Tumor suppressive effects of WEE1 gene silencing could not enhance immunopotentiation effects of CD80 and 4-1BBL co-stimulation in human T cells.

Background: Activation of T cells against tumors by recruiting co-stimulatory molecules has been an attractive approach for cancer immunotherapy. Reports suggested that targeting different genes in tumors might also boost T cell-mediated tumor destruction.

Aims: We investigated whether in vitro WEE1 gene silencing in MDA-MB-468 and MCF7 breast cancer cell lines could enhance immunopotentiating effects of CD80 and 4-1BBL co-stimulation in human T cells.

Materials And Methods: WEE1 gene was specifically silenced in the cancer cells using shRNA technology. The co-stimulatory molecules were over-expressed on the surface of the cancer cells by recombinant non-replicative adenoviruses. The immune reaction of T cells in the co-culture with tumor cells was studied. IFN-g production was assessed by intracellular staining of T cells. To assess cytotoxic activity of CD8+ T cells, the CD107a mobilization-degranulation assay was performed. Expression of granzyme B, perforin and fasl were examined by real time PCR.

Results: T cell dual co-stimulation led to a significant increase in the frequency of IFN-g producing cells and higher percentages of degranulation in CD8+ T cells. It also resulted in higher expression levels of the cytotoxicity-related genes. WEE1 gene silencing in the target cells alone however, could not produce significant immune reactivation in the cultured T cells. Likewise, the immune responses of T cells neither improved nor suppressed when dually co-stimulated PBMCs were exposed to the cancer cells with silenced WEE1.

Conclusions: In spite of antitumor effects of WEE1 silencing, combination of this approach with immune co-stimulation could not boost the reactivity of cultured T cells against the tested breast cancer cells.