Expression and Function of Phosphodiesterase Type 5 in Human Breast Cancer Cell Lines and Tissues: Implications for Targeted Therapy

Abstract

Purpose: By catalyzing cGMP hydrolysis, phosphodiesterase (PDE) 5 is a critical regulator of its concentration and effects in different (patho)physiologic processes, including cancers. As PDE5 is a known druggable target, we investigated the clinical significance of its expression in breast cancer and the underlying mechanisms by which it may contribute to tumor progression.Experimental Design: PDE5 expression was evaluated in seven breast cancer cell lines by RT-PCR and immunoblotting. To examine the impact of PDE5 on cancer phenotype, MCF-7 cells expressing lower levels of the enzyme were engineered to stably overexpress PDE5. Proliferation was evaluated by MTT assays, motility and invasion by wound-healing/transmigration/invasion assays, transcriptome-profiling by RNA-sequencing, and Rho GTPase signaling activation by GST-pulldown assays and immunoblotting. Clinical relevance was investigated by IHC on tissues and retrospective studies from METABRIC cohort.Results: PDE5 is differentially expressed in each molecular subtype of both breast cancer cell lines and tissues, with higher levels representing a startling feature of HER2-positive and triplenegative breast cancers. A positive correlation was established between elevated PDE5 levels and cancers of high histologic grade. Higher PDE5 expression correlated with shorter patient survival in retrospective analyses. On molecular level, stable PDE5 overexpression in Luminal-A-like MCF-7 cells resulted in enhanced motility and invasion through Rho GTPase signaling activation. Treatment of PDE5-stable clones with selective ROCK or PDE5 inhibitors completely restored the less motile and weak invasive behavior of control vector cells.Conclusions: PDE5 expression enhances breast cancer cell invasive potential, highlighting this enzyme as a novel prognostic candidate and an attractive target for future therapy in breast cancers.

Effect of sildenafil on human aromatase activity: From in vitro structural analysis to catalysis and inhibition in cells

“…In conclusion, due to growing evidence about the benefits of PDE5 inhibitors as anticancer drugs [51] and about PDE5 as a new potential target for breast cancer therapy [10], the results of this work can be interesting since they can offer the basis to develop a new generation of inhibitors that combine old (aromatase) and new (PDE5) targets for breast cancer therapy. …”

“…Moreover, it was demonstrated that treatment with sildenafil significantly decreases migration and invasion of MCF-7 breast cancer cell line, where PDE5 and aromatase are contemporarily overexpressed [10].…”

“…Very recently, an overexpression of phosphodiesterase-5 (PDE5) was observed in several cancer tissues and cell lines, including those of the breast and thyroid glands [10,11]. Moreover, sildenafil that is a cyclic guanosine monophosphate (cGMP)-specific PDE5 inhibitor used for the treatment of erectile dysfunction and pulmonary hypertension [12] has attracted the attention of scientists since different studies have reported that this molecule has a synergic effect with some anti-cancer drugs such as doxorubicin in breast cancer cells [13].…”

Sildenafil potentiates the antitumor activity of cisplatin by induction of apoptosis and inhibition of proliferation and angiogenesis

“…A recent study by Fallahian et al60 concluded that increased activation of protein kinase G by cGMP induces apoptosis and growth arrest in breast cancer MCF-7 and MDA-MB-468 cells. Furthermore, the nonspecific PDE-5 inhibitor exisulind and its analogs selectively induce the apoptosis of various human prostate, colon, and breast cancer cells, and the effect that was attributed to inhibition of PDE-5 expression 7,61…”

“…PDE-5 has been shown to be overexpressed in multiple human carcinomas including breast cancers, colon adenocarcinoma, bladder squamous carcinoma, and lung cancers that have significantly lower cGMP levels than normal cells 1,3–7. This implies that selective inhibition of PDE-5 may have antineoplastic effects and may increase the specificity of a given chemotherapeutic agent.…”