Biomedical subjects

M T Ling

Publications and source records attributed to M T Ling.

7 recordsLinked to original sources

PubMed2004

Classification between normal and tumor tissues based on the pair-wise gene expression ratio.

BACKGROUND: Precise classification of cancer types is critically important for early cancer diagnosis and treatment. Numerous efforts have been made to use gene expression profiles to improve precision of tumor classification. However, reliable cancer-related signals are generally lacking. METHOD: Using recent datasets on colon and prostate cancer, a data transformation procedure from single gene expression to pair-wise gene expression ratio is proposed. Making use of the internal consistency of each expression profiling dataset this transformation improves the signal to noise ratio of the dataset and uncovers new relevant cancer-related signals (features). The efficiency in using the transformed dataset to perform normal/tumor classification was investigated using feature partitioning with informative features (gene annotation) as discriminating axes (single gene expression or pair-wise gene expression ratio). Classification results were compared to the original datasets for up to 10-feature model classifiers. RESULTS: 82 and 262 genes that have high correlation to tissue phenotype were selected from the colon and prostate datasets respectively. Remarkably, data transformation of the highly noisy expression data successfully led to lower the coefficient of variation (CV) for the within-class samples as well as improved the correlation with tissue phenotypes. The transformed dataset exhibited lower CV when compared to that of single gene expression. In the colon cancer set, the minimum CV decreased from 45.3% to 16.5%. In prostate cancer, comparable CV was achieved with and without transformation. This improvement in CV, coupled with the improved correlation between the pair-wise gene expression ratio and tissue phenotypes, yielded higher classification efficiency, especially with the colon dataset - from 87.1% to 93.5%. Over 90% of the top ten discriminating axes in both datasets showed significant improvement after data transformation. The high classification efficiency achieved suggested that there exist some cancer-related signals in the form of pair-wise gene expression ratio. CONCLUSION: The results from this study indicated that: 1) in the case when the pair-wise expression ratio transformation achieves lower CV and higher correlation to tissue phenotypes, a better classification of tissue type will follow. 2) the comparable classification accuracy achieved after data transformation suggested that pair-wise gene expression ratio between some pairs of genes can identify reliable markers for cancer.

Colon↗

PubMed2004

Epstein-Barr virus latent membrane protein 1 (LMP1) upregulates Id1 expression in nasopharyngeal epithelial cells.

Nasopharyngeal carcinoma is closely associated with Epstein-Barr virus (EBV) infection. The EBV-encoded LMP1 has cell transformation property. It suppresses cellular senescence and enhances cell survival in various cell types. Many of the downstream events of LMP1 expression are mediated through its ability to activate NF-kappaB. In this study, we report a novel function of LMP1 to induce Id1 expression in nasopharyngeal epithelial cells (NP69) and human embryonal kidney cells (HEK293). The Id1 is a basic helix-loop-helix (bHLH) protein and a negative transcriptional regulator of p16(INK4a). Expression of Id1 facilitates cellular immortalization and stimulates cell proliferation. With the combination of both specific chemical inhibitors and genetic inhibitors of cell signaling, we showed that induction of Id1 by LMP1 was dependent on its NF-kappaB activation domain at the carboxy-terminal region, CTAR1 and CTAR2. Induction of Id1 by LMP1 may facilitate clonal expansion of premalignant nasopharyngeal epithelial cells infected with EBV and may promote their malignant transformation.

Carcinoma↗

PubMed2003

Prostate development and carcinogenesis.

The process involved in the development and carcinogenesis of the prostate gland is complex. During early prostate development, the androgenic hormone from embryonic testicles is required for ductal formation, growth, and branching morphogenesis of the prostate gland. From this early stage, interactions between the epithelium and mesenchyme become firmly established through paracrine influence (i.e., growth factors) from mesenchyme (stroma), in response to testosterone, acting on epithelium to stimulate its proliferation, morphogenetic differentiation, and function. In return, the epithelium also exerts its paracrine effects on mesenchyme by regulating the differentiation and specific organizational pattern of its stromal smooth muscle. In a normal adult prostate, the maintenance of normal glandular structure and function is dependent not only on the constant presence of testosterone, but also on a normal intact and stable stroma. This chapter will concentrate first on factors involved in the normal development of the prostate gland and then on the aberrant changes in the homeostatic balance arising either from within (i.e., mutations) or outside (i.e., changes in hormonal balance) that result in derangements of the prostate gland. Finally, environmental and genetic factors that lead to prostate carcinogenesis including activation of oncogenes and mutations of tumor suppressor genes are also discussed.

Animals↗

PubMed2002

Down-regulation of Id-1 expression is associated with TGF beta 1-induced growth arrest in prostate epithelial cells.

Transforming growth factor beta1 (TGF beta 1) plays important roles in the regulation of cell growth and differentiation in both normal and malignant prostate epithelial cells. Although certain pathways have been suggested, the mechanisms responsible for the action of TGF beta 1 are not well understood. In the present study, using a human papilloma virus 16 E6/E7 immortalized prostate epithelial cell line, HPr-1, we report that TGF beta 1 was able to suppress the expression of Id-1, a helix-loop-helix (HLH) protein, which plays important roles in the inhibition of cell differentiation and growth arrest. In addition, a decrease at both Id-1 mRNA and protein expression levels was associated with TGF beta 1-induced growth arrest and differentiation, indicating that Id-1 may be involved in TGF beta 1 signaling pathway. The fact that up-regulation of p21(WAF1), one of the downstream effectors of Id-1, was observed after exposure to TGF beta 1 further indicates the involvement of Id-1 in the TGF beta 1-induced growth arrest in HPr-1 cells. However, increased expression of p27(KIP1) was also observed in the TGF beta 1-treated cells, suggesting that in addition to down-regulation of Id-1, other factors may be involved in the TGF beta 1-induced cell growth arrest and differentiation in prostate epithelial cells. Our results provide evidence for the first time that TGF beta 1 may be one of the upstream regulators of Id-1.

Blotting, Western↗

PubMed2001

Androgen induces differentiation of a human papillomavirus 16 E6/E7 immortalized prostate epithelial cell line.

Androgen signaling is crucial for the growth and development, as well as for tumorigenesis of the prostate. However, many of the prostate epithelial cell lines developed previously, either normal or tumorigenic, do not express androgen receptor (AR) or respond to androgen. In order to advance our understanding on how androgen signaling regulates the growth and the differentiation status, and affects tumorigenicity of the epithelial cell, we performed experiments on HPr-1, a prostate cell line recently immortalized from normal human prostate epithelial cells. In the present study, AR was stably transfected into HPr-1 cells by replication-defective retrovirus. Treatment of HPr-1AR cells with androgen resulted in cell differentiation and growth retardation accompanied with up-regulation of cytokeratins K8 and K18, prostate specific antigen, p21 and p27, and down-regulation of c-myc, bcl-2 and telomerase activity. Our results suggest that androgen promotes the process of differentiation in a human papillomavirus 16 E6/E7 immortalized prostate epithelial cell line which may reflect the normal effects of androgen on prostate cells.

Androgens↗

PubMed2000

Retrovirus-mediated delivery of HPV16 E7 antisense RNA inhibited tumorigenicity of CaSki cells.

OBJECTIVE: In cervical cancer, high-risk human papillomavirus (HPV) genes are expressed solely in cancerous cells and have been proposed to be the most important etiological factors for cervical cancer, thus making them suitable targets for gene therapy. In this study, we aim to inactivate the HPV16 E7 in CaSki cells and test the possibility of reducing the tumorigenicity of these cells. METHODS: The full-length HPV16 E7 cDNA was cloned in the pBabe-puro or pWZL-Hygro retrovirus vector in reverse orientation and was stably transfected into CaSki cells by replication-defective retrovirus infection giving rise to CaSki-E7AS and CaSki-E7AS2X cells. Immunoprecipitation/Western analysis and real-time RT-PCR were performed to document the levels of HPV16 E7 gene product. Flow cytometry was performed to study changes in the cell cycle in response to reduced E7 protein. The expression of bcl-2, RB, and E2F-1 was studied using Western blot analysis. Tumorigenicity of CaSki, CaSki-E7AS, and CaSki-E7AS2X cells was assayed with subepidermal tumor growth in nude mice. RESULTS: We have documented that the delivery of the antisense gene construct resulted in the reduction of HPV16 E7 protein expression and cell proliferation in CaSki cells. Furthermore, we demonstrated that these changes were accompanied by cell cycle arrest, up-regulation of RB, and down-regulation of E2F-1 and bcl-2 proteins. More importantly, dose-dependent transduction of the antisense HPV16E7 construct was able to inhibit and/or retard the tumorigenicity of CaSki cells in vivo. CONCLUSIONS: Down-regulation of HPV16 E7 with antisense RNA is beneficial in reducing the tumorigenicity of CaSki cells and can potentially be useful for HPV-associated malignancy gene therapy.

Animals↗

PubMed1999

Immortalization of human prostate epithelial cells by HPV 16 E6/E7 open reading frames.

BACKGROUND: The exact pathogenesis for prostate cancer is not known. Progress made in prostate cancer research has been slow, largely due to the lack of suitable in vitro models. Here, we report our work on the immortalization of a human prostate epithelial cell line and show that it can be used as a model to study prostate tumorigenesis. METHODS: Replication-defective retrovirus harboring the human papillomavirus (HPV) type 16 E6 and E7 open reading frames was used to infect primary human prostate epithelial cells. Polymerase chain reaction, followed by Southern hybridization for the HPV 16 E6/E7, Western blot for prostatic acid phosphatase, telomeric repeat amplification protocol assay for telomerase activity, two-dimensional gels for cytokeratins, and cytogenetic analysis were undertaken to characterized the infected cells. RESULTS: The retrovirus-infected cell line, HPr-1, continued to grow in culture for more than 80 successive passages. Normal primary cells failed to proliferate after passage 6. HPr-1 cells bore close resemblance to normal primary prostate epithelial cells, both morphologically and biochemically. However, they possessed telomerase activity and proliferated indefinitely. Cytogenetic analysis of HPr-1 cells revealed a human male karyotype with clonal abnormalities and the appearance of multiple double minutes. CONCLUSIONS: The HPr-1 cells expressed prostatic acid phosphatase and cytokeratins K8 and K18, proving that they were prostate epithelial cells. They were benign in nude mice tumor formation and soft agar colony formation assay. The HPr-1 cell line is an in vitro representation of early prostate neoplastic progression.

Acid Phosphatase↗