Long-term resistance to 5-fluorouracil promotes epithelial-mesenchymal transition, apoptosis evasion, autophagy, and reduced proliferation rate in colon cancer cells.

The drug, 5-fluorouracil (5FU) is a standard first-line treatment for colorectal cancer (CRC) patients. However, drug resistance acquisition remains an important challenge for effective clinical outcomes. Here, we established a long-term drug-resistant CRC model and explored the cellular events underlying 5FU resistance. We showed that 5FU-treated cells (HCT-116 5FUR) using a prolonged treatment protocol were significantly more resistant than parental cells. Likewise, cell viability and IC50 values were also observed to increase in HCT-116 5FUR cells when treated with increasing doses of oxaliplatin, indicating a cross-resistance mechanism to other cytotoxic agents. Moreover, HCT-116 5FUR cells exhibited metabolic and molecular changes, as evidenced by increased thymidylate synthase levels and upregulated mRNA levels of ABCB1. HCT-116 5FUR cells were able to overcome S phase arrest and evade apoptosis, as well as activate autophagy, as indicated by increased LC3B levels. Cells treated with low and high doses displayed epithelial-mesenchymal transition (EMT) features, as observed by decreased E-cadherin and claudin-3 levels, increased vimentin protein levels, and increased SLUG, ZEB2 and TWIST1 mRNA levels. Furthermore, HCT-116 5FUR cells displayed enhanced migration and invasion capabilities. Interestingly, we found that the 5FU drug-resistance gene signature is positively associated with the mesenchymal signature in CRC samples, and that ABCB1 and ZEB2 co-expressed at high levels could predict poor outcomes in CRC patients. Overall, the 5FU long-term drug-resistance model established here induced various cellular events, and highlighted the importance of further efforts to identify promising targets involved in more than one cellular event to successfully overcome drug-resistance.

The Tumor Suppressor SCRIB is a Negative Modulator of the Wnt/ß-Catenin Signaling Pathway.

SCRIB is a scaffold protein containing leucine-rich repeats (LRR) and PSD-95/Dlg-A/ZO-1 domains (PDZ) that localizes at the basolateral membranes of polarized epithelial cells. Deregulation of its expression or localization leads to epithelial defects and tumorigenesis in part as a consequence of its repressive role on several signaling pathways including AKT, ERK, and HIPPO. In the present work, a proteomic approach is used to characterize the protein complexes associated to SCRIB and its paralogue LANO. Common and specific sets of proteins associated to SCRIB and LANO by MS are identified and an extensive landscape of their associated networks and the first comparative analysis of their respective interactomes are provided. Under proteasome inhibition, it is further found that SCRIB is associated to the ß-catenin destruction complex that is central in Wnt/ß-catenin signaling, a conserved pathway regulating embryonic development and cancer progression. It is shown that the SCRIB/ß-catenin interaction is potentiated upon Wnt3a stimulation and that SCRIB plays a repressing role on Wnt signaling. The data thus provide evidence for the importance of SCRIB in the regulation of the Wnt/ß-catenin pathway.

Revitalizing the AZT Through of the Selenium: An Approach in Human Triple Negative Breast Cancer Cell Line.

Triple-negative breast cancer represents about 15% of all cases of breast cancer, and still represents a therapeutic challenge. 3'-Azido-3'-deoxythymidine (AZT) is a nucleoside reverse transcriptase inhibitor with antitumor activity. Chalcogenides compounds, such as selenium, are very important intermediates applied in organic synthesis. Our objective was to investigate the effect and the underlying cell death mechanisms of AZT and its derivatives, in human breast cancer cell lines. The inhibitory effect of AZT and derivatives (1072, 1073, and 1079) was determined by MTT assay (0.1, 1, 10, 50, and 100 µM for concentrations and times 4, 24, 48, and 72 h) and Live/Dead in tumor cell lines MCF-7, MDA-MB 231 and also in non-tumor cell line CHO. Gene expression profiles related to apoptosis were investigated by qRT-PCR and induction of apoptosis was investigated by flow cytometry. MTT and Live/Dead assays showed that AZT derivatives decreased the rate of cell proliferation at concentrations of 50 and 100 µM in tumor cell lines MCF-7 and MDA-MB 231 while the commercial AZT presented a low antitumoral potential in all strains tested. In flow cytometry analysis we demonstrated that derivatives of AZT induced apoptosis, with an increase in both initial and late stages in both tumor cell lines evaluated, especially in MDA-MB 231. Our data show that the AZT derivative 1072 increased the expression of transcripts of the genes caspase 3 and 8 in MDA-MB 231 cell line when compared to control, suggesting that the extrinsic pathway of apoptosis was activated. In conclusion, derivatives of AZT, especially 1072, induce cytotoxicity in vitro in the triple negative breast cancer cell line through activation of the extrinsic pathway of apoptosis. These compounds containing selenium in its formulation are potential therapeutic agents for breast cancer.

Up-regulating telomerase and tumor suppressors: focusing on anti-aging interventions at the population level.

Most human populations are undergoing a demographic transition regarding their age structure. This transition is reflected in chronic non-communicable diseases featuring among the main contributors to burden of disease. Considering that the aging process is a major risk factor for such conditions, understanding the mechanisms underlying aging and age-related diseases is critical to develop strategies to impact human health at population and/or individual-levels. Two different aspects of aging process (namely, telomere shortening and DNA damage accumulation) were shown to interact in positively impacting mice median survival. However, strategies aimed at translating such knowledge into actual human health benefits have not yet been discussed. In this manuscript, we present potential exposures that are suited for population-level interventions, and contextualize the roles of population (based on behavioral exposures) and individual-level (based on small-molecule administration) anti-aging interventions in different levels of disease prevention. We suggest that exposures such as moderate wine consumption, reducing calorie intake and active lifestyle are potentially useful for primordial and primary prevention, while small-molecules that activate telomerase and/or tumor suppression responses are more suited for secondary and tertiary prevention (although important for primary prevention in specific population subgroups). We also indicate the need of studying the impacts, on aging and age-related diseases, of different combinations of these exposures in well-conducted randomized controlled trials, and propose Mendelian randomization as a valuable alternative to gather information in human populations regarding the effects of potential anti-aging interventions.