Intravesical instillation-based mTOR-STAT3 dual targeting for bladder cancer treatment

Abstract

Abstract Background Recent intravesical administration of adenoviral vectors, either as a single injection or in combination with immune checkpoint inhibitors, exemplified by cretostimogene grenadenorepvec and nadofaragene firadenovec, has demonstrated remarkable efficacy in clinical trials for non-muscle invasive bladder cancer. Despite their ability to induce an enhanced immune reaction within the lesion, the intracellular survival signaling of cancer cells has not been thoroughly addressed. Methods An analysis of the prognostic data revealed a high probability of therapeutic efficacy with simultaneous inhibition of mTOR and STAT3. Considering the challenges of limited pharmaco-accessibility to the bladder due to its pathophysiological structure and the partially undruggable nature of target molecules, we designed a dual siRNA system targeting both mRNAs. Subsequently, this dual siRNA system was encoded into the adenovirus 5/3 (Ad 5/3) to enhance in vivo delivery efficiency. Results Gene-targeting efficacy was assessed using cells isolated from xenografted tumors using a single-cell analysis system. Our strategy demonstrated a balanced downregulation of mTOR and STAT3 at the single-cell resolution, both in vitro and in vivo. This approach reduced tumor growth in bladder cancer xenograft and orthotopic animal experiments. In addition, increased infiltration of CD8+ T cells was observed in a humanized mouse model. We provided helpful and safe tissue distribution data for intravesical therapy of siRNAs coding adenoviruses. Conclusions The bi-specific siRNA strategy, encapsulated in an adenovirus, could be a promising tool to augment cancer treatment efficacy and overcome conventional therapy limitations associated with “undruggability.” Hence, we propose that dual targeting of mTOR and STAT3 is an advantageous strategy for intravesical therapy using adenoviruses. Graphical Abstract The current investigation introduces an innovative conceptualization of bispecific short hairpin RNA (bs_shRNA) tailored for the equilibrated modulation of dual genes within a singular cellular context. This novel bs_shRNA was loaded into the genome of an oncolytic adenovirus to augment the therapeutic efficacy of oncolytic viral interventions via the targeted inhibition of mTOR and STAT3 pathways. In addition, the administration of BSV significantly reduced the volume of bladder cancer tumors, concomitantly facilitating an enhanced recruitment of CD8+T lymphocytes in vivo.

Keywords

• Bladder cancer
• mTOR
• STAT3
• siRNA
• Cancer therapy