Given the multifaceted roles of lactate in promoting BC cell survival, invasion, immune evasion, metastasis, and angiogenesis, targeting lactate metabolism and its associated enzymes might provide a promising therapeutic strategy (
Table 1). Examination of fibroblasts isolated from patients with benign breast tissue and BC, as well as various animal models, has indicated that CAFs can undergo a metabolic shift toward the production of lactate and pyruvate, thereby supporting cancer cells’ biosynthetic pathways. Depleting or inhibiting lactate production in CAFs alters tumor metabolic profiles and slows tumor growth
114,115. Moreover, inhibiting the key signaling molecules ERK/STAT3 in the lactate signaling pathway decreases tumor development and angiogenesis through the elimination of lactate-mediated polarization of M2 macrophages. Studies on the natural product withanolide D have revealed that the ERK/STAT3 pathway might provide a target for BC prevention and treatment
101. Kar et al. have reported that PFKFB4 enhances lactate-induced migration of BC cells, given that silencing of PFKFB4 decreases lactate levels and BC cell invasion
108. Zhang et al. have used a polyphenol nanocomplex to inhibit LDH activity, decrease lactate production, and alleviate the acidic immune-suppressive TME. This polyphenol nanocomplex has been found to elicit effective antitumor immunity in a BC mouse model
109. Analysis of paired biopsy samples from BC tissue and cancer-associated adipose tissue from overweight/obese and normal-weight premenopausal women has revealed that elevated lactate levels in tumor tissues are accompanied by changes in the isozyme pattern to “muscle-type” LDH, and associated alterations in LDH A and B protein levels. In contrast, the considerably elevated LDH activity in cancer-associated adipose tissue suggests that LDH activity primarily facilitates lactate oxidation
116. In contrast, treatment with various inhibitors of LDH activity decreases lactate levels outside cells, cell growth, motility, and migration in estrogen receptor-positive (ER+) and -negative (ER−) BC cells
110. These findings highlight that LDH, along with its isoforms, may be used for BC treatment and that significant differences exist among BC tissues in various regions, thus providing promising directions for future BC diagnostic research. Additionally, targeted knockdown of MCT4
via miR-425-5p decreases lactate secretion from CAFs and impairs their ability to support BC cell angiogenesis, invasion, survival, and proliferation
111. Combined therapy with the MCT inhibitor quercetin and doxorubicin inhibits lactate metabolism, suppresses the HIF-1α/VEGF pathway and angiogenesis, and repolarizes tumor-associated macrophages
24. The tamoxifen-resistant BC cell line MCF-7 (TAMR-MCF-7) shows elevated conversion of lactate to pyruvate—a process in which MCT1 and LDHB have critical roles. In contrast, the MCT1 inhibitor AR-C155858 effectively inhibits TAMR-MCF-7 cell growth, invasion, spheroid formation, and tumor development
in vivo. Therefore, targeting MCT1-mediated and LDHB-mediated lactate production is a promising modality for treating tamoxifen-resistant BC
112. Tang et al. have developed nanoparticles containing vascular endothelial growth factor (VEGF) siRNA (siVEGF) and lactate oxidase/catalase for delivery into 4T1 cells. This approach promotes lactate consumption and silences VEGF expression, thereby synergistically inhibiting TNBC proliferation and angiogenesis
107. To further ameliorate the breast TME and overcome immune evasion, Tang et al. have developed nanoparticles containing lactate oxidase and PD-L1 siRNA (siPD-L1). This technique regulates the acidic TME in TNBC by depleting lactate, thereby ameliorating the immunosuppressive TME through activating exhausted CD8
+ T cells and decreasing the percentage of immunosuppressive Tregs. Additionally, siPD-L1 administration synergistically enhances the therapeutic effect of PD-1/PD-L1 blockade on TNBC
113.