Disruption of microfilaments by cytochalasin B decreases accumulation of cisplatin in human epidermal carcinoma and liver carcinoma cell lines

Impaired actin filaments decrease cisplatin sensitivity via dysfunction of volume-sensitive Cl- channels in human epidermoid carcinoma cells

Cisplatin is a widely used platinum-based anticancer drug in the chemotherapy of numerous human cancers. However, cancer cells acquire resistance to cisplatin. So far, functional loss of volume-sensitive outwardly rectifying (VSOR) Cl^- channels has been reported to contribute to cisplatin resistance of cancer cells. Here, we analyzed protein expression patterns of human epidermoid carcinoma KB cells and its cisplatin-resistant KCP-4 cells. Intriguingly, KB cells exhibited higher β-actin expression and clearer actin filaments than KCP-4 cells. The β-actin knockdown in KB cells decreased VSOR Cl^- currents and inhibited the regulatory volume decrease (RVD) process after cell swelling. Consistently, KB cells treated with cytochalasin D, which depolymerizes actin filaments, showed smaller VSOR Cl^- currents and slower RVD. Cytochalasin D also inhibited cisplatin-triggered apoptosis in KB cells. These results suggest that the disruption of actin filaments cause the dysfunction of VSOR Cl^- channels, which elicits resistance to cisplatin in human epidermoid carcinoma cells.

Pro-chemotherapeutic effects of antibody against extracellular domain of claudin-4 in bladder cancer

Bladder cancer displays an aggressive phenotype in the muscle-invasive phase, and is associated with a high mortality rate. Therefore, novel molecular therapeutic targets are needed to improve patient survival. A monoclonal antibody against the extracellular domain of the claudin-4 (CLDN4) tight junction protein was established by immunizing rats with a plasmid vector encoding human CLDN4. A hybridoma clone, producing a rat monoclonal antibody recognizing CLDN4 (clone 4D3), was obtained. Immunohistochemistry by using the 4D3 antibody showed that CLDN4 expression was associated with local invasion, nodal metastasis, distant metastasis, and advanced stage in 86 cases of bladder cancer. The 4D3 antibody inhibited growth, invasion, and survival, associated with abrogation of the intratumoral microenvironment; lowered concentrations of epidermal growth factor and vascular endothelial growth factor were found in three-dimensional cultures of T24 and RT4 cells. In combination with cisplatin therapy, 4D3 enhanced cisplatin cytotoxicity by increasing cellular permeability, leading to increased intracellular cisplatin concentrations. In mouse models of subcutaneous tumors and lung metastasis, 4D3 enhanced tumor growth inhibition, alone and with concurrent cisplatin treatment. The anti-tumor activity of the newly established 4D3 antibody suggests that it may be a powerful tool in CLDN4-targeting therapy, and in combination with chemotherapy.

Cinnamic Acid and Cinnamaldehyde Ameliorate Cisplatin-Induced Splenotoxicity in Rats

Cinnamic acid (CA) and cinnamaldehyde (CD) are major constituents of cinnamon species. They possess various pharmacological properties of which their antioxidant activity is a prime one. This study aims to investigate potential protective effects against cisplatin (CP)-induced splenotoxicity in rats. A single dose of CP (5 mg/kg) injected i.p. caused a significant decrease in hemoglobin content (18%), total leucocytic count (46%), neutrophils (78%), and catalase (CAT) splenic activity (64%) with a marked increase in lymphocytes (26%) and splenic content of malondialdehyde (68%) and TNF-α (69%) as compared with the control group. Contrarily, CA (50 mg/kg, p.o.) or CD (40 mg/kg, p.o.) administration for 7 days before CP ameliorated CP-induced splenotoxicity as indicated by mitigation of the biochemical parameters and histopathological changes. These results revealed the promising protective effects of CA and CD on CP-induced splenotoxicity in rats; an effect that might be attributed to antioxidant and anti-inflammatory activities.

Inhibition of Glucose Transporter 1 (GLUT1) Chemosensitized Head and Neck Cancer Cells to Cisplatin

Glucose transporter 1 (GLUT1) facilitates the cellular uptake of glucose and is overexpressed in most cancers. The altered expression of GLUT1 may influence the sensitivity of tumor cells to chemotherapy. This study investigated whether the knockdown of GLUT1 expression to sensitize head and neck cancer cells to the chemotherapy drug cisplatin in vitro. Anti-GLUT1 antibody was used to block activity of GLUT1 protein, and GLUT1-shRNA was used to knock down its mRNA expression in Cal27 cells. Immunocytochemistry, Western blot, and qRT-PCR were used to detect expression of GLUT1 mRNA and protein, respectively. Lentivirus was used to carrying GLUT1-shRNA to knockdown GLUT1 expression in Cal27 cells for MTT and flow cytometry analyses of cell viability and apoptosis, respectively. Glucose uptake assay was used to assess the changes in glucose levels in Cal27 cells. It showed that GLUT1 mRNA and protein were expressed in Cal27 cells, and GLUT1 protein was localized on the cell membrane. Both anti-GLUT1 antibody and GLUT1-shRNA sensitized Cal27 cells to cisplatin treatment under both normoxia and hypoxia conditions. Anti-GLUT1 antibody and GLUT1-shRNA inhibited tumor cell growth in vitro and induced them to undergo apoptosis. GLUT1-shRNA also suppressed tumor cell uptake of glucose into the cells. Our findings suggest that inhibition of GLUT1 activity and expression can sensitize Cal27 cells to cisplatin treatment in both normoxic and hypoxic conditions. These data could be further verified in animal xenografts before potential application as a clinical adjuvant or neoadjuvant therapy of head and neck cancer with cisplatin.

The transcription factor GCF2 is an upstream repressor of the small GTPAse RhoA, regulating membrane protein trafficking, sensitivity to doxorubicin, and resistance to cisplatin

Our aim was to explore the involvement of the transcriptional suppressor GCF2 in silencing RhoA, disorganization of the cytoskeleton, mislocalization of MRP1, and sensitivity to anticancer agents as an upstream gene target in cancer therapy. Increased expression of GCF2 was found in human cisplatin-resistant cells, and overexpression in GCF2-transfected cells results in loss of RhoA expression and disruption of the actin/filamin network. In consequence, the membrane transporter MRP1 was internalized from the cell surface into the cytoplasm, rendering cells sensitive to doxorubicin by more than 10-fold due to increased accumulation of doxorubicin in the cells. The GCF2 transfectants also showed reduced accumulation of cisplatin and increased resistance. siRNA targeted to GCF2 suppressed the expression of GCF2 in cisplatin-resistant cells, reactivated RhoA expression, and restored the fine structure of actin microfilaments. MRP1 was also relocated to the cell surface. siRNA targeted to RhoA increased resistance 3-fold in KB-3-1 and KB-CP.5 cells. These data for the first time demonstrate a novel complex regulatory pathway downstream from GCF2 involving the small GTPase RhoA, actin/filamin dynamics, and membrane protein trafficking. This pathway mediates diverse responses to cytotoxic compounds, and also provides a molecular basis for further investigation into the pleiotropic resistance mechanism at play in cisplatin-resistant cells.

Specific hemosiderin deposition in spleen induced by a low dose of cisplatin: altered iron metabolism and its implication as an acute hemosiderin formation model

Cisplatin is one of the commonly-used chemotherapeutic drugs to efficiently treat malignant tumors in clinic, however, the adverse effects of cisplatin such as nephrotoxicity, neurotoxicity, and hemolytic uremic syndrome are often observed at its clinical doses (approximately 60 mg/m(2)), which limit its broader application. In earlier studies, little attention was paid to the subtle changes in the architecture of lymphatic organs after low doses of cisplatin treatment. This paper reviews current understanding of cisplatin-induced erythrocyte injury, and presents our latest finding that a low dose of cisplatin (3.6 mg/m(2)/day, 14 days) could induce specific hemosiderin deposition in spleen of both normal and hepatoma-22 (H22) inoculated Balb/C mice. This dose of cisplatin significantly inhibited H22-induced acute ascites development. No significant toxicity was induced by this dose of cisplatin to tissues except for hemosiderin accumulation in the spleen of both normal and H22 tumor-bearing mice. Increased splenic iron content and erythrocyte injury were observed after treatment with the low dose of cisplatin. The mRNA levels of ferroportin (FPN1) and ferritin were upregulated by 25 and 5-fold in spleen, respectively. Overexpression of FPN1 and ferritin protein were also been observed at protein levels by Western blotting analysis. In addition, the mRNA expression of hepcidin was also increased, suggesting blockage of iron recycling through FPN1 in spleen with cisplatin treatment. In conclusion, cisplatin treatment damages the erythrocytes which accumulate in the red pulp of spleen with defective recycling of FPN1 and ferritin protein. Hepcidin inhibits the function of FPN1 as iron-exporter leading to iron overloaded inside ferritins of splenic cells, which are stained with abnormal hemosiderin accumulation. These results demonstrate that cisplatin-caused hemosiderin deposition in spleen provides a valuable clue for understanding the molecular basis of toxicity of cisplatin and hemosiderin accumulation and iron metabolism in vivo.