Uncovering Tumor-Promoting Roles of Activin A in Pancreatic Ductal Adenocarcinoma

Activin A induces apoptosis of human lung adenocarcinoma A549 cells through endoplasmic reticulum stress pathway

Activin A, a member of the transforming growth factor‑β (TGF‑β) superfamily, has been implicated in the tumorigenesis and progression of various cancers. However, it remains unclear whether activin A induces apoptosis in human lung adenocarcinoma cells through the endoplasmic reticulum (ER) stress pathway. In the present study, BrdU, flow cytometry and western blotting were used to examine cell proliferation, apoptosis and protein expression, respectively. The present study revealed that activin A inhibited human lung adenocarcinoma A549 cell proliferation, induced apoptosis, and upregulated the protein levels of C/EBP homologous protein (CHOP), growth arrest and DNA damage‑inducible protein 34 (GADD34), cleaved‑caspase‑3 and caspase‑12. Furthermore, the administration of activin A did not alter the levels of suppressor of mothers against decapentaplegic 3 (Smad3) or phosphorylated (p)‑Smad3 proteins, whereas, it significantly elevated the levels of ActRIIA and p‑extracellular signal regulated kinase proteins 1 and 2 (ERK1/2) proteins in A549 cells. The apoptotic effects of activin A on A549 cells were attenuated by the ERK inhibitor FR180204, which also downregulated CHOP and caspase‑12 protein levels. Additionally, activin A increased intracellular calcium flux in A549 cells, and the calcium ion chelator BAPTA acetoxymethyl ester (BAPTA‑AM) inhibited activin A‑induced A549 cell apoptosis, whereas the calcium agonist ionomycin significantly increased apoptosis of A549 cells induced by activin A. These findings indicated that the activation of the ER stress pathway resulting in apoptosis of A549 cells triggered by activin A is facilitated by the ActRIIA‑ERK1/2 signaling and calcium signaling. The present findings suggest that the agonists of ERK and calcium signaling exhibit promising clinical therapeutic potential for the induction of apoptosis in lung adenocarcinoma.

Oncogenic KRAS, Mucin 4, and Activin A-Mediated Fibroblast Activation Cooperate for PanIN Initiation

Over 90% of patients with pancreatic ductal adenocarcinoma (PDAC) have oncogenic KRAS mutations. Nevertheless, mutated KRAS alone is insufficient to initiate pancreatic intraepithelial neoplasia (PanIN), the precursor of PDAC. The identities of the other factors/events required to drive PanIN formation remain elusive. Here, optic-clear 3D histology is used to analyze entire pancreases of 2-week-old Pdx1-Cre; LSL-KrasG12D/+ (KC) mice to detect the earliest emergence of PanIN and observed that the occurrence is independent of physical location. Instead, it is found that the earliest PanINs overexpress Muc4 and associate with αSMA+ fibroblasts in both transgenic mice and human specimens. Mechanistically, KrasG12D/+ pancreatic cells upregulate Muc4 through genetic alterations to increase proliferation and fibroblast recruitments via Activin A secretion and consequently enhance cell transformation for PanIN formation. Inhibition of Activin A signaling using Follistatin (FST) diminishes early PanIN-associated fibroblast recruitment, effectively curtailing PanIN initiation and growth in KC mice. These findings emphasize the vital role of interactions between oncogenic KrasG12D/+ -driven genetic alterations and induced microenvironmental changes in PanIN initiation, suggesting potential avenues for early PDAC diagnostic and management approaches.

Non-Canonical Activin A Signaling Stimulates Context-Dependent and Cellular-Specific Outcomes in CRC to Promote Tumor Cell Migration and Immune Tolerance

We have shown that activin A (activin), a TGF-β superfamily member, has pro-metastatic effects in colorectal cancer (CRC). In lung cancer, activin activates pro-metastatic pathways to enhance tumor cell survival and migration while augmenting CD4+ to CD8+ communications to promote cytotoxicity. Here, we hypothesized that activin exerts cell-specific effects in the tumor microenvironment (TME) of CRC to promote anti-tumoral activity of immune cells and the pro-metastatic behavior of tumor cells in a cell-specific and context-dependent manner. We generated an Smad4 epithelial cell specific knockout (Smad4-/-) which was crossed with TS4-Cre mice to identify SMAD-specific changes in CRC. We also performed IHC and digital spatial profiling (DSP) of tissue microarrays (TMAs) obtained from 1055 stage II and III CRC patients in the QUASAR 2 clinical trial. We transfected the CRC cells to reduce their activin production and injected them into mice with intermittent tumor measurements to determine how cancer-derived activin alters tumor growth in vivo. In vivo, Smad4-/- mice displayed elevated colonic activin and pAKT expression and increased mortality. IHC analysis of the TMA samples revealed increased activin was required for TGF-β-associated improved outcomes in CRC. DSP analysis identified that activin co-localization in the stroma was coupled with increases in T-cell exhaustion markers, activation markers of antigen presenting cells (APCs), and effectors of the PI3K/AKT pathway. Activin-stimulated PI3K-dependent CRC transwell migration, and the in vivo loss of activin lead to smaller CRC tumors. Taken together, activin is a targetable, highly context-dependent molecule with effects on CRC growth, migration, and TME immune plasticity.

[ZEB2 Regulates the Migration and Invasion of PANC-1 Pancreatic Cancer Cells: An Experimental Study]

Objective

To investigate the effects and mechanisms of zinc finger E-box binding homeobox transcription factor-2 ( ZEB2) on the proliferation, colony formation, migration, and invasion abilities and the epithelial-mesenchymal transition (EMT) of PANC-1 cells, a human pancreatic cancer cell line.

Methods

Data on the expression of ZEB2 in pancreatic cancer tissues and paracancerous tissues from The Cancer Genome Atlas (TCGA) database were analyzed. PANC-1 pancreatic cancer cells were divided into si-NC group, si- ZEB2 group, pcDNA3.1 group, and pcDNA3.1- ZEB2 group. qRT-PCR and Western blot were conducted to confirm the effectiveness of ZEB2 knockdown or overexpression. CCK-8, colony formation, wound healing, and Transwell assays were conducted to examine the effects of ZEB2 on the proliferation, colony formation, migration, and invasion of PANC-1 cells. qRT-PCR and immunofluorescence assays were performed to examine the expression of E-cadherin and vimentin, the EMT markers, in the cells. Prediction of proteins interacting with ZEB2 was made through the STRING database.

Results

TCGA database analysis showed that the expression level of ZEB2 in pancreatic cancer tissues was significantly higher than that in adjacent tissues ( P<0.05). Compared with those of cells in the control group, the proliferation, colony formation, migration, and invasion of cells in the si- ZEB2 group were decreased ( P<0.05). Compared with those of cells in the pcDNA3.1 group, the proliferation, colony formation, migration and invasion of cells in the pcDNA3.1- ZEB2 group were increased (all P<0.05). According to the results of qRT-PCR and immunofluorescence assays, compared with those of the si-NC group, the expression of E-cadherin mRNA, an epithelial marker, in the si- ZEB2 group increased, while the expression of vimentin mRNA, an mesenchymal marker, and the protein decreased. Compared with those of the pcDNA3.1 group, the expression of E-cadherin mRNA in the PANC-1 cells of the pcDNA3.1- ZEB2 group decreased, while the expression of vimentin mRNA and the protein increased (all P<0.05). Analysis with the STRING database predicted that 10 proteins had close interaction with ZEB2.

Conclusion

Overexpression of ZEB2 promotes the migration, invasion, and the EMT process of PANC-1 pancreatic cancer cells.