Investigating the role of Teneurin-4 in cancer

Breast Cancer (BC) is the most prevalent tumor in the world and the first cause of women cancer mortality. Among the different breast tumor subtypes, Triple Negative Breast Cancer (TNBC) exhibits a very aggressive phenotype, characterized by a high frequency of Cancer Stem Cells (CSC), a population of cancer cells capable of self-renewal which resembles the adult stemness phenotype. CSC are pivotal in sustaining tumor growth and progression, as well as drug resistance and metastasis. Specifically, their detrimental role is underscored by the worst prognosis observed in TNBC patients with a higher percentage of CSC. Therefore, to identify novel CSC targets for innovative therapeutic approaches, our research group employed RNA-sequencing (RNA-seq) to compare gene expression in TNBC epithelial cells and mammospheres enriched in CSC. Among the overexpressed genes in mammospheres, Teneurin-4 (TENM4) emerged as an interesting target given its higher expression in TNBC patients with poorer prognosis. Although some studies suggest a potential role for TENM4 in tumorigenesis, its specific function in TNBC remains unknown. To address this, we demonstrated that TENM4 plays a functional role in stemness, as evidenced by the reduced self-renewal ability of both human (MDA-MB231) and murine (4T1) TENM4-deficient cells. Moreover, we also demonstrated a decreased migratory capacity of TENM4-deficient cells, accompanied by a decreased phosphorylation of FAK, AKT, ERK and a reduced expression of MMP9, suggesting an involvement of TENM4 also in Extracellular Matrix (ECM) remodeling. Additionally, although no differences in tumor growth were observed in mice injected with TENM4-deficient cells as compared to control ones, in line with the in vitro experiments, a reduction in metastatic lesions was observed in mice injected with TENM4-deficient cells. Furthermore, considering the CSC pivotal role in driving drug resistance, we also showed that TENM4 induces Doxorubicin (Doxo) resistance both in vitro and in vivo. Specifically, we found that TENM4, by influencing the phosphorylation of Elf2α, indirectly induces autophagy, which consequently alleviates Endoplasmic Reticulum Stress (ERS), contributing to chemoresistance. In light of these findings, we decided to target TENM4 through DNA electrovaccination, which induces a specific immune response and a reduction in lung metastases. Finally, we also identified a pivotal role of TENM4 in Colorectal Cancer (CRC) cell proliferation, migration, and tumor growth. Overall, we demonstrate for the first time, the role played by TENM4 in TNBC and CRC, emphasizing its potential as a valuable, yet understudied, therapeutic target.