• IMMUNE NETWORK
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• v.14 no.6
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• pp.321-327
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• 2014

TGF-${\beta}$ induces IgA class switching by B cells. We previously reported that Smad3 and Smad4, pivotal TGF-${\beta}$ signal-transducing transcription factors, mediate germline (GL) ${\alpha}$ transcription induced by TGF-${\beta}1$, resulting in IgA switching by mouse B cells. Post-translational sumoylation of Smad3 and Smad4 regulates TGF-${\beta}$-induced transcriptional activation in certain cell types. In the present study, we investigated the effect of sumoylation on TGF-${\beta}1$-induced, Smad3/4-mediated $GL{\alpha}$ transcription and IgA switching by mouse B cell line, CH12F3-2A. Overexpression of small ubiquitin-like modifier (SUMO)-1, SUMO-2 or SUMO-3 did not affect TGF-${\beta}1$-induced, Smad3/4-mediated $GL{\alpha}$ promoter activity, expression of endogenous $GL{\alpha}$ transcripts, surface IgA expression, and IgA production. Next, we tested the effect of the E3 ligase PIASy on TGF-${\beta}1$-induced, Smad3/4-mediated $GL{\alpha}$ promoter activity. We found that PIASy overexpression suppresses the $GL{\alpha}$ promoter activity in cooperation with histone deacetylase 1. Taken together, these results suggest that SUMO itself does not affect regulation of $GL{\alpha}$ transcription and IgA switching induced by TGF-${\beta}1$/Smad3/4, while PIASy acts as a repressor.

• IMMUNE NETWORK
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• v.4 no.4
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• pp.216-223
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• 2004

Background: It is well known that IgA isotype switching is induced by $TGF-{\beta}1$. LPS-activated mouse normal B cells well differentiate into IgA secreting plasma cells under the influence of $TGF-{\beta}1$. Nevertheless, there are lots of difficulties in studying normal B cells in detail because it is not simple to obtain highly purified B cells, showing low reproducibility and transfection efficacy, moreover impossible to keep continuous culture. To overcome these obstacles, it is desperately needed to develop B cell line which acts like normal B cells. In the present study, we investigated whether CH12F3-2A lymphoma cells are appropriate for studying IgA isotype switching event. Methods: CH12F3-2A B cell line was treated with LPS and $TGF-{\beta}1$, then levels of germ-line (GL) transcripts were measured by RT-PCR, and $GL{\alpha}$ promoter activity was measured by luciferase assay. In addition, membrane IgA (mIgA) expression and IgA secretion were determined by FACS and ELISA, respectively. Results: $TGF-{\beta}1$, regardless of the presence of LPS, increased level of $GL{\alpha}$ transcripts but not $GL{\gamma}2b$ transcripts. However, IgA secretion was increased dramatically by co-stimulation of LPS and $TGF-{\beta}1$. Both mIgA and IgA secretion in the presence of $TGF-{\beta}1$ were further increased by over-expression of Smad3/4. Finally, $GL{\alpha}$ promoter activity was increased by $TGF-{\beta}1$. Conclusion: CH12F3-2A cell line acts quite similarly to the normal B cells which have been previously reported regarding IgA expression. Thus, CH12F3-2A lymphoma cell line appears to be adequate for the investigation of the mechanism(s) of IgA isotype switching at the cellular and molecular levels.

• BMB Reports
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• v.55 no.8
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• pp.401-406
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• 2022

Ahnak, a large protein first identified as an inhibitor of TGF-β signaling in human neuroblastoma, was recently shown to promote TGF-β in some cancers. The TGF-β signaling pathway regulates cell growth, various biological functions, and cancer growth and metastasis. In this study, we used Ahnak knockout (KO) mice that underwent a 70% partial hepatectomy (PH) to investigate the function of Ahnak in TGF-β signaling during liver regeneration. At the indicated time points after PH, we analyzed the mRNA and protein expression of the TGF -β/Smad signaling pathway and cell cycle-related factors, evaluated the cell cycle through proliferating cell nuclear antigen (PCNA) immunostaining, analyzed the mitotic index by hematoxylin and eosin staining. We also measured the ratio of liver tissue weight to body weight. Activation of TGF-β signaling was confirmed by analyzing the levels of phospho-Smad 2 and 3 in the liver at the indicated time points after PH and was lower in Ahnak KO mice than in WT mice. The expression levels of cyclin B1, D1, and E1; proteins in the Rb/E2F transcriptional pathway, which regulates the cell cycle; and the numbers of PCNA-positive cells were increased in Ahnak KO mice and showed tendencies opposite that of TGF-β expression. During postoperative regeneration, the liver weight to body weight ratio tended to increase faster in Ahnak KO mice. However, 7 days after PH, both groups of mice showed similar rates of regeneration, following which their active regeneration stopped. Analysis of hepatocytes undergoing mitosis showed that there were more mitotic cells in Ahnak KO mice, consistent with the weight ratio. Our findings suggest that Ahnak enhances TGF-β signaling during postoperative liver regeneration, resulting in cell cycle disruption; this highlights a novel role of Ahnak in liver regeneration. These results provide new insight into liver regeneration and potential treatment targets for liver diseases that require surgical treatment.

• Molecules and Cells
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• v.45 no.5
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• pp.329-342
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• 2022

The liver is the predominant metastatic site for pancreatic cancer. However, the factors that determine the liver metastasis and the specific molecular mechanisms are still unclear. In this study, we used human pancreatic cancer cell line Hs766T to establish Hs766T-L3, a subline of Hs766T with stable liver metastatic ability. We performed RNA sequencing of Hs766T-L3 and its parental cell line Hs766T, and revealed huge differences in gene expression patterns and pathway activation between these two cell lines. We correlated the difference in pathway activation with the expression of the four core transcriptional factors including STAT1, NR2F2, GATA2, and SMAD4. Using the TCGA database, we examined the relative expression of these transcription factors (TFs) in pan-cancer and their relationship with the prognosis of the pancreatic cancer. Among these TFs, we considered GATA2 is closely involved in tumor metastasis and may serve as a potential metastatic driver. Further in vitro and in vivo experiments confirmed that GATA2-mediated transcriptional activation of Notch3 promotes the liver metastasis of Hs766T-L3, and knockdown of either GATA2 or Notch3 reduces the metastatic ability of Hs766T-L3. Therefore, we claim that GATA2 may serve as a metastatic driver of pancreatic cancer and a potential therapeutic target to treat liver metastasis of pancreatic cancer.