Abstract 3420: Mutational status, expression and functional behaviors of FAM134B in colorectal cancer
Authors: Islam Farhadul , Gopalan Vinod , Wahab Riajul , Lee Katherine Ting-wei , Mamoori Afraa , Lu Cu-tai , Smith Robert A , Lam Alfred K-Y 
Published: July 2017

Background: Family with sequence similarity 134B (FAM134B) is an ER-autophagy regulator and involved in the pathogenesis of neuronal disorders, vascular diseases and carcinomas. In colorectal carcinomas, FAM134B plays important role in the pathogenesis and associated with aggressiveness of the disease. However, the frequency of mutations, expression pattern and functional roles in cell have never been studied in colorectal cancer.

Objectives: To investigate FAM134B mutations in tissues samples from patients with colorectal cancer and cell lines. Also, the expression of FAM134B at protein and mRNA levels were examined. In addition, functional roles of FAM134B in colon cancer were studied.

Methods: Mutations in FAM134B sequence in eighty-eight cancer tissues and matched non-cancer samples was studied by high-resolution melt curve analysis followed by Sanger sequencing. FAM134B expression was studied and quantified in cell lines and cancer tissues samples using immunofluorescence, immunocytochemistry, Western blot and real-time PCR. In vitro functional assays were performed to unveil the molecular roles of FAM134B in colon cancer pathogenesis followed by shRNA-mediated silencing in cells. Mouse xenotransplantation model was used to confirm the functional behavior of FAM134B in colon cancer.

Results: In this study, 46.5% (41/88) patients with colorectal cancer were identified as FAM134B mutations positive. Thirty-one novel pathogenic mutations were detected. Of the 31 mutations, 8 novel frameshift mutations caused nonsense-mediated mRNA decay and associated with gender of the patients, presence of metachronous cancer, size, T staging, presence of distant metastases and positivity of microsatellite instability (MSI) in the cancer (p &lt; 0.05). FAM134B expression in cancer cells derived from advanced stages (stage III; SW48 and stage IV; HCT116) of colon cancer was significantly (p&lt;0.01) reduced when compared to non-neoplastic colon cells (FHC) and cancer cells derived from stage II colon cancer (SW480). Expression of FAM134B mRNA in cancer tissues was noted significantly (p&lt;0.001) downregulated when compared to that of non-cancer tissues samples. FAM134B suppression significantly (p&lt;0.05) increased the proliferation of colon cancer cells, remarkably increased (34-52%; p&lt;0.05) the clonogenic, migration capacity, and increases the proportion of cells in S phase of cell-cycle (p&lt;0.01). Xenotransplantation model showed that larger and higher-grade tumors were formed in mice treated with FAM134B knockdown cells.

Conclusion: In vitro and in vivo functional studies implied that FAM134B acts as a cancer inhibitor in colon cancer. Also, FAM134B mutation is common in colorectal cancer and the association of mutation with adverse clinical and pathological parameters are in concur with the tumour suppressive property of the gene.

Note: This abstract was not presented at the meeting.

Citation Format: Farhadul Islam, Vinod Gopalan, Riajul Wahab, Katherine Ting-wei Lee, Afraa Mamoori, Cu-tai Lu, Robert A Smith, Alfred K-Y Lam. Mutational status, expression and functional behaviors of FAM134B in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3420. doi:10.1158/1538-7445.AM2017-3420