College of Medicine, Southwest Jiaotong University, North Section 1 No.111, Second Ring Road, Chengdu, 610000, People's Republic of China.
Department of Orthopedics, General Hospital of Western Theater Command, Rongdu Avenue No. 270, Chengdu, 610000, People's Republic of China.
Cell Commun Signal. 2021 Jan 21;19(1):9. doi: 10.1186/s12964-020-00667-x.
To investigate the effect of lactic acid (LA) on the progression of bone metastasis from colorectal cancer (CRC) and its regulatory effects on primary CD115 (+) osteoclast (OC) precursors.
The BrdU assay, Annexin-V/PI assay, TRAP staining and immunofluorescence were performed to explore the effect of LA on the proliferation, apoptosis and differentiation of OC precursors in vitro and in vivo. Flow cytometry was performed to sort primary osteoclast precursors and CD4(+) T cells and to analyze the change in the expression of target proteins in osteoclast precursors. A recruitment assay was used to test how LA and Cadhein-11 regulate the recruitment of OC precursors. RT-PCR and Western blotting were performed to analyze the changes in the mRNA and protein expression of genes related to the PI3K-AKT pathway and profibrotic genes. Safranin O-fast green staining, H&E staining and TRAP staining were performed to analyze the severity of bone resorption and accumulation of osteoclasts.
LA promoted the expression of CXCL10 and Cadherin-11 in CD115(+) precursors through the PI3K-AKT pathway. We found that CXCL10 and Cadherin-11 were regulated by the activation of CREB and mTOR, respectively. LA-induced overexpression of CXCL10 in CD115(+) precursors indirectly promoted the differentiation of osteoclast precursors through the recruitment of CD4(+) T cells, and the crosstalk between these two cells promoted bone resorption in bone metastasis from CRC. On the other hand, Cadherin-11 mediated the adhesion between osteoclast precursors and upregulated the production of specific collagens, especially Collagen 5, which facilitated fibrotic changes in the tumor microenvironment. Blockade of the PI3K-AKT pathway efficiently prevented the progression of bone metastasis caused by lactate.
LA promoted metastatic niche formation in the tumor microenvironment through the PI3K-AKT pathway. Our study provides new insight into the role of LA in the progression of bone metastasis from CRC. Video Abstract.
研究乳酸（LA）对结直肠癌（CRC）骨转移进展的影响及其对原代 CD115（+）破骨细胞（OC）前体的调节作用。
采用 BrdU 检测、Annexin-V/PI 检测、TRAP 染色和免疫荧光法研究 LA 对 OC 前体体外和体内增殖、凋亡和分化的影响。采用流式细胞术分选原代破骨细胞前体和 CD4（+）T 细胞，并分析破骨细胞前体中靶蛋白表达的变化。采用招募试验检测 LA 和 Cadhein-11 如何调节 OC 前体的募集。采用 RT-PCR 和 Western blot 分析与 PI3K-AKT 通路和促纤维化基因相关的基因的 mRNA 和蛋白表达变化。采用番红 O-快绿染色、H&E 染色和 TRAP 染色分析骨吸收和破骨细胞堆积的严重程度。
LA 通过 PI3K-AKT 通路促进 CD115（+）前体中 CXCL10 和 Cadherin-11 的表达。我们发现，CXCL10 和 Cadherin-11 分别受 CREB 和 mTOR 的激活调节。LA 诱导 CD115（+）前体中 CXCL10 的过表达通过募集 CD4（+）T 细胞间接促进破骨细胞前体的分化，这两种细胞之间的串扰促进了 CRC 骨转移中的骨吸收。另一方面，Cadherin-11 介导破骨细胞前体之间的黏附，并上调特定胶原，尤其是胶原 5 的产生，促进肿瘤微环境中的纤维变性变化。PI3K-AKT 通路的阻断可有效阻止乳酸引起的骨转移进展。
LA 通过 PI3K-AKT 通路促进肿瘤微环境中的转移灶形成。我们的研究为 LA 在 CRC 骨转移进展中的作用提供了新的见解。视频摘要。
