Protocadherin-1 serves as a prognostic biomarker and promotes pancreatic cancer progression by suppressing CD8+ T cell infiltration through CCL5-CCR5 axis

Previous studies have shown that Protocadherins (PCDHs) enhance tumor proliferation, invasion, and metastasis; yet their role in pancreatic cancer (PC) progression and the tumor immune microenvironment remains unclear. This study aims to elucidate the role of PCDH1 in different cancer types, with a particular focus on its impact on immune suppression in PC. Utilizing data from TCGA, GTEx, and Gent2 databases, we assessed the expression of PCDH1 across various cancer types. The prognostic value of PCDH1 was demonstrated through Cox regression, Kaplan-Meier analysis, and ROC curve, while its relationship with gene mutations, tumor mutational burden (TMB), immune cell infiltration, and other clinical factors was investigated using Spearman correlation. Furthermore, the effect of PCDH1 on PC malignancy was experimentally validated by a series of in vitro and in vivo assays. Our results show a significant upregulation of PCDH1 in various tumor types, which is associated with poor prognosis, suggesting its potential application as an independent prognostic biomarker. Notably, in PC, PCDH1 exhibited significant associations with gene mutations, TMB, and immune cell infiltration. Clinical validations revealed a correlation between high PCDH1 expression and poor prognosis, coupled with a low level of CD8+ T cell infiltration. Furthermore, both in vitro and in vivo experiments confirmed the role of PCDH1 in promoting PC cell proliferation and migration while inhibiting CD8+ T cell recruitment through its modulation of CCL5-CCR5 axis. In conclusion, PCDH1 regulates the proliferation and migration of PC cells as well as CD8+ T cell infiltration in PC. PCDH1 may serve as a prognostic biomarker in multiple tumor types.

Protocadherin-1 is expressed in the notochord of mouse embryo but is dispensable for its formation

Notochord is an embryonic midline structure that serves as mechanical support for axis elongation and the signaling center for the surrounding tissues. Precursors of notochord are initially induced in the dorsal most mesoderm region in gastrulating embryo and separate from the surrounding mesoderm/endoderm tissue to form an elongated rod-like structure, suggesting that cell adhesion molecules may play an important role in this step. In Xenopus embryo, axial protocadherin (AXPC), an orthologue of mammalian Protocadherin-1 (PCDH1), is indispensable for the assembly and separation from the surrounding tissue of the notochord cells. However, the role of PCDH1 in mammalian notochord remains unknown. We herein report that PCDH1 is expressed in the notochord of mouse embryo and that PCDH1-deficient mice form notochord normally. First, we examined the temporal expression pattern of pcdh1 and found that pcdh1 mRNA was expressed from embryonic day (E) 7.5, prior to the stage when notochord cells detach from the surrounding endoderm tissue. Second, we found that PCDH1 protein is expressed in the notochord of mouse embryos in addition to the previously reported expression in endothelial cells. To further investigate the role of PCDH1 in embryonic development, we generated PCDH1-deficient mice using the CRISPR-Cas9 system. In PCDH1-deficient embryos, notochord formation and separation from the surrounding tissue were normal. Structure and marker gene expression of notochord were also unaffected by loss of PCDH1. Major vascular patterns in PCDH1-deficient embryo were essentially normal. These results suggest that PCDH1 is dispensable for notochord formation, including the tissue separation process, in mammalian embryos. We successfully identified the evolutionary conserved expression of PCDH1 in notochord, but its function may differ among species.