Figure 6.

IFNγ overcomes the inhibitory effects of TGFβ/SMAD signaling on PD-L1 expression both in vivo and in vitro. (A) Excisional biopsies from 44 PDAC patients in cohort A and 36 PDAC patients in cohort B were sectioned and stained with H&E, lymphocytes quantified per 40X field, and arranged by PD-L1 status. (B-D) Using the TCGA genomic database of pancreatic cancer patients, CD274 mRNA expression was plotted against that of CD3E, CD3G, and IFNG. (E-G) Also, using the TCGA genomic database, IFNG mRNA expression was plotted against that of CD3E, CD3G, or SMAD4. (H) The 36 excisional PDAC specimens from cohort B were stained by immunohistochemistry for IFNγ, as well as dual-stained for either the duct marker CK19 and IFNγ, epithelial surrogate marker E-Cadherin and IFNγ, or the T-cell marker CD3 and IFNγ. The percent area positive for IFNγ was quantified as described and related to SMAD4 status. (I) The number of CD3+IFNγ+ cells were quantified per 40X field and arranged by both SMAD4 and PD-L1 status. (J) PANC-1 cells were incubated with 1ng/mL of recombinant IFNγ in the presence of increasing doses of recombinant TGFβ1, and PD-L1 expression evaluated by western blot after 24 hours. (K) PANC-1 cells were again incubated with either siControl or siSMAD4 and, after 24 hours, stimulated with 10ng/mL of recombinant TGFβ1. This experiment was also conducted in the presence of 1ng/mL recombinant IFNγ given concurrently with TGFβ1, and 24-hours after stimulation, cells were evaluated by western blot. (*p < 0.05).