Environmental control of mammary carcinoma cell expansion by acidification and spheroid formation in vitro

Abstract

Breast cancer is the leading cause of cancer death among women worldwide. Like other cancers, mammary carcinoma progression involves acidification of the tumor microenvironment, which is an important factor for cancer detection and treatment strategies. However, the effects of acidity on mammary carcinoma cell morphology and phenotype have not been thoroughly characterized. Here, we evaluated fundamental effects of environmental acidification on mammary carcinoma cells in standard two-dimensional cultures and three-dimensional spheroids. Acidification decreased overall mammary carcinoma cell viability, while increasing their resistance to the anthracycline doxorubicin. Environmental acidification also increased extracellular vesicle production by mammary carcinoma cells. Conditioned media containing these vesicles appeared to increase fibroblast motility. Acidification also increased mammary carcinoma cell motility when cultured with fibroblasts in spheroids. Taken together, results from this study suggest that environmental acidification induces drug resistance and extracellular vesicle production by mammary carcinoma cells that promote tumor expansion.

Mechanobiological Implications of Cancer Progression in Space

“…MCF7 mammary carcinoma cells cultured for 24 h at pH 6.0 showed more than 30% decrease in both cell viability and proliferation relative to those cultured at pH 7.2 (normal physiological condition). Both 24 and 48-h growth at the acidic pH exhibited more than 50% reduction in migration, examined as the percentage of the area of the cells covering the wound, compared to cells grown at normal pH (Ralph et al, 2020). Moreover, 24-h incubation of MCF7 cells at pH 6.2 resulted in four-fold production of extracellular vesicles compared to that at pH 7.2, although no significant difference in size was observed (Ralph et al, 2020).…”

“…MCF7 mammary carcinoma cells cultured for 24 h at pH 6.0 showed more than 30% decrease in both cell viability and proliferation relative to those cultured at pH 7.2 (normal physiological condition). Both 24 and 48-h growth at the acidic pH exhibited more than 50% reduction in migration, examined as the percentage of the area of the cells covering the wound, compared to cells grown at normal pH ( Ralph et al, 2020 ).…”

“…Moreover, 24-h incubation of MCF7 cells at pH 6.2 resulted in four-fold production of extracellular vesicles compared to that at pH 7.2, although no significant difference in size was observed ( Ralph et al, 2020 ). Addition of the conditioned media containing these vesicles to non-transformed human fibroblasts at pH 6.2 showed a migration rate equivalent to that of cells cultured in nascent media at pH 7.2, five-fold higher than the acidic pH without the vesicle supplement ( Ralph et al, 2020 ). These results imply the impact of extracellular pH on the exocytosis of tumorigenic cells during secretion of certain signaling molecules that activate the associated fibroblasts.…”

“…Both 24 and 48-h growth at the acidic pH exhibited more than 50% reduction in migration, examined as the percentage of the area of the cells covering the wound, compared to cells grown at normal pH (Ralph et al, 2020). Moreover, 24-h incubation of MCF7 cells at pH 6.2 resulted in four-fold production of extracellular vesicles compared to that at pH 7.2, although no significant difference in size was observed (Ralph et al, 2020). Addition of the conditioned media containing these vesicles to non-transformed human fibroblasts at pH 6.2 showed a migration rate equivalent to that of cells cultured in nascent media at pH 7.2, five-fold higher than the acidic pH without the vesicle supplement (Ralph et al, 2020).…”

Impact of cancer metabolism on therapy resistance – Clinical implications

“…For example, an increase in the number of EVs released by human melanoma cells and low pH was associated with the reduced effectiveness of cisplatin (Federici et al, 2014). Moreover, microenvironment acidification obtained by lowering the pH in 2D cultures and 3D spheroids caused an increase in the production of EVs by mammary carcinoma cells, leading to doxorubicin resistance (Ralph et al, 2020).…”