Reference Detail

Ref Type

Journal Article

PMID

(33322618)

Authors

Knebel FH, Barber LJ, Newey A, Kleftogiannis D, Woolston A, Griffiths B, Fenwick K, Bettoni F, Ribeiro MFSA, da Fonseca L, Costa F, Capareli FC, Hoff PM, Sabbaga J, Camargo AA, Gerlinger M

Title

Circulating Tumour DNA Sequencing Identifies a Genetic Resistance-Gap in Colorectal Cancers with Acquired Resistance to EGFR-Antibodies and Chemotherapy.

Journal	Vol	Issue	Date	Pages	Journal Short Title
Cancers	12	12	2020 Dec 11		Cancers (Basel)

URL

Abstract Text

Epidermal growth factor receptor antibodies (EGFR-Abs) confer a survival benefit in patients with RAS wild-type metastatic colorectal cancer (mCRC), but resistance invariably occurs. Previous data showed that only a minority of cancer cells harboured known genetic resistance drivers when clinical resistance to single-agent EGFR-Abs had evolved, supporting the activity of non-genetic resistance mechanisms. Here, we used error-corrected ctDNA-sequencing (ctDNA-Seq) of 40 cancer genes to identify drivers of resistance and whether a genetic resistance-gap (a lack of detectable genetic resistance mechanisms in a large fraction of the cancer cell population) also occurs in RAS wild-type mCRCs treated with a combination of EGFR-Abs and chemotherapy. We detected one MAP2K1/MEK1 mutation and one ERBB2 amplification in 2/3 patients with primary resistance and KRAS, NRAS, MAP2K1/MEK1 mutations and ERBB2 aberrations in 6/7 patients with acquired resistance. In vitro testing identified MAP2K1/MEK1 P124S as a novel driver of EGFR-Ab resistance. Mutation subclonality analyses confirmed a genetic resistance-gap in mCRCs treated with EGFR-Abs and chemotherapy, with only 13.42% of cancer cells harboring identifiable resistance drivers. Our results support the utility of ctDNA-Seq to guide treatment allocation for patients with resistance and the importance of investigating further non-canonical EGFR-Ab resistance mechanisms, such as microenvironmentally-mediated resistance. The detection of MAP2K1 mutations could inform trials of MEK-inhibitors in these tumours.

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Molecular Profile	Treatment Approach

Gene Name	Source	Synonyms	Protein Domains	Gene Description	Gene Role

Therapy Name	Drugs	Efficacy Evidence	Clinical Trials

Drug Name	Trade Name	Synonyms	Drug Classes	Drug Description

Gene	Variant	Impact	Protein Effect	Variant Description	Associated with drug Resistance
MAP2K1	P124S	missense	unknown	MAP2K1 P124S lies within the protein kinase domain of the Map2k1 protein (UniProt.org). P124S results in increased Erk1/2 phosphorylation and confers resistance to Mek and Braf inhibitors (PMID: 19915144, PMID: 22197931) and an Egfr antibody (PMID: 33322618) in culture, but has similar induction of cell proliferation and viability levels to wild-type Map2k1 in culture (PMID: 29533785), and therefore, its effect on Map2k1 protein function is unknown.	Y

Molecular Profile	Indication/Tumor Type	Response Type	Therapy Name	Approval Status	Evidence Type	Efficacy Evidence	References
MAP2K1 P124S	colorectal cancer	predicted - resistant	Cetuximab + Irinotecan	Case Reports/Case Series	Actionable	In a clinical case study, a patient with KRAS/NRAS-wild-type colorectal cancer who progressed on treatment with Erbitux (cetuximab) and Camptosar (irinotecan) was found through ctDNA testing to have acquired MAP2K1 P124S, and preclinical analysis of colorectal cancer cells expressing MAP2K1 P124S demonstrated increased Erk phosphorylation upon treatment with Erbitux (cetuximab) in culture (PMID: 33322618).	33322618