MDR1, MRP1 and LRP expression in patients with untreated acute leukaemia: Correlation with 99mTc-MIBI bone marrow scintigraphy

Chloramidine/Bisindolylmaleimide-I-Mediated Inhibition of Exosome and Microvesicle Release and Enhanced Efficacy of Cancer Chemotherapy

Microvesicle (MV) release from tumour cells influences drug retention, contributing to cancer drug resistance. Strategically regulating MV release may increase drug retention within cancer cells and allow for lower doses of chemotherapeutic drugs. The contribution of exosomes to drug retention still remains unknown. Potential exosome and MV (EMV) biogenesis inhibitors, tested on human prostate cancer (PC3) cells for their capacity to inhibit EMV release, were also tested on PC3 and MCF-7 (breast cancer) cells for improving chemotherapy. Agents inhibiting EMV release most significantly, whilst maintaining cell viability, were chloramidine (Cl-amidine; 50 µM) and bisindolylmaleimide-I (10 µM). Apoptosis mediated by the chemotherapy drug 5-fluorouracil (5-FU) was significantly enhanced in PC3 cells in the presence of both these EMV inhibitors, resulting in a 62% (Cl-amidine + 5-FU) and 59% (bisindolylmaleimide-I + 5-FU) decrease in numbers of viable PC3 cells compared to 5-FU alone after 24 h. For MCF-7 cells, there were similar increased reductions of viable cells compared to 5-FU treatment alone ranging from 67% (Cl-amidine + 5-FU) to 58% (bisindolylmaleimide-I + 5-FU). Using combinatory treatment, the two EMV inhibitors further reduced the number of viable cancer cells tested. Neither inhibitor affected cell viability. Combining selected EMV inhibitors may pose as a novel strategy to enhance the efficacy of chemotherapeutic drug-mediated apoptosis.

MicroRNA-10a silencing reverses cisplatin resistance in the A549/cisplatin human lung cancer cell line via the transforming growth factor-β/Smad2/STAT3/STAT5 pathway

Lung cancer is one of the primary causes of mortality worldwide and drug resistance is the key contributing factor which results in the failure of lung cancer chemotherapy. Previous studies have shown that microRNA (miR)‑10a was involved in the reversal of cisplatin (DDP) resistance in numerous types of tumors; however, the underlying mechanism of action of this remains to be fully elucidated. In the present study, miR‑10a silencing in human DDP‑resistant lung cancer A549/DDP cells was demonstrated to improve DDP sensitivity, apoptosis, intracellular rhodamine‑123 content as well as the expression and activity of caspase‑3/8. In addition, miR‑10a suppressed the cellular expression of P‑glycoprotein, multi‑drug resistance protein (MDR) 1, MDR‑associated protein 1, RhoE, B cell lymphoma‑2 and survivin in A549/DDP cells. Furthermore, miR‑10a silencing inhibited the secretion of transforming growth factor (TGF)‑β, phosphorylation of Sma‑ and Mad‑related protein (Smad)2, signal transducer and activator of transcription (STAT)3 and STAT5, the transcriptional activity of hypoxia‑inducible factor and eukaryotic translation initiation factor 4E in human lung cancer A549/DDP cell line. These results therefore indicated that miR‑10a may be a potential target for improving the effectiveness of lung cancer chemotherapy via regulation of the TGF‑β/Smad2/STAT3/STAT5 pathway.

The role of microvesicles in cancer progression and drug resistance

Microvesicles are shed constitutively, or upon activation, from both normal and malignant cells. The process is dependent on an increase in cytosolic Ca2+, which activates different enzymes, resulting in depolymerization of the actin cytoskeleton and release of the vesicles. Drug resistance can be defined as the ability of cancer cells to survive exposure to a wide range of anti-cancer drugs, and anti-tumour chemotherapeutic treatments are often impaired by innate or acquired MDR (multidrug resistance). Microvesicles released upon chemotherapeutic agents prevent the drugs from reaching their targets and also mediate intercellular transport of MDR proteins.