Journal: Frontiers in Oncology
Article Title: Loss of SMAD4 Is Associated With Poor Tumor Immunogenicity and Reduced PD-L1 Expression in Pancreatic Cancer
doi: 10.3389/fonc.2022.806963
Figure Lengend Snippet: TGFβ/SMAD signaling downregulates PD-L1 expression in vitro , yet SMAD4-intact tumors have higher expression of PD-L1 in vivo. (A) Non-malignant HPNE cells and human PDAC cell lines PANC-1, MIA PaCa-2, CaPan-1, CaPan-2, BxPC-3, and AsPC-1 were lysed and analyzed for basal expression of SMAD4, PD-L1, and HLA-A,B,C by western blot. (B-D) PANC-1, BxPC-3, and AsPC-1 cells were incubated with either a saline vehicle or 10ng/mL of recombinant TGFβ1 and evaluated after 24 hours by western blot. (E) PANC-1 and MIA PaCa-2 cells were incubated with either a control siRNA (siControl) or siRNA against SMAD4 (siSMAD4), and after 24 hours, CD274 (PD-L1) mRNA was evaluated by qPCR. (F, G) PANC-1 and MIA PaCa-2 cells were incubated with either siControl or siSMAD4 and, after 24 hours, stimulated with 10ng/mL of recombinant TGFβ1. Cells were lysed after another 24-hour period and evaluated by western blot analysis. (H) BxPC-3 cells were transfected with a wild-type SMAD4 plasmid (SMAD4 WT ). After 24 hours, cells were stimulated with 10ng/mL of recombinant TGFβ1 and evaluated by western blot analysis after another 24 hours. (I) Using the TCGA genomic database of pancreatic cancer patients (N=186), the 149 fully sequenced tumors were separated into two groups: those with no SMAD4 alteration (SMAD4 wild-type or WT), and those with presumptive SMAD4 loss via a known inactivating mutation, mRNA downregulation, and/or copy number deletion. We then compared the mRNA expression of CD274 in each group. (J) SMAD4 mRNA expression was plotted against that of CD274 . All mRNA expression values are plotted in log scale and are displayed with the associated p and Spearmen (S) coefficient values. (K) Excisional biopsies from two cohorts of PDAC patients (N=44 and N=36, respectively) were sectioned and stained via immunohistochemistry for SMAD4 or PD-L1. (L-N) Patients were grouped as being either SMAD4-expressing (SMAD4+) or SMAD4-non-expressing (SMAD4-), and the percent of each group also positive for PD-L1 displayed as a pie chart. (*p < 0.05).
Article Snippet: The pRK DPC4 Flag (SMAD4 WT ) plasmid has been previously reported , and was purchased from Addgene (Watertown, MA, plasmid #12627; http://n2t.net/addgene:12627 ; RRID: Addgene_12627), expanded in bacterial culture, purified using the Qiagen miniprep kit (Qiagen, Hilden, Germany), and used at a final concentration of 4μg per each well of a 6-well plate.
Techniques: Expressing, In Vitro, In Vivo, Western Blot, Incubation, Saline, Recombinant, Control, Transfection, Plasmid Preparation, Mutagenesis, Staining, Immunohistochemistry