Effects of triggers of senescence and senolysis in murine pancreatic cancer cells.

BACKGROUND: The combination of senescence triggers with senolytic drugs is considered a promising new approach to cancer therapy. Here, we studied the efficacy of the genotoxic agent etoposide (Eto) and irradiation in inducing senescence of Panc02 pancreatic cancer cells, and the capability of the Bcl-2 inhibitor navitoclax (ABT-263; Nav) to trigger senolysis. METHODS: Panc02 cells were treated with Eto or irradiated with 5-20 Gy before exposure to Nav. Cell survival, proliferation, and senescence were assessed by trypan blue staining, quantification of DNA synthesis, and staining of senescence-associated ß-galactosidase (SA-ß-Gal)-positive cells, respectively. Levels of mRNA were determined by real-time polymerase chain reaction, and protein expression was analyzed by immunoblotting. Panc02 cells were also grown as pancreatic tumors in mice, which were subsequently treated with Eto and Nav. RESULTS: Eto and irradiation had an antiproliferative effect on Panc02 cells that was significantly or tendentially enhanced by Nav. In vivo, Eto and Nav together, but not Eto alone, significantly reduced the proportion of proliferating cells. The expression of the senescence marker γH2AX and tumor infiltration with T-cells were not affected by the treatment. In vitro, almost all Eto-exposed cells and a significant proportion of cells irradiated with 20 Gy were SA-ß-Gal-positive. Application of Nav reduced the percentage of SA-ß-Gal-positive cells after irradiation but not after pretreatment with Eto. In response to triggers of senescence, cultured Panc02 cells showed increased protein levels of γH2AX and the autophagy marker LC3B-II, and higher mRNA levels of Cdkn1a, Mdm2, and PAI-1, while the effects of Nav were variable. CONCLUSIONS: In vitro and in vivo, the combination of senescence triggers with Nav inhibited tumor cell growth more effectively than the triggers alone. Our data also provide some evidence for senolytic effects of Nav in vitro.

Uncoupling protein 2 deficiency of non-cancerous tissues inhibits the progression of pancreatic cancer in mice.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is a disease of the elderly mostly because its development from preneoplastic lesions depends on the accumulation of gene mutations and epigenetic alterations over time. How aging of non-cancerous tissues of the host affects tumor progression, however, remains largely unknown. METHODS: We took advantage of a model of accelerated aging, uncoupling protein 2-deficient (Ucp2 knockout, Ucp2 KO) mice, to investigate the growth of orthotopically transplanted Ucp2 wild-type (WT) PDAC cells (cell lines Panc02 and 6606PDA) in vivo and to study strain-dependent differences of the PDAC microenvironment. RESULTS: Measurements of tumor weights and quantification of proliferating cells indicated a significant growth advantage of Panc02 and 6606PDA cells in WT mice compared to Ucp2 KO mice. In tumors in the knockout strain, higher levels of interferon-γ mRNA despite similar numbers of tumor-infiltrating T cells were observed. 6606PDA cells triggered a stronger stromal reaction in Ucp2 KO mice than in WT animals. Accordingly, pancreatic stellate cells from Ucp2 KO mice proliferated at a higher rate than cells of the WT strain when they were incubated with conditioned media from PDAC cells. CONCLUSIONS: Ucp2 modulates PDAC microenvironment in a way that favors tumor progression and implicates an altered stromal response as one of the underlying mechanisms.