The Frequencies and Clinical Implications of Mutations in 33 Kinase-Related Genes in Locally Advanced Rectal Cancer: A Pilot Study
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Locally advanced rectal cancer (LARC: T3/4 and/or node-positive) is treated with preoperative/neoadjuvant chemoradiotherapy (CRT), but responses are not uniform. The phosphatidylinositol 3-kinase (PI3K), MAP kinase (MAPK), and related pathways are implicated in rectal cancer tumorigenesis. Here, we investigated the association between genetic mutations in these pathways and LARC clinical outcomes.
We genotyped 234 potentially clinically relevant nonsynonymous mutations in 33 PI3K and MAPK pathway–related genes, including PIK3CA, PIK3R1, AKT, STK11, KRAS, BRAF, MEK, CTNNB1, EGFR, MET, and NRAS, using the Sequenom platform. DNA samples were extracted from pretreatment LARC biopsy samples taken from 201 patients who were then treated with long-course neoadjuvant CRT followed by surgical resection.
Sixty-two mutations were detected in 15 genes, with the highest frequencies occurring in KRAS (47 %), PIK3CA (14 %), STK11 (6.5 %), and CTNNB1 (6 %). Mutations were detected in BRAF, NRAS, AKT1, PIK3R1, EGFR, GNAS, MEK1, PDGFRA, ALK, and TNK2, but at frequencies of <5 %. As expected, a pathologic complete response (pCR) was associated with improved 5-year recurrence-free survival (RFS; hazard ratio, 0.074; 95 % CI 0.01–0.54; p = 0.001). Mutations in PI3K pathway–related genes (odds ratio, 5.146; 95 % CI 1.17–22.58; p = 0.030), but not MAPK pathway–related genes (p = 0.911), were associated with absence of pCR after neoadjuvant CRT. In contrast, in patients who did not achieve pCR, mutations in PI3K pathway–related genes were not associated with recurrence-free survival (p = 0.987). However, in these patients, codon 12 (G12D/G12 V/G12S) and 13 mutations in KRAS were associated with poor recurrence-free survival (hazard ratio, 1.579; 95 % confidence ratio, 1.00–2.48; p = 0.048).
Mutations in kinase signaling pathways modulate treatment responsiveness and clinical outcomes in LARC and may constitute rational targets for novel therapies.
KeywordsRectal Cancer KRAS Mutation PI3K Pathway PIK3CA Mutation Rectal Adenocarcinoma
This work was supported by Grant funding from SLICR (St. Lukes Institute of Cancer Research), NECRET (North East Cancer Research and Education Trust), NESERT (North East Surgical Education Research Trust), and Science Foundation Ireland under Grant No. 08/SRC/B1410.
Conflict of interest
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