Abstract 1716: The role of CD44v9+ colorectal cancer stem cells in the resistance to cetuximab treatment

Abstract

Recent studies found that conventional therapy combined with cetuximab treatment (EGFR inhibitor) to treat metastatic colorectal cancer, had no improvement of patient survival rate in some population. One of possibilities might be cancer stem cells (CSCs) population resist to cetuximab treatment and modulate metastasis, however, the detail mechanism has not been addressed in colorectal cancer. Thus, our study is to decipher the mechanism of resistance to cetuximab in CD44v9+ specific colorectal cancer stem cells. First, to reveal clinical significance of CD44v9, the tumor samples of colorectal cancer patients were analyzed by immunohistochemistry to evaluate CD44v9 expression status in patients. To further investigate the biological mechanism, single cell analysis in CD44v9+ population of HT29 cells was performed with Fluidigm Biomark™ HD system. The results showed that 67% patients had highly expressed CD44v9 with lower survival rate. In vitro studies showed that when HT29 cells were in 5uM cetuximab treatment for 48 hours, CD44v9, Oct4, CD133, CD24, Lgr5, CSCs markers, were up-regulated in RNA level. Furthermore, CD44v9+/Oct4+ cancer cell population was increased but CD44v9+/pEGFR+ cancer cells were eliminated according to immunofluorescence results. The results of single cell analysis demonstrated that CD44v9+/Oct4+ cancer cells highly expressed proliferation markers consistently with cetuximab treatment. Trans-well migration results showed that CD44v9+/Oct4+ cancer cells migrated collectively via mediating E-cadherin dynamics. Furthermore, in clinical outcome, CD44v9 and E-cadherin co-expression were associated with recurrence and metastasis and decreased survival rate significantly. In conclusion, cetuximab failed to target CD44v9+/Oct4+ cancer cells, which characterized as cancer stem cells and might modulate collective cell migration. This finding suggested that new therapeutic strategy to against CSCs would be the potential clinical treatment in colon cancer.

Citation Format: Chia-Nung Hung, Ching-Yu Chang, Jou Hsiao, Wan-Chen Wei, Wei-Ting Chao. The role of CD44v9+ colorectal cancer stem cells in the resistance to cetuximab treatment. [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 1716.