Zhiqiang Zou

Serum Protein Expression Profiling for Cancer Detection: Validation of a SELDI-Based Approach for Prostate Cancer

Multiple studies have reported that analysis of serum and other bodily fluids using surface enhanced laser desorption/ionization time of flight mass spectroscopy (SELDI-TOF-MS) can identify a “fingerprint” or “signature” of spectral peaks that can separate patients with a specific disease from normal control patients. Ultimately, classification by SELDI-TOF-MS relies on spectral differences in position and amplitude of resolved peaks. Since the reproducibility of quantitation, resolution and mass accuracy of the SELDI-TOF-MS, or any high throughput mass spectrometric technique, has never been determined this method has come under some skepticism as to its clinical usefulness. This manuscript describes a detailed design of a three-phase study to validate the clinical usefulness of SELDI-TOF-MS in the identification of patients with prostatic adenocarcinoma (PCA). At the end of this validation study, the usefulness of the general SELDI-TOF-MS approach to identifying patients with PCA will be demonstrated and how it compares with PCA diagnosis by measuring prostate specific antigen.

p53-dependent induction of heat shock protein 27 (HSP27) expression

Transcriptional activation of the p53 target genes plays a critical role in the cellular response to DNA damage, hypoxia, cellular stress and other signals regulating the cell cycle and apoptosis. The discovery of new p53 target genes continues to reveal novel mechanisms of action of this multifaceted protein. We used cDNA arrays to search for p53‐regulated genes in prostate cancer cells. In this report, we describe robust induction of heat shock protein 27 (hsp27) in prostate cancer cells (DU145, LNCaP, PC3) following wild‐type p53 expression from an adenoviral p53 expression vector (AdWTp53). A mutant p53 (R175H)–containing adenoviral expression vector did not induce hsp27. hsp27 expression was not altered in prostate cancer cells following expression of cyclin‐dependent kinase inhibitors: p21waf1/cip1 and p27(kip1) from adenoviral expression vectors. Treatment of cells with staurosporine, an apoptosis‐inducing agent, did no affect hsp27 expression. These observations provide evidence that induction of hsp27 expression was wild‐type p53–specific and was not due to non‐specific effects of cell growth arrest and/or apoptosis. Previous studies and the experiment reported here show induction of hsp27 expression in response to androgen ablation, a physiological state that induces apoptosis in prostatic epithelial cells. The nature of p53 and hsp27 interactions in the regulation of apoptosis and/or cell growth needs to be further defined. Int. J. Cancer 88:191–194, 2000.

Interferon-γ induces altered oncogene expression and terminal differentiation in A431 cells

Abstract In tumor cell lines in which oncogene expression is abnormal, modulation of the expression of the oncogene (myc, src, or ras) by interferons (IFNs) has been observed concurrently with cell growth inhibition or phenotypic reversion. Oncogene expression has also been reported to vary during the differentiation of several neoplastic cell lines. Treatment of monolayer cultures of A431, a human epidermoid carcinoma cell line, with IFN-γ resulted in rapid morphological alterations and cell death not seen with either IFN-α or IFN-β These changes were accompanied by elevated expression of mRNAs for p21 (the c-ras gene product) and the epidermal growth factor receptor as well as increases in the biosynthetic rate of their respective proteins. These effects likewise appeared to be specific for IFN-γ. Growth inhibition by IFN-γ was also observed when A431 cells were grown in a three dimensional in vitro culture system. Immunohistochemical staining of these “tumoroids” with a differentiation specific, anti-keratin antibody indicated that IFN-γ enhanced expression of this keratin. This observation suggests that the killing by IFN-γ of A431 cells may result from an acceleraton of terminal differentiation.

An Inherited P53 Point Mutation in a Cancer Prone Family with Li-Fraumeni Syndrome

Somatic cells derived from members of a cancer-prone family representing three generations were used to assess mutations in selected regions of p53. Fibroblast DNAs from four family members--the proband, his brother, their father and a paternal aunt, yielded an identical point mutation in codon 245 in only one allele of the p53 gene. This mutation, involving G to A transition (GGC -> GAC) leads to substitution of aspartic acid for glycine at that codon in p53 protein and is not present in NSF DNAs of the proband’s mother or his paternal grandfather, neither of whom are in the cancer-prone lineage. Despite the observed mutation, the level of p53 protein detected in these fibroblasts is comparable to low levels observed in normal control fibroblasts. This is in contrast to the high levels of mutant p53 usually found in tumor cell lines. Thus the mutant p53 in these fibroblasts appears to behave differently as compared to the mutant p53 previously detected in transformed cells. Given the inherited nature of this p53 mutation, the demonstrated role of p53 in tumorigenesis and the location of mutation in a region of the gene known to be critical for its function, it appears that we have identified a primary genetic alteration in this Li-Fraumeni family, a defect which may predispose them to increased susceptibility to cancer.