Phosphodiesterase 5 Inhibitors Enhance Chemotherapy Killing in Gastrointestinal/Genitourinary Cancer Cells

Abstract

The present studies determined whether clinically relevant phosphodiesterase 5 (PDE5) inhibitors interacted with clinically relevant chemotherapies to kill gastrointestinal/genitourinary cancer cells. In bladder cancer cells, regardless of H-RAS mutational status, at clinically achievable doses, PDE5 inhibitors interacted in a greater than additive fashion with doxorubicin/mitomycin C/gemcitabine/ cisplatin/paclitaxel to cause cell death. In pancreatic tumor cells expressing mutant active K-RAS, PDE5 inhibitors interacted in a greater than additive fashion with doxorubicin/gemcitabine/ paclitaxel to cause cell death. The most potent PDE5 inhibitor was sildenafil. Knock down of PDE5 expression recapitulated the combination effects of PDE5 inhibitor drugs with chemotherapy drugs. Expression of cellular FLICE-like inhibitory protein-short did not significantly inhibit chemotherapy lethality but did significantly reduce enhanced killing in combination with sildenafil. Overexpression of B-cell lymphoma-extra large suppressed individual and combination drug toxicities. Knock down of CD95 or Fasassociated death domain protein suppressed drug combination toxicity. Combination toxicity was also abolished by necrostatin or receptor interacting protein 1 knock down. Treatment with PDE5 inhibitors and chemotherapy drugs promoted autophagy, which was maximal at ∼24 hour posttreatment, and 3-methyl adenine or knock down of Beclin1 suppressed drug combination lethality by ∼50%. PDE5 inhibitors enhanced and prolonged the induction of DNA damage as judged by Comet assays and ghistone 2AX (gH2AX) and checkpoint kinase 2 (CHK2) phosphorylation. Knock down of ataxia telangiectasia mutated suppressed gH2AX and CHK2 phosphorylation and enhanced drug combination lethality. Collectively our data demonstrate that the combination of PDE5 inhibitors with standard of care chemotherapy agents for gastrointestinal/genitourinary cancers represents a novel modality.

Regulation of OSU-03012 Toxicity by ER Stress Proteins and ER Stress–Inducing Drugs

“…New therapeutic approaches that could translate to the clinic for this malignancy are urgently required. In two recently published studies we demonstrated that phosphodiesterase 5 (PDE5) inhibitors enhanced the toxicity of standard of care chemotherapies in bladder and pediatric CNS tumors (22, 23). In the present studies, we determined whether PDE5 inhibitors interacted with OSU-03012 to kill glioma cells and we defined the molecular mechanisms by which ER stress effector pathways regulated OSU-03012 toxicity.…”

BRD4 Regulates EZH2 Transcription through Upregulation of C-MYC and Represents a Novel Therapeutic Target in Bladder Cancer

“…These data further support our findings that BRD4 is a critical regulator in bladder cancer progression (35). It has been demonstrated that a number of therapeutic strategies enhanced chemotherapy in human bladder cancer cells (36,37). Whether treatment with JQ1 combined with other chemotherapeutics simultaneously exert the synergistic effect in bladder cancer therapy needs to be answered in the future.…”

Regulation of dimethyl-fumarate toxicity by proteasome inhibitors

“…Antibody reagents, other kinase inhibitors, caspase inhibitors cell culture reagents, and non-commercial recombinant adenoviruses have been previously described. [39][40][41][42] Previously characterized semi-established GBM5 / GBM6 / GBM12 / GBM14 glioblastoma cells were supplied by Dr. C.D. James (University of California, San Francisco) and Dr. J.N.…”

“…Samples were isolated at the indicated times and SDS PAGE and immunoblotting was performed as described in refs. [39][40][41][42] Blots were observed by using an Odyssey IR imaging system (LI-COR Biosciences, Lincoln, NE).…”

“…[39][40][41][42] Cells were infected with these adenoviruses at an approximate m.o.i. as indicated in the figure legend (usually an moi of 50).…”