Gene expression and genetic variants in Parkinson's disease (PD) genes to predict outcome in metastatic colorectal cancer (mCRC): Data from FIRE-3 phase III trial.

Abstract

3595 Background: PD is one of the most common age-related neurodegenerative disorders. Large epidemiological studies have consistently reported a reduced risk of CRC in PD patients (pts), but the biology behind this evidence is unclear. The methylation status of SNCA, one of the causal PD genes, has been identified as a tool for CRC screening and early diagnosis when detected in stool samples, and alterations in core PD genes are prevalent across human malignancies including CRC. Methods: The impact on outcome of 13 SNPs within 6 core PD genes ( SNCA, PRKN, UCHL1, PINK1, DJ-1, LRRK2) was analyzed in pts enrolled in the randomized FIRE-3 trial. Genomic DNA from blood samples of pts treated with first-line FOLFIRI-cetuximab (cet, n = 129) and FOLFIRI-bevacizumab (bev, n = 107) was genotyped through the OncoArray, a custom array manufactured by Illumina. Gene expression levels were measured from 102 tumor samples of pts in the cet arm by HTG EdgeSeq Oncology Biomarker Panel. Results: In the cet cohort, pts carrying the G/G variants of SNCA rs356165 and rs2736990 had significantly shorter mOS (30 vs 41.1 mo) compared to any A genotype in both uni- and multivariable analysis (adjusted P[ Padj] = .047 and .042, respectively). LRKK2 rs3761863 T/T allele carriers showed shorter mPFS (9.5 vs 13.3 mo, Padj = .01), while rs11564148 any A carriers had longer mPFS (14.2 vs 10.2 mo, Padj = .01) compared to reference genotypes. LRKK2 rs11564148 any A carriers also showed longer mOS in multivariable analysis (43.7 vs 33.2 mo, Padj = .044). Any C allele carriers of PINK1 rs1043424 showed longer mPFS in uni- and multivariable analysis ( Padj < .001). No significant interaction was found with gender, tumor location and RAS status. These associations were not observed in bev arm. High SNCA expression was associated with worse mPFS (log2 > 7.89, 5.9 vs 11.2 mo) and mOS (log2 > 7.68, 17.9 vs 31.1 mo) in FIRE-3 cet arm ( P < .05). Conclusions: We provide the first evidence that gene expression and genetic variants in PD genes may have a predictive value in mCRC pts receiving first-line cetuximab-based treatment. Our findings open new perspectives on the role of PD genes in CRC biology warranting further investigation.