ABSTRACT
BACKGROUND & AIMS: The highly heterogeneous cellular and molecular makeup of pancreatic ductal adenocarcinoma (PDAC) not only fosters exceptionally aggressive tumor biology, but contradicts the current concept of one-size-fits-all therapeutic strategies to combat PDAC. Therefore, we aimed to exploit the tumor biological implication and therapeutic vulnerabilities of a clinically relevant molecular PDAC subgroup characterized by SMAD4 deficiency and high expression of the nuclear factor of activated T cells (SMAD4-/-/NFATc1High). METHODS: Transcriptomic and clinical data were analyzed to determine the prognostic relevance of SMAD4-/-/NFATc1High cancers. In vitro and in vivo oncogenic transcription factor complex formation was studied by immunoprecipitation, proximity ligation assays, and validated cross model and species. The impact of SMAD4 status on therapeutically targeting canonical KRAS signaling was mechanistically deciphered and corroborated by genome-wide gene expression analysis and genetic perturbation experiments, respectively. Validation of a novel tailored therapeutic option was conducted in patient-derived organoids and cells and transgenic as well as orthotopic PDAC models. RESULTS: Our findings determined the tumor biology of an aggressive and chemotherapy-resistant SMAD4-/-/NFATc1High subgroup. Mechanistically, we identify SMAD4 deficiency as a molecular prerequisite for the formation of an oncogenic NFATc1/SMAD3/cJUN transcription factor complex, which drives the expression of RRM1/2. RRM1/2 replenishes nucleoside pools that directly compete with metabolized gemcitabine for DNA strand incorporation. Disassembly of the NFATc1/SMAD3/cJUN complex by mitogen-activated protein kinase signaling inhibition normalizes RRM1/2 expression and synergizes with gemcitabine treatment in vivo to reduce the proliferative index. CONCLUSIONS: Our results suggest that PDAC characterized by SMAD4 deficiency and oncogenic NFATc1/SMAD3/cJUN complex formation exposes sensitivity to a mitogen-activated protein kinase signaling inhibition and gemcitabine combination therapy.
Subject(s)
Carcinoma, Pancreatic Ductal , Pancreatic Neoplasms , Humans , Gemcitabine , Cell Line, Tumor , Pancreatic Neoplasms/drug therapy , Pancreatic Neoplasms/genetics , Pancreatic Neoplasms/metabolism , Carcinoma, Pancreatic Ductal/drug therapy , Carcinoma, Pancreatic Ductal/genetics , Carcinoma, Pancreatic Ductal/metabolism , Smad4 Protein/genetics , Smad4 Protein/metabolism , Mitogen-Activated Protein Kinases/metabolism , Smad3 Protein/metabolismABSTRACT
Recent new data in the pathogenesis of serous pelvic cancer and the introduction of serous tubal in situ carcinoma (STIC) and its precursors have raised the question that whether all primary peritoneal cancers (PPC) are in fact of tubal origin. Therefore, the present study evaluates the frequency of STIC and its precursor lesions in cases that were diagnosed as PPC using the morphologic criteria of the most recent WHO classification. The present study evaluates immunohistochemically (Ki-67 and p53 staining) the presence of STIC and its precursor lesions (p53 signature, serous tubal intraepithelial lesion [STIL]) in the completely processed Fallopian tubes of 46 consecutive PPCs. STIC was detected in 10 patients (21.7%) and p53 signature in 9 cases (19.6%). No STIL was observed. All except 1 STIC occurred at the fimbriated end of the Fallopian tube, and a bilateral involvement was detected in 2 cases. These precursor lesions were missed during the initial routine screening. Repeated staining for p53 was negative in STIC in 2 cases. STIC and p53 signature as precursor lesions of pelvic serous cancer are detected in some but not all the cases of primary serous peritoneal cancer. There might be the 2 different carcinogenetic pathways within PPC, and further studies are required to identify the source of serous cancer in cases without an STIC lesion.