DCLK1 mediated cooperative acceleration of EMT by avian leukosis virus subgroup J and Marek's disease virus via the Wnt/β-catenin pathway promotes tumor metastasis.

Co-infection with oncogenic retrovirus and herpesvirus significantly facilitates tumor metastasis in human and animals. Co-infection with avian leukosis virus subgroup J (ALV-J) and Marek's disease virus (MDV), which are typical oncogenic retrovirus and herpesvirus, respectively, leads to enhanced oncogenicity and accelerated tumor formation, resulting in increased mortality of affected chickens. Previously, we found that ALV-J and MDV cooperatively promoted tumor metastasis. However, the molecular mechanism remains elusive. Here, we found that doublecortin-like kinase 1 (DCLK1) mediated cooperative acceleration of epithelial-mesenchymal transition (EMT) by ALV-J and MDV promoted tumor metastasis. Mechanistically, DCLK1 induced EMT via activating Wnt/β-catenin pathway by interacting with β-catenin, thereby cooperatively promoting tumor metastasis. Initially, we screened and found that DCLK1 was a potential mediator for the cooperative activation of EMT by ALV-J and MDV, and enhanced cell proliferation, migration, and invasion. Subsequently, we revealed that DCLK1 physically interacted with β-catenin to promote the formation of the β-catenin-TCF4 complex, inducing transcription of the Wnt target gene, c-Myc, promoting EMT by increasing the expression of N-cadherin, Vimentin, and Snail, and decreasing the expression of E-cadherin. Taken together, we discovered that jointly activated DCLK1 by ALV-J and MDV accelerated cell proliferation, migration and invasion, and ultimately activated EMT, paving the way for tumor metastasis. This study elucidated the molecular mechanism underlying cooperative metastasis induced by co-infection with retrovirus and herpesvirus. IMPORTANCE: Tumor metastasis, a complex phenomenon in which tumor cells spread to new organs, is one of the greatest challenges in cancer research and is the leading cause of cancer-induced death. Numerous studies have shown that oncoviruses and their encoded proteins significantly affect metastasis, especially the EMT process. ALV-J and MDV are classic tumorigenic retrovirus and herpesvirus, respectively. We found that ALV-J and MDV synergistically promoted EMT. Further, we identified the tumor stem cell marker DCLK1 in ALV-J and MDV co-infected cells. DCLK1 directly interacted with β-catenin, promoting the formation of the β-catenin-TCF4 complex. This interaction activated the Wnt/β-catenin pathway, thereby inducing EMT and paving the way for synergistic tumor metastasis. Exploring the molecular mechanisms by which ALV-J and MDV cooperate during EMT will contribute to our understanding of tumor progression and metastasis. This study provides new insights into the cooperative induced tumor metastasis by retroviruses and herpesviruses.