Targeting the Δ133p53 isoform can restore chemosensitivity in 5-fluorouracil-resistant cholangiocarcinoma cells

Lack of the normal p53 transactivation domain, Delta 133p53 isoform exhibits anti-p53 function. Many studies report the correlation between Delta 133p53 expression and poor survival in various cancers, including cholangiocarcinoma (CCA), which is a cancer of the bile ducts. CCA almost always results in short survival times. The relevance of Delta 133p53 to drug resistance in CCA is not yet well understood. This study aimed to demonstrate the association between Delta 133p53 and 5-fluorouracil (5-FU) resistance in CCA. Delta 133p53 protein was highly expressed in CCA patients with poor outcome compared to favorable outcome but was not statistically significant. However, a significant correlation was found between normalized Delta 133p53 levels and 5-FU resistance which was defined by an ex vivo histoculture drug response assay (P=0.019). Two stable 5-FU-resistant CCA cell lines, KKU-M139R (IC50 38.8 mu M) and KKU-M214R (IC50 39.5 mu M), were used as a model to evaluate the role of Delta 133p53. Increased Delta 133p53 was correlated with 5-FU in a dose-dependent manner. The transient knockdown of Delta 133p53 expression can restore drug sensitivity in both resistant CCA cells with 11- to 45-fold reduction of IC50 compared to control. Upon Delta 133p53 silencing, apoptotic signaling was enhanced by the upregulation of Bax and downregulation of Bcl-2. Additionally, p21 and p27 were upregulated, resulting in cell cycle arrest at G2. Inhibition of colony formation and prolong doubling time were also observed. Our findings demonstrated that chemosensitivity can be modulated via targeting of Delta 133p53 suggesting the potential use of Delta 133p53 as a candidate for targeting therapy in CCA.