cAMP Elevation Down-Regulates β3 Integrin and Focal Adhesion Kinase and Inhibits Leptin-Induced Migration of MDA-MB-231 Breast Cancer Cells

Abstract

Breast cancer is one of the most common malignancies and a major cause of cancer death among women worldwide. The high mortality rate associated with breast cancer is mainly due to a propensity of the tumor to metastasize, even if small or undetectable. Given the relevant role of leptin in breast cancer growth and metastasis, novel strategies to counteract biological effects of this obesity-linked cytokine are warranted. Recently, we demonstrated that in MDA-MB-231 breast cancer cells, intracellular cAMP elevation completely abrogates both ERK1/2 and STAT3 phosphorylation in response to leptin. Very surprisingly, this provided evidence that when cAMP levels are increased, leptin drives cells towards apoptosis associated with a marked decrease of Bcl2 protein levels and accompanied by down-regulation of protein kinase A (PKA). The aim of the current study was to investigate the role of cAMP in leptin-associated motility of breast cancer cells. Here we show that cAMP elevation completely prevents leptin-induced migration of MDA-MB-231 breast cancer cells. Interestingly, the inhibition by cAMP-elevating agents of leptin-mediated cell migration is accompanied by a strong decrease of β3 integrin subunit and focal adhesion kinase (FAK) protein levels. Analysis of the underlying cAMP-dependent molecular mechanisms revealed that PKA blockers partly counteract the inhibition of leptin-induced migration and completely prevent the antiproliferative action by cAMP elevation. Moreover, a cAMP analogue that specifically activates Epac and not PKA has an inhibitory effect on leptin-induced cell migration as well. The present study confirms initial evidence for the efficacy of cAMP elevation against oncogenic effects of leptin, identifies β3 integrin subunit and FAK as proteins strongly down-regulated by cAMP elevation, and suggests that both cAMP/PKA- and cAMP/Epac-dependent pathways are involved in inhibition of leptin-induced migration of MDA-MB-231 breast cancer cells. The potential clinical significance and therapeutic applications of our data are discussed.

Inhibition of breast cancer cell migration by activation of cAMP signaling

“…Under the conditions used in our study, we find no significant effect of cAMP analogs or cAMP PDE inhibitors on proliferation of the breast cancer cells, indicating that the reduction of cell migration observed is functionally selective and not due to a lowering of cell numbers. Similar to these findings, another study also showed that forskolin significantly inhibited leptin-induced migration of MDA-MB-231 cells at levels in which it had no effect on cell proliferation [52].…”

Dosage‐dependent regulation of cell proliferation and adhesion through dual β2‐adrenergic receptor/cAMP signals

“…cAMP also inhibits migration of highly invasive MDA‐MB‐231 cells (6, 7) and the expression of relevant proteins involved in breast cancer metastasis. These effects are mediated by both PKA‐ and Epac‐dependent pathways (30).…”

The Natural cAMP Elevating Compound Forskolin in Cancer Therapy: Is It Time?

“…Very surprisingly, we provided evidence that when cAMP levels are increased upon forskolin treatment, leptin drives cells toward apoptosis associated with a marked decrease of Bcl2 protein levels and accompanied by down‐regulation of protein kinase A (PKA). In addition, we also found that the inhibition by forskolin of leptin‐mediated cell migration is accompanied by a strong decrease of β3 integrin subunit and FAK protein levels (Naviglio et al, , 2010; Spina et al, , 2013). Overall, our above findings provide initial evidence of forskolin as a simple natural agent able to neutralize leptin‐induced oncogenic effects in breast cancer cells and extend the evidence for the potential efficacy of cAMP elevation in breast cancer therapy.…”