ABSTRACT
BACKGROUND: Topotecan (TPT) is a Topo I inhibitor and shows obvious anti-cancer effects on gastric cancer. Cancer cells reprogram their metabolic pathways to increase nutrients uptake, which has already been a hallmark of cancer. But the effect of TPT on metabolism in gastric cancer remains unknown. PURPOSE: To investigate the effect of TPT on metabolism in gastric cancer. METHODS: ATP production was measured by ATP Assay kit. Glucose and glutamine uptake were measured by Glucose (HK) Assay Kit and Glutamine/Glutamate Determination Kit respectively. To detect glutathione (GSH) concentration and reactive oxygen species (ROS) generation, GSH and GSSG Assay Kit and ROS Assay Kit were adopted. Apoptosis rates, mitochondrial membrane potential (MMP) were determined by flow cytometry and protein levels were analyzed by immumohistochemical staining and western blotting. RESULTS: TPT increased ATP production. TPT promoted glucose uptake possibly via up-regulation of hexokinase 2 (HK2) or glucose transporter 1 (GLUT1) expression, while decreased glutamine uptake by down-regulation of ASCT2 expression. ASCT2 inhibitor GPNA and ASCT2 knockdown significantly suppressed the growth of gastric cancer cells. Inhibition of ASCT2 reduced glutamine uptake which led to decreased production of GSH and increased ROS level. ASCT2 knockdown induced apoptosis via the mitochondrial pathway and weakened anti-cancer effect of TPT. CONCLUSION: TPT inhibits glutamine uptake via down-regulation of ASCT2 which causes oxidative stress and induces apoptosis through the mitochondrial pathway. Moreover, TPT inhibits proliferation partially via ASCT2. These observations reveal a previously undescribed mechanism of ASCT2 regulated gastric cancer proliferation and demonstrate ASCT2 is a potential anti-cancer target of TPT.
Subject(s)
Amino Acid Transport System ASC/metabolism , Antineoplastic Agents/pharmacology , Minor Histocompatibility Antigens/metabolism , Oxidative Stress/drug effects , Stomach Neoplasms/drug therapy , Topotecan/pharmacology , Amino Acid Transport System ASC/genetics , Animals , Apoptosis/drug effects , Cell Line, Tumor , Down-Regulation/drug effects , Female , Gene Expression Regulation, Neoplastic , Glutamine/metabolism , Glutathione/metabolism , Humans , Membrane Potential, Mitochondrial/drug effects , Mice, Inbred BALB C , Minor Histocompatibility Antigens/genetics , Mitochondria/drug effects , Mitochondria/metabolism , Molecular Targeted Therapy/methods , Stomach Neoplasms/metabolism , Stomach Neoplasms/mortality , Stomach Neoplasms/pathologyABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of chemokine stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 on liver metastasis of human colon cancer.</p><p><b>METHODS</b>Expression of CXCR4 in different colon cancer cell lines and SDF-1 in different tissues were detected by using Western-blot technique. Effect of SDF-1 and anti-CXCR4 monoclonal antibody (McAb) on proliferation and migration of HT-29 cells were measured using MTT methods. Model mimicking liver metastasis of human colon cancer was established by injecting HT-29 cells intrasplenically into BALB/C nude mice. Mice were randomly divided into AMD3100 treated group and control group. Liver metastatic rate and tumor foci were measured 7 weeks after.</p><p><b>RESULTS</b>HT-29 cells expressed higher level of CXCR4 protein, and liver tissue expressed higher level of SDF-1 protein. Compared with the control, SDF-1 could significantly induced the proliferation and migration of the HT-29 cells, and anti-CXCR4 McAb could inhibited both functions of SDF-1. The liver metastasis rate in the control group was 100%, and it was 40% in the AMD3100 treating group (P < 0.05). The mean liver metastasis number also significantly decreased by AMD3100 (7.8 +/- 2.6 vs 22.4 +/- 8.6, P < 0.05).</p><p><b>CONCLUSIONS</b>SDF-1/CXCR4 biological axis play an important role in liver metastasis of human colon cancer. Arrest of CXCR4 can inhibit liver metastasis of colon cancer through blocking cell proliferation and migration induced by SDF-1.</p>
