BackgroundEpidemiology and animal models suggest that dietary monosodium glutamate (MSG) may contribute to the onset of obesity and the metabolic syndrome.MethodsFamilies (n = 324) from a rural area of Thailand were selected and provided MSG as the sole source for the use in meal preparation for 10 days. Three hundred forty-nine subjects aged 35–55 years completed the study and were evaluated for energy and nutrient intake, physical activity, and tobacco smoking. The prevalence of overweight and obesity (BMI ≥ 25 kg/m2), insulin resistance (HOMA-IR >3), and the metabolic syndrome (ATP III criteria) were evaluated according to the daily MSG intake.ResultsThe prevalence of the metabolic syndrome was significantly higher in the tertile with the highest MSG intake. Further, every 1 g increase in MSG intake significantly increased the risk of having the metabolic syndrome (odds ratio 1.14, 95% confidence interval-CI- 1.12 - 1.28) or being overweight (odds ratio 1.16, 95% CI 1.04 - 1.29), independent of the total energy intake and the level of physical activity.ConclusionHigher amounts of individual MSG consumption are associated with the risk of having the metabolic syndrome and being overweight independent of other major determinants.
BackgroundCancer-associated fibroblasts and high mobility group box 1 (HMGB1) protein have been suggested to mediate cancer progression and chemotherapy resistance. The role of such fibroblasts in HMGB1 production in breast cancer is unclear. This study aimed to investigate the effects of cancer-associated fibroblasts on HMGB1 expression in breast cancer cells and its role in chemotherapeutic response.MethodsBreast cancer-associated fibroblasts (BCFs) and non-tumor-associated fibroblasts (NTFs) were isolated from human breast cancers or adjacent normal tissues and established as primary cultures in vitro. After confirmation of the activated status of these fibroblasts, conditioned-media (CM) were collected and applied to MDA-MB-231 human triple negative breast cancer cells. The levels of intracellular and extracellular HMGB1 were measured by real-time PCR and/or Western blot. The response of BCF-CM-pre-treated cancer cells to doxorubicin (Dox) was compared with those pre-treated with NTF-CM or control cultures. The effect of an HMGB1 neutralizing antibody on Dox resistance induced by extracellular HMGB1 from non-viable Dox-treated cancer cells or recombinant HMGB1 was also investigated.ResultsImmunocytochemical analysis revealed that BCFs and NTFs were alpha-smooth muscle actin (ASMA) positive and cytokeratin 19 (CK19) negative cells: a phenotype consistent with that of activated fibroblasts. We confirmed that the CM from BCFs (but not NTFs), could significantly induce breast cancer cell migration. Intracellular HMGB1 expression was induced in BCF-CM-treated breast cancer cells and also in Dox-treated cells. Extracellular HMGB1 was strongly expressed in the CM after Dox-induced MDA-MB-231 cell death and was higher in cells pre-treated with BCF-CM than NTF-CM. Pre-treatment of breast cancer cells with BCF-CM induced a degree of resistance to Dox in accordance with the increased level of secreted HMGB1. Recombinant HMGB1 was shown to increase Dox resistance and this was associated with evidence of autophagy. Anti-HMGB1 neutralizing antibody significantly reduced the effect of extracellular HMGB1 released from dying cancer cells or of recombinant HMGB1 on Dox resistance.ConclusionsThese findings highlight the potential of stromal fibroblasts to contribute to chemoresistance in breast cancer cells in part through fibroblast-induced HMGB1 production.
Trefoil factor 1 (TFF1) is a small secretory protein expressed in various types of carcinomas including breast cancer. The TFF1 gene contains an estrogen response element and its expression can be regulated by estrogen. Previous reports showed that TFF1 could protect cells from induced apoptosis in vitro. In the present study, the effect of estrogen on the promotion of doxorubicin-induced apoptosis resistance and the role of TFF1 in this process was demonstrated using the MCF-7 breast cancer cell model. Stable knockdown of the TFF1 gene in MCF-7 cells was generated and used to test the sensitivity to doxorubicin treatment compared to mock control cells in the presence or absence of 17β-estradiol. The apoptotic cells were measured by flow cytometry. The results showed that with the stimulation of apoptosis by doxorubicin, 17β-estradiol could suppress this process in mock cells but not in TFF1 knockdown cells. Moreover, using a viable cell counting method, it was shown that the anti-TFF1 antibody could reverse the anti-apoptotic effect of estrogen in mock cells and recombinant TFF1 could recover doxorubicin-induced cell death in TFF1 knockdown cells. This process, however, could not be inhibited by fulvestrant, an estrogen antagonist. An apoptosis protein array experiment reflected the role of the anti-oxidative enzyme catalase in estrogen and TFF1-modulated apoptosis and this was confirmed by enzymatic assay. These phenomena determine the role of TFF1 in estrogen-promoted resistance to apoptosis induced by doxorubicin in MCF-7 breast cancer cells. The TFF1 gene may be a target for enhancing the sensitivity to chemotherapy in breast cancer treatment.
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