CD4 and neoplasm: In an early effort using an in situ gene therapy, HSV-tk (ADV-HSV-tk) in combination with ganciclovir therapy, and EBRT in the RM1/C56BL/6 murine prostate tumor model, it was shown that the combination group had the most significant inhibition of tumor growth and survival compared to either therapy alone, with a significantly higher frequency of infiltrating CD4+ T cells [110].