Biomedical subjects
D Fabbro
Publications and source records attributed to D Fabbro.
Phorbol ester and epidermal growth factor receptors in human breast cancer.
Recently hormone - dependent mammary carcinoma cell lines were shown to exhibit in vitro significantly lower protein kinase C (PKC) activities and epidermal growth factor receptor (EGF-R) as compared to hormone - independent cell lines. Measurements of EGF-R levels in primary human breast cancer biopsies were determined by [125I]-EGF binding. The EGF binding correlated inversely with the estrogen (ER) (p less than 0.001), progesterone receptor (PR) (p less than 0.005) contents and with the age of the patients. In contrast, the amounts of PKC, determined by phorbol ester binding, correlated inversely only with the PR (p less than 0.001), but not with the ER (p = 0.065). There was, however, a significant inverse correlation (p less than 0.05) between phorbol ester binding and ER levels if ER positive biopsies but with a PR negative value (i.e. with a non functional estrogen receptor) were excluded from statistical analysis. These data suggest an inverse relationship between the EGF-R or the phorbol ester receptor and the steroid receptor system in human breast cancer.
Correlation of estrogen receptors and charge alterations of regulatory subunits of cAMP-dependent protein kinases in human mammary tumor cells.
The soluble cAMP-dependent protein kinase activities of two estrogen receptor-containing (MCF-7 and ZR-75-1) and two estrogen receptor-lacking (BT-20 and MDA-MB-231) established human mammary tumor cell lines were analyzed by DEAE-cellulose chromatography and photoaffinity labeling with 8-azido-[32P]cAMP. Predominantly, type I isoenzyme was present in MDA-MB-231 cells, type II protein kinase was the main form in ZR-75-1 and BT-20 cells; whereas MCF-7 cytosols contained equal amounts of both protein kinase types. No correlations between estrogen receptor content and cAMP-dependent protein kinase holoenzyme ratios of isoenzymes were found. A distinctly greater heterogeneity of charge isomers of cAMP-binding proteins (regulatory subunits) was observed in estrogen receptor-containing cells.
Immunocharacterization of protein kinase C isoenzymes in rat kidney glomeruli, and cultured glomerular epithelial and mesangial cells.
Protein kinase C (PKC) is a key enzyme in the signalling pathways that regulate glomerular functions. To understand the role of PKC in renal homeostasis, the expression and localization of PKC isoenzymes have been investigated. The isoforms of PKC present in rat kidney glomeruli, primary cultures and cell lines of glomerular epithelial and mesangial cells, were identified by immunoblot analysis with isotype-specific antibodies. Glomeruli were isolated from rat kidney cortex by differential sieving and found to express five PKC isoenzymes, PKC-alpha, -beta, -delta, -epsilon and -zeta. No PKC-gamma isoenzyme was detected. Outgrowth of cells from isolated glomeruli after 5 days in culture, considered to be mainly epithelial in nature, displayed strong immunoreactivity to PKC-alpha, -delta, -epsilon and zeta isoenzymes. No PKC-beta and -gamma isoforms were detectable. Outgrowth from isolated glomeruli after 21 days of culture, considered to be mainly mesangial cells, similarly expressed PKC-alpha, -delta, -epsilon and -zeta isotypes, but not PKC-beta and -gamma isoforms. The PKC isoenzyme content of a stable cell line of rat kidney glomerular parietal epithelial cells was also characterized. We have demonstrated previously that a cloned rat mesangial cell line expresses PKC-alpha, -delta, -epsilon and -zeta isoenzymes. Here we report that a cloned parietal epithelial cell line also expressed PKC-alpha, -delta, -epsilon and -zeta isoforms. No beta- and gamma-isoenzymes of PKC were detected. Subcellular distribution of PKC isotypes displayed clear differences, depending on the cell type and the isoenzyme examined. Phorbol 12-myristate 13-acetate stimulation of PKC caused down-regulation of PKC-alpha, -delta and -epsilon isoenzymes in epithelial and mesangial cells.(ABSTRACT TRUNCATED AT 250 WORDS)