Cytopathic effects and local immune responses in repeated neoadjuvant HSV-tk+ ganciclovir gene therapy for prostate cancer

Objective:Cytopathic effects and local immune response were analyzed histologically in prostatic cancer(PCa)with in situ herpes simplex virus-thymidine kinase(HSV-tk)/ganciclovir(GCV)gene therapy(GT).Methods:Four high-risk PCa patients who received HSV-tk/GCV GT were investigated.After two cycles of intraprostatic injection of HSV-tk and administration of GCV,radical prostatectomy was performed.Formalin-fixed,paraffin-embedded sections were evaluated using immunohistochemistry.PCa with hormone therapy(HT,n=3)or without neoadjuvant therapy(NT,n=4)that were equivalent in terms of risk were also examined as reference.Immunoreactively-positive cells were counted in at least three areas in cancer tissue.Labeling indices(LI)were calculated as percentage values.Results:ssDNA LI in GT increased,indicating apoptosis,as well as tumor-infiltrating lymphocytes and CD68-positive macrophages,compared with their biopsies.GT cases showed significantly higher numbers of single-stranded DNA(ssDNA)LI,CD4/CD8-positive T cells and CD68-positive macrophages including M1/M2 macrophages than HT or NT cases.However,there was no significant difference in CD20-positive B cells among the types of case.There were strong correlations between CD8+T cells and CD68+macrophages(ρ=0.656,p<0.0001)as well as CD4+T cells and CD20+B cells(ρ=0.644,p<0.0001)in PCa with GT.Conclusions:Enhanced cytopathic effect and local immune response might be indicated in PCa patients with HSV-tk/GCV gene therapy.