Abstract 2556: Functional characterization of the pancreatic cancer TERT-CLPTM1L risk locus on chr5p15.33.
Authors: Jia Jinping , Collins Irene , Dzyadyk Marta , Thompson Abbey , Cheuk Adam , Parikh Hemang , Wang Zhaoming , Westlake Chris , Bosley Allen , Petersen Gloria , Andresson Thorkell , Amundadottir Laufey 
Published: August 2014

Pancreatic cancer is a highly lethal cancer with few well established risk factors. PanScan, a genome wide association study (GWAS) of pancreatic cancer has identified four pancreatic cancer susceptibility loci in populations of European ancestry. One of these is in a multi cancer locus on chr5p15.33 where the most significant SNP from the GWAS (rs401681, P=3.7x10-7, ORAllele=1.19) lies in a region containing two genes, TERT and CLPTM1L. The TERT gene encodes the catalytic subunit of telomerase, well known for its essential role in maintaining telomere ends. The function of CLPTM1L is not as clear, although it has been proposed to play a role in apoptosis. It is predicted to encode a protein with 6 transmembrane (TM) domains and two large hydrophilic domains: a loop of 253 aa between the first and second TM domains, and a C-terminal tail of 89 aa.

We have performed imputation to fine-map the signal to a SNP three orders of magnitude more significant than the GWAS SNP (PImputed=1.4x10-10, ORAllele=1.30). As this SNP is located in the CLPTM1L gene we have performed a series of experiments to investigate the function of the CLPTM1L gene and its encoded protein. Immunofluorescence analysis in pancreatic cancer cells (PANC-1) indicates that it localizes to the endoplasmic reticulum. Affinity purification and mass spectrometry (HEK-293T, hTERT-HPNE and PANC-1 cells) identified MYH9, a non-muscle heavy chain myosin, as a potential interacting protein. The interaction has been validated by co-immunoprecipitation and co-localization experiments. To examine if CLPTM1L plays a role in growth control, we created stable PANC-1 cell lines overexpressing the full length CLPTM1L gene as well as two deletions, a C-terminal deletion and a loop deletion, and assayed growth in vitro and in vivo. Cell lines overexpressing full length CLPTM1L grow faster in vitro and in vivo as compared to cells containing empty vector. Interestingly, the two CLPTM1L mutants abolish this effect. Furthermore, we have shown by RNA-seq that the CLPTM1L gene is overexpressed in pancreatic tumors as compared to normal pancreatic tissues. Our results indicate that CLPTM1L may play a role in the control of cell growth and oncogenesis in the pancreas. Our current efforts aim at further characterizing the function of CLPTM1L and to correlate pancreatic cancer risk variants on 5p15.33 to molecular phenotypes to attempt to explain the underlying biology of the risk.

Citation Format: Jinping Jia, Irene Collins, Marta Dzyadyk, Abbey Thompson, Adam Cheuk, Hemang Parikh, Zhaoming Wang, Chris Westlake, Allen Bosley, Gloria Petersen, Thorkell Andresson, Laufey Amundadottir. Functional characterization of the pancreatic cancer TERT-CLPTM1L risk locus on chr5p15.33. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2556. doi:10.1158/1538-7445.AM2013-2556

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.