Pericytes recruited by CCL28 promote vascular normalization after anti-angiogenesis therapy through RA/RXRA/ANGPT1 pathway in lung adenocarcinoma

Abstract

Background: It has been proposed that anti-angiogenesis therapy could induce tumor "vascular normalization" and further enhance the efficacy of chemotherapy, radiotherapy, target therapy, and immunotherapy for nearly twenty years. However, the detailed molecular mechanism of this phenomenon is still obscure.

Method: Overexpression and knockout of CCL28 in human lung adenocarcinoma cell line A549 and murine lung adenocarcinoma cell line LLC, respectively, were utilized to establish mouse models. Single-cell sequencing was performed to analyze the proportion of different cell clusters and metabolic changes in the tumor microenvironment (TME). Immunofluorescence and multiplex immunohistochemistry were conducted in murine tumor tissues and clinical biopsy samples to assess the percentage of pericytes coverage. Primary pericytes were isolated from lung adenocarcinoma tumor tissues using magnetic-activated cell sorting (MACS). These pericytes were then treated with recombinant human CCL28 protein, followed by transwell migration assays and RNA sequencing analysis. Changes in the secretome and metabolome were examined, and verification of retinoic acid metabolism alterations in pericytes was conducted using quantitative real-time PCR, western blotting, and LC-MS technology. Chromatin immunoprecipitation followed by quantitative PCR (ChIP-qPCR) was employed to validate the transcriptional regulatory ability and affinity of RXRα to specific sites at the ANGPT1 promoter.

Results: Our study showed that after undergoing anti-angiogenesis treatment, the tumor exhibited a state of ischemia and hypoxia, leading to an upregulation in the expression of CCL28 in hypoxic lung adenocarcinoma cells by the hypoxia-sensitive transcription factor CEBPB. Increased CCL28 could promote tumor vascular normalization through recruiting and metabolic reprogramming pericytes in the tumor microenvironment. Mechanistically, CCL28 modified the retinoic acid (RA) metabolism and increased ANGPT1 expression via RXRα in pericytes, thereby enhancing the stability of endothelial cells.

Conclusion: We reported the details of the molecular mechanisms of "vascular normalization" after anti-angiogenesis therapy for the first time. Our work might provide a prospective molecular marker for guiding the clinical arrangement of combination therapy between anti-angiogenesis treatment and other therapies.

Keywords: Anti-angiogenesis therapy; CCL28; Lung adenocarcinoma; Pericytes; Retinoic acid; Vascular normalization.

Fig. 1

CCL28 expression is upregulated after anti-angiogenesis therapy by hypoxia-sensitive transcription factor CEBPB in lung adenocarcinoma

Fig. 2

Tumor-derived CCL28 recruits pericytes to promote vascular normalization in the tumor microenvironment

Fig. 3

Tumor-derived CCL28 promotes the expression of angiopoietin-1 via CCR3 in pericytes

Fig. 4

Retinoic acid signaling is activated by CCL28 in pericytes through CCR3 A, Volcano plot of changes in metabolic pathways after CCL28 stimulation. B Volcano plot of the enrichment of gene expression after CCL28 stimulation. C Diagram of the metabolic conversion process in the retinoic acid metabolic signaling pathway. D and E Expression of RDH13 and DHRS11 detected by qPCR and western blot with or without exogenous supplement of CCL28. F Correlation of expression of CCL28 with RDH13 in lung adenocarcinoma. G The protein level of DHRS11 and RDH13 stimulated with or without CCL28 and CCR3 neutralizing antibody in pericytes (left) and gray value was calculated(right). H Knockdown efficiency of RDH13 was confirmed by qPCR. I and J Relative expression of RXRα and ANGPT1 after knockdown of RDH13 with or without stimulation of CCL28. K Representative immunofluorescence images of PAN-CK, NG2, CCL28 with DHRS11 or RDH13 or Angiopoietin-1 on biopsy tissues from lung cancer patients (left panel). Scale bar = 100 μm. The correlation between the expression of CCL28 and the levels of DHRS11, RDH13, and angiopoietin-1 (right panel). Data with error bars are shown as mean ± SEM. Each symbol represents data from a replicate. Each panel is a representative experiment of at least three independent biological replicates. *, **, *** represent p < 0.05, p < 0.01 and p < 0.001, respectively. Abbreviation: MFI, Mean fluorescence intensity

Fig. 5

Both CCL28 and retinoic acid could promote vascular normalization in vivo

Fig. 6

CCL28 is involved in bevacizumab-mediated vascular normalization

Fig. 7

A schematic diagram of tumor microenvironment modulation effects of CCL28