# Metabolic Crosstalk in Triple-Negative Breast Cancer Lung Metastasis: Differential Effects of Vitamin D and E in a Co-Culture System

## TL;DR

This study explores how triple-negative breast cancer cells interact with lung cells and how vitamins D and E affect these interactions.

## Contribution

The study reveals distinct effects of Vitamins D and E on metabolic crosstalk in a TNBC lung metastasis co-culture system.

## Key findings

- Co-culture activated fibroblasts into cancer-associated fibroblasts with increased α-SMA and FAP expression.
- Vitamin D reduced fibroblast lactate metabolism and TCA cycle activity in cancer cells.
- Vitamin E increased TCA cycle and oxidative metabolism in cancer cells without affecting fibroblast glycolysis.

## Abstract

Triple-negative breast cancer (TNBC) is more likely to spread to the lungs than other types of breast cancer, yet the interplay between cancer cells and the lung microenvironment is not well characterised. In this study, a co-culture system of TNBC cells and lung fibroblasts was employed to study their metabolic interactions. The effects of Vitamin D and Vitamin E on these interactions were also assessed. Fibroblasts showed increased supportive characteristics toward cancer cells, while cancer cells exhibited alterations in energy and nutrient metabolism. Vitamin D appeared to reduce some of these supportive metabolic activities in fibroblasts and cancer cells, whereas Vitamin E was associated with increased metabolic activity in cancer cells. These observations provide insights into how cancer cells and lung fibroblasts interact and suggest that Vitamins D and E may influence these metabolic interactions, warranting further investigation in metastatic TNBC.

Background: Triple-negative breast cancer (TNBC) is more likely to metastasise to the lungs than other breast cancer (BrCa) types, yet the molecular interactions within the tumour microenvironment (TME) at secondary sites remain poorly understood. Methods: This pilot study aimed to explore the metabolic crosstalk between MDA-MB-231 TNBC cells and MRC-5 lung fibroblasts within a co-culture system to replicate the lung metastatic TME. Co-cultures were also treated with Vitamin D or Vitamin E to evaluate the effects of these nutraceuticals on the metabolic crosstalk between TNBC cells and fibroblasts. Results: Our findings demonstrate that co-culture induced the activation of fibroblasts into cancer-associated fibroblasts (CAFs), evidenced by increased α-SMA and FAP expression. Metabolic profiling revealed that TNBC cells in co-culture displayed increased expression of enzymes associated with oxidative phosphorylation (OXPHOS) and glutamine metabolism, while fibroblasts exhibited a metabolic profile consistent with glycolysis and lactate metabolism. Vitamin D inhibited lactate metabolism and HIF-1α expression in fibroblasts while suppressing TCA cycle activity in cancer cells, suggesting a potential role in disrupting oncogenic metabolic crosstalk. Conversely, Vitamin E treatment was associated with increased expression of TCA cycle and oxidative metabolism-related markers in BrCa cells without significantly affecting fibroblast glycolysis. Such differential metabolic responses may contribute to metabolic heterogeneity within the tumour microenvironment. Conclusions: These results provide valuable insights into the metabolic dynamics of TNBC metastases in the lung TME and demonstrate that Vitamins D and E exert distinct effects on metabolic crosstalk between cancer cells and fibroblasts. These findings may have significant implications for the potential supplementation of Vitamins D and E in patients with metastatic TNBC and justify further in-depth analysis.