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Chronic myelogenous leukemia (CML) is the most common myeloproliferative disease. Protein tyrosine phosphatase receptor type γ (PTPRG) is a tumor suppressor gene and a myeloid cell marker expressed by CD34(+) cells. Downregulation of PTPRG increases colony formation in the PTPRG-positive megakaryocytic cell lines MEG-01 and LAMA-84 but has no effect in the PTPRG-negative cell lines K562 and KYO-1. Its overexpression has an oncosuppressive effect in all these cell lines and is associated with myeloid differentiation and inhibition of BCR/ABL-dependent signaling. The intracellular domain of PTPRG directly interacts with BCR/ABL and CRKL, but not with signal transducers and activators of transcription 5. PTPRG is downregulated at the mRNA and protein levels in leukocytes of CML patients in both peripheral blood and bone marrow, including CD34(+) cells, and is reexpressed following molecular remission of disease. Reexpression was associated with a loss of methylation of a CpG island of PTPRG promoter occurring in 55% of the patients analyzed. In K562 cell line, the DNA hypomethylating agent 5-aza-2'-deoxycytidine induced PTPRG expression and caused an inhibition of colony formation, partially reverted by downregulation of PTPRG expression. These findings establish, for the first time, PTPRG as a tumor suppressor gene involved in the pathogenesis of CML, suggesting its use as a potential diagnostic and therapeutic target., (©2010 AACR.)

We describe a patient with primary ovarian carcinoma that developed after liver transplantation whose tumor was highly positive for prostate-specific antigen (PSA). PSA in tumor tissue was characterized by two immunoassays, HPLC, immunohistochemistry, reverse transcription-PCR, Southern blotting, and DNA sequencing. PSA in the ovarian tumor was present as free, M(r) 33,000 protein (> 90%) and as PSA bound to alpha 1-antichymotrypsin (M(r) 100,000; < 10%). Immunohistochemistry localized PSA in the cytoplasm of epithelial cells of the tumor. Two separate reverse transcription-PCRs for PSA amplified the expected products which hybridized specifically to a PSA cDNA probe on Southern blots. Sequencing of the PCR products, representing the whole coding sequence of the PSA gene, revealed identity with the sequence of PSA cDNA from prostate tissue. These data suggest that the PSA produced by the ovarian tumor was identical in molecular weight and sequence to prostatic PSA. Based on data of tissue culture experiments with breast carcinoma cell lines, we speculate that the PSA gene in the tumor of this patient was up-regulated by the therapeutically administered glucocorticoids after liver transplantation.

Prostate-specific antigen (PSA) is considered a highly specific biochemical marker of the prostate gland and is currently used for prostate cancer diagnosis and monitoring of patients with prostate adenocarcinoma. We recently demonstrated, however, that about 30% of female breast tumors produce a M(r) 33,000 protein that has striking similarities to seminal PSA. In this study we characterized the presence of PSA in 6 breast tumors and in the testosterone-stimulated T47D breast cancer cell line at the mRNA level. Using reverse transcriptase-polymerase chain reaction and DNA sequencing techniques we identified PSA mRNA in immunoreactive PSA-positive breast tumors but not in immunoreactive PSA-negative breast tumors. The sequence of the generated polymerase chain reaction products was identical to the sequence of the PSA complementary DNA derived from prostate tissue. The data presented here support the notion that breast tumors produce a M(r) 33,000 protein which is identical to PSA produced by the prostate gland. Our study suggests that the presence of PSA in breast tumors may be used as a new additional biochemical marker for breast cancer prognosis, for the spreading of hematogenous micrometastases, and/or for response to adjuvant treatment.

bcl-2 and p53 gene products have been both linked to programmed cell death pathways. We have analyzed several human breast cancer cell lines for the expression of bcl-2 and p53. We found an inverse correlation between the expression of the two proteins. The result suggested that mutant p53 could substitute for bcl-2 function in breast cancer cells and that could also down-regulate bcl-2 expression. We found, indeed, that overexpression of a mutant p53 (mut 175) in MCF-7 cells could induce down-regulation of bcl-2 both at protein and mRNA level. However, the promoter region of the human bcl-2 gene does not contain the negative regulatory element responsible for the down-regulation. If this mechanism will be proved also for the wild-type p53 allele, it may disclose a possible mechanism for p53-induced apoptosis: down-regulation of bcl-2.

The goal of this study was to determine if patients with stage D0-3 prostatic adenocarcinoma have detectable hematogenous micrometastasis. Polymerase chain reaction amplification of prostate-specific antigen mRNA, which is exclusively expressed by prostatic epithelial cells, was used to detect circulating prostatic cells. Peripheral venous blood was obtained from 17 control and 12 prostate cancer patients with stage D0-3 prostatic adenocarcinoma. Of the 12 cancer cases, four patients (stage D1-3) tested positive for prostate-specific antigen RNA, indicating the presence of circulating micrometastasis. The 17 negative controls all tested negative. Contrary to a long held hypothesis, these data point to the possibility that hematogenous metastasis may be a relatively early event in the natural history of human prostate cancer. These findings may have an important impact on our understanding and treatment of prostate cancer.