Molecular correlates of DSCR1 expression in colorectal cancer (CRC).

Abstract

185 Background: Down syndrome (DS), a genetic disorder caused by trisomy of chr 21, is associated with a considerably lower risk for solid tumors and other angiogenesis related diseases. DSCR1 belongs to a family of evolutionary conserved protein-coding genes located on chr 21 and is highly upregulated in DS patients. Its product, calcipressin-1, has been shown to reduce cancer risk by suppressing angiogenesis. We previously reported that a germline polymorphism in DSCR1 was associated with time to recurrence in resected CRC and anti-VEGF treatment outcomes in metastatic CRC. Here, we analyzed the molecular landscape of CRC according to DSCR1 expression levels. Methods: 20,237 samples from CRC tested at Caris Life Sciences (Phoenix, AZ) with WTS (Illumina NovaSeq) and NextGen DNA sequencing (NextSeq, 592 Genes and NovaSEQ, WES) were analyzed. Top quartile transcripts per million (TPM) for DSCR1 expression were considered high (Q4) while bottom quartile low (Q1). Cell infiltration (CI) in the tumor microenvironment (TME) was estimated by RNA deconvolution analysis using QuantiSEQ. Interferon-gamma and T-cell inflamed signatures were also calculated from RNA data. X2 and Fisher-Exact tests were used and statistical significance was determined as P-value adjusted for multiple comparisons ( q < 0.05). Results: DSCR1 expression was higher in primary tumors than metastases (10.5 vs 8.1 median TPM, q < 0.05). No significant difference was observed in right- versus left-sided tumors, however rectal tumors showed the highest DSCR1 expression ( P < 0.05). Overall, high DSCR1 TPM were associated with TMB-high (11.3% vs 9.3%), dMMR/MSI-H (7.9% vs 5.9%), and PD-L1 (4.7% vs 3.1%) ( q < 0.01); the association with TMB-H was not significant in pMMR/MSS. DSCR1 high was associated with lower mutation rates of APC, KRAS, TP53 and amplification of FLT1/ FLT3, while higher mutation rates of KMT2C/D, BRAF, PTEN, RNF43, and RSPO3 fusions ( q < 0.0001). Gene set enrichment analysis showed that high DSCR1 expressing tumors were enriched in alterations of several pathways including hypoxia, apoptosis, DNA repair, KRAS signaling, inflammatory response, and oxidative stress-related pathways (all P < 0.05, FDR < 0.25). B cells, macrophages, neutrophils, NK cells, Tregs, cancer associated fibroblasts and endothelial cells were more abundant in the TME of tumors with high DSCR1 while myeloid dendritic cells were lower, regardless of MMR status (all q < 0.001). DSCR1 expression was associated with a higher T-cell inflamed signature and IFN score ( q < 0.05). Conclusions: This is the first and most extensive profiling study to investigate DSCR1 expression in CRC. Our data show a strong association between tumor DSCR1 gene expression and distinct molecular features and TME cell infiltration. These findings suggest that DSCR1 holds potential as a novel therapeutic target for CRC and may be an important player in TME modulation.