Venook, Alan P.

3593 Background: CUB domain-containing protein 1 (CDCP1) is a transmembrane protein shown to be over-expressed in colorectal cancer (CRC), with an important role in tumor initiation, growth and metastasis. Through interactions with EGFR, CDCP1 promotes nuclear translocation of the key regulators of Wnt signaling, β-catenin and E-cadherin. High CDCP1 expression has been associated with poor survival outcomes in multiple solid tumors but data in CRC remains limited. We investigated associations between CDCP1 level and survival outcomes in patients with metastatic CRC (mCRC) in the phase III clinical trial CALGB/SWOG 80405 (Alliance). Methods: Data from 433 mCRC patients in the CALGB/SWOG 80405 (Alliance) trial were analyzed. Patients received bevacizumab (n = 226) or cetuximab (n = 207) plus chemotherapy as 1st-line treatment. Tumor RNA was extracted from FFPE samples and processed through the HiSeq 2500 (Illumina) platform. Overall survival (OS) and progression free survival (PFS) curves were evaluated in all treatment subgroups and stratified according to high or low CDCP1 expression. Likelihood ratio tests, hazard ratios (HRs), and 95% confidence intervals (CIs) were calculated using Cox proportional hazards multivariate models, adjusting for age, sex, ECOG performance status, tumor location, number of metastatic sites, KRAS status, consensus molecular subtypes, and treatment arm. Results: Overall, low CDCP1 expression was associated with better OS compared to high expression (HR = 1.38; 95% CI 1.07-1.77; 35.8 vs 25.0 months, p = 0.045). Subgroup analysis re-demonstrated this pattern in males (HR = 1.64; 95% CI 1.64-2.28; 35.9 vs 23.6 months, p = 0.01), patients with MSS tumors (HR = 1.56; 95% CI 1.17-2.08; 36.7 vs 25.1 months, p = 0.0094), and patients treated with cetuximab+FOLFOX (HR = 1.79; 95% CI 1.16-2.77; 40.8 vs 24.0 months, p = 0.03). The effect of CDCP1 expression on PFS was less pronounced. Relative to high expression, low expression was associated with better PFS in males (HR = 1.49; 95% CI 1.10-2.03; 13.1 vs 9.8 months, p = 0.027) and left-sided tumors (HR = 1.50; 95% CI 1.10-2.04; 14.4 vs 10.1 months, p = 0.034). Conclusions: Our findings represent real-world data of the predictive role of CDCP1 in patients with mCRC undergoing anti-EGFR or anti-VEGF treatment. Consistent with studies of other cancers, we show that low CDCP1 expression is predictive of better survival outcomes, with subgroup analysis revealing associations in males, MSS tumors, and left-sided tumors. Among treatment groups, low CDCP1 expression is predictive of better OS in cetuximab+FOLFOX-treated patients, a key finding given CDCP1’s close mechanistic ties to EGFR. Further studies should explore whether these associations are seen in other treatment modalities and whether CDCP1 blockade could represent a viable strategy in patients with high expression.

179 Background: Neuroligins are a family of postsynaptic cell adhesion molecules that play a crucial role in synapse formation and function. Recent studies suggest Neuroligin family genes (NLGN1,2,3,4X) may promote cancer cell growth and metastasis in various cancers, including colorectal cancer. Here, we investigated the association between neuroligin family gene expression and first-line treatment outcomes in mCRC. Methods: We evaluated the expression of 4 genes in the neuroligin family (NLGN1, NLGN2, NLGN3 and NLGN4X) on treatment outcomes of 433 pts with mCRC treated with either bevacizumab (Bev, n = 226) or cetuximab (Cet, n = 207) in combination with first-line chemotherapy within the CALGB/SWOG 80405 trial. mRNA was isolated from FFPE tumor samples and sequenced on the HiSeq 2500 (Illumina). Overall survival (OS) and progression-free survival (PFS) were compared between groups of pts categorized by low expression (Q1) (≤25 percentile), medium expression (Q2-3) (25th-75th percentile) and high expression (Q4)(>75th percentile) of NLGN family genes. The associations between gene expression and clinical outcomes were assessed via the multivariable Cox model and plotted with Kaplan-Meier curve. Treatment-gene interactions were evaluated using the likelihood ratio test. False discovery rate (FDR) was controlled through the Benjamini-Hochberg procedure. Results: High NLGN2 expression was associated with shorter PFS (median 10.0 mos, 95% CI (8.3, 11.3)) and OS (median 25.2mos, 95%CI (20.9, 30.0)) compared to low NLGN2 expression (PFS: median 11.2mos, 95% CI (9.8,14.3))(HR 1.41, 95% CI (1.06, 1.89)), P = 0.029). (OS: (median 31.8mos, 95%CI (26.8, 37.5)( HR 1.49, 95% CI (1.10, 2.01) P =0.0095) in multivariate analysis. Patients treated in the cetuximab arm(n=207), high HLGN2 expression significantly associated with shorter PFS (median 8.0 vs 13.4, HR 2.02, 95% CI (1.35, 3.03), P = 0.0021) and OS (median19.6 vs 36.3, HR 2.30, 95% CI (1.50, 3.53), P =8.3e-05). High NLGN3 expression was associated with shorter OS (23.9 vs 36.0 mos, P =0.0083) in cetuximab treatment arms, no significance found in PFS. We found significant treatment interaction for OS with NLGN2 and NLGN3 favoring cetuximab. In pts treated with cetuximab, High NLGN2 expression was significantly associated with shorter OS (median 29.1vs 36.3) (p=0.024) compared to pts treated with bevacizumab. For NLGN3, pts treated with cetuximab, high NLGN3 expression was significantly associated with shorter OS (median 25.0 vs 36.0) (p=0.018) compared to pts treated with bevacizumab. No significant association was found in NLGN1 and NLGN4X. Conclusions: Our results suggest NLGN2/3 gene expression may predict mCRC treatment outcomes. Potential therapeutic drug target NLGN in combination with anti-EGFR treatment in mCRC is warranted.