Enhanced antitumoral efficacy and immune response following conditionally replicative adenovirus containing constitutive HSF1 delivery to rodent tumors

In the present study, intra-dermal murine models of melanoma (B16) and colorectal carcinoma (CT26) were treated with E1B55kD deleted oncolytic adenovirus Adel55 or Adel55 incorporated with cHSF1, HSF1i, HSP70, or HSP90 by intra-tumoral injection. Tumors were surgically excised 72？h post injection and animals were analyzed for tumor resistance and survival rate.Approximately 95% of animals in the Adel55-cHSF1 treated group showed sustained resistance upon re-challenge with autologous tumor cells, but not in PBS, Adel55, or Adel55-HSF1i treated groups. Only 50–65% animals in the Adel55-HSP70 and Adel55-HSP90 treated group showed tumor resistance. Tumor resistance was associated with development of tumor type specific cellular immune responses. Adel55-cHSF1 treatment also showed higher efficacy in diminishing progression of the secondary tumor focus than Adel55-HSP70 or Adel55-HSP90 treatment.Besides by increasing its burst in tumor cells, cHSF1 could also augment the potential of E1B55kD deleted oncolytic adenovirus by increasing the tumor-specific immune response, which is beneficial to prevent tumor recurrence. cHSF1 is a better gene for neoadjuvant immunotherapy than other heat shock protein genes.