Oncoimmunology lab - Elena Quaglino PI

Teneurin-4 (TENM4) is one of the oncoantigens that has been identified, via the pipeline setup by the OncoImmunology Lab, as being overexpressed by triple negative breast cancer (TNBC) stem cells. TENM4 is a glycosylated type-II transmembrane protein belonging to the Teneurins family, which includes four highly conserved members that are involved in cell-cell and cell-extracellular matrix interactions and play a pivotal role in neural and cellular differentiation during embryonic development. TENM4 possesses a short N-terminal intracellular (IC), a transmembrane and a large extracellular (EC) domain. There is evidence to indicate that TENM4 can form both homo- and heterodimers on the same cell and between difference, adjacent cells. Data suggests that the TENM4 EC portion can be cleaved from the plasma membrane and released. The IC domain has a predicted cleavage site with a canonical nuclear localization sequence, indicating that this protein plays a role both as a receptor and a transcriptional regulator (Figure 1). 

Figre 1 TENM4 structure and its molecular interactions

However, few data on TENM4 protein-protein interactions are available. While the involvement of TENM4 in embryonic and neuronal development has been extensively documented, its function in cancer biology is understudied and an object of controversy. Indeed, only two papers on the role of TENM4 in solid tumors exist at this time: Graumann and colleagues demonstrated that the downregulation of TENM4 in ovarian cancer cells induces an increased proliferation rate and decreased sensitivity to cisplatin; on the other hand, my research group has recently demonstrated that TENM4 has a protumoral role in TNBC. An in-silico analysis of publicly available data sets showed a significant decrease in both relapse-free and overall survival in TNBC patients bearing high, rather than low, TENM4-expressing tumors. Using RNA interference-based silencing and CRISPR/Cas9 technology, we have generated TENM4-deficient and TENM4 knock out (TENM4 KO) murine TNBC cells, showing a significant reduction in tumorsphere-forming ability, clonogenicity, migration and invasion, compared to their TENM4 wild type (TENM4 WT) counterpart. No significant differences in the tumor growth rate of TENM4-deficient were observed, compared to TENM4 WT cells. However, TENM4 was demonstrated, for the first time, to have a significant role in in-vivo TNBC-derived lung metastasization. Thanks to the collaboration with Prof. Castellano (Department of Medical Science, Pathology Unit, University of Turin), we found that patients bearing TENM4-high expressing TNBC do recur and/ or metastasize at a significantly higher frequency than those with TENM4-low expressing TNBC (Figure 2). 

Figure 2. TENM4 role in TNBC biology

Since several mechanisms are involved in TNBC progression, including tumor-cell features and changes in the tumor microenvironment and distant organs, which become permissive environments for the outgrowth of disseminating tumor cells, our research group is now focused on: i) studying which genes can be affected by TENM4 expression; ii) identifying TENM4 molecular interactors (transcriptomic and interactomic analyses); iii) characterizing TENM4’s involvement in affecting the TNBC microenvironment and the lung pre-metastatic niche; and, iv) exploring TENM4’s role in chemoresistance via endoplasmic reticulum (ER) stress alteration. The elucidation of the mechanisms involving TENM4 in TNBC lung metastasization may validate this protein as a therapeutically relevant target and lead to the identification of novel molecular vulnerabilities to be exploited in the clinical management of TNBC patients. My team is also focused on the evaluation of the antitumor efficacy of oncolytic virotherapy against non small cell lung cancer (NSCLC). Many features, including its safety, its cytopathogenic effects against tumor cells from different histotypes, and the lack of pre-existing neutralizing antibodies in humans, make the bovine herpesvirus 4 (BoHV-4) a good candidate for introduction into the clinic. Preliminary results exploiting a preclinical model of NSCLC show that BoHV-4 blocks the proliferation of NSCLC tumor cells in vitro and, induce the regression of established NSCLC when injected intratumorally. Beside the direct antitumor effect, the cancer cell killing induced by the oncolytic activity of the BoHV-4 infection is effective in stimulating the host’s immune system, leading to the induction of a systemic anti-cancer immune response that can counteract the growth of second tumor challenge (Figure 3). 

Figure 3. BoHV-4-based oncolytic virotherapy.