Abstract 5090: α1β1 is pro-proliferative and promigratory integrin and its expression is upregulated by the MYC oncogenic factor in colorectal cancer
Authors: Boudjadi Salah , Bernatchez Gérald , Sénicourt Blanche , Beausejour Marco , Vachon Pierre-Henri , Carrier Julie , Beaulieu Jean-Francois 
Published: July 2016

Abstract
Background
Colorectal cancer (CRC) is a multi-step process that involves successive mutation, epigenetic alteration and gene dysregulation. Integrins are a family of heterodimeric glycoproteins involved in bidirectional cell signaling and participate in the regulation of cell shape, adhesion, migration, survival and proliferation. The integrin α1 subunit is known to be involved in RAS/ERK proliferative pathway activation and plays an important role in mammary carcinoma cell proliferation and migration. In the small intestine, α1 is present in the crypt proliferative compartment and absent in the villus. In mouse models, the α1β1 integrin, together with the Kras oncogenic factor, potentiates tumor growth. Very little is known about α1β1 function in CRC.
Aims: As we have recently shown that α1 is present in 65% of CRC (Boudjadi et al, 2013), that its expression is controlled by the MYC oncogenic factor and that the expressions of α1 and MYC correlate in 72.3% of colon adenocarcinomas (Boudjadi et al, Oncogene 2015) we postulated that integrin α1β1 has a pro-tumoral contribution to CRC related to α1 function.
METHODS: α1β1 function was studied in HT29, T84 and SW480 CRC cell lines using shRNA silencing targeting α1 (shα1) compared to an shRNA control (shCtrl). Cell proliferation was assessed by cell count and BrdU incorporation. Migration was tested by the scratch test assay. For the anoikis test, cells were kept in suspension without serum for 24 hours on poly-2-hydroxyethyl methacrylate (polyHEMA)-coated dishes and were then lysed and subjected to caspase3 activity measurement and cleaved PARP expression. To test tumorigenic capacity, shα1 and shCtrl HT29 cells were injected into the dorsal subcutaneous tissue of female CD1 nu/nu mice. The tumor volume was assessed by external measurement. After resection, α1 knockdown was confirmed at the mRNA and protein levels.
RESULTS: In HT29, T84 and SW480 cells, α1 mRNA silencing resulted in reduced cell growth and proliferation compared to the control. Caspase3 activity measurement and cleaved PARP expression in HT29 and T84 cells showed that resistance to anoikis was altered in shα1 cells compared to shCtrl. Wound healing was delayed in shα1 HT29 and T84 cells compared to shCtrl. Moreover, tumor development in xenografts was reduced in HT29 shα1 cells. Histopathological analysis showed extensive necrosis areas and low mitotic index in shα1 tumors compared to the shCtrl tumors.
CONCLUSION: Our results show that α1β1 is involved in tumor cell proliferation, survival and migration. This finding suggests that α1β1 is involved in colorectal cancer progression. (Supported by the CIHR)
Citation Format: Salah Boudjadi, Gérald Bernatchez, Blanche Sénicourt, Marco Beausejour, Pierre-Henri Vachon, Julie Carrier, Jean-Francois Beaulieu. α1β1 is pro-proliferative and promigratory integrin and its expression is upregulated by the MYC oncogenic factor in colorectal cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5090.