Impact of SLC16A8 on tumor microenvironment and angiogenesis in colorectal cancer: New therapeutic target insights

Figure 1 The expression characteristics of SLC16A8 in colorectal cancer. A: The difference in the expression of SLC16A8 in colorectal cancer (CRC) tissues and adjacent tissues; B: The correlation between SLC16A8 and the prognosis of patients with CRC; C: SLC16A8 expression feature varying with stage of CRC; D: Pathways enriched in relation to SLC16A8. ^aP < 0.01. OS: Overall survival.

Figure 2 Effects of hypoxia on SLC16A8 expression and metabolic reprogramming of colorectal cancer cells. A: The expression level of SLC16A8 in colorectal cancer cell lines; B: The expression characteristics of SLC16A8 under hypoxia; C: The effect of hypoxia on the ECAR of RKO and LoVo; D: The effect of hypoxia on the extracellular lactate levels of RKO and LoVo; E: The effect of hypoxia on the expression of PKM2 and LDHA, the key proteins of metabolic reprogramming; F: The effect of hypoxia on glucose consumption in RKO and LoVo cells. ^aP < 0.05, ^bP < 0.01, ^cP < 0.001.

Figure 3 Effect of hypoxia on endothelial-mesenchymal transition of HUVEC co-cultured with colorectal cancer cells. A and B: Effect of hypoxia on cell viability; C and D: Effect of hypoxia on migration (C) and invasion (D) of HUVECs; E: Effect of hypoxia on the ability of endothelial cells’ tube formation; F: Hypoxia affected the expression of E-cadherin, N-cadherin and Vimentin in HUVECs. ^aP < 0.05, ^bP < 0.01.

Figure 4 the knock-down efficiency of SLC16A8 siRNAs. A and B: qRT-PCR (A) and Western blot (B) methods were used to screen the siRNA with the highest knockdown efficiency; C: SLC16A8 expression was elevated to hypoxia condition. ^aP < 0.05, ^bP < 0.01, ^cP < 0.001.

Figure 5 SLC16A8 siRNA reverses the effects of hypoxia on cell metabolic reprogramming. A: SLC16A8 siRNA affects the expression of SLC16A8 in hypoxia treated cells; B: Effect of SLC16A8 siRNA on ECAR of hypoxia treated cells; C: SLC16A8 siRNA can affect the level of extracellular lactic acid after hypoxia treatment; D: SLC16A8 siRNA affects the expression of PKM2 and LDHA in hypoxia treated cells; E: Effect of SLC16A8 siRNA on glucose consumption in hypoxia treated cells. ^aP < 0.05, ^bP < 0.01, ^cP < 0.001. 2-DG: 2-deoxyglucose.

Figure 6 SLC16A8 siRNA reverses the effects of hypoxia on cell endothelial-mesenchymal transition of HUVECs. A and B: The effect of SLC16A8 siRNA on the proliferation of hypoxia treated cells; C and D: SLC16A8 siRNA can affect the migration (C) and invasion (D) of hypoxic HUVECs; E: SLC16A8 siRNA can affect the expression level of E-cadherin, N-cadherin and Vimentin in hypoxia treated cells; F: Effect of SLC16A8 siRNA on the ability of endothelial cells to form tubes after co culture of colorectal cancer cells with hypoxia. ^aP < 0.05, ^bP < 0.01.

Figure 7 Effect of SLC16A8 on tumor growth. A-C: The impact of SLC16A8 knockdown on tumor growth; D: Effect of SLC16A8 knockdown on Ki67 expression in tumor; E: The effect of SLC16A8 knockdown on expression of HIF-1α and SLC16A8; F: Effect of SLC16A8 knockdown on HIF-1α expression; G: SLC16A8 knockdown promoted apoptosis in tumor; H: H&E staining was used to have a histopathological examination of tumors; I: SLC16A8 knockdown suppressed lactic acid in serum; J and K: SLC16A8 knockdown altered expression of Warburg effect- and endothelial-mesenchymal transition-related proteins’ expression. ^aP < 0.05, ^bP < 0.01, vs NC.

Figure 8 Graphical abstract. Under hypoxic conditions, the metabolic pathways in tumor tissues change, and lactate production increases. The expression of SLC16A8 is upregulated, causing the extrusion of lactate from cells. This leads to an increase in the distribution of tumor microvessels, providing conditions for tumor metastasis. EndMT: Endothelial-mesenchymal transition.