Midkine and pleiotrophin concentrations in needle biopsies of breast and lung masses

Pleiotrophin drives a prometastatic immune niche in breast cancer

Metastatic cancer cells adapt to thrive in secondary organs. To investigate metastatic adaptation, we performed transcriptomic analysis of metastatic and non-metastatic murine breast cancer cells. We found that pleiotrophin (PTN), a neurotrophic cytokine, is a metastasis-associated factor that is expressed highly by aggressive breast cancers. Moreover, elevated PTN in plasma correlated significantly with metastasis and reduced survival of breast cancer patients. Mechanistically, we find that PTN activates NF-κB in cancer cells leading to altered cytokine production, subsequent neutrophil recruitment, and an immune suppressive microenvironment. Consequently, inhibition of PTN, pharmacologically or genetically, reduces the accumulation of tumor-associated neutrophils and reverts local immune suppression, resulting in increased T cell activation and attenuated metastasis. Furthermore, inhibition of PTN significantly enhanced the efficacy of immune checkpoint blockade and chemotherapy in reducing metastatic burden in mice. These findings establish PTN as a previously unrecognized driver of a prometastatic immune niche and thus represents a promising therapeutic target for the treatment of metastatic breast cancer.

miR-627-3p inhibits osteosarcoma cell proliferation and metastasis by targeting PTN

Dysregulation of microRNA (miRNA) has been observed in several types of tumors, including osteosarcoma. Biochip analysis was used to identify miRNAs differentially expressed in osteosarcoma tissues. The targeting sites of miR-627-3p were analyzed using miRDB software and fluorescein reporter gene. MTT and Transwell assays were used to analyze the effects of miR-627-3p on the growth and migration of osteosarcoma cells. Western blotting and real-time PCR were used to detect the effects of miR-627-3p on related proteins. In vivo experiments were conducted to verify the effect of miR-627-3p on osteosarcoma. We focused on miR-627-3p because it was the most significantly downregulated miRNA in our screening study. Through luciferase reporter assays, western blotting and real-time PCR we found that miR-627-3p directly targets PTN, and that expression levels of miR-627-3p and PTN are negatively correlated in osteosarcoma cells. Downregulation of miR-627-3p promoted osteosarcoma cell proliferation and metastasis, while its overexpression had the opposite effect. By targeting PTN, miR-627-3p also suppressed expression of Cyclin D1 and MMP2. MiR-627-3p inhibited osteosarcoma metastasis in vivo. Thus, miR-627-3p may be a useful therapeutic target for the treatment osteosarcoma or prevention of metastasis.