Pkn3, also known as Protein kinase N3, is an AGC-family member serine/threonine kinase. It is involved in multiple cellular functions and signaling pathways. Pkn3 has been implicated in cell growth, cytoskeletal arrangement, and cell adhesion. It is also associated with the phosphoinositide 3-kinase (PI3K) pathway and Rho signaling pathway, which are crucial for normal cell function and can be dysregulated in diseases [2,3,5,7,8].

PKN3 knockout (KO) mice have been instrumental in understanding its in vivo functions. The KO mice are viable and develop normally, but show marked suppressions of micro-vessel sprouting in ex vivo aortic ring assay and in vivo corneal pocket assay, indicating its role in angiogenesis. Also, they exhibit an impaired lung metastasis of melanoma cells when administered from the tail vein, suggesting Pkn3's importance in tumor metastasis [4]. In osteoclasts, Pkn3-deficient mice have greater trabecular bone mass due to decreased bone-resorbing activity of osteoclasts, showing its role in bone metabolism [2].

In conclusion, Pkn3 plays critical roles in angiogenesis, tumor metastasis, and osteoclast-mediated bone resorption as revealed through KO mouse model-based research. These findings suggest that Pkn3 could be a potential therapeutic target in diseases such as breast cancer, prostate cancer, osteoporosis, and other inflammatory bone-destructive diseases [1,2,6,7,8].