Biomedical subjects

Tong Tong

Publications and source records attributed to Tong Tong.

11 recordsLinked to original sources

PubMed2026

A Foundation Model Based CT Biomarker for Non-Invasive Prediction of Response to Neoadjuvant Immunochemotherapy in Non-Small Cell Lung Cancer.

Predicting pathological complete response (pCR) to neoadjuvant immunochemotherapy in non-small cell lung cancer (NSCLC) is clinically important yet remains challenging. Here, we introduce a foundation model-derived computed tomography (CT) imaging biomarker established from a multi-center cohort of 702 patients. Specifically, we developed and validated a non-invasive baseline CT-based model for risk stratification of pathological response. To address scanner and protocol heterogeneity, we first built a 3D Vision Mamba-based CT super-resolution model trained on 2494 cases for image standardization. We then fine-tuned a lung cancer-specific CT foundation model from a pretrained 3D model (VoCo) using 6643 chest CT scans. Finally, we constructed a multi-task Swin Transformer that jointly performs risk stratification and segments tumors to generate the imaging biomarker. Across five centers, the model achieved consistently strong generalization (AUC: 0.75-0.87) for pCR prediction. Genomic analysis revealed that the biomarker was independent of tumor mutational burden but significantly associated with TP53 mutations, suggesting an association with a radiogenomic phenotype related to this alteration. Together, these results demonstrate a generalizable and biologically meaningful foundation model-based biomarker for non-invasive risk stratification of pathological response in NSCLC.

Female↗

PubMed2006

Tissue microarray analysis reveals a tight correlation between protein expression pattern and progression of esophageal squamous cell carcinoma.

BACKGROUND: The development of esophageal squamous cell carcinoma (ESCC) progresses a multistage process, collectively known as precursor lesions, also called dysplasia (DYS) and carcinoma in situ (CIS), subsequent invasive lesions and final metastasis. In this study, we are interested in investigating the expression of a variety of functional classes of proteins in ESCC and its precursor lesions and characterizing the correlation of these proteins with ESCC malignant progression. METHODS: Fas, FADD, caspase 8, CDC25B, fascin, CK14, CK4, annexin I, laminin-5gamma2 and SPARC were analyzed using immunohistochemistry on tissue microarray containing 205 ESCC and 173 adjacent precursor lesions as well as corresponding normal mucosa. To confirm the immunohistochemical results, three proteins, fascin, CK14 and laminin-5gamma2, which were overexpressed in ESCC on tissue microarray, were detected in 12 ESCC cell lines by Western blot assay. RESULTS: In ESCC and its precursor lesions, FADD, CDC25B, fascin, CK14, laminin-5gamma2 and SPARC were overexpressed, while Fas, caspase 8, CK4 and annexin I were underexpressed. The abnormalities of these proteins could be classified into different groups in relation to the stages of ESCC development. They were "early" corresponding to mild and moderate DYS with overexpression of fascin, FADD and CDC25B and underexpression of Fas, caspase 8, CK4 and annexin I, "intermediate" to severe DYS and CIS with overexpression of FADD and CK14, and "late" to invasive lesions (ESCC) and to advanced pTNM stage ESCC lesions with overexpression of CK14, laminin-5gamma2 and SPARC. CONCLUSION: Analyzing the protein expression patterns of Fas, FADD, caspase 8, CDC25B, fascin, CK14, CK4, annexin I, laminin-5gamma2 and SPARC would be valuable to develop rational strategies for early detection of lesions at risk in advance as well as for prevention and treatment of ESCC.

Adult↗

PubMed2006

Gadd45a interacts with aurora-A and inhibits its kinase activity.

Centrosome stability is required for successful mitosis in mammalian cells. Amplification of the centrosome leads to chromosomal missegregation and generation of aneuploidy, which are closely associated with cell transformation and tumorigenesis (Doxsey, S. J. (2001) Nat. Cell Biol. 3, E105-E108; Hinchcliffe, E. H., and Sluder, G. (2001) Genes Dev. 15, 1167-1181; Pihan, G. A., Purohit, A., Wallace, J., Malhotra, R., Liotta, L., and Doxsey, S. J. (2001) Cancer Res. 61, 2212-2219). However, there are currently limited insights into mechanism(s) for this critical biological event. Here we show that Gadd45a, a DNA damage-inducible protein that is regulated by tumor suppressors p53 and BRCA1, participates in the maintenance of centrosome stability. Mouse embryonic fibroblasts derived from gadd45a knock-out mice exhibit centrosome amplification (designated as increased centrosome numbers). Introduction of exogenous Gadd45a into mouse embryonic fibroblasts isolated from gadd45a-null mice substantially restored the normal centrosome profile. In contrast to p21(waf1/cip1), which ensures coordinated initiation of centrosome, Gadd45a had no significant effect on centrosome duplication in S phase. Interestingly Gadd45a was found to physically associate with Aurora-A protein kinase, whose deregulated expression results in centrosome abnormality. Furthermore Gadd45a was demonstrated to strongly inhibit Aurora-A kinase activity and to antagonize Aurora-A-induced centrosome amplification. These findings identify a novel mechanism for Gadd45a in the maintenance of centrosome stability and broaden understandings of p53- and BRCA1-regulated signaling pathways in maintaining genomic fidelity.

Animals↗

PubMed2005

Gadd45a expression induces Bim dissociation from the cytoskeleton and translocation to mitochondria.

Gadd45a, a p53- and BRCA1-regulated stress protein, has been implicated in the maintenance of genomic fidelity, probably through its roles in the control of cell cycle checkpoint and apoptosis. However, the mechanism(s) by which Gadd45a is involved in the induction of apoptosis remains unclear. We show here that inducible expression of Gadd45a protein causes dissociation of Bim, a Bcl2 family member, from microtubule-associated components and translocation to mitochondria. The Bim accumulation in mitochondria enhances interaction of Bim with Bcl-2, relieves Bax from Bcl-2-bound complexes, and subsequently results in release of cytochrome c into the cytoplasm. Suppression of endogenous Bim greatly inhibits Gadd45a induction of apoptosis. Interestingly, Gadd45a interacts with elongation factor 1alpha (EF-1alpha), a microtubule-severing protein that plays an important role in maintaining cytoskeletal stability, and inhibits EF-1alpha-mediated microtubule bundling, indicating that the interaction of Gadd45a with EF-1alpha disrupts cytoskeletal stability. A mutant form of Gadd45a harboring a deletion of EF-1alpha-binding domain fails to inhibit microtubule stability and to induce Bim translocation to mitochondria. Furthermore, coexpression of EF-1alpha antagonizes Gadd45a's property of suppressing cell growth and inducing apoptosis. These findings identify a novel link that connects stress protein Gadd45a to the apoptotic machinery and address the importance of cytoskeletal stability in apoptotic response to DNA damage.

Apoptosis↗

PubMed2004

Overexpression of Aurora-A contributes to malignant development of human esophageal squamous cell carcinoma.

PURPOSE: Aurora-A/STK15/BTAK, a centrosome-associated oncogenic protein, is implicated in the control of mitosis. Overexpression of Aurora-A has been shown to result in chromosomal aberration and genomic instability. Multiple lines of evidence indicate that Aurora-A induces cell malignant transformation. In the current study, we are interested in investigating the expression of Aurora-A in human esophageal squamous cell carcinoma (ESCC) and characterizing the association of Aurora-A with ESCCmalignant progression. EXPERIMENTAL DESIGN: Aurora-A protein expression was examined in 84 ESCC tissues and 81 paired normal adjacent tissues by either immunohistochemistry or Western blot analysis. In addition, a gene-knockdown small interfering RNA technique was used in ESCC cells to investigate whether Aurora-A contributes to the ability of a tumor to grow invasively. RESULTS: The amount of Aurora-A protein in ESCC was considerably higher than that in normal adjacent tissues. Overexpression of Aurora-A was observed in 57 of 84 (67.5%) ESCC samples. In contrast, <2% of normal adjacent tissue displayed high expression of Aurora-A. Interestingly, overexpression of Aurora-A seemed to correlate with the invasive malignancy of ESCC. Disruption of endogenous Aurora-A using small interfering RNA technique substantially suppressed cell migrating ability. CONCLUSION: The findings presented in this report show that Aurora-A expression is elevated in human esophageal squamous cell carcinoma and is possibly associated with tumor invasion, indicating that overexpression of Aurora-A may contribute to ESCC occurrence and progression.

Aurora Kinase A↗

PubMed2004

[Gadd45 mediated G2/M cell cycle arrest induced by BRCA1].

BACKGROUND & OBJECTIVE: It is considered that tumor suppressor gene BRCA1 is an important factor in the regulation of cell cycle checkpoint, but the molecular mechanism by which BRCA1 regulates cell cycle G(2)/M arrest is less known. The objective of this study was to investigate the effects of Gadd45 on the BRCA1-induced cell growth suppression. METHODS: BRCA1 induction of Gadd45 protein was analyzed using Western-blot assay following cells transfection with BRCA1 expression vector and cell sorting. Activation of the Gadd45 promoter by BRCA1 was determined by CAT assay. Effect of antisense Gadd45 on the BRCA1-induced cell cycle G(2)-M arrest was examined by flow cytometry analysis. And the effects of antisense Gadd45 on BRCA1-mediated growth suppression in HeLa and HCT116 cell lines was determined by colony formation assay. RESULTS: Gadd45 protein was highly induced after expression of BRCA1. BRCA1 strongly activated the Gadd45 promoter. Antisense Gadd45 substantially abrogated BRCA1-activated cell cycle G(2)-M arrest and BRCA1-induced cell growth suppression on HeLa and HCT116 cell lines. CONCLUSION: Gadd45 is a BRCA1-regulated downstream gene and mediates the role of BRCA1 in the control of cell cycle G(2)/M arrest and growth suppression.

BRCA1 Protein↗

PubMed2003

Gadd45a contributes to p53 stabilization in response to DNA damage.

p53 is an important molecule in cellular response to DNA damage. After genotoxic stress, p53 protein stabilizes transiently and accumulates in the nucleus, where it functions as a transcription factor and upregulates multiple downstream-targeted genes, including p21(Waf1/Cip1), Gadd45a and Bax. However, regulation of p53 stabilization is complex and may mainly involve post-translational modification of p53, such as phosphorylation and acetylation. Using mouse embryonic fibroblasts (MEFs) derived from Gadd45a knockouts, we found that disruption of Gadd45a greatly abolished p53 protein stabilization following UVB treatment. Phosphorylation of p53 at Ser-15 was substantially reduced in Gadd45a-/- MEFs. In addition, p53 induction by UVB was shown to be greatly abrogated in the presence of p38 kinase inhibitor, but not c-Jun N-terminal kinase (JNK) and extracellular-signal regulated kinase (ERK), suggesting that p38 protein kinase is involved in the regulation of p53 induction. Along with the findings presented above, inducible expression of Gadd45a enhanced p53 accumulation after cell exposure to UVB. Taken together, the current study demonstrates that Gadd45a, a conventional downstream gene of p53, may play a role as an upstream effector in p53 stabilization following DNA damage, and thus has defined a positive feedback signal in the activation of the p53 pathway.

Animals↗

PubMed2003

[Suppression of HCT116 growth of cells by Gadd45].

OBJECTIVE: To study the mechanism of suppression of growth of HCT116 human colon carcinoma cells by Gadd45 gene. METHODS: HCT116 human colon carcinoma cells were transfected with pTRE-Gadd45 vector so as to establish Gadd45-inducible cell line that was cultured in medium with tetracycline. Then tetracycline was withdrawn. The number of cell clones was counted. Flow cytometry was used to detect the percentages of cells at the G1, S, and G2-M phases. TUNEL technique was used to detect the apoptosis of cells. Western blotting was used to analyze the expression of Gadd45 protein, and apoptosis-related proteins: poly-ADP-ribose polymerase (PARP), and caspase 3 protein. RESULTS: Gadd45 protein was not expressed in the HCT116 cells cultured in the medium with tetracycline, however, it was expressed with a gradually increased level in the cells cultured in the medium from which tetracycline was withdrawn, The clone formation rate of HCT116 cells was 100% in the medium with tetracycline, however, was only 14.2% in the medium with tetracycline withdrawal, with a suppression rate of more than 85%. The percentage of cells in G(2)-M phase was significantly increased in the cells cultured in the medium with tetracycline withdrawal. 24-36 hours after the withdrawal of tetracycline, PARP and caspase 3 protein were activated remarkably. CONCLUSION: High expression of Gadd45 inhibits the growth of HCT116 cells, through inducing G2-M arrest and activating apoptotic pathway.

Blotting, Western↗

PubMed2002

GADD45-induced cell cycle G2-M arrest associates with altered subcellular distribution of cyclin B1 and is independent of p38 kinase activity.

In response to DNA damage, the cell cycle checkpoint is an important biological event in maintaining genomic fidelity. Gadd45, a p53-regulated and DNA damage inducible protein, has recently been demonstrated to play a role in the G2-M checkpoint in response to DNA damage. In the current study, we further investigated the biochemical mechanism(s) involved in the GADD45-activated cell cycle G2-M arrest. Using the tetracycline-controlled system (tet-off), we established GADD45-inducible lines in HCT116 (wild-type p53) and Hela (inactivated p53 status) cells. Following inducible expression of the Gadd45 protein, cell growth was strongly suppressed in both HCT116 and Hela cells. Interestingly, HCT116 cells revealed a significant G2-M arrest but Hela cells failed to arrest at the G2-M phases, indicating that the GADD45-activated G2-M arrest requires normal p53 function. The GADD45-induced G2-M arrest was observed independent of p38 kinase activity. Importantly, induction of Gadd45 protein resulted in a reduction of nuclear cyclin B1 protein, whose nuclear localization is critical for the completion of G2-M transition. The reduced nuclear cyclin B1 levels correlated with inhibition of Cdc2/cyclin B1 kinase activity. Additionally, overexpression of cyclin B1 substantially abrogated the GADD45-induced cell growth suppression. Therefore, GADD45 inhibition of Cdc2 kinase activity through alteration of cyclin B1 subcellular localization may be an essential step in the GADD45-induced cell cycle G2-M arrest and growth suppression.

Checkpoint Kinase 1↗

PubMed2002

ATF3 induction following DNA damage is regulated by distinct signaling pathways and over-expression of ATF3 protein suppresses cells growth.

Mammalian cells have a remarkable diverse repertoire of response to genotoxic stress that damage DNA. Cellular responses to DNA damaging agents will initially exhibit gene induction, which is regulated by complex mechanism(s) and probably involves multiple signaling pathways. In this paper, we demonstrate that induction of ATF3 protein, a member of the ATF/CREB family of transcription factors, by ionizing radiation (IR) requires normal cellular p53 function. In contrast, induction of ATF3 after UV radiation (UV) or Methyl methanesulphonate (MMS) is independent of p53 status. Induction of ATF3 by DNA damage is rapid, transient, and through a transcriptional mechanism. The ATF3 promoter is induced by UV and MMS, but not by IR. In addition, ATF3 promoter can be activated by MEKK1, an upstream activator of the ERK and JNK kinase pathway, but not induced following p53 expression. Those results indicate that regulation of ATF3 induction after DNA damage utilizes both the p53-dependent and -independent pathways, and may also involve MAP kinase signaling pathways. Using the tetracycline-inducible system (tet-off), we have found that over-expression of ATF3 protein moderately suppresses cell growth. Interestingly, over-expression of ATF3 protein is able to slow down progression of cells from G1 to S phase, indicating that ATF3 protein might play a negative role in the control of cell cycle progression.

Activating Transcription Factor 3↗

PubMed2002

BRCA1 regulates GADD45 through its interactions with the OCT-1 and CAAT motifs.

BRCA1, a breast and ovarian cancer susceptibility gene, has been implicated in gene regulation. Previous studies demonstrate that BRCA1 induces GADD45, a p53-regulated and stress-inducible gene that plays an important role in cellular response to DNA damage. However, the mechanism(s) by which BRCA1 regulates GADD45 remains unclear. In this report, we have shown that BRCA1 activation of the GADD45 promoter is mediated through the OCT-1 and CAAT motifs located at the GADD45 promoter region. Site-directed mutations of both OCT-1 and CAAT motifs abrogate induction of the GADD45 promoter by BRCA1. Both OCT-1 and CAAT motifs are able to confer BRCA1 inducibility in a non-related minimal promoter. Physical associations of BRCA1 protein with transcription factors Oct-1 and NF-YA, which directly bind to the OCT-1 and CAAT motifs, are established by biotin-streptavidin pull-down and coimmunoprecipitation assays. Such protein interactions are required for interaction of BRCA1 with the GADD45 promoter because either immunodepletion of Oct-1 and NF-YA proteins or mutations in the OCT-1 and CAAT motifs disrupt BRCA1 binding to the GADD45 promoter. These findings indicate that BRCA1 can up-regulate its targeted genes through protein-protein interactions and provide a novel mechanism by which BRCA1 participates in transcriptional regulation.

Amino Acid Motifs↗