Hong Jian Xie

HDAC2 overexpression confers oncogenic potential to human lung cancer cells by deregulating expression of apoptosis and cell cycle proteins

Histone deacetylase 2 (HDAC2) is crucial for embryonic development, affects cytokine signaling relevant for immune responses, and is often significantly overexpressed in solid tumors, but little is known of its role in human lung cancer. In this study, we demonstrated the aberrant expression of HDAC2 in lung cancer tissues and investigated oncogenic properties of HDAC2 in human lung cancer cell lines. HDAC2 inactivation resulted in regression of tumor cell growth and activation of cellular apoptosis via p53 and Bax activation and Bcl2 suppression. In cell cycle regulation, HDAC2 inactivation caused induction of p21WAF1/CIP1 expression, and simultaneously suppressed the expressions of cyclin E2, cyclin D1, and CDK2, respectively. Consequently, this led to the hypophosphorylation of pRb protein in G1/S transition and thereby inactivated E2F/DP1 target gene transcriptions of A549 cells. In addition, we demonstrated that HDAC2 directly regulated p21WAF1/CIP1 expression in a p53‐independent manner. However, HDAC1 was not related to p21WAF1/CIP1 expression and tumorigenesis of lung cancer. Lastly, we observed that sustained‐suppression of HDAC2 in A549 lung cancer cells attenuated in vitro tumorigenic properties and in vivo tumor growth of the mouse xenograft model. Taken together, we suggest that the aberrant regulation of HDAC2 and its epigenetic regulation of gene transcription in apoptosis and cell cycle components play an important role in the development of lung cancer. J. Cell. Biochem. 113: 2167–2177, 2012.

HDAC1 inactivation induces mitotic defect and caspase-independent autophagic cell death in liver cancer

Histone deacetylases (HDACs) are known to play a central role in the regulation of several cellular properties interlinked with the development and progression of cancer. Recently, HDAC1 has been reported to be overexpressed in hepatocellular carcinoma (HCC), but its biological roles in hepatocarcinogenesis remain to be elucidated. In this study, we demonstrated overexpression of HDAC1 in a subset of human HCCs and liver cancer cell lines. HDAC1 inactivation resulted in regression of tumor cell growth and activation of caspase-independent autophagic cell death, via LC3B-II activation pathway in Hep3B cells. In cell cycle regulation, HDAC1 inactivation selectively induced both p21WAF1/Cip1 and p27Kip1 expressions, and simultaneously suppressed the expression of cyclin D1 and CDK2. Consequently, HDAC1 inactivation led to the hypophosphorylation of pRb in G1/S transition, and thereby inactivated E2F/DP1 transcription activity. In addition, we demonstrated that HDAC1 suppresses p21WAF1/Cip1 transcriptional activity through Sp1-binding sites in the p21WAF1/Cip1 promoter. Furthermore, sustained suppression of HDAC1 attenuated in vitro colony formation and in vivo tumor growth in a mouse xenograft model. Taken together, we suggest the aberrant regulation of HDAC1 in HCC and its epigenetic regulation of gene transcription of autophagy and cell cycle components. Overexpression of HDAC1 may play a pivotal role through the systemic regulation of mitotic effectors in the development of HCC, providing a particularly relevant potential target in cancer therapy.

Aberrant Regulation of HDAC2 Mediates Proliferation of Hepatocellular Carcinoma Cells by Deregulating Expression of G1/S Cell Cycle Proteins

Histone deacetylase 2 (HDAC2) is crucial for embryonic development, affects cytokine signaling relevant for immune responses and is often significantly overexpressed in solid tumors; but little is known about its role in human hepatocellular carcinoma (HCC). In this study, we showed that targeted-disruption of HDAC2 resulted in reduction of both tumor cell growth and de novo DNA synthesis in Hep3B cells. We then demonstrated that HDAC2 regulated cell cycle and that disruption of HDAC2 caused G1/S arrest in cell cycle. In G1/S transition, targeted-disruption of HDAC2 selectively induced the expression of p16INK4A and p21WAF1/Cip1, and simultaneously suppressed the expression of cyclin D1, CDK4 and CDK2. Consequently, HDAC2 inhibition led to the down-regulation of E2F/DP1 target genes through a reduction in phosphorylation status of pRb protein. In addition, sustained suppression of HDAC2 attenuated in vitro colony formation and in vivo tumor growth in a mouse xenograft model. Further, we found that HDAC2 suppresses p21WAF1/Cip1 transcriptional activity via Sp1-binding site enriched proximal region of p21WAF1/Cip1 promoter. In conclusion, we suggest that the aberrant regulation of HDAC2 may play a pivotal role in the development of HCC through its regulation of cell cycle components at the transcription level providing HDAC2 as a relevant target in liver cancer therapy.

Targeted disruption of Nemo-like kinase inhibits tumor cell growth by simultaneous suppression of cyclin D1 and CDK2 in human hepatocellular carcinoma

The Wnt/β‐catenin signaling pathway regulates various aspects of development and plays important role in human carcinogenesis. Nemo‐like kinase (NLK), which is mediator of Wnt/β‐catenin signaling pathway, phosphorylates T‐cell factor/lymphoid enhancer factor (TCF/LEF) factor and inhibits interaction of β‐catenin/TCF complex. Although, NLK is known to be a tumor suppressor in Wnt/β‐catenin signaling pathway of colon cancer, the other events occurring downstream of NLK pathways in other types of cancer remain unclear. In the present study, we identified that expression of NLK was significantly up‐regulated in the HCCs compared to corresponding normal tissues in five selected tissue samples. Immunohistochemical analysis showed significant over‐expression of NLK in the HCCs. Targeted‐disruption of NLK suppressed cell growth and arrested cell cycle transition. Suppression of NLK elicited anti‐mitogenic properties of the Hep3B cells by simultaneous inhibition of cyclinD1 and CDK2. The results of this study suggest that NLK is aberrantly regulated in HCC, which might contribute to the mitogenic potential of tumor cells during the initiation and progression of hepatocellular carcinoma; this process appears to involve the induction of CDK2 and cyclin D1 and might provide a novel target for therapeutic intervention in patients with liver cancer. J. Cell. Biochem. 110: 687–696, 2010.

Identification of characteristic molecular signature for volatile organic compounds in peripheral blood of rat.

In a previous report we demonstrated that the transcriptomic response of liver tissue was specific to toxicants, and a characteristic molecular signature could be used as an early prognostic biomarker in rats. It is necessary to determine the transcriptomic response to toxicants in peripheral blood for application to the human system. Volatile organic compounds (VOCs) comprise a major group of pollutants which significantly affect the chemistry of the atmosphere and human health. In this study we identified and validated the specific molecular signatures of toxicants in rat whole blood as early predictors of environmental toxicants. VOCs (dichloromethane, ethylbenzene, and trichloroethylene) were administered to 11-week-old SD male rats after 48h of exposure, peripheral whole blood was subjected to expression profiling analysis. Unsupervised gene expression analysis resulted in a characteristic molecular signature for each toxicant, and supervised analysis identified 1,217 outlier genes as distinct molecular signatures discerning VOC exposure from healthy controls. Further analysis of multi-classification suggested 337 genes as early detective molecular markers for three VOCs with 100% accuracy. A large-scale gene expression analysis of a different VOC exposure animal model suggested that characteristic expression profiles exist in blood cells and multi-classification of this VOC-specific molecular signature can discriminate each toxicant at an early exposure time. This blood expression signature can thus be used as discernable surrogate marker for detection of biological responses to VOC exposure in an environment.

Overexpression of SIRT2 contributes tumor cell growth in hepatocellular carcinomas

The mammalian homolog of yeast Sir2 protein is the sirtuin family of histone deacetylases (HDACs), a NAD+-dependent protein deacetylase in humans. Accumulating evidence suggests that sirtuin 2 (SIRT2) co-localizes with the microtubule network and deacetylates α-tubulin, and is involved in various cellular processes including calorie restriction-dependent life span extension, mitotic cell cycle regulation, cellular apoptosis, DNA damage repair, and genomic silencing. However, the underlying mechanisms of action remains poorly understood, especially in hepatocarcinogenesis. Hence in this study, to determine the association between the aberrant expression of SIRT2 and liver cancer development and progression, SIRT2 expression was investigated in ten selected hepatocellular carcinoma (HCC) tissues and matched normal liver tissues, using RT-PCR and Western blot analysis. Next, SIRT2 was disrupted by siRNA-mediated protein knockdown method to investigate the biological role of SIRT2 in hepatocarcinogenesis in Hep3B cells. As a result, we identified that SIRT2 expression was significantly up-regulated in HCC tissues compared to corresponding normal liver tissues. In addition, suppression of SIRT2 caused regression of tumor cell growth and proliferation. We also found that SIRT2 could interact with α-tubulin and regulates the acetylation status of α-tubulin in Hep3B cells. In conclusion, we suggest that SIRT2 is aberrantly regulated in HCCs which may contribute to the mitogenic potential of tumor cells during the development and progression of HCC, and could be a novel molecular target for therapeutic intervention in liver cancer.

Decreased expression of TFF2 and gastric carcinogenesis

The trefoil factor family (TFF) of peptides, which are protease-resistant and have a strong affinity for mucins, play an important role in gastrointestinal mucosal protection and restitution. Prior studies have indicated that dysregulation of TFF2 was associated with cell migration, resistance to apoptosis, and gastric cancer invasion; however, the underlying mechanism associated with these actions remains unclear. Thus, to investigate the relationship between TFF2 and carcinogenesis in gastric cancer, TFF2 expression was analyzed by Western blot analysis in nine selected gastric cancer tissues and immunohistochemical staining was performed in paraffin-embedded samples from 157 gastric cancers. A reduced TFF2 expression was observed by Western blot analysis in the gastric cancer tissues. However, there was no significant difference in the TFF2 expression according to clinical and pathological parameters of the gastric cancers. To investigate the biological role of TFF2 in the development and progression of gastric cancer, a TFF2 expression plasmid was constructed for in vitro experiments of function. Introduction of TFF2 cDNA into a gastric cancer cell line did not affect tumor cell growth, cell migration or invasion. In conclusion, down-regulation of TFF2 in gastric cancer cells and restoration of TFF2 did not affect the tumorigenic potential of gastric cancer cells in vitro. The loss of TFF2 expression might be an early event of the multi-step process of gastrocarcinogenesis and may play a limited role in the mucosal protection of the normal gastric physiology.

Abstract 1079: Targeted disruption of Nemo-like kinase inhibits tumor cell growth by simultaneous suppression of cyclin D1 and CDK2 in human hepatocellular carcinoma

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC The wnt/β-catenin signaling pathway regulates various aspects of development and plays important role in human carcinogenesis. Nemo-like kinase (NLK), which is mediator of wnt/β-catenin signaling pathway, phosphorylates T-cell factor/lymphoid enhancer factor (TCF/LEF) factor and inhibits interaction of β-catenin/TCF complex. Although, NLK is known to be a tumor suppressor in wnt/β-catenin signaling pathway of colon cancer, the other events occurring downstream of NLK pathways in other types of cancer remain unclear. In the present study, we identified that expression of NLK was significantly up-regulated in the HCCs compared to corresponding normal tissues in five selected tissue samples. Immunhistochemical analysis showed significant over-expression of NLK in the HCCs. Targeted-disruption of NLK suppressed cell growth and arrested cell-cycle transition. Suppression of NLK elicited anti-mitogenic properties of the Hep3B cells by simultaneous inhibition of cyclinD1 and CDK2. The results of this study suggest that NLK is aberrantly regulated in HCC, which might contribute to the mitogenic potential of tumor cells during the initiation and progression of hepatocellular carcinoma; this process appears to involve the induction of CDK2 and cyclin D1 and might provide a novel target for therapeutic intervention in patients with liver cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1079.