Comparison of oncolytic adenoviruses for selective eradication of oral cancer and pre-cancerous lesions.

Oncolytic adenoviruses are being investigated as potential anti-cancer agents. Selective lytic replication in cancer cells is essential for an effective and safe treatment. In this study, we compared 11 oncolytic adenoviruses in relevant cell cultures to assess their use for treating oral cancer and pre-cancerous lesions. We determined the cytotoxicity of oncolytic adenovirus infection and calculated selectivity indices for cytotoxicity to cancer cells compared with normal oral keratinocytes and fibroblasts. Keratinocytes were very sensitive to wild-type adenovirus serotype 5 (Ad5); 1- to 3-log more than head and neck squamous cell carcinoma (HNSCC) cells. The potencies of oncolytic adenoviruses to kill HNSCC cells within 7 days after infection ranged from approximately 10 times less potent to approximately 10 times more potent than Ad5. The selectivity indices determined on fibroblasts and keratinocytes differed markedly. Two oncolytic adenoviruses were more selective than Ad5 for HNSCC cells compared with fibroblasts; and five viruses showed selective replication on HNSCC cells compared with keratinocytes. Overall, CRAd-S.RGD with E1A driven by the survivin promoter and an infectivity-enhancing capsid modification showed the most favourable cytotoxicity pattern; being very potent in killing HNSCC cells, only slightly less effective than Ad5 in killing pre-neoplastic keratinocytes and the least toxic to normal keratinocytes.

Conditionally replicative adenovirus expressing a targeting adapter molecule exhibits enhanced oncolytic potency on CAR-deficient tumors.

Conditionally replicative adenoviruses (CRAds) are potentially useful agents for anticancer virotherapy approaches. However, lack of coxsackievirus and adenovirus receptor (CAR) expression on many primary tumor cells limits the oncolytic potency of CRAds. This makes the concept of targeting, that is, redirecting infection via CAR-independent entry pathways, relevant for CRAd development. Bispecific adapter molecules constitute highly versatile means for adenovirus targeting. Here, we constructed a CRAd with the Delta24 E1A mutation that produces a bispecific single-chain antibody directed towards the adenovirus fiber knob and the epidermal growth factor receptor (EGFR). This EGFR-targeted CRAd exhibited increased infection efficiency and oncolytic replication on CAR-deficient cancer cells and augmented lateral spread in CAR-deficient 3-D tumor spheroids in vitro. When compared to its parent control with native tropism, the new CRAd exhibited similar cytotoxicity on CAR-positive cancer cells, but up to 1000-fold enhanced oncolytic potency on CAR-deficient, EGFR-positive cancer cells. In addition, EGFR-targeted CRAd killed primary human CAR-deficient brain tumor specimens that were refractory to the parent control virus. We conclude, therefore, that CRAds expressing bispecific targeting adapter molecules are promising agents for cancer treatment. Their use is likely to result in enhanced oncolytic replication in cancerous tissues and thus in more effective tumor regression.

Interleukin-2-induced, melanoma-specific T cells recognize CAMEL, an unexpected translation product of LAGE-1.

Melanoma-specific cytotoxic T lymphocytes (CTLs) were induced by in vitro stimulation of peripheral blood mononuclear cells of a melanoma patient with autologous IL-2-producing melanoma 518/IL2.14 cells. CTL clone 1/29 recognized, in addition to autologous melanoma cell lines, a panel of HLA-A*0201-expressing allogeneic melanoma cell lines but was not reactive with normal melanocytes. Here, we report the full molecular characterization of the target structure for CTL 1/29, which was identified by cDNA expression cloning. The recognized antigen was named CAMEL (CTL-recognized antigen on melanoma). The CAMEL cDNA turned out to be derived from the LAGE-1 gene, a recently described tumor antigen that is strongly homologous to NY-ESO-1. CAMEL, however, is not encoded by the putative open reading frame (ORF) of LAGE-1 but by an alternative frame starting from the second ATG of the mRNA. The first 11 amino acids of the CAMEL protein, MLMAQEALAFL, constitute the epitope of CTL 1/29. This epitope is also encoded by a similar alternative ORF in NY-ESO-1. In summary, CTL induction with IL-2-transfected melanoma cells has revealed a new tumor antigen that may serve as a target for immunotherapy.