Combined Treatment with Exendin-4 and Metformin Attenuates Prostate Cancer Growth

Abstract

IntroductionRecently, the pleiotropic benefits of incretin-based therapy have been reported. We have previously reported that Exendin–4, a glucagon-like peptide–1 (GLP–1) receptor agonist, attenuates prostate cancer growth. Metformin is known for its anti-cancer effect. Here, we examined the anti-cancer effect of Exendin–4 and metformin using a prostate cancer model.MethodsProstate cancer cells were treated with Exendin–4 and/or metformin. Cell proliferation was quantified by growth curves and 5-bromo–2′-deoxyuridine (BrdU) assay. TUNEL assay and AMP-activated protein kinase (AMPK) phosphorylation were examined in LNCaP cells. For in vivo experiments, LNCaP cells were transplanted subcutaneously into the flank region of athymic mice, which were then treated with Exendin–4 and/or metformin. TUNEL assay and immunohistochemistry were performed on tumors.ResultsExendin–4 and metformin additively decreased the growth curve, but not the migration, of prostate cancer cells. The BrdU assay revealed that both Exendin–4 and metformin significantly decreased prostate cancer cell proliferation. Furthermore, metformin, but not Exendin–4, activated AMPK and induced apoptosis in LNCaP cells. The anti-proliferative effect of metformin was abolished by inhibition or knock down of AMPK. In vivo, Exendin–4 and metformin significantly decreased tumor size, and further significant tumor size reduction was observed after combined treatment. Immunohistochemistry on tumors revealed that the P504S and Ki67 expression decreased by Exendin–4 and/or metformin, and that metformin increased phospho-AMPK expression and the apoptotic cell number.ConclusionThese data suggest that Exendin–4 and metformin attenuated prostate cancer growth by inhibiting proliferation, and that metformin inhibited proliferation by inducing apoptosis. Combined treatment with Exendin–4 and metformin attenuated prostate cancer growth more than separate treatments.

Impact of metabolic disorders on prostate cancer growth: Androgen and insulin resistance perspectives

“…Particularly, it was observed that GLP‐1R expression in human PC tissue and PC cell lines and Ex‐4 attenuated PC growth both in vitro and in vivo via the inhibition of extracellular signal‐regulated kinase–mitogen‐activated protein kinase activation, leading to the inhibition of cell proliferation (Figure ) . The authors’ further study revealed that both Ex‐4 and metformin significantly decreased PC cell proliferation, as shown by the decrease of Ki67 expression . In this study, metformin, but not Ex‐4, induced apoptosis in the LNCaP cells through the activation of 5′ adenosine monophosphate (AMP)‐activated protein kinase (Figure ).…”

“…61 The authors' further study revealed that both Ex-4 and metformin significantly decreased PC cell proliferation, as shown by the decrease of Ki67 expression. 62 In this study, metformin, but not Ex-4, induced apoptosis in the LNCaP cells through the activation of 5′ adenosine monophosphate (AMP)-activated protein kinase ( Figure 2).…”

“…In this study, metformin, but not Ex‐4, induced apoptosis in the LNCaP cells through the activation of 5′ adenosine monophosphate (AMP)‐activated protein kinase (Figure ). The combined treatment of Ex‐4 and metformin attenuated PC growth more than by the separate treatments …”

Activation of AMPKα mediates additive effects of solamargine and metformin on suppressing MUC1 expression in castration-resistant prostate cancer cells

“…Metformin, a potential anticancer agent, has been shown to inhibit growth and induce apoptosis though AMPK-dependent and -independent signaling pathways in CRPC cells5556. One study found that combination of metformin with other therapeutic agents, such as anti-AR agent bicalutamide, enhanced the growth inhibition of CRPC via AR-mediated signaling57.…”

GLP-1 receptor agonist as treatment for cancer as well as diabetes: beyond blood glucose control

“…Based on this, we next examined the anti-prostate cancer effect of combined treatment with exendin-4 and metformin [72]. Exendin-4 and metformin additively decreased the growth rate, but not migration, of prostate cancer cells.…”