Synergistic promoting effects of pentoxifylline and simvastatin on the apoptosis of triple-negative MDA-MB-231 breast cancer cells

Abstract

Pentoxifylline (PTX), a xanthine family molecule and simvastatin (SIM), an anti-hypercholesterolemic agent, have recently been considered as sensitizers to chemotherapy and radiotherapy. The present in vitro study evaluated their antitumor synergistic effects on MDA‑MB‑231 breast cancer cells characterized by the triple‑negative phenotype (TNP). The anti-proliferative effects of these two agents were evaluated by MTT and clonogenic assays. Cell cycle progression was examined using propidium iodide staining. Apoptosis was investigated by Annexin V labeling, and by examining caspase 3 activity and DNA fragmentation. Autophagic vesicles and reactive oxygen species (ROS) levels were monitored by flow cytometry. Western blot analysis was performed to evaluate molecular targets. Our results revealed that when used alone, PTX and SIM exerted antitumor effects. Nevertheless, used in combination, the inhibition of cell proliferation was synergistically superior (80% vs 42%) than that observed following treatment with each agent alone after 48 h. PTX alone (0.5 mM) induced both apoptosis (25%) and autophagy (25%); however, when used in combination with SIM (0.5 µM), the balance between these processes was disrupted and the cells underwent apoptosis (>65%) as opposed to autophagy (<13%). This imbalance was associated with an increase in ERK1/2 and AKT activation, but not with an increase in mTOR phosphorylation, and with the suppression of the NF-κB pathway. In addition, in the cells treated with both agents, almost 78% of the cells were arrested at the G0/G1 phase and lost their colony-forming ability (38±5%) compared to the cells treated with PTX alone (115±5%). On the whole, these results suggest that the induction of autophagy may be a protective mechanism preventing MDA‑MB‑231 cancer cell death. The combined use of PTX and SIM may drive dormant autophagic cancer cells to undergo apoptosis and thus this may be a novel treatment strategy for breast cancer characterized by the TNP.

Attempts to use statins in cancer therapy: An update

“…For instance, in vitro studies demonstrated a synergistic effect of pentoxifylline, a drug used to treat muscle pain in peripheral artery disease, and simvastatin in breast cancer cells of triple-negative phenotype. 42 Both in vitro and in vivo results confirmed that the combination of atorvastatin and aspirin exerts a stronger inhibitory effect on growth and stimulates apoptosis in prostate cancer cells than either drug alone. 43 Another in vitro study showed that simvastatin, together with the anti-angiogenic agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA), is able to suppress the aggressive phenotype of melanoma cells co-cultured with tumour-associated macrophages under hypoxia-mimicking conditions.…”

Pentoxifylline Sensitizes Cisplatin-Resistant Human Cervical Cancer Cells to Cisplatin Treatment: Involvement of Mitochondrial and NF-Kappa B Pathways

“…PTX is a xanthine and a non-specific Phosphodiesterase inhibitor, which can act as a potent tumor necrosis factor alpha (TNF-α) inhibitor and can reduce inflammation through the inhibition of IκB phosphorylation in serines 32 and 36 ( 8 , 10 , 11 ). It has been demonstrated that PTX, in combination with some antitumor drugs, significantly increases cell apoptosis in several types of human cancer cell lines, such as cervical cancer cells (HeLa and SiHa) ( 9 ), retinoblastoma cells (Y79) ( 12 ), leukemia cells (U937) ( 13 ), and breast cancer cells (MCF-7 and MDA-MB-231) ( 14 ). Additionally, our earlier studies demonstrated that L5178Y lymphoma-bearing mice treated with PTX + ADRyamicin (ADR) survived more than 1 year after receiving only one half of the standard therapeutically active ADR dose, compared to single treatments of ADR ( 8 ).…”

Melatonin May Increase Anticancer Potential of Pleiotropic Drugs

“…In vitro studies on various cell lines demonstrated the role of statins as growth inhibitors, by the induction of the G0/G1-arrest [216], G2/M arrest or cell death [217,218]. Proposed mechanisms for statin-mediated apoptosis include an upregulation of pro-apoptotic protein expression (Bax, Bim), together with decreased anti-apoptotic protein expression (Bcl-2), or activation of caspase-3, caspase-8 and caspase-9 [219,220]. In experiments of our group, the significant preventive effects of atorvastatin and simvastatin in rat mammary carcinogenesis were accompanied by an increase in the Bax/Bcl-2 ratio [221] and expression decrease of proliferating cell nuclear antigen (Ki67) [222] in mammary cancer in vivo.…”