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Genomic stratification based on SMAD4 in pancreatic cancer reveals biological implications of aberrant TGFβ signaling and susceptibility to TGFβ inhibition

ABSTRACT: Only 13% of newly diagnosed pancreatic cancer cases are surgically resectable, emphasizing the importance of systemic therapy. Yet, the 5-year overall survival rate for pancreatic cancer remains ~13%, underscoring the urgent need for new treatment strategies. TGFβ is a promising target due to its significant involvement in the desmoplasia, immune suppression, and chemoresistance characteristic of pancreatic cancer. Over 300 clinical trials targeting TGFβ have been conducted in unselected patient cohorts; however, none have gained FDA approval. Nevertheless, TGFβ blockade may hold promise for a subset of cancers with non-functional TGFβ signaling. Greater than 25% of pancreatic cancers carry mutations in SMAD4, a key component of canonical TGFβ signaling. In this study, we investigate the potential for stratifying patients based on SMAD4 mutational status to identify tumors susceptible to TGFβ inhibition. Analysis of SMAD4 expression in human pancreatic tumors reveals that SMAD4 mutation or loss is associated with worse disease-free survival. Intriguingly, we observe heterogeneity in intratumoral SMAD4 expression among human pancreatic cancer samples. To investigate the consequences of SMAD4 mutation, we employed SMAD4-deficient genetically engineered mouse models and orthotopic SMAD4 knockout models, which exhibited reduced survival, increased metastasis, and alterations in the tumor microenvironment compared to SMAD4 wildtype controls, consistent with gene and protein expression changes in the absence of functional SMAD4. Importantly, mice bearing SMAD4-deficient tumors treated with a blocking TGFβ antibody exhibited reduced tumor weight and improved survival. These findings suggest that targeting TGFβ signaling in TGFβ-deficient tumors has potential utility in pancreatic cancer.

ORGANISM(S): Mus musculus

PROVIDER: GSE296094 | GEO | 2025/05/15

REPOSITORIES: GEO

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Project description:Transforming growth factor beta (TGFβ) superfamily signaling is a prime inducer of epithelial-mesenchymal transitions (EMT) that foster cancer cell invasion and metastasis, a major cause of cancer-related deaths. Yet, TGFβ signaling is frequently inactivated in human tumor entities including colorectal cancer (CRC) and pancreatic adenocarcinoma (PAAD) with a high proportion of mutations incapacitating SMAD4, which codes for a transcription factor (TF) central to canonical TGFβ and bone morphogenetic protein (BMP) signaling. Beyond its role in initiating EMT, SMAD4 was reported to crucially contribute to subsequent gene regulatory events during EMT execution. It is therefore widely assumed that SMAD4-mutant (SMAD4mut) cancer cells are unable to undergo EMT. Here, we scrutinized this notion and probed for potential SMAD4-independent EMT execution using SMAD4mut CRC cell lines. We show that SMAD4mut cells exhibit morphological changes, become invasive, and regulate EMT marker genes upon induction of the EMT-TF SNAIL1. Furthermore, SNAIL1-induced EMT in SMAD4mut cells was found to be entirely independent of TGFβ/BMP receptor activity. Global assessment of the SNAIL1‑dependent transcriptome confirmed the manifestation of an EMT gene regulatory program in SMAD4mut cells highly related to established EMT signatures. Finally, analyses of human tumor transcriptomes showed that SMAD4 mutations are not underrepresented in mesenchymal tumor samples and that expression patterns of EMT‑associated genes are similar in SMAD4mut and SMAD4 wild-type cases. Altogether, our findings reveal considerable plasticity of gene regulatory networks operating in EMT execution and establish that EMT is not categorically precluded in SMAD4mut tumors, which is relevant for their diagnostic and therapeutic evaluation. To identify genes regulated during EMT execution in HT29 cells, two clonal HT29 cell populations (4F5 and 3C2) overexpressing Snail1-HA in a doxycycline (Dox)-inducible manner, as well as control cells were treated with Dox for different periods of time.

Project description:Chemoresistance to gemcitabine limits its clinical implementation for pancreatic ductal adenocarcinoma (PDAC). We previously generated an antibody drug conjugate (ADC) -like agent, EGFR/HER2 dual-targeting ligand-based lidamycin (DTLL), and studied the effect of DTLL combined with gemcitabine and the potential role of SMAD4 in the chemoresistance of PDAC. On the basis of SMAD4 profiles in in vitro and in vivo models, we investigated the antitumor effects of DTLL, gemcitabine and their combination, followed with mechanistic characterization. The results suggested that DTLL combination treatment with gemcitabine significantly repressed tumors with remarkably enhanced efficacy as compared to gemcitabine or DTLL alone given in either SMAD4-deficient/gemcitabine-resistant or SMAD4-sufficient/gemcitabine-sensitive cell line derived xenograft (CDX) and patient derived xenograft (PDX) tumors, respectively. Functional studies indicated that SMAD4 genetic status is responsible for SMAD4 protein level which determines different cellular susceptibility of PDAC. R100T mutation contributes to loss of SMAD4 protein and function with rapid protein degradation, leading to resistance to gemcitabine in PDAC cells. Moreover, DTLL significantly altered the protein half-life time and level of mutant and wild-type SMAD4 by inhibiting protein degradation at different velocities and distinctly changing the interaction of SMAD4 with TRIM33. Mechanism studies implied that DTLL combinational treatment might not only prevent from neoplastic proliferation via blockage of ATK/mTOR signaling and anti-apoptotic proteins (Bcl-2 and MCL1) mediated by impaired NF-B function in SMAD4-sufficient/gemcitabine-sensitive PDAC cells, but also restore the bioactivity of SMAD4 as a tumor suppressor to trigger its downstream NF-B-regulated signaling of cell apoptosis in SMAD4-deficient/gemcitabine-resistant tumors. In conclusion, SMAD4 is the key central mediator of not only the occurrence and development but also susceptibility in PDAC. DTLL sensitized gemcitabine efficacy via distinct action mechanisms based on SMAD4 profiles in SMAD4-sufficient/gemcitabine-sensitive and SMAD4-deficient/-resistant PDAC, respectively. Our findings provide insight into a rational SMAD4-directed precision treatment strategy and reveal a promising DTLL combination therapy to overcome chemoresistance in gemcitabine-resistant PDAC.

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Genomic stratification based on SMAD4 in pancreatic cancer reveals biological implications of aberrant TGFβ signaling and susceptibility to TGFβ inhibition

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