Replenishment of myeloid-derived suppressor cells (MDSCs) overrides CR-mediated protection against tumor growth in a murine model of triple-negative breast cancer

Long-term intermittent caloric restriction remodels the gut microbiota in mice genetically prone to breast cancer

OBJECTIVES

Gut microbiota dysbiosis is among the risk factors for breast cancer development, together with genetic background and dietary habits. However, caloric restriction has been shown to remodel the gut microbiota and slow tumor growth. Here, we investigated whether the gut microbiota mediates the preventive effects of long-term chronic or intermittent caloric restriction on breast cancer predisposition.

METHODS

10-week-old transgenic breast cancer-prone mice were randomly assigned to dietary groups (ad libitum, chronic caloric restriction, and intermittent caloric restriction groups) and fed up to week 81. Stool samples were collected at weeks 10 (baseline), 17 (young), 49 (adult), and 81 (old). 16S rRNA gene sequencing was performed to identify the gut microbiota profile of the different groups. In order to investigate the breast cancer gut microbiota profile within genetically predisposed individuals regardless of diet, mammary tumor-bearing mice and mammary tumor-free but genetically prone mice were selected from the ad libitum group (n = 6).

RESULTS

Intermittent caloric restriction increased the microbial diversity of adult mice and modified age-related compositional changes. A total of 13 genera were differentially abundant over time. Pathogenic Mycoplasma was enriched in the re-feeding period of the old intermittent caloric restriction group compared with baseline. Furthermore, mammary tumor-free mice showed shared gut microbiota characteristics with mammary tumor-bearing mice, suggesting an early link between genetic predisposition, gut microbiota, and breast cancer development.

CONCLUSIONS

Our study revealed the role of gut microbes in the preventive effects of caloric restriction against breast cancer development, implying the significance of diet and microbiome interplay.

Unlocking the Potential: Caloric Restriction, Caloric Restriction Mimetics, and Their Impact on Cancer Prevention and Treatment

Caloric restriction (CR) and its related alternatives have been shown to be the only interventions capable of extending lifespan and decreasing the risk of cancer, along with a reduction in burden in pre-clinical trials. Nevertheless, the results from clinical trials have not been as conclusive as the pre-clinical results. Recognizing the challenges associated with long-term fasting, the application of caloric restriction mimetics (CRMs), pharmacological agents that mimic the molecular effects of CR, to harness the potential benefits while overcoming the practical limitations of fasting has resulted in an interesting alternative. This review synthesizes the findings of diverse clinical trials evaluating the safety and efficacy of CR and CRMs. In dietary interventions, a fast-mimicking diet was the most tolerated to reduce tumoral growth markers and chemotherapy side effects. CRMs were well tolerated, and metformin and aspirin showed the most promising effect in reducing cancer risk in a selected group of patients. The application of CR and/or CRMs shows promising effects in anti-cancer therapy; however, there is a need for more evidence to safely include these interventions in standard-of-care therapies.

Decanoylcarnitine Inhibits Triple-Negative Breast Cancer Progression via Mmp9 in an Intermittent Fasting Obesity Mouse

Purpose: Treatment of triple-negative breast cancer (TNBC) remains challenging. Intermittent fasting (IF) has emerged as a promising approach to improve metabolic health of various metabolic disorders. Clinical studies indicate IF is essential for TNBC progression. However, the molecular mechanisms underlying metabolic remodeling in regulating IF and TNBC progression are still unclear. Methods: In this study, we utilized a robust mouse model of TNBC and exposed subjects to a high-fat diet (HFD) with IF to explore its impact on the metabolic reprogramming linked to cancer progression. To identify crucial serum metabolites and signaling events, we utilized targeted metabolomics and RNA sequencing (RNA-seq). Furthermore, we conducted immunoblotting, real-time quantitative polymerase chain reaction (RT-qPCR), cell migration assays, lentivirus-mediated Mmp9 overexpression, and Mmp9 inhibitor experiments to elucidate the role of decanoylcarnitine/Mmp9 in TNBC cell migration. Results: Our observations indicate that IF exerts notable inhibitory effects on both the proliferation and cancer metastasis. Utilizing targeted metabolomics and RNA-seq, we initially identified pivotal serum metabolites and signaling events in the progression of TNBC. Among the 349 serum metabolites identified, decanoylcarnitine was picked out to inhibit TNBC cell proliferation and migration. RNA-seq analysis of TNBC cells treated with decanoylcarnitine revealed its suppressive effects on extracellular matrix-related protein components, with a notable reduction observed in Mmp9. Further investigations confirmed that decanoylcarnitine could inhibit Mmp9 expression in TNBC cells, primary tumors, lung, and liver metastasis tissues. Mmp9 overexpression abolished the inhibitory effect of decanoylcarnitine on cell migration. Conclusion: This study pioneers the exploration of IF intervention and the role of decanoylcarnitine/Mmp9 in the progression of TNBC in obese mice, enhancing our comprehension of the potential roles of various dietary patterns in the process of cancer treatment.