Multifaceted effects of LRP6 in cancer: exploring tumor development, immune modulation and targeted therapies.

Low-density lipoprotein receptor (LDLR)-related protein 6 (LRP6), a member of the LDLR superfamily of cell surface receptors, is most widely known as a crucial co-receptor in the activation of canonical Wnt/β-catenin signaling. This signaling pathway is implicated in multiple biological processes, such as lipoprotein metabolism, protease regulation, cell differentiation, and migration. LRP6 is frequently overexpressed in a variety of tumors, including liver cancer, colorectal cancer, and prostate cancer, and is generally considered an oncogene that promotes tumor proliferation, migration, and invasion. However, there are exceptions; some studies have reported that LRP6 inhibits lung metastasis of breast cancer through its ectodomain (LRP6N), and patients with low LRP6 expression tend to have a poor prognosis. Thus, the role of LRP6 in tumors remains controversial. Although limited studies have shown that LRP6 is associated with the expression and roles of a variety of immune cells in tumors, the interaction of LRP6 with the tumor microenvironment (TME) is not fully understood. Furthermore, it is crucial to acknowledge that LRP6 can engage with alternative pathways, including the mTORC1, CXCL12/CXCR4, and KRAS signaling pathways mentioned earlier, resulting in the regulation of biological functions independent of canonical Wnt/β-catenin signaling. Due to the potential of LRP6 as a molecular target for cancer therapy, various treatment modalities have been developed to directly or indirectly inhibit LRP6 function, demonstrating promising anti-cancer effects across multiple cancer types. This review will concentrate on exploring the expression, function, and potential therapeutic applications of LRP6 in different cancer types, along with its influence on the TME.