Inhibition of proliferation and apoptosis induced by a Na+/H+ exchanger-1 (NHE-1) antisense gene on drug-resistant human small cell lung cancer cells

Abstract

Abstract. The goal of this study was to evaluate the effect of the Na + /H + exchanger-1 (NHE-1) antisense gene on drugresistant human small cell lung cancer (SCLC) cell proliferation and apoptosis. A recombinant NHE-1 antisense gene was transfected into drug-resistant human SCLC H446/CDDP cells. Intracellular pH (pHi) was measured with fluorescence spectrophotometry. Cell proliferation was assayed cytometrically, and expression of the apoptosis gene caspase-3 was assayed using immunohistochemistry. Apoptosis and the cell cycles were imaged using a flow cytometer. pHi decreased significantly in transfected cells compared with control cells transfected with an empty vector (6.86±0.01 and 7.25±0.02, respectively, P<0.01). Cell proliferation began to decrease 48 h after antisense gene transfection, and the expression of the caspase-3 was stronger in transfected cells compared to the control group. The drug resistant exponent was significantly decreased (P<0.01), and there were more cells in G1 in the transfected group compared to the control group (70 and 57%, respectively, P<0.05). The rate of apoptosis in transfected cells was significantly higher than in the control group (12.18±1.86 and 2.37±0.33%, respectively, P<0.01). The NHE-1 antisense gene was able to induce drugresistant human SCLC H446/CDDP cells to become acidified and apoptotic, which could provide a novel therapy for multidrug resistance SCLC. IntroductionSmall cell lung cancer (SCLC) is a non-resectable and highly metastatic neoplastic disease, accounting for about 20% of all lung cancers (1). It is particularly aggressive and has a poor prognosis, with the 5-year survival rate at diagnosis rarely exceeding 10% (2). SCLC is a chemosensitive and radiosensitive disease; chemotherapy for SCLC typically involves a combination of etoposide, doxorubicin, vincristine, paclitaxel, and platinum-based regimens (3-5). First-line combination chemotherapy (with or without regional radiotherapy) induces a positive response in 70% of patients, with 50% of patients showing complete remission (6,7). However, 90% of these complete remission patients relapse with multidrug resistant tumours, making chemotherapy ineffective (8,9). Multidrug resistance is a serious clinical problem, which often severely limits the effectiveness of cancer chemotherapy (10). Thus, treating SCLC presents a significant clinical challenge.However, an effective way to treat SCLC multi-drug resistance has been reported (11). NHE-1 can directly interact with other regulatory cellular signaling pathways and is a multifaceted regulator of cell migration, proliferation, and cell death (12-14). The Na + /H + exchanger NHE-1 isoform is expressed ubiquitously and plays the crucial role of regulating intracellular pH by catalyzing the exchange of one extracellular sodium ion against one intracellular proton. Maintaining a steady-state intracellular pH during physiological conditions requires the continuous cellular export of acidic equivalents (15,16). Na + /H + exchangers (NHE) are membrane transport...

ABC294640, a sphingosine kinase 2 inhibitor, enhances the antitumor effects of TRAIL in non-small cell lung cancer

“…18 Our previous study indicated that certain interventions could restore SW480 and Hep-2R cell line's sensitivity to TRAIL by upregulating the cell surface expression of death receptors. 19,20 Therefore, further study is required to unravel the mechanism regulating TRAIL resistant signaling and to identify molecular switches that may set the system into the "apoptosis position." Previous study has indicated that targeting the sphingosine signaling could help to bring the misguided apoptosis back to the right track.…”

Inhibition of NHE-1 Increases Smoke-Induced Proliferative Activity of Barrett’s Esophageal Cell Line

“…Among the ion transporters NHE-1 is an ubiquitously expressed plasma membrane protein that plays an essential role in maintaining physiological pH i . Inadequate function of this transporter has been described in several cancer types, including esophageal cancer [13,16,[33][34][35][36][37]; therefore, NHE-1 emerged as a potential target in anti-cancer therapy [37,38]. We showed that, in the case of acute CSE exposure, higher concentrations of CSE increased NHE-1 activity in the metaplastic cells; this is presumably a defense mechanism by which the cells try to maintain the normal pH homeostasis.…”

“…Among the ion transporters NHE-1 is an ubiquitously expressed plasma membrane protein that plays an essential role in maintaining physiological pHi. Inadequate function of this transporter has been described in several cancer types, including esophageal cancer [13,16,[33][34][35][36][37]; therefore,…”