Somatic alterations of NF1 in colorectal cancer.

Authors

null

Hiroyuki Arai

Chiba Cancer Center, Chibashi, Japan

Hiroyuki Arai , Andrew Elliott , Joanne Xiu , Jingyuan Wang , Francesca Battaglin , Shivani Soni , Wu Zhang , Davendra Sohal , Richard M. Goldberg , Michael J. Hall , Aaron James Scott , Mohd Khushman , Jimmy J. Hwang , Emil Lou , Benjamin A. Weinberg , John Marshall , Albert Craig Lockhart , Anthony Frank Shields , W. Michael Korn , Heinz-Josef Lenz

Organizations

Chiba Cancer Center, Chibashi, Japan, CARIS Life Sciences, Irving, TX, Caris Life Sciences, Phoenix, AZ, USC Norris Comprehensive Cancer Center, Los Angeles, CA, Division of Medical Oncology, USC Norris Comprehensive Cancer Center, Keck School of Medicine, Los Angeles, CA, USC Keck School of Medicine, Los Angeles, CA, Cleveland Clinic, Cleveland, OH, West Virginia University Cancer Institute, Morgantown, WV, Fox Chase Cancer Center, Philadelphia, PA, Banner-University of Arizona Cancer Center, Division of Hematology and Oncology, Tucson, AZ, Mitchell Cancer Institute, Mobile, AR, Levine Cancer Institute, Charlotte, NC, University of Minnesota School of Medicine, Minneapolis, MN, Georgetown University Medical Center, Washington, DC, Georgetown University, Washington, DC, University of Miami Sylvester Cancer Center, Miami, FL, Karmanos Cancer Institute, Wayne State University, Detroit, MI

Research Funding

No funding received
None

Background: NF1 encodes neurofibromin, which is a key GTPase-activating protein that downregulates RAS activation. Inactivating mutations in NF1 result in sustained activation of RAS signaling, a key driver for development of colorectal cancer (CRC), and have been suggested to be a potential mechanism of resistance to EGFR inhibition in RAS-wild type (WT) CRC. Little is known about molecular characteristics of NF1-mutated (MT) CRC. Methods: Tumor profiles from 8150 CRC patients (pts) with available NF1 mutation status were retrospectively reviewed. NextGen sequencing by a customized 592-gene panel was performed. Microsatellite instability (MSI) / mismatch repair (MMR) status, tumor mutational burden (TMB) and PD-L1 expression were tested. Molecular profiles between NF1-MT and NF1-WT pts were compared. Results: Out of 8150 pts, 176 (2.2%) had somatic NF1 mutations with pathogenic or presumed pathogenic function. A higher NF1-MT frequency was observed in MSI-H/dMMR vs MSS/pMMR (13.5% vs 1.4%, p < 0.0001), in right-sided vs left sided (2.9% vs 1.8%, p < 0.01), and in RAS-WT vs RAS-MT (3.0% vs 1.4%, p < 0.0001). In MSS/pMMR tumors, no association with sidedness was observed (right: 1.3% vs left: 1.2%, NS). The most prevalent co-mutations with NF-1 were APC (63.2%), ARID1A (57.5%), TP53 (51.5%), KMT2D (32.9%) and KRAS (32.4%) in all cases, and APC (76.2%), TP53 (69.5%), KRAS (38.8%), ARID1A (34.4%) and FBXW7 (21.5%) in MSS/pMMR cases. POLE mutation was observed in 18.4% of NF1-MT/MSS/pMMR pts. Compared to NF1-WT pts, NF1-MT pts had more frequent mutations in ARID1A (All: 57.5% vs 23.3%, p < 0.0001; MSS/pMMR: 34.4% vs 15.2%, p < 0.05), and less frequent mutations in KRAS (All: 32.4% vs 49.0%, p < 0.0001; MSS/pMMR: 38.8% vs 50.3%, p < 0.05). Also, NF1-MT pts had more frequent alterations in homologous recombination pathway compared to NF1-WT pts (All: 39.8% vs 7.5%, p < 0.0001; MSS/pMMR: 17.5% vs 4.4%, p < 0.0001). Mean TMB was significantly greater in NF1-MT than NF1-WT (All: 48.9/Mb vs 10.0/Mb, p < 0.0001; MSS/pMMR: 48.3/Mb vs 8.2/Mb, p < 0.0001). Also, PD-L1 positivity was higher in NF1-MT compared to NF1-WT (All: 12.9% vs 3.6%, p < 0.0001; MSS/pMMR: 7.1% vs 2.6%, p < 0.05). Conclusions: While more frequent than in RAS-MT pts, NF1-MT CRC was a small subset in RAS-WT pts. NF1-MT was associated with alterations in chromatin remodeling and DNA damage response pathways, as well as elevated TMB and PD-L1 expression, which may provide alternative therapeutic strategies beyond EGFR inhibition.

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Abstract Details

Meeting

2020 ASCO Virtual Scientific Program

Session Type

Poster Session

Session Title

Gastrointestinal Cancer—Colorectal and Anal

Track

Gastrointestinal Cancer—Colorectal and Anal

Sub Track

Biologic Correlates

Citation

J Clin Oncol 38: 2020 (suppl; abstr 4066)

DOI

10.1200/JCO.2020.38.15_suppl.4066

Abstract #

4066

Poster Bd #

58

Abstract Disclosures

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