Innate immune cells can constitute a substantial proportion of the cells within the tumor microenvironment and have been associated with tumor malignancy in patients and animal models of cancer; however, the mechanisms by which they modulate cancer progression are incompletely understood. Here, we show that high levels of cathepsin protease activity are induced in the majority of macrophages in the microenvironment of pancreatic islet cancers, mammary tumors, and lung metastases during malignant progression. We further show that tumor-associated macrophage (TAM)-supplied cathepsins B and S are critical for promoting pancreatic tumor growth, angiogenesis, and invasion in vivo, and markedly enhance the invasiveness of cancer cells in culture. Finally, we demonstrate that interleukin-4 (IL-4) is responsible for inducing cathepsin activity in macrophages in vitro and in vivo. Together, these data establish IL-4 as an important regulator, and cathepsin proteases as critical mediators, of the cancer-promoting functions of TAMs.[Keywords: Tumor-associated macrophage; tumor microenvironment; cysteine cathepsin; protease; interleukin-4; invasion] Supplemental material is available at http://www.genesdev.org.

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Human papillomavirus (HPV) causes greater than 5% of cancers worldwide, including all cervical cancers and an alarmingly increasing proportion of oropharyngeal cancers (OPCs). Despite markedly reduced cervical cancer incidence in industrialized nations with organized screening programs, cervical cancer remains the second most common cause of death from cancer in women worldwide, as developing countries lack resources for universal, high-quality screening. In the United States, HPV-related OPC is only 1 of 5 cancers with a rising incidence since 1975 and now has taken over the cervix as the most common site of HPV-related cancer. Similar trends follow throughout North America and Europe. The need for early detection and prevention is paramount. Despite the common etiologic role of HPV in the development of cervical cancer and HPV-associated OPC, great disparity exists between incidence, screening modalities (or lack thereof), treatment, and prevention in these 2 very distinct cohorts. These differences in cervical cancer and HPV-associated OPC and their impact are discussed here. Cancer 2017;123:2219-2229. © 2017 American Cancer Society.