Prohibitin expression is associated with high grade breast cancer but is not a driver of amplification at 17q21.33.

AIMS: In a study of ductal carcinoma in situ of the breast, we identified five genes at chromosome 17q21.33 that were over-expressed in high grade cases, and showed a correlation between expression and gene copy number. The aim of this study was to investigate potential drivers of genomic amplification at 17q21.33. METHODS: Analysis of high resolution comparative genomic hybridisation and published data specified a minimum region of amplification at 17q21.33. Prohibitin (PHB) expression was examined by immunohistochemistry in 285 invasive breast cancers. Gene copy number was examined by fluorescence in situ hybridisation. RESULTS: The minimum region of amplification at 17q21.33 included ten genes with PHB selected as a candidate driver. Increased PHB expression was associated with higher grade breast cancer and poorer survival. Amplification of PHB was detected in 13 of 235 cases (5.5%) but was not associated with PHB expression. PHB amplification was most common in the ERBB2+ breast cancer subtype, although high expression was most prevalent in basal-like and luminal B cancers. CONCLUSIONS: Amplification at 17q21.33 is a recurrent feature of breast cancer that forms part of a 'firestorm' pattern of genomic aberration. PHB is not a driver of amplification, however PHB may contribute to high grade breast cancer.

Molecular grading of ductal carcinoma in situ of the breast.

PURPOSE: Increased incidence of ductal carcinoma in situ (DCIS) associated with mammographic screening for breast cancer has emphasized the challenges of managing this condition. The aim of this study was to identify informative clinical indicators of DCIS biology by molecular profiling. EXPERIMENTAL DESIGN: Areas of in situ carcinoma, atypical ductal hyperplasia, and benign epithelium were microdissected from 46 invasive breast cancers. Oligonucleotide probes showing differential expression between DCIS associated with grade 1 and 3 invasive cancer were identified by microarray-based gene expression profiling. Expression at these probes was used to define a "molecular grade" subcategorization of all samples. The genomic basis of molecular grade was examined by array-based comparative genomic hybridization. Clinical course was examined in a cohort of 134 patients with DCIS treated by surgery alone. RESULTS: DCIS samples were designated as low or high molecular grade based on expression at 173 probes. The low molecular grade subgroup included low (n = 10) and intermediate (n = 11) nuclear grade DCIS as well as all samples of atypical ductal hyperplasia (n = 4) and benign epithelium (n = 7). The high molecular grade subgroup included DCIS of intermediate (n = 7) and high (n = 19) nuclear grade. The character and degree of genomic aberration were distinct between molecular grade subgroups. A classification tree model including nuclear grade and Ki67 score accurately predicted molecular grade for 95.7% of samples. In an independent cohort, this showed a pattern of rapid disease recurrence for high molecular grade DCIS. CONCLUSIONS: Molecular profiling indicates a binary grading scheme for DCIS. This practical approach has potential to improve clinical evaluation of DCIS.

Poor-prognosis estrogen receptor-positive breast cancer identified by histopathologic subclassification.

PURPOSE: Identification of biologically and clinically distinct breast cancer subtypes could improve prognostic assessment of primary tumors. The characteristics of "molecular" breast cancer subtypes suggest that routinely assessed histopathologic features in combination with limited biomarkers may provide an informative classification for routine use. EXPERIMENTAL DESIGN: Hierarchical cluster analysis based on components of histopathologic grade (tubule formation, nuclear pleomorphism, and mitotic score), expression of ER, cytokeratin 5/6, and HER2 amplification identified four breast cancer subgroups in a cohort of 270 cases. Cluster subgroup membership was compared with observed and Adjuvant! Online predicted 10-year survival. Survival characteristics were confirmed in an independent cohort of 300 cases assigned to cluster subgroups using a decision tree model. RESULTS: Four distinct breast cancer cluster subgroups (A-D) were identified that were analogous to molecular tumor types and showed a significant association with survival in both the original and validation cohorts (P < 0.001). There was a striking difference between survival for patients in cluster subgroups A and B with ER(+) breast cancer (P < 0.001). Outcome for all tumor types was well estimated by Adjuvant! Online, with the exception of cluster B ER(+) cancers where Adjuvant! Online was too optimistic. CONCLUSIONS: Breast cancer subclassification based on readily accessible pathologic features could improve prognostic assessment of ER(+) breast cancer.

MRP2 (ABCC2) and cisplatin sensitivity in hepatocytes and human ovarian carcinoma.

OBJECTIVE: The ABC transporter MRP2 (ABCC2) can mediate cisplatin efflux, and over-expression of MRP2 has been associated with cisplatin resistance in cancer cell lines. The aim of this study was to determine the role of MRP2 in modulating cisplatin cytotoxicity in normal cells as well as the relationship between MRP2 expression and clinical response to platinum-based agents in ovarian cancer. METHODS: The effect of absence of MRP2 expression on cisplatin sensitivity was investigated using primary hepatocyte cultures from the TR- rat strain, which is deficient in Mrp2. We also examined MRP2 expression immunohistochemically in human ovarian tumors exhibiting extremes of clinical response to platinum-based chemotherapy, either absolute platin resistance or patients with residual disease after surgery who experienced extremely long complete response to primary platinum-based chemotherapy. RESULTS: Primary hepatocyte cultures from Mrp2-deficient TR- rats were over threefold more sensitive to cisplatin and accumulated a twofold greater amount of platinum on DNA that wild-type rat hepatocytes. In human ovarian carcinomas, MRP2 was detected by immunohistochemistry in 3/13 (23%) tumors from patients with absolute platin resistance compared with 5/9 (56%) tumors from patients with prolonged survival following treatment including a platinum-based agent. CONCLUSION: These studies indicate that MRP2 may play an important role in modulating normal tissue response to cisplatin. However, MRP2 expression occurred only in a subset of primary ovarian cancers, was frequently aberrant in location and was not correlated with clinical response to platinum-based chemotherapy.

Expression of progesterone receptor A and B isoforms in low-grade endometrial stromal sarcoma.

The progesterone receptor (PR) exists as two isoforms, PRA and PRB. In vitro studies have shown that these proteins are functionally distinct, suggesting that their relative expression can influence progesterone response. Low-grade endometrial stromal sarcoma (LGESS) is an uncommon tumor that usually expresses PR. In normal endometrial stroma, both PR isoforms are present with PRA predominant throughout the menstrual cycle. The relative expression of PRA and PRB in LGESS has not been previously reported. All nine cases of primary LGESS (seven uterine, two extrauterine) expressed PRB. Eight tumors also contained PRA and it was the predominant isoform in seven cases. These tumors had similar histopathologic appearances, whereas a case with approximately equal PR isoform expression showed features of sex cord or smooth muscle differentiation. An extrauterine tumor expressing only PRB had myxoid stroma. Recurrent tumor in two cases, which expressed predominantly PRA in the primary, contained reduced levels of PR consisting predominantly or entirely of PRB after prolonged interval progestin therapy. Most primary LGESSs showed PR isoform expression similar to normal endometrial stroma, consistent with the highly differentiated phenotype of this tumor. Variant differentiation or disease recurrence was accompanied by an altered PR isoform profile that could impact on hormone response.

Organophosphate-based pesticides and genetic damage implicated in bladder cancer.

Organophosphate-based pesticides have been associated with pathology and chromosomal damage in humans. There are also epidemiologic links with cancer. The few screening tests for low-level occupational exposure are of doubtful sensitivity; this investigation evaluated four methods. Blood samples were studied from 10 farmers before and after occupational exposure to organophosphate-based pesticides and five unexposed controls. The standard cholinesterase test was insensitive to the exposure (P=0.815). However, a significant increase in Howell-Jolly bodies within erythrocytes was observed (P=0.001). Cytogenetic studies on routine and aphidicolin-induced blood cultures revealed that following organophosphate exposure the total number of gaps and breaks on human chromosomes was significantly increased (P=0.004 and P=0.0006, respectively). We concluded that Howell-Jolly body and fragile site analysis were sensitive indicators of nuclear damage resulting from low-level occupational exposure to organophosphate. Such nuclear damage could be implicated in carcinogenesis. The development of bladder cancer is one such example.