Anaplastic thyroid cancer (ATC) is one of the most lethal human malignancies but its genetic drivers remain little understood. In this study, we report losses in expression of the microRNA miR-30a which is downregulated in ATC compared to differentiated thyroid cancer and normal tissue. miR-30a downregulation was associated with advanced differentiated thyroid cancer and higher mortality. Mechanistically, we found miR-30a decreased cellular invasion and migration, epithelial-mesenchymal transition marker levels, lysyl oxidase (LOX) expression and metastatic capacity. LOX was identified as a direct target of miR-30a that was overexpressed in ATC and associated with advanced differentiated thyroid cancer and higher mortality rate. Consistent with its role in other cancers, we found that LOX inhibited cell proliferation, cellular invasion and migration and metastasis in vitro and in vivo. Together, our findings establish a critical functional role for miR-30a downregulation in mediating LOX upregulation and thyroid cancer progression, with implications for LOX targeting as a rational therapeutic strategy in ATC.

Many epithelial–mesenchymal transition (EMT)–promoting transcription factors have been implicated in tumorigenesis and metastasis as well as chemoresistance of cancer. However, the underlying mechanisms mediating these processes are unclear. Here, we report that Foxq1, a forkhead box-containing transcription factor and EMT-inducing gene, promotes stemness traits and chemoresistance in mammary epithelial cells. Using an expression profiling assay, we identified Twist1, Zeb2, and PDGFRα and β as Foxq1 downstream targets. We further show that PDGFRα and β can be directly regulated by Foxq1 or indirectly regulated through the Foxq1/Twist1 axis. Knockdown of both PDGFRα and β results in more significant effects on reversing Foxq1-promoted oncogenesis in vitro and in vivo than knockdown of either PDGFRα or β alone. In addition, PDGFRβ is a more potent mediator of Foxq1-promoted stemness traits than PDGFRα. Finally, pharmacologic inhibition or gene silencing of PDGFRs sensitizes mammary epithelial cells to chemotherapeutic agents in vitro and in vivo. These findings collectively implicate PDGFRs as critical mediators of breast cancer oncogenesis and chemoresistance driven by Foxq1, with potential implications for developing novel therapeutic combinations to treat breast cancer. Cancer Res; 75(3); 1–10. ©2014 AACR.

Many epithelial-mesenchymal transition (EMT)-promoting transcription factors have been implicated in tumorigenesis and metastasis, as well as chemoresistance of cancer. However, the underlying mechanisms mediating these processes are unclear. Here we report that Foxq1, a forkhead box-containing transcription factor and EMT-inducing gene, promotes stemness traits and chemoresistance in mammary epithelial cells. Using an expression profiling assay, we identified Twist1, Zeb2, and PDGFRα and β as Foxq1 downstream targets. We further show that PDGFRα and β can be directly regulated by Foxq1 or indirectly regulated through the Foxq1/Twist1 axis. Knockdown of both PDGFRα and β results in more significant effects on reversing Foxq1-promoted oncogenesis in vitro and in vivo than knockdown of either PDGFRα or β alone. In addition, PDGFRβ is a more potent mediator of Foxq1-promoted stemness traits than PDGFRα. Finally, pharmacological inhibition or gene silencing of PDGFRs sensitizes mammary epithelial cells to chemotherapeutic agents in vitro and in vivo. These findings collectively implicate PDGFRs as critical mediators of breast cancer oncogenesis and chemoresistance driven by Foxq1, with potential implications for developing novel therapeutic combinations to treat breast cancer.

Cancer metastasis can occur at early stages of tumor development due to facilitative alterations in the tumor microenvironment. Although imaging techniques have considerably improved our understanding of metastasis, early events remain challenging to study due to the small numbers of malignant cells involved that are often undetectable. Using a novel zebrafish model to investigate this process, we discovered that tumor-associated macrophages (TAM) acted to facilitate metastasis by binding tumor cells and mediating their intravasation. Mechanistic investigations revealed that IL6 and TNFα promoted the ability of macrophages to mediate this step. M2 macrophages were particularly potent when induced by IL4, IL10, and TGFβ. In contrast, IFNγ-lipopolysaccharide–induced M1 macrophages lacked the capability to function in the same way in the model. Confirming these observations, we found that human TAM isolated from primary breast, lung, colorectal, and endometrial cancers exhibited a similar capability in invasion and metastasis. Taken together, our work shows how zebrafish can be used to study how host contributions can facilitate metastasis at its earliest stages, and they reveal a new macrophage-dependent mechanism of metastasis with possible prognostic implications. Cancer Res; 75(2); 1–10. ©2014 AACR.

Cancer metastasis can occur at early stages of tumor development due to facilitative alterations in the tumor microenvironment. While imaging techniques have considerably improved our understanding of metastasis, early events remain challenging to study due to the small numbers of malignant cells involved which are often undetectable. Using a novel zebrafish model to investigate this process, we discovered that tumor-associated macrophages (TAM) acted to facilitate metastasis by binding tumor cells and mediating their intravasation. Mechanistic investigations revealed that IL-6 and TNF-α promoted the ability of macrophages to mediate this step. M2 macrophages were particularly potent when induced by IL-4, IL-10 and TGF-β. In contrast, IFN-γ-LPS-induced M1 macrophages lacked the capability to function in the same way in the model. Confirming these observations, we found that human TAM isolated from primary breast, lung, colorectal and endometrial cancers exhibited a similar capability in invasion and metastasis. Taken together, our work shows how zebrafish can be used to study how host contributions can facilitate metastasis at its earliest stages, and they reveal a new macrophage-dependent mechanism of metastasis with possible prognostic implications.