LIN7A is a major determinant of cell-polarity defects in breast carcinomas.

BACKGROUND: Polarity defects are a hallmark of most carcinomas. Cells from invasive micropapillary carcinomas (IMPCs) of the breast are characterized by a striking cell polarity inversion and represent an interesting model for the analysis of polarity abnormalities. METHODS: In-depth investigation of polarity proteins in 24 IMPCs and a gene expression profiling, comparing IMPC (n = 73) with invasive carcinomas of no special type (ICNST) (n = 51) have been performed. RESULTS: IMPCs showed a profound disorganization of the investigated polarity proteins and revealed major abnormalities in their subcellular localization. Gene expression profiling experiments highlighted a number of deregulated genes in the IMPCs that have a role in apico-basal polarity, adhesion and migration. LIN7A, a Crumbs-complex polarity gene, was one of the most differentially over-expressed genes in the IMPCs. Upon LIN7A over-expression, we observed hyperproliferation, invasion and a complete absence of lumen formation, revealing strong polarity defects. CONCLUSION: This study therefore shows that LIN7A has a crucial role in the polarity abnormalities associated with breast carcinogenesis.

High Ki67 expression is a risk marker of invasive relapse for classical lobular carcinoma in situ patients.

BACKGROUND: The clinical management of lobular carcinoma in situ lesions remains challenging. Our aim was to evaluate the risk of relapse for lobular carcinoma in situ (LCIS) patients, diagnosed on mammography performed for microcalcifications and according to proliferation assessed by Ki67 staining. METHODS: A series of 47 patient's files with LCIS and followed in our institution were retrospectively selected. All patients underwent lumpectomy without radiation therapy. The expression of E-cadherin, estrogen receptor (ER), progesterone receptor (PR), EGFR and Ki67 were determined. Four different classes were then defined with the following criteria: ER+ and Ki67 ≤ 10%; ER+, Ki67 >10%; ER-; ER-PR- and EGFR+. RESULTS: Patient's mean age was 51.3 yrs. The majority of the lesions were classical LCIS (97%). All cases were E-cadherin either negative (71%) or weak and incomplete (29%). Among the 44 evaluable cases, 34 cases were ER or PR positive with KI67 ≤ 10% (79%), 9 cases ER positive with KI67 > 10% (21%), 1 case was ER and PR negative and expressed EGFR. At five years, all patients were alive, 1/34 ER positive and Ki67 low experienced a relapse contrasting with 3 out of 9 ER positive and Ki67 high (3 invasive carcinomas including 2 ductal and 1 lobular) (p = 0.0054). CONCLUSION: In this retrospective study, we observed a higher risk of relapse associated with a high proliferative activity of classical LCIS. If confirmed in larger series, this observation suggests that radiation therapy or hormonotherapy could be discussed for patients with Ki67 high classical LCIS in order to decrease their risk of relapse.