Genes v1 Flashcards
EGFR
3
EGFR (Epidermal Growth Factor Receptor) – Detailed Overview
The EGFR gene encodes a receptor tyrosine kinase that regulates cell growth, survival, proliferation, and differentiation through signaling pathways such as RAS-RAF-MEK-ERK and PI3K-AKT-mTOR. EGFR is frequently mutated in cancer, especially non-small cell lung cancer (NSCLC), and is a key target for tyrosine kinase inhibitors (TKIs).
our assays
IDEGFR-SENSI RUO
optimisé propose une solution multiplexée permettant, pour chaque échantillon, l’amplification simultanée en une seule réaction PCR des mutations de l’EGFR incluant les délétions au niveau de l’exon 19 et deux substitutions L858R et L861Q dans l’exon 21.
Ce kit IDEGFR-SENSI peut être utilisé en combiné avec les produits IDEGFR-RESIST et IDEGFR-RARE.
IDEGFR Resist RUO
une seule réaction PCR des mutations de l’EGFR incluant Les mutations T790M et C797S (cis/trans) situées dans l’exon 20
IDEGFR RARE
seule réaction PCR des mutations de l’EGFR incluant les mutations G719X dans Ex18 & Ins20/S768I dans Ex20
- EGFR Mutations and Their Clinical Significance
EGFR mutations can be categorized based on their clinical implications:
A. Prognostic Biomarker Mutations
(Prognostic mutations provide information about the likely course of the disease, independent of treatment.)
EGFR overexpression/amplification → Seen in colorectal cancer, glioblastoma, and NSCLC. Poor prognosis in glioblastoma.
EGFR T790M (pre-existing) → May indicate an intrinsically aggressive tumor in NSCLC.
EGFR exon 20 insertions → Poor prognosis and associated with TKI resistance.
B. Predictive Biomarker Mutations (Treatment-Related Mutations)
(Predictive mutations determine response to EGFR-targeted therapies.)
Sensitizing Mutations – Respond to 1st and 2nd Gen TKIs
Exon 19 deletions (ΔE746-A750) → Most common EGFR mutation (~45% of all cases). Strong predictor of response to gefitinib, erlotinib, afatinib.
L858R (exon 21) → Second most common mutation (~40%). High sensitivity to EGFR TKIs, but slightly less than exon 19 deletions.
G719X (exon 18, rare mutation) → Moderate response to 1st-gen EGFR TKIs (gefitinib, erlotinib) but better with afatinib.
S768I (exon 20, rare mutation) → Better response to afatinib than first-generation TKIs.
L861Q (exon 21, rare mutation) → Sensitive to afatinib, osimertinib.
2. EGFR Mutations Associated with Resistance to Treatment
While many EGFR mutations initially respond to TKIs, resistance eventually develops in most patients. Resistance can be primary (intrinsic) or acquired (secondary after treatment).
A. Primary Resistance Mutations (Pre-Existing at Diagnosis)
EGFR exon 20 insertions (T790M-negative) → Resistant to 1st/2nd-gen TKIs.
EGFR amplification in glioblastoma → Resistant to EGFR TKIs.
KRAS mutations (e.g., G12C, G13D) → Mutually exclusive with EGFR mutations in NSCLC and predicts lack of response to TKIs.
Exactly — you nailed it.
The mutual exclusivity between EGFR and KRAS mutations in NSCLC (and other similar pairs) isn’t because they biologically cannot coexist — it’s because they don’t need to. Here’s why:
Mutual exclusivity in cancer = functional redundancy
EGFR mutations activate the MAPK/ERK pathway.
KRAS mutations also activate the same downstream pathway, but further down the line.
So if one is already mutated and constitutively active, there’s no additional selective advantage in mutating the other.
Natural selection in cancer favors efficiency: once the pathway is “on,” there’s no pressure to activate it again upstream or downstream.
Why do we observe this statistically?
In a tumor with EGFR L858R, a KRAS G12C mutation may still happen randomly, but:
It confers no further advantage.
The clone doesn’t expand because it’s not fitter than the existing EGFR-driven clone.
So over time, tumors evolve with one or the other, not both — hence, statistical mutual exclusivity.
Key insight:
> Mutual exclusivity = a signal of overlapping function in oncogenesis, not a technical or physical incompatibility.
This concept also holds for other pairs like:
BRAF vs KRAS in colorectal cancer
IDH1 vs IDH2 in gliomas or
HER2 amplifications → EGFR TKIs have reduced efficacy due to parallel signaling.
B. Acquired Resistance Mutations (After TKI Treatment)
T790M (exon 20, “gatekeeper” mutation) → Resistance to 1st/2nd-gen TKIs
Accounts for ~50-60% of resistance cases to gefitinib, erlotinib, afatinib.
Mechanism: Increases ATP affinity, making the TKIs ineffective.
Solution: Osimertinib (Tagrisso) is a third-generation TKI that selectively inhibits T790M-mutant EGFR while sparing wild-type EGFR.
C797S (exon 20) → Resistance to osimertinib (3rd-gen TKI)
Mechanism: Mutation prevents covalent binding of osimertinib.
Solution: Combination therapy strategies (e.g., EGFR + MET or EGFR + MEK inhibitors) are under investigation.
MET amplification → Bypass resistance mechanism
Accounts for ~15-20% of EGFR TKI resistance cases.
Mechanism: Activates PI3K-AKT signaling independently of EGFR inhibition.
Solution: Combination with MET inhibitors (capmatinib, tepotinib) is under investigation.
HER2 amplification → Bypass resistance mechanism
Mechanism: HER2 activation compensates for EGFR blockade.
Solution: Combining EGFR TKIs with HER2 inhibitors (e.g., trastuzumab).
Transformation to Small Cell Lung Cancer (SCLC) → Phenotypic resistance
Accounts for ~3-5% of resistance cases.
Mechanism: Tumors lose EGFR dependence and transform into SCLC phenotype.
Solution: Treated with platinum-based chemotherapy, similar to SCLC.
KRAS mutations acquired after EGFR TKI treatment
Mechanism: Activates RAS-RAF-MEK pathway, bypassing EGFR blockade.
Solution: KRAS G12C inhibitors (sotorasib, adagrasib) under investigation.
3. FDA/EMA-Approved Targeted Therapies for EGFR Mutations
Drug Generation Targets FDA/EMA Approval Companion Diagnostic?
Gefitinib (Iressa) 1st-gen Exon 19 del, L858R ✅ Yes (NSCLC) ✅ Yes
Erlotinib (Tarceva) 1st-gen Exon 19 del, L858R ✅ Yes (NSCLC) ✅ Yes
Afatinib (Gilotrif) 2nd-gen Exon 19 del, L858R, rare mutations ✅ Yes (NSCLC) ✅ Yes
Osimertinib (Tagrisso) 3rd-gen T790M, Exon 19 del, L858R ✅ Yes (NSCLC) ✅ Yes
Dacomitinib 2nd-gen Exon 19 del, L858R ✅ Yes (NSCLC) ✅ Yes
Mobocertinib 3rd-gen Exon 20 insertions ✅ Yes (NSCLC) ✅ Yes
Amivantamab (Rybrevant) Bispecific Ab Exon 20 insertions ✅ Yes (NSCLC) ✅ Yes
Companion Diagnostics: FDA-approved tests for EGFR mutations (NGS, PCR) required before TKI use.
4. Emerging Trends & Future Research in EGFR Targeting
Combination Therapies to Prevent Resistance
EGFR TKIs + MET inhibitors → Targeting EGFR T790M + MET amplification.
EGFR TKIs + KRAS inhibitors → Preventing KRAS-driven resistance.
Fourth-Generation TKIs for C797S Mutation
New irreversible TKIs designed to target EGFR C797S mutation.
Antibody-Drug Conjugates (ADCs) Against EGFR
Depatuxizumab mafodotin (Depatux-M) → Under study in glioblastoma.
Liquid Biopsy for Real-Time EGFR Mutation Monitoring
Circulating tumor DNA (ctDNA) tests to track resistance emergence.
Final Summary
EGFR mutations are crucial predictive biomarkers for NSCLC treatment.
1st-gen TKIs (gefitinib, erlotinib) target common activating mutations.
3rd-gen TKI (osimertinib) overcomes T790M resistance.
New research focuses on C797S mutations, bypass signaling, and ADCs.
Would you like to explore any specific EGFR inhibitors, resistance pathways, or emerging treatments in more detail? 🚀
Tirosin Kinase
A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine residues of specific proteins inside a cell. It functions as an “on” or “off” switch in many cellular functions.
A kinase is a type of enzyme that transfers phosphate groups (see below) from high-energy donor molecules, such as ATP (see below) to specific target molecules (substrates); the process is termed phosphorylation. The opposite, an enzyme that removes phosphate groups from targets, is known as a phosphatase. Kinase enzymes that specifically phosphorylate tyrosine amino acids are termed tyrosine kinases.
What is the function of RTK
Receptor tyrosine kinases (RTKs) are a subclass of tyrosine kinases that are involved in mediating cell-to-cell communication and controlling a wide range of complex biological functions, including cell growth, motility, differentiation, and metabolism.
There are 58 known RTKs in humans [1, 2], and all RTKs share a similar protein structure comprised of an extracellular ligand binding domain, a single transmembrane helix, and an intracellular region that contains a juxtamembrane regulatory region, a tyrosine kinase domain (TKD) and a carboxyl (C-) terminal tail [3].
Dysregulation of RTK signaling leads to many human diseases, especially cancer. Given the advent of the genomic era and the implementation of next generation sequencing (NGS) in cancer research as well as routine clinical practice, mutational landscapes have been established in almost all types of human tumors [4]. These genomic studies have revealed the presence of several different types of alterations in the genes encoding RTKs such as EGFR, HER2/ErbB2, MET, amongst many others. The presence of recurrent RTK genomic alterations raises the question about how they function in cancer development and how to best treat cancer patients whose tumors harbor certain RTK mutations. In this manuscript, we review the processes whereby RTKs are activated under normal physiological conditions and discuss several mechanisms whereby RTKs can be aberrantly activated in human cancers, which have important implications for selection of anti-cancer therapies.
RTK class I (EGF receptor family) (ErbB family)
RTK class II (Insulin receptor family)
RTK class III (PDGF receptor family)
RTK class IV (VEGF receptors family)
RTK class V (FGF receptor family)
RTK class VI (CCK receptor family)
RTK class VII (NGF receptor family)
RTK class VIII (HGF receptor family)
RTK class IX (Eph receptor family)
RTK class X (AXL receptor family)
RTK class XI (TIE receptor family)
RTK class XII (RYK receptor family)
RTK class XIII (DDR receptor family)
RTK class XIV (RET receptor family)
RTK class XV (ROS receptor family)
RTK class XVI (LTK receptor family)
RTK class XVII (ROR receptor family)
RTK class XVIII (MuSK receptor family)
RTK class XIX (LMR receptor)
RTK class XX (Undetermined)
https://molecular-cancer.biomedcentral.com/articles/10.1186/s12943-018-0782-4#:~:text=Receptor%20tyrosine%20kinases%20(RTKs)%20are,motility%2C%20differentiation%2C%20and%20metabolism.
TP53
Normal Function: Master tumor suppressor gene regulating cell cycle, apoptosis, and DNA repair.
Mutation Effect: Loss-of-function mutations lead to uncontrolled cell growth and genomic instability.
Associated Cancers: Breast, lung, colon, ovarian, brain, and nearly all cancers.
Diagnostics: NGS, IHC, ddPCR.
Targeted Therapies: No FDA/EMA-approved drugs directly targeting TP53 mutations.
Companion Diagnostic? ❌ No official companion diagnostic.
Emerging Trends: Restoration therapies (APR-246) and synthetic lethality strategies in trials.
KRAS
KRAS (Kirsten rat sarcoma viral oncogene homolog
Normal Function: Regulates cell proliferation via MAPK and PI3K pathways.
Mutation Effect: G12C, G12D, G13D mutations lock KRAS in an active state, driving cancer growth.
Associated Cancers: NSCLC, colorectal, pancreatic cancer.
Diagnostics: NGS, PCR.
Targeted Therapies:
Sotorasib (Lumakras) → FDA-approved (KRAS G12C NSCLC).
Adagrasib (Krazati) → FDA-approved (KRAS G12C NSCLC).
Companion Diagnostic? ✅ Yes (FDA-approved tests).
Emerging Trends: Combinations with MEK/EGFR inhibitors to prevent resistance.
EGFR
Normal Function: Tyrosine kinase receptor regulating cell growth and survival.
Mutation Effect: L858R and exon 19 deletions lead to ligand-independent activation.
Associated Cancers: NSCLC, glioblastoma, colorectal cancer.
Diagnostics: NGS, PCR, IHC.
Targeted Therapies:
Osimertinib (Tagrisso) → FDA/EMA-approved (NSCLC).
Erlotinib (Tarceva), Gefitinib (Iressa) → FDA/EMA-approved (NSCLC).
Companion Diagnostic? ✅ Yes (FDA-approved EGFR mutation tests).
Emerging Trends: Third-generation TKIs for resistant mutations.
HER2 (ERBB2)
Normal Function: Promotes cell growth via tyrosine kinase signaling.
Mutation Effect: HER2 amplification leads to constant proliferative signaling.
Associated Cancers: Breast, gastric, esophageal cancers.
Diagnostics: IHC, FISH.
Targeted Therapies:
Trastuzumab (Herceptin), Pertuzumab (Perjeta) → FDA/EMA-approved (HER2+ breast/gastric cancer).
Trastuzumab deruxtecan (Enhertu) → FDA-approved (HER2-low breast cancer).
Companion Diagnostic? ✅ Yes (FDA-approved IHC/FISH tests).
Emerging Trends: Antibody-drug conjugates (ADCs) for HER2-low cancers.
BRAF
Normal Function: MAPK signaling kinase regulating cell growth.
Mutation Effect: BRAF V600E mutation leads to constant pathway activation.
Associated Cancers: Melanoma, colorectal, thyroid cancer.
Diagnostics: NGS, PCR.
Targeted Therapies:
Vemurafenib (Zelboraf), Dabrafenib (Tafinlar) → FDA/EMA-approved (BRAF V600E melanoma).
BRAF + MEK inhibitors (Trametinib, Cobimetinib) → FDA/EMA-approved (melanoma, NSCLC).
Companion Diagnostic? ✅ Yes (FDA-approved BRAF tests).
Emerging Trends: Resistance prevention via dual BRAF/MEK inhibition.
PIK3CA
Normal Function: PI3K signaling component regulating cell survival.
Mutation Effect: Activating mutations (H1047R) enhance PI3K-AKT pathway activation.
Associated Cancers: Breast, colorectal, endometrial cancer.
Diagnostics: NGS, PCR.
Targeted Therapies:
Alpelisib (Piqray) → FDA/EMA-approved (HR+/HER2- breast cancer).
Companion Diagnostic? ✅ Yes (FDA-approved PIK3CA test).
Emerging Trends: Combinations with CDK4/6 inhibitors.
KRAS
IDKRAS (G12X, G13X, Q61X)
“KRAS – Kirsten Rat Sarcoma Viral Oncogene Homolog
1. Normal Function
KRAS encodes a GTPase that cycles between active (GTP-bound) and inactive (GDP-bound) forms to transmit signals from receptor tyrosine kinases (e.g., EGFR) to downstream pathways such as:
MAPK (RAF–MEK–ERK) → Cell proliferation
PI3K–AKT–mTOR → Cell survival
When bound to GTP, KRAS activates these pathways to promote normal cell growth. KRAS has intrinsic GTPase activity that hydrolyzes GTP to GDP, turning itself off.
- Mutation Effects in Cancer
Mutations impair KRAS’s GTPase activity, leaving it locked in an active (GTP-bound) state, resulting in continuous pro-growth signaling. KRAS is one of the most frequently mutated oncogenes, particularly in:
Pancreatic ductal adenocarcinoma (~90%)
Colorectal cancer (~40%)
Non-small cell lung cancer (~30%)
- KRAS Mutations by Clinical Relevance
A. Predictive Mutations (Treatment-Related)
Mutation Codon Cancer Relevance
G12C Codon 12 NSCLC, CRC Predicts response to KRAS G12C inhibitors (e.g., sotorasib, adagrasib)
G12D Codon 12 Pancreatic, CRC Most common in pancreatic cancer; currently no FDA-approved targeted therapy, but drugs in development
G13D Codon 13 CRC Historically resistant to EGFR inhibitors; some modest responses in selected patients
Q61H/R/L Codon 61 Multiple Activating but currently undruggable
🧪 These mutations are detected by NGS or ddPCR, and define eligibility for targeted KRAS inhibitors (for G12C only, as of now).
B. Prognostic Mutations
KRAS mutation (any codon) → Associated with worse prognosis in CRC, pancreatic, and NSCLC.
G12V and G12C may carry poorer survival outcomes than G13D in colorectal cancer.
In colorectal cancer, KRAS mutations are both prognostic and predictive of non-response to anti-EGFR therapies like cetuximab and panitumumab.
C. Resistance-Associated Mutations
KRAS mutations confer intrinsic resistance to anti-EGFR monoclonal antibodies in colorectal cancer.
KRAS mutation as an acquired resistance mechanism in EGFR-mutant NSCLC after osimertinib therapy (less common, but observed).
- Diagnostic Methods
Method Use
NGS Comprehensive profiling, identifies all codon mutations
ddPCR Highly sensitive, used in liquid biopsy
qPCR Fast, limited to specific mutations
KRAS testing is mandatory in metastatic CRC before using anti-EGFR therapy. - Targeted Therapies for KRAS
✅ FDA-Approved Drugs (KRAS G12C-specific only):
Drug Indication Target Status Companion Diagnostic
Sotorasib (Lumakras) NSCLC (KRAS G12C) Irreversible G12C inhibitor FDA-approved (2021) ✅ Yes (Guardant360 CDx, therascreen KRAS RGQ PCR)
Adagrasib (Krazati) NSCLC (KRAS G12C) Irreversible G12C inhibitor FDA-approved (2022) ✅ Yes (FoundationOne CDx, others)
⚠️ Not Approved Yet / In Trials:
G12D inhibitors: In early-phase trials (e.g., MRTX1133) for pancreatic and colorectal cancers.
Pan-KRAS inhibitors: Still preclinical or early-phase (targeting KRAS activation cycle or downstream effectors).
- Mechanisms of Resistance to KRAS Inhibitors
KRAS G12C inhibitors initially work well in NSCLC, but most patients relapse within 6–12 months.
Common resistance mechanisms:
Mechanism Type Example
Secondary KRAS mutations On-target Y96D, which alters drug binding
Upregulation of RTKs Bypass pathway EGFR, FGFR, activating PI3K/AKT
NRAS/HRAS mutations Parallel RAS family Restores RAS signaling
MET amplification Bypass Re-activates MAPK pathway
🧪 Serial ctDNA (liquid biopsy) is used to monitor emerging resistance mutations in real time.
- Emerging Trends in KRAS-Targeted Therapy
KRAS G12D and G12V inhibitors → Multiple compounds (e.g., MRTX1133) in development
Combination therapies:
KRAS + SHP2 inhibitors
KRAS + MEK inhibitors
KRAS inhibitors + immunotherapy (e.g., anti-PD-1)
Pan-RAS degraders → Target multiple RAS isoforms or prevent membrane localization.
Covalent inhibitors beyond G12C → Research into non-G12C alleles using new chemical scaffolds.
✅ Key Takeaways for KRAS
KRAS is the most mutated oncogene in cancer, historically undruggable but now G12C-specific inhibitors are available.
KRAS mutation testing is standard-of-care in CRC and NSCLC.
Sotorasib and adagrasib are FDA-approved and require companion diagnostics.
Resistance mechanisms are diverse, with secondary mutations and bypass signaling the most common.
Next-generation KRAS inhibitors are under active development for G12D, G12V, and pan-KRAS targeting.”
ESR1
Estrogen Receptor 1
1. Normal Function
ESR1 encodes ERα (Estrogen Receptor alpha), a nuclear hormone receptor.
When bound to estrogen, ERα dimerizes and translocates to the nucleus, where it regulates transcription of genes involved in proliferation, survival, and differentiation.
It plays a central role in normal breast development and is critical in ER-positive breast cancers.
- Mutation Effects in Cancer
Mutations in ESR1 often result in ligand-independent activation of the estrogen receptor.
This means the receptor is constantly active, even in the absence of estrogen, driving tumor growth and leading to resistance to endocrine therapies that lower estrogen levels (like aromatase inhibitors).
- ESR1 Mutations by Clinical Relevance
A. Predictive (Treatment-Related) Mutations
These mutations are rare in primary tumors but occur frequently in metastatic ER+ breast cancer, especially after treatment with aromatase inhibitors (AIs).
Mutation Domain Effect Relevance
Y537S/N/C Ligand-binding domain (LBD) Stabilizes active conformation of ERα Resistance to AIs and some SERMs
D538G LBD Same as above Same
E380Q LBD Constitutive activity Less common, still resistance-linked
🧪 These mutations predict poor response to aromatase inhibitors and some SERMs (e.g., tamoxifen), but some may still respond to SERDs (Selective Estrogen Receptor Degraders) like fulvestrant or newer oral SERDs.
B. Prognostic Role
ESR1 mutations are associated with poorer prognosis in metastatic ER+ breast cancer, especially after aromatase inhibitor exposure.
High ESR1 expression in primary tumors is generally a favorable prognostic marker, as it predicts sensitivity to endocrine therapy.
C. Resistance-Associated Mutations
ESR1 LBD mutations (especially Y537S and D538G) are acquired resistance mutations, mostly after long-term AI use.
They enable the tumor to grow without estrogen, making estrogen-depleting strategies ineffective.
🧬 Resistance Mechanisms:
Ligand-independent activation of ER (mutant ERα is constitutively active).
Reduced binding of certain SERMs/SERDs (some ESR1 mutants are less susceptible to fulvestrant degradation).
Cross-talk with PI3K/AKT/mTOR pathway → promotes resistance to endocrine therapy.
- Diagnostic Methods
Method Use
NGS Detects all common ESR1 mutations (e.g., D538G, Y537S)
ddPCR Ultra-sensitive detection in circulating tumor DNA (ctDNA)
IHC Detects ERα protein expression, not mutations
✅ ESR1 mutation testing via liquid biopsy (ctDNA) is becoming routine in ER+/HER2- metastatic breast cancer to guide treatment selection. - Targeted Therapies for ESR1-Mutant Cancers
✅ Approved Drugs (not mutation-specific, but active in ESR1+)
Drug Class Effect FDA/EMA Approval Effective Against ESR1 Mutants?
Fulvestrant SERD Binds and degrades ERα ✅ Yes ✅ Partial (but not all mutants)
Elacestrant Oral SERD Selective ER degrader ✅ Yes (FDA 2023) ✅ Yes, active in Y537S/D538G
Tamoxifen SERM ER modulator (partial antagonist) ✅ Yes ❌ Often ineffective in mutants
Aromatase inhibitors (e.g., letrozole, anastrozole) AI Block estrogen synthesis ✅ Yes ❌ ESR1 mutants resist AIs
🧪 Companion Diagnostics?
❌ No official FDA companion diagnostics yet, but ESR1 mutation testing is strongly recommended before prescribing oral SERDs (e.g., elacestrant).
ctDNA-based ESR1 mutation testing is often used in clinical trials and real-world settings.
- Emerging Therapies and Trials
Next-generation oral SERDs (improved degradation of mutant ER):
Camizestrant, Giredestrant, Rintodestrant → Phase II/III trials
PROTACs targeting ERα (e.g., ARV-471):
Induce ubiquitin-mediated degradation of ERα, including resistant mutants
Combination therapies:
SERDs + CDK4/6 inhibitors (e.g., elacestrant + palbociclib)
SERDs + PI3K/mTOR inhibitors (to block parallel resistance pathways)
AI resistance profiling via liquid biopsy:
Real-time ESR1 mutation monitoring to personalize treatment switches
✅ Key Takeaways for ESR1
ESR1 mutations are acquired resistance mechanisms in ER+ breast cancer, especially post-AI.
D538G, Y537S/N/C are the most common clinically relevant mutations.
Fulvestrant and elacestrant are effective in many ESR1-mutant cases, but not all.
Testing for ESR1 mutations in ctDNA is increasingly recommended in the metastatic setting.
Multiple oral SERDs and ER degraders (PROTACs) are under development.
BRAF
B-Raf Proto-Oncogene, Serine/Threonine Kinase
1. Normal Function
BRAF encodes a serine/threonine kinase in the MAPK signaling pathway (RAS–RAF–MEK–ERK).
It transduces signals from activated RAS proteins to MEK, promoting cell proliferation, differentiation, and survival.
- Mutation Effects in Cancer
BRAF mutations — especially V600E — lead to constitutive activation of the MAPK pathway, resulting in RAS-independent proliferation.
These are driver mutations and are often mutually exclusive with RAS mutations.
- BRAF Mutations by Clinical Relevance
A. Predictive (Treatment-Related) Mutations
Mutation Codon Effect Response to Therapy
V600E Codon 600 Substitution of valine with glutamic acid → 10x increased kinase activity ✅ Strong response to BRAF/MEK inhibitors
V600K Codon 600 Valine to lysine ✅ Responds, but slightly less than V600E
V600D/R/M Codon 600 Rare substitutions ⚠️ Limited data, some response to BRAF-targeted therapy
These mutations predict sensitivity to BRAF inhibitors like vemurafenib, dabrafenib, and encorafenib.
B. Prognostic Role
BRAF V600E in melanoma → Associated with more aggressive disease but predicts strong response to targeted therapy.
In colorectal cancer, BRAF V600E is a poor prognostic marker and less responsive to monotherapy with BRAF inhibitors.
C. Resistance-Associated Mechanisms
📌 Resistance is common, especially in monotherapy. Mechanisms include:
Mechanism Type Explanation
Reactivation of MAPK pathway On-pathway MEK or ERK activation despite BRAF inhibition
NRAS mutations Bypass Activates CRAF to continue MAPK signaling
BRAF splice variants On-target Dimerize and become resistant to monomeric BRAF inhibitors
Upregulation of RTKs (e.g., EGFR in CRC) Bypass EGFR signals downstream despite BRAF inhibition
PI3K/AKT pathway activation Parallel Bypass via alternate survival signaling
💡 Solution: Combination therapies — BRAF + MEK inhibitors, or BRAF + EGFR in CRC.
- Diagnostic Methods
Method Use
NGS Detects all V600 mutations and other rare alterations
Real-time PCR Fast, widely used for V600E
IHC (VE1 antibody) For protein detection of V600E in FFPE tissue
ddPCR High-sensitivity detection in ctDNA
✅ BRAF testing is standard of care in melanoma, CRC, thyroid, and NSCLC when considering targeted therapy. - Targeted Therapies for BRAF-Mutated Cancers
✅ FDA/EMA-Approved Therapies
Drug(s) Type Indication Companion Diagnostic?
Vemurafenib (Zelboraf) BRAF inhibitor Melanoma (V600E) ✅ Yes (e.g., cobas 4800)
Dabrafenib (Tafinlar) + Trametinib (Mekinist) BRAF + MEK inhibitor Melanoma, NSCLC, thyroid (V600E) ✅ Yes
Encorafenib (Braftovi) + Binimetinib (Mektovi) BRAF + MEK inhibitor Melanoma (V600E/K) ✅ Yes
Dabrafenib + Trametinib BRAF + MEK inhibitor Adjuvant therapy in resected melanoma ✅ Yes
Encorafenib + Cetuximab BRAF + EGFR combo Colorectal cancer (V600E) ✅ Yes
🧪 Companion diagnostics are FDA-approved and required to confirm BRAF V600 mutations before initiating therapy. - Emerging Therapies and Strategies
Next-generation BRAF inhibitors
Target dimeric BRAF forms resistant to current drugs (e.g., PLX8394)
Triple-combination therapy
BRAF + MEK + EGFR inhibitors in BRAF-mutant CRC → Overcome EGFR-mediated resistance
Combination with immunotherapy
Trials combining BRAF/MEK inhibitors + anti-PD-1 (e.g., pembrolizumab) in melanoma
Liquid biopsy monitoring
ctDNA tracking of emergent resistance mutations (e.g., MEK, NRAS)
✅ Key Takeaways for BRAF
BRAF V600E is a powerful predictive biomarker for targeted therapy.
Resistance often arises through MAPK reactivation or bypass signaling.
Combination therapy (BRAF + MEK inhibitors) is now standard to delay resistance.
BRAF testing is essential, and companion diagnostics are FDA/EMA-approved.
New agents are in development to target resistant BRAF dimer forms and enhance immunotherapy combinations.
Would you like to continue with PIK3CA, ALK, or another gene of interest?
CDK4/6.
proteins known as the cyclin-dependent kinases 4 and 6,
CDK4/6 inhibitors are a class of medicines used to treat certain types of hormone receptor-positive, HER2-negative breast cancer. These medicines interrupt the process through which breast cancer cells divide and multiply. To do this, they target specific proteins known as the cyclin-dependent kinases 4 and 6, abbreviated as CDK4/6. That’s why you may hear them referred to as targeted therapies.
https://www.breastcancer.org/treatment/targeted-therapy/what-are-cdk46-inhibitors
