Department of Biochemistry, Biophysics and General Pathology, University of Campania "Luigi Vanvitelli", Medical School, Via L. De Crecchio 7, 80138 Naples, Italy.
Biochem Pharmacol. 2018 Jun;152:104-113. doi: 10.1016/j.bcp.2018.03.023. Epub 2018 Mar 21.
Triple negative breast cancer (TNBC) is an invasive, metastatic, highly aggressive tumor. Cytotoxic chemotherapy represents the current treatment for TNBC. However, relapse and chemo-resistance are very frequent. Therefore, new therapeutic approaches that are able to increase the sensitivity to cytotoxic drugs are needed. Forskolin, a natural cAMP elevating agent, has been used for several centuries in medicine and its safeness has also been demonstrated in modern studies. Recently, forskolin is emerging as a possible novel molecule for cancer therapy. Here, we investigate the effects of forskolin on the sensitivity of MDA-MB-231 and MDA-MB-468 TNBC cells to doxorubicin through MTT assay, flow cytometry-based assays (cell-cycle progression and cell death), cell number counting and immunoblotting experiments. We demonstrate that forskolin strongly enhances doxorubicin-induced antiproliferative effects by cell death induction. Similar effects are observed with IBMX and isoproterenol cAMP elevating agents and 8-Br-cAMP analog, but not by using 8-pCPT-2'-O-Me-cAMP Epac activator. It is important to note that the forskolin-induced potentiation of sensitivity to doxorubicin is accompanied by a strong inhibition of ERK1/2 phosphorylation, is mimicked by ERK inhibitor PD98059 and is prevented by pre-treatment with Protein Kinase A (PKA) and adenylate cyclase inhibitors. Altogether, our data indicate that forskolin sensitizes TNBC cells to doxorubicin via a mechanism depending on the cAMP/PKA-mediated ERK inhibition. Our findings sustain the evidence of anticancer activity mediated by forskolin and encourage the design of future in-vivo/clinical studies in order to explore forskolin as a doxorubicin sensitizer for possible use in TNBC patients.
三阴性乳腺癌（TNBC）是一种侵袭性、转移性、高度侵袭性的肿瘤。细胞毒性化疗是目前治疗 TNBC 的方法。然而，复发和化疗耐药性非常频繁。因此，需要新的治疗方法来提高细胞毒性药物的敏感性。毛喉素是一种天然的 cAMP 升高剂，已在医学中使用了几个世纪，现代研究也证明了其安全性。最近，毛喉素作为一种新的癌症治疗方法正在出现。在这里，我们通过 MTT 测定、基于流式细胞术的测定（细胞周期进展和细胞死亡）、细胞计数和免疫印迹实验研究了毛喉素对 MDA-MB-231 和 MDA-MB-468 TNBC 细胞对阿霉素敏感性的影响。我们证明毛喉素通过诱导细胞死亡强烈增强阿霉素诱导的抗增殖作用。用 IBMX 和异丙肾上腺素 cAMP 升高剂和 8-Br-cAMP 类似物观察到类似的效果，但用 8-pCPT-2'-O-Me-cAMP Epac 激活剂则观察不到。值得注意的是，毛喉素诱导的对阿霉素敏感性的增强伴随着 ERK1/2 磷酸化的强烈抑制，ERK 抑制剂 PD98059 模拟该作用，PKA 和腺苷酸环化酶抑制剂预处理可防止该作用。总之，我们的数据表明，毛喉素通过依赖于 cAMP/PKA 介导的 ERK 抑制的机制使 TNBC 细胞对阿霉素敏感。我们的发现支持毛喉素介导的抗癌活性的证据，并鼓励设计未来的体内/临床研究，以探索毛喉素作为阿霉素增敏剂，用于可能的 TNBC 患者。
