High-metastatic triple-negative breast-cancer variants selected in vivo become chemoresistant in vitro

Triple-Negative Breast Cancer: Basic Biology and Immuno-Oncolytic Viruses

Triple-negative breast cancer (TNBC) is the most lethal subtype of breast cancer. TNBC diagnoses account for approximately one-fifth of all breast cancer cases globally. The lack of receptors for estrogen, progesterone, and human epidermal growth factor 2 (HER-2, CD340) results in a lack of available molecular-based therapeutics. This increases the difficulty of treatment and leaves more traditional as well as toxic therapies as the only available standards of care in many cases. Recurrence is an additional serious problem, contributing substantially to its higher mortality rate as compared to other breast cancers. Tumor heterogeneity also poses a large obstacle to treatment approaches. No driver of tumor development has been identified for TNBC, and large variations in mutational burden between tumors have been described previously. Here, we describe the biology of six different subtypes of TNBC, based on differential gene expression. Subtype differences can have a large impact on metastatic potential and resistance to treatment. Emerging antibody-based therapeutics, such as immune checkpoint inhibitors, have available targets for small subsets of TNBC patients, leading to partial responses and relatively low overall efficacy. Immuno-oncolytic viruses (OVs) have recently become significant in the pursuit of effective treatments for TNBC. OVs generally share the ability to ignore the heterogeneous nature of TNBC cells and allow infection throughout a treated tumor. Recent genetic engineering has allowed for the enhancement of efficacy against certain tumor types while avoiding the most common side effects in non-cancerous tissues. In this review, TNBC is described in order to address the challenges it presents to potential treatments. The OVs currently described preclinically and in various stages of clinical trials are also summarized, as are their strategies to enhance therapeutic potential.

IL-17-CXC Chemokine Receptor 2 Axis Facilitates Breast Cancer Progression by Up-Regulating Neutrophil Recruitment

Recent evidence suggests that interactions among proinflammatory cytokines, chemokines, and cancer cell-recruited neutrophils result in enhanced metastasis and chemotherapy resistance. Nonetheless, the detailed mechanism remains unclear. Our aim was to discover the role of IL-17, CXC chemokine receptor 2 (CXCR2) ligands, and cancer-associated neutrophils in chemotherapy resistance and metastasis in breast cancer. Mice were injected with Cl66 murine mammary tumor cells, Cl66 cells resistant to doxorubicin (Cl66-Dox), or Cl66 cells resistant to paclitaxel (Cl66-Pac). Higher levels of IL-17 receptor, CXCR2 chemokines, and CXCR2 were observed in tumors generated from Cl66-Dox and Cl66-Pac cells in comparison with tumors generated from Cl66 cells. Tumors generated from Cl66-Dox and Cl66-Pac cells had higher infiltration of neutrophils and T helper 17 cells. In comparison with primary tumor sites, there were increased levels of CXCR2, CXCR2 ligands, and IL-17 receptor within the metastatic lesions. Moreover, IL-17 increased the expression of CXCR2 ligands and cell proliferation of Cl66 cells. The supernatant of Cl66-Dox and Cl66-Pac cells enhanced neutrophil chemotaxis. In addition, IL-17-induced neutrophil chemotaxis was dependent on CXCR2 signaling. Collectively, these data demonstrate that the IL-17-CXCR2 axis facilitates the recruitment of neutrophils to the tumor sites, thus allowing them to play a cancer-promoting role in cancer progression.