a b s t r a c tRecent studies have shown microRNA-21 (miR-21) is overexpressed in several types of cancer and contributes to tumor resistance to chemotherapy. In this study, we investigated whether miR-21 mediated resistance of the leukaemia cell line K562 to the chemotherapeutic agent daunorubicin (DNR). miR-21 expression was upregulated in the DNR resistant cell line K562/DNR compared to its parental line K562. Stable transfection of miR-21 induced drug resistance in K562, while suppression of miR-21 in K562/DNR led to enhanced DNR cytotoxicity. Additional experiments indicate that the mechanism of miR-21 drug resistance involves the PI3K/Akt pathway and changes following PTEN protein expression. This study provides a novel mechanism for understanding leukaemia drug resistance.

No abstract

Abstract. microRNA-125b (miR-125b) is overexpressed in several types of cancer and contributes to tumor resistance to chemotherapy. The present study investigated the effect of miR-125b on the resistance of leukemia cell lines to the chemotherapeutic agent daunorubicin (DNR). miR-125b expression was found to be upregulated in patients who had failed therapy compared with those who demonstrated event-free survival. The overexpression of miR-125b was observed to induce DNR resistance in K562, THP-1 and Jurkat cells by reducing apoptosis, whereas the suppression of miR-125b was found to enhance DNR cytotoxicity in REH cells. Furthermore, miR-125b was observed to mediate DNR resistance in leukemia cell lines through decreasing expression of G protein-coupled receptor kinase 2 and p53-upregulated modulator of apoptosis, which were shown to be direct targets of miR-125b using a dual-luciferase reporter. The present study provides a novel mechanism for understanding leukemia drug resistance and provides a novel method for calculating patient prognosis.

BackgroundThe purpose of the current study was to evaluate the efficacy and safety of a dose increased weekly Bortezomib (Bor) based combination therapy in multiple myeloma (MM) patients.ResultsThe overall response rate (ORR) in the modified Bor group was 76.6%, composed of 40% complete response (CR), 3.3% very good partial response (VGPR) and 33.3% partial response (PR). The ORR was 82.3%, with 26.5% CR, 5.9% VGPR and 50% PR in control. A subgroup analysis showed both groups had equal efficacy in newly diagnosed MM patients (P = 1.000). The median progression free survival was 16 (11.7–20.3) months for the modified Bor group and 12 (10.5–13.5) months for the control (P = 0.503), and the median overall survival was 36 (9.4–62.6) vs 28 (21.6–34.4) months (P = 0.759). The incidences of AEs were similar except grade 1–4 peripheral neuropathy (PN) rate was 10% in modified regime group and 32.4% in control (P = 0.038).Materials and MethodsThis was a monocentric, prospective, non-randomized, phase IV, non-inferiority trial. Thirty MM patients were treated with modified Bor-based combination therapy (Bor 1.6 mg/m2 on day 1, 8), with 34 MM patients on conventional Bor-based combination therapy (1.3 mg/m2 on day 1, 4, 8, 11) as control. The responses and adverse events (AEs) were compared.ConclusionsThe increased-dose weekly Bor-based combination therapies were not inferior to conventional ones in terms of response and survival benefit, but showed lower rate of peripheral neuropathy (PN).