RESUMEN
Solid tumors are formed by cancer cells and the surrounding non-cancer stromal cells under hypoxic conditions, collectively referred to as the tumor microenvironment (TME). Lysophosphatidic acid (LPA) receptor (LPA1 to LPA6) signaling is crucial in regulating tumor progression. This study investigated the impact of LPA receptor signaling on the biological behaviors of colon cancer DLD-1 cells co-cultured with lymphatic endothelial SVEC4-10 cells under hypoxic conditions. Expression levels of LPAR1, LPAR2 and LPAR5 genes were significantly higher in DLD-1 cells co-cultured with SVEC4-10 cells compared to those cultured alone. Co-culturing with SVEC4-10 cells increased the motility of DLD-1 cells at 21â¯% O2. LPA stimulated the motility of DLD-1 cells co-cultured with SVEC4-10 cells but had no effect on DLD-1 cells cultured alone. Furthermore, under 1â¯% O2 conditions, expression levels of LPAR1, LPAR2, and LPAR5 genes were markedly elevated in DLD-1 cells co-cultured with SVEC4-10 cells compared to 21â¯% O2. The motility of DLD-1 cells co-cultured with SVEC4-10 cells was enhanced under 1â¯% O2 conditions. Viability of DLD-1 cells to fluorouracil (5-FU) in SVEC4-10 cell supernatants increased at 21â¯% O2 and decreased at 1â¯% O2. Additionally, the LPA2 agonist GRI-977143 increased viability to 5-FU. These findings indicate that LPA receptor signaling plays a critical role in regulating the biological behaviors of DLD-1 cells co-cultured with SVEC4-10 cells under hypoxic conditions.
RESUMEN
Lysophosphatidic acid (LPA) signaling via LPA receptors (LPA1 to LPA6) mediates various aspects of cancer cell behaviors. This study aimed to investigate the variation in intracellular ATP levels and its impact on cell viability in response to fluorouracil (5-FU) through LPA4 and LPA6 in colon cancer DLD-1 cells. LPA4 and LPA6 are linked to Gs and Gi proteins. Gs protein stimulates the activity of adenylyl cyclase, which catalyzes the conversion of ATP to cAMP, whereas Gi protein inhibits this activity. In cell survival assay, cells were treated with 5-FU every 24 h for 3 days. The viability in response to 5-FU in DLD-1 cells was enhanced by LPA4 and LPA6 knockdowns. Furthermore, LPA4 and LPA6 knockdowns reduced the expression of cleaved-PARP1 protein when cells were treated with 5-FU. Since ethidium bromide (EtBr) reduces mitochondrial DNA level in cultured cells, EtBr-treated (DLD-EtBr) cells were generated from DLD-1 cells. The viability to 5-FU in DLD-EtBr cells was higher than that of DLD-1 cells. Additionally, culturing DLD-1 cells in a low glucose-containing medium led to increased viability to 5-FU. LPAR4 and LPAR6 expressions were reduced in both DLD-EtBr and low glucose-treated cells. The cellular ATP levels were significantly decreased in DLD-1 cells following EtBr treatment and exposure to low glucose conditions. Conversely, in the presence of LPA, LPA4 and LPA6 knockdowns resulted in a marked elevation of ATP levels. These results suggest that cell viability to 5-FU is negatively regulated via the activation of LPA4-and LPA6-Gs protein pathways in DLD-1 cells rather than Gi protein.
RESUMEN
The tumor microenvironment (TME) comprises cancer and non-cancerous stromal cells, including fibroblasts. Free fatty acids (FFAs) regulate various biological responses by binding to G protein-coupled FFA receptors (FFARs). In this study, we examined the impact of FFAR1 and FFAR4 on the cell migration of pancreatic cancer PANC-1 cells co-cultured with 3T3 fibroblast cells under hypoxic conditions. PANC-1 cells cultured at 1 % O2 exhibited elevated FFAR1 expression and decreased FFAR4 expression compared to those at 21 % O2. Cell migration of PANC-1 cells was reduced under 1 % O2 conditions. FFAR1 knockdown enhanced PANC-1 cell migration, whereas FFAR4 knockdown inhibited it. Co-culture of PANC-1 cells with 3T3 cells at 1 % O2 significantly increased FFAR4 expression, while FFAR1 expression remained unchanged. To evaluate the effects of FFAR1 and FFAR4 on PANC-1 cell migration in co-culture with 3T3 cells, we conducted a wound healing assay using the Culture-Insert 2 Well. PANC-1 and 3T3 cells were individually seeded into the two wells and incubated at both 21 % and 1 % O2 for 13 h. The cell migration of PANC-1 cells co-cultured with 3T3 cells at 1 % O2 was notably higher compared to 21 % O2. TUG-770 reduced and TUG-891 enhanced the cell migration of PANC-1 cells co-cultured with 3T3 cells under both 21 % and 1 % O2 conditions. These findings suggest that FFAR1 and FFAR4 play important roles in regulating the cell migration of PANC-1 cells co-cultured with 3T3 cells under hypoxic conditions.