Cellular retinol binding protein-1 expression in endometrial hyperplasia and carcinoma: diagnostic and possible therapeutic implications

Abstract

Cellular retinol binding protein-1 (CRBP-1) contributes to the maintenance of the differentiative state of endometrial glandular cells through the regulation of bioavailability of retinol and derivatives, but its role in endometrial oncogenetic process remains unclear. Antibodies to CRBP-1, estrogen and progesterone receptors (ER and PR) were applied to paraffin sections of proliferative (n ¼ 10) and secretory endometrium (n ¼ 9), and to endometrial polyps (n ¼ 6), simple (n ¼ 7), complex (n ¼ 3) and atypical endometrial hyperplasias (n ¼ 9) as well as to 47 endometrioid carcinomas of different histological grade (G) (G1, n ¼ 18; G2, n ¼ 19; G3, n ¼ 10). Four serous and two clear cell carcinomas were also examined. In glandular cells, CRBP-1 positivity was mainly cytoplasmic and rarely in the nuclei. CRBP-1 immunodetection was weakly positive in proliferative and low and focal in secretory endometrium and higher in atypical as compared to simple and complex hyperplasias. CRBP-1 expression in G1 endometrioid carcinomas was similar to that in atypical hyperplasias. In the latter, the highest CRBP-1 expression was observed in areas of squamous differentiation. Semiquantitative evaluation revealed a significant decrease of cytoplasmic CRBP-1 immunoreactivity with the increase of tumor grade. Among G3 endometrioid carcinomas, 60% were CRBP-1 negative, whereas the remaining cases showed a very low and focal positivity. Serous carcinomas were also CRBP-1 negative. When areas of different grading were present within the same tumor, less differentiated areas retained a lower CRBP-1 immunoreaction. The progressive decrease of CRBP-1 paralleled that of ER and PR immunodetection. RT-PCR in eight endometrioid carcinomas suggested a decrease of CRBP-1 with the increase of tumor grade also at transcriptional level. Our results indicate that CRBP-1 immunodetection may constitute an additional tool for histological grading of endometrial carcinoma. The CRBP-1 loss during the progression of endometrial cancer suggests a new potential target for pharmacological strategies aimed to counteract its progression by increased intracellular retinol bioavailability.

Protein expression patterns associated with advanced stage ovarian cancer

“…They have been shown to inhibit the growth of human cancer cells in vitro [40], and to be effective chemopreventive and chemotherapeutic agents in ovarian and in other human epithelial and hemotopoietic tumors [41]. A reduction of RPB-1 gene expression has already been reported in breast [42], endometrial [43] and ovarian carcinoma [44], suggesting that a reduction of RBP-1 expression may significantly contribute to the oncogenic process, through altering the vitamin A metabolism. While the reduction of RBP-1 expression is reported in less differentiated endometrial carcinomas, it has been demonstrated that in breast [45] and serous ovarian tumors [44], its reduction appears to be associated with early stage carcinogenesis process: a correlation with tumor stage and grade has been demonstrated.…”

Liver protein profiles in insulin receptor-knockout mice reveal novel molecules involved in the diabetes pathophysiology

“…High-mobility group-B1 (HMGB1), CD3, CD19, and F4/80 protein expression was performed by immunohistochemistry (32) on 4-mthick paraffin sections using antibodies from Abcam. The positive immunostaining was assessed using a semiquantitative scale modified as follows: 3, strong; 2, moderate; 1, weak; 0, absent (30). Measurements were performed by two different investigators in at least 10 fields at ϫ200 magnification for each case, with an inter observer variability of Ͻ5%.…”

Insulin-degrading Enzyme (IDE)

“…Semi-quantitative evaluation of IDE immunoreaction was estimated at 200ϫ magnification in at least 10 fields by two of the authors, who used a grading system in arbitrary units (a.u.) as follows: negative ϭ 0; Ͻ25% of cells weakly positive ϭ 0.5; diffuse weakly positive ϭ 1; moderately positive ϭ 2 and strongly positive ϭ 3 (26). The results were expressed as mean number Ϯ S.E., with an interobserver reproducibility of Ͼ95%.…”

“…As a control for the tumors of the nervous system, we used paraffin sections of bioptic material, which contained small fragments of non-neoplastic cerebral tissue that had been removed during the surgical excision of benign tumors (n ϭ 4). For the immunohistochemical procedure (26), serial 4-m-thick paraffin sections were stained with hematoxylin/eosin or used for immunohistochemistry. Regarding the latter, we performed deparaffinization, blocking of endogenous peroxidase activity with 0.2% H 2 O 2 (20 min) and incubation with normal goat serum (30 min).…”