Examination of drug resistance activity of human TAP-like (ABCB9) expressed in yeast

Dissecting the Transcriptomes of Multiple Metronidazole-Resistant and Sensitive Trichomonas vaginalis Strains Identified Distinct Genes and Pathways Associated with Drug Resistance and Cell Death

Trichomonas vaginalis is the causative agent of trichomoniasis, the most prevalent non-viral sexually transmitted infection worldwide. Metronidazole (MTZ) is the mainstay of anti-trichomonal chemotherapy; however, drug resistance has become an increasingly worrying issue. Additionally, the molecular events of MTZ-induced cell death in T. vaginalis remain elusive. To gain insight into the differential expression of genes related to MTZ resistance and cell death, we conducted RNA-sequencing of three paired MTZ-resistant (MTZ-R) and MTZ-sensitive (MTZ-S) T. vaginalis strains treated with or without MTZ. Comparative transcriptomes analysis identified that several putative drug-resistant genes were exclusively upregulated in different MTZ-R strains, such as ATP-binding cassette (ABC) transporters and multidrug resistance pumps. Additionally, several shared upregulated genes among all the MTZ-R transcriptomes were not previously identified in T. vaginalis, such as 5′-nucleotidase surE and Na⁺-driven multidrug efflux pump, which are a potential stress response protein and a multidrug and toxic compound extrusion (MATE)-like protein, respectively. Functional enrichment analysis revealed that purine and pyrimidine metabolisms were suppressed in MTZ-S parasites upon drug treatment, whereas the endoplasmic reticulum-associated degradation (ERAD) pathway, proteasome, and ubiquitin-mediated proteolysis were strikingly activated, highlighting the novel pathways responsible for drug-induced stress. Our work presents the most detailed analysis of the transcriptional changes and the regulatory networks associated with MTZ resistance and MTZ-induced signaling, providing insights into MTZ resistance and cell death mechanisms in trichomonads.

Identification of a mechanogenetic link between substrate stiffness and chemotherapeutic response in breast cancer

Mechanical feedback from the tumor microenvironment regulates an array of processes underlying cancer biology. For example, increased stiffness of mammary extracellular matrix (ECM) drives malignancy and alters the phenotypes of breast cancer cells. Despite this link, the role of substrate stiffness in chemotherapeutic response in breast cancer remains unclear. This is complicated by routine culture and adaptation of cancer cell lines to unnaturally rigid plastic or glass substrates, leading to profound changes in their growth, metastatic potential and, as we show here, chemotherapeutic response. We demonstrate that primary breast cancer cells undergo dramatic phenotypic changes when removed from the host microenvironment and cultured on rigid surfaces, and that drug responses are profoundly altered by the mechanical feedback cells receive from the culture substrate. Conversely, primary breast cancer cells cultured on substrates mimicking the mechanics of their host tumor ECM have a similar genetic profile to the in situ cells with respect to drug activity and resistance pathways. These results suggest substrate stiffness plays a significant role in susceptibility of breast cancer to clinically-approved chemotherapeutics, and presents an opportunity to improve drug discovery efforts by integrating mechanical rigidity as a parameter in screening campaigns.

MicroRNA-31 Regulates Chemosensitivity in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is associated with an extremely poor prognosis, and most patients initially are or rapidly become unresponsive to platinum-based chemotherapy. MicroRNA-31 (miR-31) is encoded on a genomic fragile site, 9p21.3, which is reportedly lost in many MPM tumors. Based on previous findings in a variety of other cancers, we hypothesized that miR-31 alters chemosensitivity and that miR-31 reconstitution may influence sensitivity to chemotherapeutics in MPM. Reintroduction of miR-31 into miR-31 null NCI-H2452 cells significantly enhanced clonogenic resistance to cisplatin and carboplatin. Although miR-31 re-expression increased chemoresistance, paradoxically, a higher relative intracellular accumulation of platinum was detected. This was coupled to a significantly decreased intranuclear concentration of platinum. Linked with a downregulation of OCT1, a bipotential transcriptional regulator with multiple miR-31 target binding sites, we subsequently identified an indirect miR-31-mediated upregulation of ABCB9, a transporter associated with drug accumulation in lysosomes, and increased uptake of platinum to lysosomes. However, when overexpressed directly, ABCB9 promoted cellular chemosensitivity, suggesting that miR-31 promotes chemoresistance largely via an ABCB9-independent mechanism. Overall, our data suggest that miR-31 loss from MPM tumors promotes chemosensitivity and may be prognostically beneficial in the context of therapeutic sensitivity.

Overexpression of microRNA-24 increases the sensitivity to paclitaxel in drug-resistant breast carcinoma cell lines via targeting ABCB9

Paclitaxel has been widely used in the treatment of breast cancer. However, the development of drug resistance often increases the failure of chemotherapy. Growing evidence has reported the significant role of microRNAs (miRs) in drug resistance. The present study identified that miR-24 was significantly downregulated in paclitaxel-resistant (PR) breast cancer patients and in MCF-7/PR human breast carcinoma cells, and that overexpression of miR-24 could increase the effect of paclitaxel on drug-resistant breast carcinoma cells. Furthermore, miR-24 could directly bind to the 3′-untranslated region of ATP binding cassette B9 to downregulate its expression, thereby reducing drug transportation and improving the anti-tumor effect of paclitaxel on breast cancer cells. In vivo experiments also demonstrated that overexpression of miR-24 could increase the sensitivity of drug-resistant MCF-7 cells to paclitaxel. In conclusion, the present results suggested a novel function for miR-24 in reducing paclitaxel resistance in breast cancer, which may be of important clinical significance.

Normal formation of a subset of intestinal granules in Caenorhabditis elegans requires ATP-binding cassette transporters HAF-4 and HAF-9, which are highly homologous to human lysosomal peptide transporter TAP-like

TAP-like (TAPL; ABCB9) is a half-type ATP-binding cassette (ABC) transporter that localizes in lysosome and putatively conveys peptides from cytosol to lysosome. However, the physiological role of this transporter remains to be elucidated. Comparison of genome databases reveals that TAPL is conserved in various species from a simple model organism, Caenorhabditis elegans, to mammals. C. elegans possesses homologous TAPL genes: haf-4 and haf-9. In this study, we examined the tissue-specific expression of these two genes and analyzed the phenotypes of the loss-of-function mutants for haf-4 and haf-9 to elucidate the in vivo function of these genes. Both HAF-4 and HAF-9 tagged with green fluorescent protein (GFP) were mainly localized on the membrane of nonacidic but lysosome-associated membrane protein homologue (LMP-1)-positive intestinal granules from larval to adult stage. The mutants for haf-4 and haf-9 exhibited granular defects in late larval and young adult intestinal cells, associated with decreased brood size, prolonged defecation cycle, and slow growth. The intestinal granular phenotype was rescued by the overexpression of the GFP-tagged wild-type protein, but not by the ATP-unbound form of HAF-4. These results demonstrate that two ABC transporters, HAF-4 and HAF-9, are related to intestinal granular formation and some other physiological aspects.