Combating Drug Resistance by Exploiting miRNA-200c-Controlled Phase II Detoxification.

Acquired drug resistance constitutes a serious obstacle to the successful therapy of cancer. In the process of therapy resistance, microRNAs can play important roles. In order to combat resistance formation and to improve the efficacy of chemotherapeutics, the mechanisms of the multifaceted hsa-miR-200c on drug resistance were elucidated. Upon knockout of hsa-miR-200c in breast carcinoma cells, a proteomic approach identified altered expression of glutathione S-transferases (GSTs) when cells were treated with the chemotherapeutic drug doxorubicin. In different hsa-miR-200c expression systems, such as knockout, inducible sponge and inducible overexpression, the differential expression of all members of the GST family was evaluated. Expression of hsa-miR-200c in cancer cells led to the repression of a multitude of these GSTs and as consequence, enhanced drug-induced tumor cell death which was evaluated for two chemotherapeutic drugs. Additionally, the influence of hsa-miR-200c on the glutathione pathway, which is part of the phase II detoxification mechanism, was investigated. Finally, the long-term effects of hsa-miR-200c on drug efficacy were studied in vitro and in vivo. Upon doxycycline induction of hsa-miR-200c, MDA-MB 231 xenograft mouse models revealed a strongly reduced tumor growth and an enhanced treatment response to doxorubicin. A combined treatment of these tumors with hsa-miR-200c and doxorubicin resulted in complete regression of the tumor in 60% of the animals. These results identify hsa-miR-200c as an important player regulating the cellular phase II detoxification, thus sensitizing cancer cells not expressing this microRNA to chemotherapeutics and reversing drug resistance through suppression of GSTs.

HELLS Is Negatively Regulated by Wild-Type P53 in Liver Cancer by a Mechanism Involving P21 and FOXM1.

The major tumor suppressor P53 (TP53) acts primarily as a transcription factor by activating or repressing subsets of its numerous target genes, resulting in different cellular outcomes (e.g., cell cycle arrest, apoptosis and senescence). P53-dependent gene regulation is linked to several aspects of chromatin remodeling; however, regulation of chromatin-modifying enzymes by P53 is poorly understood in hepatocarcinogenesis. Herein, we identified Helicase, lymphoid specific (HELLS), a major epigenetic regulator in liver cancer, as a strong and selective P53 repression target within the SNF2-like helicase family. The underlying regulatory mechanism involved P53-dependent induction of P21 (CDKN1A), leading to repression of Forkhead Box Protein M1 (FOXM1) that in turn resulted in downregulation of HELLS expression. Supporting our in vitro data, we found higher expression of HELLS in murine HCCs arising in a Trp53-/- background compared to Trp53+/+ HCCs as well as a strong and highly significant correlation between HELLS and FOXM1 expression in different HCC patient cohorts. Our data suggest that functional or mutational inactivation of P53 substantially contributes to overexpression of HELLS in HCC patients and indicates a previously unstudied aspect of P53's ability to suppress liver cancer formation.

Comparative safety of dipeptidyl peptidase-4 inhibitors and sulfonylureas among frail older adults.

BACKGROUND: Studies comparing dipeptidyl peptidase-4 inhibitors (DPP4Is) to sulfonylureas (SUs) are unavailable for frail older adults, especially nursing home (NH) residents. We examined the effects of DPP4Is versus SUs on severe adverse glycemic events, cardiovascular events, and death among NH residents. METHODS: We conducted a national retrospective cohort study of long-stay NH residents aged ≥65 years using 2008-2010 national US Minimum Data Set clinical assessment data and linked Medicare claims. Exposure was new DPP4I versus new SU use assessed via Medicare Part D drug claims. One-year outcomes were severe hypoglycemia, severe hyperglycemia, acute myocardial infarction (AMI), heart failure (HF), major adverse cardiovascular events plus HF (MACE+HF), and death. We compared outcomes after propensity score matching using Cox proportional hazards regression models. RESULTS: The cohort (N = 2016) had a mean (SD) age of 81 (8.1) years and was 72% female. Compared with SU users, DPP4I users had a lower 1-year rate of severe hypoglycemic events (HR = 0.57, 95% CI 0.34-0.94), but statistically similar rates of severe hyperglycemic events (HR = 0.94, 95% CI 0.52-1.72), AMI (HR = 0.76, 95% CI 0.44-1.30), HF (HR = 1.01, 95% CI 0.79-1.30), MACE+HF (HR = 0.90, 95% CI 0.72-1.12), and death (HR = 0.97, 95% CI 0.86-1.10). CONCLUSIONS: DPP4Is should be a preferred treatment option over SUs for NH residents and other frail older adults given the importance of avoiding hypoglycemia.

Inducible microRNA-200c decreases motility of breast cancer cells and reduces filamin A.

Cancer progression and metastases are frequently related to changes of cell motility. Amongst others, the microRNA-200c (miR-200c) was shown to maintain the epithelial state of cells and to hamper migration. Here, we describe two miR-200c inducible breast cancer cell lines, derived from miR-200c knock-out MCF7 cells as well as from the miR-200c-negative MDA-MB-231 cells and report on the emerging phenotypic effects after miR-200s induction. The induction of miR-200c expression seems to effect a rapid reduction of cell motility, as determined by 1D microlane migration assays. Sustained expression of miR200c leads to a changed morphology and reveals a novel mechanism by which miR-200c interferes with cytoskeletal components. We find that filamin A expression is attenuated by miRNA-200c induced downregulation of the transcription factors c-Jun and MRTF/SRF. This potentially novel pathway that is independent of the prominent ZEB axis could lead to a broader understanding of the role that miR200c plays in cancer metastasis.