Slug inhibition upregulates radiation-induced PUMA activity leading to apoptosis in cholangiocarcinomas

Abstract

Resistance of cholangiocarcinoma to irradiation therapy is a major problem in cancer treatment. Slug, a snail family transcription factor, is a suppressor of PUMA (p53 upregulated modulator of apoptosis), which has been shown to be involved in the control of apoptosis. In this study, we investigated whether the modulation of Slug expression, using adeno-associated-virus-mediated transfer of siRNA targeting Slug gene (rAAV2-Slug siRNA), affects cholangiocarcinoma sensitivity to radiation. In the present study, we used rAAV2-Slug siRNA to downregulate the expression of Slug in QBC939 cholangiocarcinoma cell lines in vitro before γ-irradiation. In vivo studies were done with orthotopic cholangiocarcinoma, and radiosensitivity was evaluated both in vitro and in vivo. rAAV2-Slug siRNA transfection resulted in downregulation of the levels of Slug in QBC939 cells. In addition, rAAV2-Slug siRNA, in combination with radiation, increased levels of the PUMA, which contributes to the radiosensitivity of cholangiocarcinomas. Finally, treatment with rAAV2-Slug siRNA plus γ-irradiation completely regressed tumor growth in orthotopic cholangiocarcinomas model. In summary, integrating gene therapy with radiotherapy could have a synergistic effect, thereby improving the survival of patients with cholangiocarcinomas.

Slug inhibition increases radiosensitivity of nasopharyngeal carcinoma cell line C666‑1

“…It has been demonstrated that Slug may be involved in the radioresistance of different types of cancer, including colorectal cancer, cholangiocarcinoma and ovarian cancer (14,15,30,31). However, there have been few studies on the function of Slug in association with radioresistance in NPC.…”

“…However, the mechanisms underlying the radioresistance of cancer remain unclear. PUMA is a pivotal protein in apoptosis and it has been suggested that PUMA may increase sensitivity to radiation-induced apoptosis in different types of cancer (15,33,34). Slug is a suppressor of PUMA transcription, which inhibits the expression of PUMA resulting in cell survival (35).…”

“…Slug inhibition also increases the radiosensitivity of HSC3 and HSC6 cells by upregulating PUMA in oral squamous carcinoma (13). In addition, Slug expression inhibits calcitriol-mediated sensitivity to radiation in colorectal cancer (14) and upregulates radiation-induced PUMA in cholangiocarcinoma (15). However, whether Slug inhibition may enhance radiosensitivity of NPC remains unknown.…”

Deletion of Snai2 and Snai3 Results in Impaired Physical Development Compounded by Lymphocyte Deficiency

“…The loss of only Snai2 also negatively impacts the development of marrow B cells and peripheral blood levels of the cells however, only the DKO animal shows significant loss of B cells in the splenic populations again suggesting that the combined loss of both Snai2 and Snai3 in these cell lineages has a greater developmental impact than the loss of only a single family member. The loss of B cells in the DKO may be related to the anti-apoptotic responses associated with the Snail proteins [13,18,44,45]. V(D)J recombination of B (and T) cells primes lymphocytes to undergo apoptosis in the event that the recombinations are non-productive [46–48].…”

Adeno-associated virus (AAV) vectors in cancer gene therapy

“…Intratumoral AAV2 encoding siRNA against Snail, a transcription factor involved in anti-apoptotic and chemoresistance upregulated in pancreatic cancer, to a PANC-1 xenograft model of pancreatic cancer suppressed tumor growth by 76% [162]. Subsequently, the same group delivered AAV encoding siRNA targeting the Slug gene, a suppressor of apoptosis, to an orthotopic QBC939 model of cholangiocarcinoma, a type of liver cancer [163]. Intratumoral injection of AAV2-SlugsiRNA led to 51% reduced tumor growth alone and complete tumor regression when combined with radiation treatment.…”