Expression and localization of the uptake transporters OATP2B1, OATP3A1 and OATP5A1 in non-malignant and malignant breast tissue

Organic anion transporting polypeptides (OATPs, gene family SLCO/SLC21) mediate the uptake of multiple endogenous substances such as estrogens and estrogen metabolites and of several widely prescribed drugs (e.g. statins, antibiotics and anticancer agents) into cells. Since several anticancer agents have been identified as substrates for OATPs, these transporters may also have an impact on cancer treatment. Expression of OATPs has been identified in colon, pancreatic and gastric carcinomas but to date little is known about the expression and localization of OATP family members in non-malignant breast tissue and breast cancer. We therefore analyzed the mRNA expression of all human OATP family members and further evaluated the mRNA amount of the highly-expressed OATPs OATP2B1, OATP3A1 and OATP5A1 in 10 paired samples of normal breast tissue and breast cancer. Furthermore, the tissue-specific localization of these OATPs was investigated. The results demonstrated that the mRNA expression of OATPs in normal and malignant breast tissue shows a high interindividual variability and that no significant differences in the mRNA amount between normal and malignant tissue could be detected. Furthermore, we localized OATP3A1 and OATP5A1 to the plasma membrane of epithelial cells of the lactiferous ducts in normal breast tissue. In breast cancer, both OATPs are highly expressed in the plasma membrane and in the cytoplasm. Since estrogen and estrogen metabolites as well as anticancer agents are substrates for OATPs these results indicate the possibility of OATP-mediated uptake of hormones during breast cancer development and an impact of certain OATPs on chemotherapeutic cancer treatment.     

Early results of bladder-cancer screening in a high-risk population of heavy smokers

OBJECTIVE

To report first results of an early bladder‐cancer detection programme, and to evaluate the detection rate and the diagnostic value of the tests used.

SUBJECTS AND METHODS

Urine samples of 183 screened subjects with a history of smoking of ≥40 pack‐years were collected for analysis with a urinary dipstick test for haematuria, the nuclear matrix protein‐22 test (BladderChek®, Matritech, Inc., Newton, MA, USA), voided urine cytology and a molecular cytology test (UroVysion, Abbott Molecular Inc., Des Plaines, IL, USA). Participants with at least one positive test result had a further evaluation including cystoscopy and radiological imaging. The subjects’ risk factors, test results and histological findings were analysed.

RESULTS

In all, 75 subjects had at least one positive test result and were evaluated further; abnormal histological findings were detected in 18 (24% of those who had cystoscopy, 9.8% of the original 183), 15 of those in the urinary bladder, with pTaG1 (one), carcinoma in situ (two), dysplastic lesions (11) and one an inverted papilloma. In the upper urinary tract, two urothelial tumours (pTaG1 and pTxN2G3) and one renal cell carcinoma (pT1G2) were detected by computed tomography. In summary, six of 183 subjects (3.3%) had a histologically confirmed malignant tumour and another 12 (6.6%) were identified with a possible pre‐cancerous lesion of the urinary tract. The urinary dipstick, BladderChek, cytology and UroVysion detected (i.e. were true‐positive in) nine (50%), one (6%), seven (39%) and 11 (61%) of the 18 tumours found, while they failed to detect nine (50%), 17 (94%), 11 (61%) and seven (39%) of these lesions, respectively. Omitting the urine dipstick test, the BladderChek, cytology or UroVysion from the test setting could have spared 40, five, two or one subjects(s) from unnecessary invasive interventions; however, three, none, two or six lesions, would have been missed. More positive screening tests per subject was associated with a higher probability of a (pre)‐malignant lesion.

CONCLUSION

Screening a high‐risk group with a history of smoking of ≥40 pack‐years showed a significant proportion (3.3%) with malignancy. These first results are encouraging and warrant continuation of the screening programme. In this series the most efficient screening tool was the combination of UroVysion, cytology and urinary dipstick testing. Of special scientific interest will be the follow‐up of those patients with a possible pre‐cancerous lesion.     

Frequent loss of SFRP1 expression in multiple human solid tumours: association with aberrant promoter methylation in renal cell carcinoma

Oncogenic wingless-related mouse mammary tumour virus (Wnt) signalling, caused by epigenetic inactivation of specific pathway regulators like the putative tumour suppressor secreted frizzled-related protein 1 (SFRP1), may be causally involved in the carcinogenesis of many human solid tumours including breast, colon and kidney cancer. To evaluate the incidence of SFRP1 deficiency in human tumours, we performed a large-scale SFRP1 expression analysis using immunohistochemistry on a comprehensive tissue microarray (TMA) comprising 3448 tumours from 36 organs. This TMA contained 132 different tumour subtypes as well as 26 different normal tissues. Although tumour precursor stages of, for example kidney, colon, endometrium or adrenal gland still exhibited moderate to abundant SFRP1 expression, this expression was frequently lost in the corresponding genuine tumours. We defined nine novel tumour entities with apparent loss of SFRP1 expression, i.e., cancers of the kidney, stomach, small intestine, pancreas, parathyroid, adrenal gland, gall bladder, endometrium and testis. Renal cell carcinoma (RCC) exhibited the highest frequency of SFRP1 loss (89% on mRNA level; 75% on protein level) and was selected for further analysis to investigate the cause of SFRP1 loss in human tumours. We performed expression, mutation and methylation analysis in RCC and their matching normal kidney tissues. SFRP1 promoter methylation was frequently found in RCC (68%, n=38) and was correlated with loss of SFRP1 mRNA expression (p<0.05). Although loss of heterozygosity was found in 16% of RCC, structural mutations in the coding or promoter region of the SFRP1 gene were not observed. Our results indicate that loss of SFRP1 expression is a very common event in human cancer, arguing for a fundamental role of aberrant Wnt signalling in the development of solid tumours. In RCC, promoter hypermethylation seems to be the predominant mechanism of SFRP1 gene silencing and may contribute to initiation and progression of this disease.     

p53 Codon 72 polymorphism, loss of heterozygosity and high-risk human papillomavirus infection in a low-incidence German esophageal squamous cell carcinoma patient cohort

Epidemiological studies in endemic geographic regions for esophageal squamous cell carcinoma (ESCC) suggested a number of risk factors, including modifications of the p53 tumor suppressor by codon Arg72Pro polymorphism, loss of heterozygosity (LOH) or human papillomavirus type 16 or 18 (HPV 16/18) infection. The p53 Arg72 variant has been suggested to be a high-risk factor in HPV-associated tumors. The present study analysed these associations in a low incidence geographic region in Germany. Fifty-three paraffin-embedded tumors and 53 surrounding normal squamous epithelium were investigated. For detection of p53 codon Arg72Pro polymorphism, direct sequencing for exon 4 was conducted. LOH analysis was performed using three microsatellite markers at the p53 gene locus, and all cases were screened for high-risk HPV infection (HPV 16 and 18) with primer specific PCR and confirmed by sequencing. The p53 codon 72 genotype distribution was identical to published studies of normal Caucasian population, suggesting no general influence of this polymorphism on esophageal cancer risk in Germany. One case showed a p53 mutation in exon 4. p53 LOH was found in 13/44 (30%) informative cases without any correlation to histopathological characteristics. Of 53 (17%) samples, 9 showed HPV 16 or 18 infection. We found no association between p53 codon 72 genotypes and increasing HPV infection rates. Interestingly, 8/9 HPV-positive cases showed at least one p53 Arg72 allele. These results indicate an important role of p53 in ESCC also in low-incidence regions. In combination with the p53 Arg72 variant HPV infection could contribute to the risk of ESCC development in these cases, as has been demonstrated for high-risk regions.     

Interdisziplinäres Networking für klinische und molekulare Fragestellungen beim nicht-muskelinvasiven Urothelkarzinom der Harnblase

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