a potential novel candidate for specific targeted therapy in this cluster of patients”. This begs the question of which factor or combination of markers is the actual driver in cancer cell survival and proliferation? By targeting only a marker of singular focus such as NOTCH1-m genes would that therapeutic approach permit an escape for the cancer cell or be addressing the dominant driver(s)?
Now that new evidence points to other than NOTCH1-m as driving CLL coupled to therapy options GSI (Gamma secretase Inhibitors) and siRNA (short interference RNA) now being explored on several other cancers and diseases in Clinical Trials we need to be aware of the cautionary side to these therapies as well as what implications for NOTCH signal impairment has for standard therapies.
Because of linkage to RT and the lacking for an origin-cell/causal-agent of CLL, HSCs (Hematopoietic Stem Cells) and NOTCH signaling are getting closer attention as a possible host/mechanism complex. This would be really big news if proven elevating NOTCH proteins to the top of the list for intervention.
Skin cancers, specifically SCC (Squamous Cell Carcinoma) are a frequent side order to the main dish of CLL. When multiple SCCs occur, the danger of metastasis to other organs gets higher. In this Plos One article we find another link to NOTCH signaling. PLOS One M. J. Kluk et al., “Gauging NOTCH1 Activation in Cancer Using Immunohistochemistry “
NOTCH1 is a double-edged sword with respect to tumorigenesis, being capable of serving as a tumor suppressor as well as an oncoprotein. Staining tests that reliably detect activated NOTCH1 (NICD1) may also prove useful in identifying tumors with NOTCH1 loss-of-function mutations, which are present in a subset of squamous cell carcinomas.
The assay [The IHC test] is specific for NOTCH1, and therefore cannot be used to assess activation of other NOTCH receptors, which have been implicated in certain cancers. Specifically, activating NOTCH2 mutations have been identified in marginal zone B-cell lymphoma and diffuse large B-cell lymphoma, and biochemical analyses have detected activation of NOTCH2 as well as NOTCH1 in CLL.”
NOTCH1 activation in CLL is not confined to tumors with NOTCH1 mutations and appears to be augmented by factors expressed in the nodal microenvironment. These findings raise questions about how best to gauge and target NOTCH1 activation in CLL patients who are being considered for treatment with Notch pathway inhibitors.
Observations suggest that NOTCH1 activation in CLL may be largely ligand-mediated; if true, this would have significant therapeutic implications, since ligand-specific blocking antibodies with anti-tumor activity have been developed.
HSC (Hematopoietic Stem Cell)
These cells are the mothers of all of our blood cells. There is an ongoing suspicion of defects either inherent or acquired in HSCs are where CLL and other blood cancers get an initial start so they are literally under the microscope to discover if and how that may be true. I had a fortunate chance meeting with a talented young researcher at OSU Medical Center who is studying a GATA transcription protein in an effort to discover if HSCs have a role in the etiology of blood cancers.
In a 2018 “Frontiers in Oncology” Journal article https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5919960/ M. Ianni et al., states: “Additionally, we showed here that the NOTCH1 mutational burden increased along specific stages of HSC differentiation in NOTCH1-mutated CLL patients. This suggests that the NOTCH1 lesion is selected and expands during HSC differentiation toward a B neoplastic cell, thus strengthening the hypothesis that the genetic alteration is an initial event associated with the stepwise malignant transformation of CLL.” … “We conclude that activated NOTCH1 is an early event in CLL that may contribute to aberrant HSCs in this disease.”
CSC (Cancer Stem Cells)
These cells are analogous to HSCs in that they are the mothers of all our CLL cells and might be further along in development of blood-cell differentiation when they become cancer Moms. The dark side of Motherhood to be sure.
From the 2018 article “Cancer stem cells as targets for immunotherapy“ in the Journal Immunology https://onlinelibrary.wiley.com/doi/full/10.1111/imm.12866, the paper addresses NOTCH impacts in the context of CSCs. A. Codd et al., identifies NOTCH target genes such as HES, c-myc, PI3K, AKT, NF-kB, PPAR, cyclin D1 for which you should note that several are recurrent in and relevant to CLL in settings of diagnosis. Authors go on to state: “There are numerous ongoing Phase I and II clinical trials in cancer with a range of targets and mechanisms investigating the usefulness of Notch targeting, alone or in combination with other therapies.” and point out that “NOTCH signaling has also been linked to peripheral T‐cell maturation into effector cells, such as developing cytotoxic T‐cell function or cytokine production. T‐cell activity has been shown to be impaired by Notch‐inhibition with a γ‐secretase inhibitor.“
Ibrutinib and NOTCH1
Ibrutinib has been a breakthrough drug keeping many of us alive and well including yours truly. Nothing works for all of us yet.
New data in a Poster presentation of interest to those who are on Ibrutinib.
NOTCH1 MUTATIONS ARE AN INDEPENDENT PROGNOSTIC FACTOR IN IBRUTINIB- TREATED CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) PATIENTS
Giovanni Del Poeta et al., https://learningcenter.ehaweb.org/eha/2018/stockholm/215407/giovanni.del.poeta.notch1.mutations.are.an.independent.prognostic.factor.in.html?f=menu=6*ce_id=1346*ot_id=19041*media=3*marker=167 You can see the Kaplan Meier curves on Progression-free survival and Overall Survival within the article.
NOTCH1 therapeutic interventions (Coming to CLL??)
In the section on CSCs in the article cited and other research, NOTCH1 signaling has been directly attributed to a major subset of T-ALL (T cell Acute Lymphoblastic Leukemia).
In Science Direct 2013 is the following review for NOTCH1 signaling intervention https://www.sciencedirect.com/science/article/pii/S0005273613001946 “therapeutic inhibition of γ-secretase has been most often associated with reduced Notch1 signaling; GSIs [Gamma-Secretase Inhibitors] are often thought of in these settings as “Notch1 inhibitors”. γ-Secretase has now been proposed to be a therapeutic target in various cancers, immunologic disorders including graft versus host disease, vasculitis, macular degeneration, diabetic nephropathy, ischemic reperfusion injury in the kidney, ischemic stroke, traumatic brain injury,, hearing loss and fibrosis. It is also likely that additional disease indications may emerge.”
GSIs – Snake oil or wonder drug?? Promise vs Reality – Think back to the concept of “Pleiotropic”
“It is also important to consider the findings that GSI based inhibition of Notch1 and perhaps other substrates of γ-secretase, can actually promote oncogenic transformation in certain tissues such as the skin. Thus, even if acute toxicities can be managed, there are concerns that GSI like many anti-cancer therapies could promote other cancers.”
In another research study addressing the conventional therapies of anti CD20 mAbs e.g. Rituximab, Ofatumumab, Ublituximab or Obinutuzumab. Hints are made that indeed it is activated NOTCH1-m CLL that may drive epigenetic dysregulation causing a subset of CLL with a distinct characteristic of low CD20 expression. Journal Leukemia, F. Pozzo et al., https://www.nature.com/articles/leu2015182. If you are a patient with low CD20, does being treated with anti-CD20 monoclonal antibodies make sense? Revisit videos with Dr. Tom Kipps 3 years ago https://www.youtube.com/watch?v=AzOCIaFxGvY and 9 months ago a view from Dr. Anna Schuh https://www.youtube.com/watch?v=t9jyXf8jCls .
In the Journal Oncotarget “Notch signaling: its roles and therapeutic potential in hematological malignancies” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5045435/ Y. Gu et al., reports both NOTCH 1 & 2 as expressed in CLL cells with signaling not observed in normal B lymphocytes. Genetic alterations in Notch1 PEST domain conferred adverse prognosis but importantly was found to be mutually exclusive with genetic alterations in The TP53 tumor suppressor gene. Would this finding provide a rationale for NGS (Next Generation Sequencing)? Will a finding like this help to explain why some patients who have a profile of being younger, fit and not showing 17p-p53 deletion/mutations yet fail to achieve durable remissions via FCR? Will insurance be willing to pay for pre-therapy screening by NGS?
Reduction of NOTCH signal (jagged1) stimulation of CLL cell survival marker production (NF-kB, cIAP2 & XIAP) and NOTCH2 silencing has been demonstrated by GSIs and siRNA therapies. There is convincing evidence that Notch1, Notch2 and Notch4 signaling is involved in stromal-dependent (connective tissue of any organ – specifically in this context the tissue in the bone marrow) CLL cell resistance to chemo therapy and that CLL patients transforming to DLBCL have a higher frequency of NOTCH mutations. Is that a strong enough rationale to both look for NOTCH mutations and offer current therapies to mitigate aberrant signaling when efficacy and risk are unknown?
We patients must be knowledgeable in how various therapies work so we can better assess tumor resistance vs efficacy and the risk of likely side effects. The knowledge input will be uneven given the heterogeneous (unique differences) in the many subtypes of CLL. It will be argued by many doctors that drug development will give a vast majority of patients long-term control or even “cures” as seen in the data of a subset of IGHV mutated good marker CLL patients who have been given FCR. It might look good statistically or on paper or at a CLL conference when you are in Wait & Watch but if you are the one for whom it does not work the glow of expectation based on statistical probability fades real fast.
GSIs (Gamma Secretase Inhibitors) are a highly questionable therapy path at this point in time due to their inhibition of all NOTCH1, 2, 3, & 4 signaling as well as other gamma-secretase pathways. To get around the lack of GSI specificity in targeting just the CLL cells the development of mAbs (Monoclonal antibodies) looks more promising in preserving normal NOTCH signaling function. All that may be positive but like most therapies, current anti-Notch therapies are subject to toxicities notably with GSIs from gastrointestinal issues. I urge you to explore the section on NOTCH targeting therapies in the above linked paper.
Could it be that these questions raised with actionable answers must be addressed through an individualized analysis of each patient’s DNA/RNA via NGS or will a combination of the right drugs already in various stages of use and testing be good enough to “Cure” all but the most complex fraction of CLL patients? Appropriately designed therapeutic strategies might be an end run around the need to fit all the protein-marker pieces into the puzzle of CLL. I question the goal of curing a clinically expressed cancer as being short sighted. If we could fit the needed pieces of the puzzle that are directly related to the origins of cancer at the HSC level or CSC level we might then intervene before people would even be aware of having CLL.
As always – comments critical or otherwise are encouraged.
I hope if you have persisted through this maze of research that it has been worth the ride. Now at least you can relax with a scrabble game armed with a few winning words!😁
Wayne Wells is a member of the CLL Society Patient Advisory Board: I was diagnosed with CLL on Sept. 11, 2006 and told I had a “good cancer” and as such, might never need treatment. Prognosis testing results from IGHV mutation status, FISH and CD38 all predicted an indolent disease course. The one test (ZAP-70), which CLL specialists dismissed as inaccurate, was 58% positive contradicting the other good markers. The rapid rate of tumor burden increase marked by bulky lymphadenopathy indicated I was discordant to the favorable markers. After failing 1st and 2nd standard therapy options I signed up for a Phase Ib Clinical Trial in June of 2011 with a new agent called PCI-32765 later branded Ibrutinib (Imbruvica). I have been on Ibrutinib ever since in remission currently stagnating with a small cancer cell population only detectable by sophisticated detection techniques.
Originally published in The CLL Tribune Q2 2018.