Leukocyte subtyping predicts for treatment failure and poor survival in anal squamous cell carcinoma.

BACKGROUND: Anal squamous cell carcinoma (SCC) generally carries a favorable prognosis, as most tumors are highly sensitive to standard of care chemoradiation. However, outcomes are poor for the 20-30% of patients who are refractory to this approach, and many will require additional invasive procedures with no guarantee of disease resolution. METHODS: To identify the patients who are unlikely to respond to the current standard of care chemoradiation protocol, we explored a variety of objective clinical findings as a potential predictor of treatment failure and/or mortality in a single center retrospective study of 42 patients with anal SCC. RESULTS: Patients with an increase in total peripheral white blood cells (WBC) and/or neutrophils (ANC) had comparatively poor clinical outcomes, with increased rates of death and treatment failure, respectively. Using pre-treatment biopsies from 27 patients, tumors with an inflamed, neutrophil dominant stroma also had poor therapeutic responses, as well as reduced overall and disease-specific survival. Following chemoradiation, we observed uniform reductions in nearly all peripheral blood leukocyte subtypes, and no association between peripheral white blood cells and/or neutrophils and clinical outcomes. Additionally, post-treatment biopsies were available from 13 patients. In post-treatment specimens, patients with an inflamed tumor stroma now demonstrated improved overall and disease-specific survival, particularly those with robust T-cell infiltration. CONCLUSIONS: Combined, these results suggest that routinely performed leukocyte subtyping may have utility in risk stratifying patients for treatment failure in anal SCC. Specifically, pre-treatment patients with a high WBC, ANC, and/or a neutrophil-dense tumor stroma may be less likely to achieve complete response using the standard of care chemoradiation regimen, and may benefit from the addition of a subsequent line of therapy.

Loss of SMAD4 Is Associated With Poor Tumor Immunogenicity and Reduced PD-L1 Expression in Pancreatic Cancer.

Transforming Growth Factor ß (TGFß) is a key mediator of immune evasion in pancreatic ductal adenocarcinoma (PDAC), and the addition of TGFß inhibitors in select immunotherapy regimens shows early promise. Though the TGFß target SMAD4 is deleted in approximately 55% of PDAC tumors, the effects of SMAD4 loss on tumor immunity have yet to be fully explored. Using a combination of genomic databases and PDAC specimens, we found that tumors with loss of SMAD4 have a comparatively poor T-cell infiltrate. SMAD4 loss was also associated with a reduction in several chemokines with known roles in T-cell recruitment, which was recapitulated using knockdown of SMAD4 in PDAC cell lines. Accordingly, JURKAT T-cells were poorly attracted to conditioned media from PDAC cells with knockdown of SMAD4 and lost their ability to produce IFNγ. However, while exogenous TGFß modestly reduced PD-L1 expression in SMAD4-intact cell lines, SMAD4 and PD-L1 positively correlated in human PDAC samples. PD-L1 status was closely related to tumor-infiltrating lymphocytes, particularly IFNγ-producing T-cells, which were more abundant in SMAD4-expressing tumors. Low concentrations of IFNγ upregulated PD-L1 in tumor cells in vitro, even when administered alongside high concentrations of TGFß. Hence, while SMAD4 may have a modest inhibitory effect on PD-L1 in tumor cells, SMAD4 indirectly promotes PD-L1 expression in the pancreatic tumor microenvironment by enhancing T-cell infiltration and IFNγ biosynthesis. These data suggest that pancreatic cancers with loss of SMAD4 represent a poorly immunogenic disease subtype, and SMAD4 status warrants further exploration as a predictive biomarker for cancer immunotherapy.

TGFß Signaling in the Pancreatic Tumor Microenvironment.

Pancreatic ductal adenocarcinoma (PDAC) is associated with poor clinical outcomes, largely attributed to incomplete responses to standard therapeutic approaches. Recently, selective inhibitors of the Transforming Growth Factor ß (TGFß) signaling pathway have shown early promise in the treatment of PDAC, particularly as a means of augmenting responses to chemo- and immunotherapies. However, TGFß is a potent and pleiotropic cytokine with several seemingly paradoxical roles within the pancreatic tumor microenvironment (TME). Although TGFß signaling can have potent tumor-suppressive effects in epithelial cells, TGFß signaling also accelerates pancreatic tumorigenesis by enhancing epithelial-to-mesenchymal transition (EMT), fibrosis, and the evasion of the cytotoxic immune surveillance program. Here, we discuss the known roles of TGFß signaling in pancreatic carcinogenesis, the biologic consequences of the genetic inactivation of select components of the TGFß pathway, as well as past and present attempts to advance TGFß inhibitors in the treatment of PDAC patients.