Hurrying up to wait is, of course, the fate of most patients. But for cancer patients, waiting entails being enveloped in heightened fears about harmful protocols and the difficulty of eradicating or containing the disease.

Oncolytic viruses, including oncolytic herpes simplex virus (oHSV), have produced provocative therapeutic responses in patients with glioblastoma, the most aggressive brain tumor. Paradoxically, innate immune responses mediated by natural killer (NK) cells and macrophages/microglia appear to limit oHSV efficacy. Therefore, we investigated whether pretreatment with an immunosuppressive cytokine, TGFβ, might reverse these effects and thereby potentiate oHSV efficacy. TGFβ treatment of NK cells rendered them less cytolytic against oHSV-infected glioblastoma cells and stem-like cells in vitro. Furthermore, TGFβ treatment of NK cells, macrophages, or microglia increased viral titers of oHSV in cocultures with glioblastoma cells. In a syngeneic mouse model of glioblastoma, administering TGFβ prior to oHSV injection inhibited intracranial infiltration and activation of NK cells and macrophages. Notably, a single administration of TGFβ prior to oHSV therapy was sufficient to phenocopy NK-cell depletion and suppress tumor growth and prolong survival in both xenograft and syngeneic models of glioblastoma. Collectively, our findings show how administering a single dose of TGFβ prior to oncolytic virus treatment of glioblastoma can transiently inhibit innate immune cells that limit efficacy, thereby improving therapeutic responses and survival outcomes. Cancer Res; 75(24); 1–10. ©2015 AACR.

Cervical cancer is a consequence of persistent infection with human papillomaviruses (HPV). Progression to malignancy is linked to an inflammatory microenvironment comprising T-helper-17 (Th17) cells, a T-cell subset with protumorigenic properties. Neoplastic cells express only low endogenous levels of the Th17 chemoattractant CCL20, and therefore, it is unclear how Th17 cells are recruited to the cervical cancer tissue. In this study, we demonstrate that CCL20 was predominantly expressed in the stroma of cervical squamous cell carcinomas in situ. This correlated with stromal infiltration of CD4+/IL17+ cells and with advancing International Federation of Gynecology and Obstetrics (FIGO) stage. Furthermore, we show that cervical cancer cells instructed primary cervical fibroblasts to produce high levels of CCL20 and to attract CD4/IL17/CCR6-positive cells, generated in vitro, in a CCL20/CCR6-dependent manner. Further mechanistic investigations identified cervical cancer cell–derived IL6 as an important mediator of paracrine CCL20 induction at the promoter, mRNA, and protein level in fibroblasts. CCL20 was upregulated through the recently described CCAAT/enhancer-binding protein β (C/EBPβ) pathway as shown with a dominant-negative version of C/EBPβ and through siRNA-mediated knockdown. In summary, our study defines a novel molecular mechanism by which cervical neoplastic cells shape their local microenvironment by instructing fibroblasts to support Th17 cell infiltration in a paracrine IL6/C/EBPβ-dependent manner. Th17 cells may in turn maintain chronic inflammation within high-grade cervical lesions to further promote cancer progression. Cancer Res; 75(24); 1–12. ©2015 AACR.

Antibody–drug conjugates (ADC) target cytotoxic drugs to antigen-positive cells for treating cancer. After internalization, ADCs with noncleavable linkers are catabolized to amino acid-linker-warheads within the lysosome, which then enter the cytoplasm by an unknown mechanism. We hypothesized that a lysosomal transporter was responsible for delivering noncleavable ADC catabolites into the cytoplasm. To identify candidate transporters, we performed a phenotypic shRNA screen with an anti-CD70 maytansine-based ADC. This screen revealed the lysosomal membrane protein SLC46A3, the genetic attenuation of which inhibited the potency of multiple noncleavable antibody–maytansine ADCs, including ado-trastuzumab emtansine. In contrast, the potencies of noncleavable ADCs carrying the structurally distinct monomethyl auristatin F were unaffected by SLC46A3 attenuation. Structure–activity experiments suggested that maytansine is a substrate for SLC46A3. Notably, SLC46A3 silencing led to relative increases in catabolite concentrations in the lysosome. Taken together, our results establish SLC46A3 as a direct transporter of maytansine-based catabolites from the lysosome to the cytoplasm, prompting further investigation of SLC46A3 as a predictive response marker in breast cancer specimens. Cancer Res; 75(24); 1–12. ©2015 AACR.

p53 has been shown to mediate cancer stem–like cell function by suppressing pluripotency and cellular dedifferentiation. However, there have been no studies to date that have addressed the specific effects of p53 loss in colonic adult stem cells. In this study, we investigated the consequences of conditionally ablating p53 in the highly relevant Lgr5+ stem cell population on tumor initiation and progression in the colon. In a mouse model of carcinogen (AOM)-induced colon cancer, tamoxifen-inducible Lgr5-driven deletion of p53 reduced apoptosis and increased proliferation of crypt stem cells, but had no effect on tumor incidence or size. Conversely, in a mouse model of colitis-associated cancer, in which mice are exposed to AOM and the potent inflammation inducer DSS, stem cell–specific p53 deletion greatly enhanced tumor size and incidence in the colon. These novel findings suggest that the loss of p53 function in stem cells enables colonic tumor formation only when combined with DNA damage and chronic inflammation. Furthermore, we propose that stem cell targeting approaches are valuable for interrogating prevention and therapeutic strategies that aim to specifically eradicate genetically compromised stem cells. Cancer Res; 75(24); 1–6. ©2015 AACR.