Exogenous p53 and ASPP2 expression enhances rAdV-TK/ GCV-induced death in hepatocellular carcinoma cells lacking functional p53.

Xiuhong Liu,Jiming Yin,Shuang Wang,Xianghua Guo,Yunjin Zang,Dexi Chen,Feili Wei,Ning Li

doi:10.18632/oncotarget.7749

Abstract

Suicide gene therapy using herpes simplex virus-1 thymidine kinase (HSV-TK) in combination with ganciclovir (GCV) has emerged as a potential new method for treating cancer. We hypothesize that the efficacy of HSV-TK/GCV therapy is at least partially dependent on p53 status in hepatocellular carcinoma (HCC) patients. Using recombinant adenoviral vectors (rAdV), TK, p53, and ASPP2 were overexpressed individually and in combination in Hep3B (p53 null) and HepG2 (p53 wild-type) cell lines and in primary HCC tumor cells. p53 overexpression induced death in Hep3B cells, but not HepG2 cells. ASPP2 overexpression increased rAdV-TK/GCV-induced HepG2 cell death by interacting with endogenous p53. Similarly, ASPP2 reduced survival in rAdV-TK/GCV-treated primary HCC cells expressing p53 wild-type but not a p53 R249S mutant. Mutated p53 was unable to bind to ASPP2, suggesting that the increase in rAdV-TK/GCV-induced cell death resulting from ASPP2 overexpression was dependent on its interaction with p53. Additionally, γ-H2AX foci, ATM phosphorylation, Bax, and p21 expression increased in rAdV-TK/GCV-treated HepG2 cells as compared to Hep3B cells. This suggests that the combined use of HSV-TK, GCV, rAdV-p53 and rAdV-ASPP2 may improve therapeutic efficacy in HCC patients lacking functional p53.

Highlights

Surgical resection remains the most effective therapy for hepatocellular carcinoma (HCC); less than 15% of patients benefit from this treatment due to the presence of multiple tumor nodules
This treatment has demonstrated little efficacy in HCC cases in clinical practice, mostly due to low targeting www.impactjournals.com/oncotarget and absence of the ‘bystander effect’. One reason for this low efficacy could be the high incidence of p53 mutation in HCC, which is associated with poor HCC prognosis [24]
We evaluated whether gene therapy with recombinant adenoviral vectors (rAdV)-Apoptosis-stimulating of p53 protein 2 (ASPP2), rAdV-p53, and rAdV-thymidine kinase (TK)/GCV is more effective than gene therapy with rAdV-TK/GCV alone for the induction of tumor death with and without functional p53

Summary

Introduction

Surgical resection remains the most effective therapy for hepatocellular carcinoma (HCC); less than 15% of patients benefit from this treatment due to the presence of multiple tumor nodules. Other methods used to treat HCC, including radiofrequency ablation (RFA), microwave therapy, percutaneous ethanol injection (PEIT), radiotherapy, and biological radiotherapy, have limited success. Gene therapy, including suicide gene therapy using herpes simplex virus-1 thymidine kinase (HSV-TK) in combination with the guanosine analog ganciclovir (GCV), has emerged as a potential new method for treating cancers. The thymidine kinase (TK) gene product is involved in drug sensitivity, and plays a key role in DNA synthesis. Combined HSV-TK and GCV treatment has been studied in a variety of cancer types, including tumors of the brain, head and neck, skin, lung, liver, pancreas, colon, prostate, ovary, and breast. The results of several phase I and II clinical trials showed only slightly prolonged survival times [5, 6], possibly as a result of p53 mutation

Methods

Results

Conclusion