mCherry adenovirus

Toll-like receptor 5 (TLR5) is considered an attractive target for anticancer immunotherapy. To expand the application of TLR5-targeted anticancer immunotherapy to tumors that do not naturally express TLR5, researchers constructed an adenovirus-based intratumoral delivery vector, named Mobilan, that drives the expression of the autoactivating TLR5 signaling cassette. In cells infected with Mobilan, co-expression of the TLR5 receptor and agonist established an autocrine/paracrine TLR5 signaling loop, which triggered constitutive activation of NF-κB both in vitro and in vivo. Injection of Mobilan into primary tumors of transgenic mouse adenocarcinoma of the prostate (TRAMP) mice, which are prone to prostate cancer, strongly induced multiple genes involved in inflammatory responses and mobilization of innate immune cells, including neutrophils and NK cells, into tumors, and inhibited tumor progression. In immunocompetent hosts, injection of Mobilan into subcutaneously grown syngeneic prostate tumors improved the survival of animals after tumor surgical resection by inhibiting tumor metastasis. Furthermore, vaccination of mice with prostate tumor cells transduced with irradiated Mobilan protected them from subsequent tumor development. These results provide proof-of-concept for Mobilan as an anti-tumor vaccine tool that directs TLR5-mediated immune responses to target cancer cells without the need to recognize tumor antigens.

The researchers analyzed CAR expression using tissue microarrays containing 134 prostate cancer-derived and 134 normal prostate-derived samples. In total, 90% of prostate samples, whether normal or cancerous, were found to be strongly CAR-positive (Figure 1a). High CAR expression was also detected in TRAMP-C2 mouse prostate cancer cells (Figure 1b). These observations suggest that M-VM3 treatment may be effective in the vast majority of prostate cancer patients as well as prostate tumors in TRAMP mice. To confirm the latter expectation, mCherry adenovirus (Ad-mCherry) was injected directly into TRAMP mouse prostate tumors (Figure 1c) and human prostate tumor surgical specimens (Figure 1d). In both cases, mCherry expression was observed in CAR-positive epithelial cells 24 hours after infection. This finding supports the possibility that M-VM3 can effectively infect prostate tumors in vivo.

Figure 1. Mouse and human prostate tumors express CAR and are efficiently infected by Ad-mCherry. (Mett V, et al., 2018)