Abstract 4634
Background
Several studies in BRAFV600E colorectal cancers (CRC) have failed to replicate the efficacy of BRAF inhibitors in treatment of BRAFV600E melanomas (Mel), suggesting the existence of different resistance mechanisms as well as molecular and biological differences between the 2 tumor types. Herein, we examine these differences.
Methods
Tumor samples submitted to Caris Life Sciences for NGS DNA sequencing (592 gene panel) and RNA sequencing (54 gene panel) between the years 2015 and 2019 were retrospectively studied. Only microsatellite stable (MSS) tumors with either BRAFV600E mutation or wild type (WT) BRAF status were included in this initial analysis. Chi-square tests determined differences.
Results
A total of 8409 tumor samples were analyzed: CRC (N = 7453: BRAFV600E=373; WT = 7080) and Mel samples (N = 956: BRAFV600E=274; WT = 682). The most frequently mutated genes in BRAFV600E CRC were TP53 (81%), APC (26%), and SMAD4 (22.4%), compared to CDKN2A (22%), PTEN (13%), and TP53 (13%) in BRAFV600E Mel. Molecular alterations that are significantly more frequent in BRAFV600E CRC vs BRAFV600E Mel but not significantly different between BRAF WT CRC vs BRAF WT Mel included RSPO3 fusions (CRC=22.6% vs Mel=0%, P = 0.027); RNF43 deletions (2.0% vs 0%, p = 0.019); and mutations in RNF43 (18.8% vs 0%, P < 0.001), AKT1 (3.5% vs 0.4%, p = 0.008), and MTOR (2.4% vs 0.4%, p = 0.037). RSPO3 fusions and RNF43 mutations/deletions are mutually exclusive. Significantly more frequent alterations in BRAFV600E Mel compared to BRAFV600E CRC (but not in either WT) included deletions in PTEN (7% vs 3%, p = 0.005) and mutations in PTEN (12.9% vs 5.4%), MITF (1.9% vs 0%), STK11 (1.5% vs 0%), ERCC2 (1.1% vs 0%), FANCC (1.2% vs 0%), and CDK4 (1.5% vs 0%) (p < 0.05 for all).
Conclusions
BRAFV600E CRC carry molecular alterations that are distinct from BRAFV600E Mel. RSPO3 fusions and RNF43 alterations are prevalent in BRAFV600E CRC tumors in a mutually exclusive manner, suggesting that Wnt pathway activation via genetic alterations in upstream Wnt pathway regulators may play an important role in BRAFV600E CRC tumorigenesis and resistance to BRAF inhibitors. Drug combinations that target both the MAPK and Wnt pathways may warrant further investigation.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
M.E. Salem: Travel / Accommodation / Expenses: Caris Life Sciences. J. Xiu: Full / Part-time employment: Caris Life Sciences. A. Grothey: Travel / Accommodation / Expenses: Caris Life Sciences. R.M. Goldberg: Research grant / Funding (self), Travel / Accommodation / Expenses: Caris Life Sciences. Z. Gatalica: Full / Part-time employment: Caris Life Sciences. R. Feldman: Full / Part-time employment: Caris Life Sciences. M. Saul: Full / Part-time employment: Caris Life Sciences. W..M. Korn: Full / Part-time employment: Caris Life Sciences. A.F. Shields: Research grant / Funding (institution), Travel / Accommodation / Expenses: Caris Life Sciences. J.L. Marshall: Advisory / Consultancy: Caris Life Sciences. H.J. Lenz: Travel / Accommodation / Expenses: Caris Life Sciences. All other authors have declared no conflicts of interest.
Resources from the same session
3140 - Phase 2 study of olaparib in previously treated advanced solid tumors with homologous recombination repair mutation (HRRm) or homologous recombination repair deficiency (HRD): LYNK-002
Presenter: David Hyman
Session: Poster Display session 3
Resources:
Abstract
2655 - The K-BASKET trial: A prospective phase II biomarker-driven multiple basket trial in Korean solid cancer patients.
Presenter: Seul Kim
Session: Poster Display session 3
Resources:
Abstract
5938 - Cambridge Liquid biopsy “CALIBRATION” study: Can changes in circulating tumour DNA (ctDNA) predict durable tumour responses in patients with advanced oesophageal cancer receiving MEDI4736?
Presenter: Constanza Linossi
Session: Poster Display session 3
Resources:
Abstract
3799 - Validation of a tumour mutational burden workflow on routine histological samples of colorectal cancer and assessment of a cohort with synchronous hepatic metastases
Presenter: Andrea Mafficini
Session: Poster Display session 3
Resources:
Abstract
4647 - Microsatellite Instability Testing and Lynch Syndrome Screening For Colorectal Cancer Patients Through Tumor Sequencing
Presenter: Li Liu
Session: Poster Display session 3
Resources:
Abstract
3231 - "Liquid Withdarw" technique in CT-guided cutting needle lung biopsy: decreased incidence of complications and increased tissue amount for lung cancer molecular testing.
Presenter: Xue Wang
Session: Poster Display session 3
Resources:
Abstract
3282 - WGS Implementation in standard cancer Diagnostics for Every cancer patient (WIDE)
Presenter: Paul Roepman
Session: Poster Display session 3
Resources:
Abstract
5905 - Known and unknown gene fusion detection capabilities of solid tumor laboratories conducting next generation sequencing in 6 countries
Presenter: Steph Finucane
Session: Poster Display session 3
Resources:
Abstract
4238 - Clinical and Analytical Accuracy of a 523 Gene Panel Next-Generation Sequencing (NGS) Assay on Formalin-Fixed Paraffin-Embedded (FFPE) Solid Tumor Samples
Presenter: Ina Deras
Session: Poster Display session 3
Resources:
Abstract
2493 - Methylation analysis of MLH1 using droplet digital PCR and methylation sensitive restriction enzyme.
Presenter: Celine De Rop
Session: Poster Display session 3
Resources:
Abstract