Biological and clinical significance of PARP1 protein expression in breast cancer.

Poly(ADP-ribose) polymerase-1 (PARP1) is a key facilitator of DNA repair. PARP inhibitors have gained recent attention as promising therapeutic agents for the treatment of solid tumours including breast cancer (BC). However, the biological and clinical significance of PARP1 expression in BC and its role in DNA-damage response (DDR) remain to be defined. We investigated the expression of PARP1 expression, cleaved (PARP1c) and non-cleaved (PAR1nc) forms, in a large and well-characterised cohort of clinically annotated stage I-III operable BCs (n = 1,269) and 43 BRCA1-mutated BCs using immunohistochemistry. PARP1 expression was correlated to clinicopathological variables, outcome and expression of other key DNA repair proteins (BRCA1, RAD51, Ku70/80, PIASγ and CHK1). Expression of PARP1 was exclusively nuclear. 49 and 85 % of sporadic BC showed expression PARP1nc and PARP1c, respectively. In BRCA1-mutated tumours, PARP1nc/PARP1c was highly expressed (95 and 79 %, respectively). PARP1nc expression was positively associated with premenopausal younger age patients, larger size and higher tumour grade. PARP1 was positively associated with DDR-proteins; RAD51, BRCA1, CHK1 and PIASγ (p < 0.001). Negative association was found between PARP1nc and Ki67. PARP1c was associated with ER (p < 0.001). Different associations between PARP1 and DDR-proteins were observed when stratified based on ER/BRCA1 status. PARP1 was not an independent predictor of outcome in sporadic or BRCA1-mutated BC. Our results demonstrate a potential biological role for PARP1c and PARP1nc in DNA repair in BC based on the significant association with other key DNA damage repair proteins. These associations were not restricted to ER-negative or triple-negative subgroup.

Clinicopathological significance of KU70/KU80, a key DNA damage repair protein in breast cancer.

Although the role of BRCA1 and the homologous recombination (HR) pathway in breast cancer (BC) has been extensively studied, the alternative repair pathway for DNA double-strand breaks (DSBs), non-homologous end-joining (NHEJ) remains to be defined. Ku proteins bind to DNA DSB ends and play a key role in NHEJ. In this study we aimed to assess the expression and biological significance of the KU70/KU80 heterodimer in the different molecular classes of BC. The expression of KU70/KU80 was assessed immunohistochemically in a well-characterised and annotated series of 1302 unselected invasive BC cases with a long-term follow-up together with 25 cases with known BRCA1 mutations. The results were correlated with clinicopathological parameters, other DNA repair proteins and patient outcome. The expression of KU70/KU80 protein was further evaluated in various BC cell lines using western blotting and reverse-phase protein microarray (RPPA). Nuclear KU70/KU80 expression was correlated with features of poor prognosis including higher histological grade, lymphovascular invasion, negative oestrogen receptor expression, basal-like phenotype, P53 and CHK1 positivity. KU70/KU80 was expressed in all BRCA1-associated tumours and showed an inverse correlation with nuclear BRCA1 protein and aberrant cytoplasmic RAD51 expression. RPPA confirmed these results and showed higher expression of KU70/KU80 in BRCA1-deficient cell line compared to BRCA1-proficient cell line. KU70/KU80 expression showed an association with disease-free interval; however, it was not an independent predictor of outcome. As a conclusion, KU70/KU80 may play a role in DNA DSBs repair in HR-deficient tumours. Further study of other NHEJ markers in sporadic BC is warranted.

Prognostic value of proliferation assay in the luminal, HER2-positive, and triple-negative biologic classes of breast cancer.

INTRODUCTION: Although the prognostic significance of proliferation in early invasive breast cancer has been recognized for a long time, recent gene-expression profiling studies have reemphasized its biologic and prognostic value and the potential application of its assessment in routine practice, particularly to define prognostic subgroups of luminal/hormone receptor-positive (HR+) tumors. This study aimed to assess the prognostic value of a proliferation assay by using Ki-67 immunohistochemistry as compared with mitotic count scores. METHOD: Proliferation was assessed by using Ki-67 labeling index (Ki-67LI) and mitotic scores in a large (n = 1,550) and well-characterized series of clinically annotated primary operable invasive breast cancer with long-term follow-up. Tumors were phenotyped based on their IHC profiles into luminal/HR+, HER2+, and triple-negative (TN) classes. We used a split-sample development and validation approach to determine the optimal Ki-67LI cut-offs. RESULTS: The optimal cut-points of Ki-67LI were 10% and 50% for the luminal class. Both Ki7LI and MS were able to split luminal tumors into subgroups with significantly variable outcomes, independent of other variables. Neither mitotic count scores nor Ki-67LI was associated with outcome in the HER2+ or the TN classes. CONCLUSIONS: Assessment of proliferation by using Ki-67LI and MS can distinguish subgroups of patients within luminal/hormone receptor-positive breast cancer significantly different in clinical outcomes. Overall, both Ki-67 LI and mitotic-count scores showed comparable results. The method described could provide a cost-effective method for prognostic subclassification of luminal/hormone receptor-positive breast cancer in routine clinical practice.

A CD44⁻/CD24⁺ phenotype is a poor prognostic marker in early invasive breast cancer.

A CD44(-)/CD24(+) phenotype is a poor prognostic marker in early invasive breast cancer. Breast cancer cells with high CD44 and low or absent CD24 (i.e. CD44(+)CD24(-)/low phenotype) are reported to have stem cell features. However, the clinical impact of CD24 and CD44 expression in tumours remains unclear. To explore the immunohistochemical expression of CD44 and CD24 (individually and combined) and their clinical value as prognostic and predictive markers. Immunohistochemical expression of CD24 and CD44 was studied in a large series of early primary invasive breast cancer tumours (n = 1036) prepared as a tissue microarray. Associations between the expression of each marker individually and in combination and clinico-pathological, molecular variables and patients' outcome were investigated. CD24 cytoplasmic expression was significantly associated with poor prognostic variables including high tumour grade, ER-, PR-, HER2(+), p53+ and triple negative (TN) phenotype; P < 0.05. However, CD24 expression was not significantly associated with patients' outcome. Conversely, CD44 expression was associated with favourable prognostic criteria including lower Nottingham prognostic index, ER+, HER2- and luminal phenotype; P < 0.05. Moreover, CD44 expression was found to be an independent predictor of good prognosis. In combination, the CD44(+)/CD24(-) phenotype was associated with the most favourable outcome (84 and 80% 10 year breast cancer survival [BCSS] and metastasis free survival [MFS], respectively). Contrasting this, the CD44(-)/CD24(+) phenotype was associated with the most dismal outcome (62 and 60% 10 years BCSS and MFS, respectively). CD24 and CD44 expression can individually yield prognostic data in breast cancer, but importantly, when both markers are considered; the CD44(+)/CD24(-) phenotype had the best prognosis, while the CD44(-)/CD24(+) phenotype had the worst prognosis. This shows that the relationship between basic cell biology and clinical behaviour is not always straightforward and warrants further investigations of the true clinical impact of breast cancer stem cells.

CTEN (C-terminal tensin-like), a novel oncogene overexpressed in invasive breast carcinoma of poor prognosis.

C-terminal tensin-like (CTEN) gene is a member of the TENSIN gene family, involved in cell migration and localised at focal adhesion sites. This study was designed to explore the prevalence and clinical significance of CTEN expression in a large and well-characterised series (n = 1,409) invasive breast cancer (BC) cases with long term follow-up (median 11 years), using immuno-histochemistry and tissue microarray. Moderate to strong cytoplasmic immunoreactivity for CTEN was observed in 90% of the studied cases. CTEN expression was significantly associated with poor prognostic variables including larger tumour size (P = 0.044), higher histological grade (P = 0.019), axillary nodal involvement (P = 0.035) and poor Nottingham Prognostic Index (P = 0.016). Significant associations were observed between increased CTEN expression and up-regulation of phosphorylated-Akt (P-Akt), PIK3 and N-cadherin proteins (P\0.001). Kaplan-Meier survival analysis demonstrated that patients with high CTEN expression had significantly shorter Breast Cancer Specific Survival (P = 0.004) and Metastasis-Free Survival (P = 0.041) than those with low-CTEN expression. Multivariate analysis showed that CTEN was not an independent prognostic marker in BC. In conclusion, our results demonstrated the oncogenetic role of increased CTEN expression and its association with poor prognostic parameters. These data could help in prognostic assessment in BC patients.

Clinical and biological significance of E-cadherin protein expression in invasive lobular carcinoma of the breast.

BACKGROUND: Although virtually all cases of lobular carcinoma in situ lack E-cadherin expression, a proportion of morphologically typical invasive lobular carcinomas (ILCs) retain its expression. The frequency and significance of E-cadherin expression in ILC remain to be elucidated. In this study, we have assessed E-cadherin protein expression in a well-characterized series of histologically defined ILC (239 cases) with a long-term clinical follow-up to determine the frequency, clinical and biological significance of its expression. E-cadherin-positive ILCs (ILC+) were subsequently examined to assess the expression of component members of the E-cadherin membrane complex (E-cadherin, p120, α, ß, and γ-catenins) to determine its integrity. RESULTS: Thirty-eight ILC cases (16%) showed positive E-cadherin expression (ILC+). Membranous expression of E-cadherin was mainly circumferential with frequent coexisting perimembranous cytoplasmic expression. No association between E-cadherin expression and any of the clinicopathologic variables, immunophenotype, or tumor behavior was identified, apart from an association with lobular histologic subtype and vascular invasion. Analysis of the E-cadherin-catenin complex showed abnormal expression of one or more of the catenin complex members in the majority of cases. The most frequent observation was the diffuse cytoplasmic expression of catenins, in particular p120, which showed similar expression to that reported in E-cadherin-negative ILCs. CONCLUSIONS: These results provide evidence that E-cadherin is expressed in a proportion of ILC, however, unlike ductal carcinoma, its expression seems to be of limited significance and it is usually associated with evidence of impaired integrity of the E-cadherin-catenin membrane complex. Our data offer a possible explanation for the presence but lack functionality of E-cadherin in some cases of ILC and imply that immunohistochemical expression of E-cadherin per se in ILC histologic phenotypic tumors should not preclude its diagnosis.

Triple-negative breast cancer: distinguishing between basal and nonbasal subtypes.

PURPOSE: Triple-negative (TN; estrogen receptor, progesterone receptor, and HER-2 negative) cancer and basal-like breast cancer (BLBC) are associated with poor outcome and lack the benefit of targeted therapy. It is widely perceived that BLBC and TN tumors are synonymous and BLBC can be defined using a TN definition without the need for the expression of basal markers. EXPERIMENTAL DESIGN: We have used two well-defined cohorts of breast cancers with a large panel of biomarkers, BRCA1 mutation status, and follow-up data to compare the clinicopathologic and immunohistochemical features of TN tumors expressing one or more of the specific basal markers (CK5/6, CK17, CK14, and epidermal growth factor receptor; BLBC) with those TN tumors that express none of these markers (TN3BKE-). RESULTS: Here, we show that although the morphologic features of BLBC are not significantly different from that of TN3BKE- tumors, BLBC showed distinct clinical and immunophenotypic differences. BLBC showed a statistically significant association with the expression of the hypoxia-associated factor (CA9), neuroendocrine markers, and other markers of poor prognosis such as p53. A difference in the expression of cell cycle-associated proteins and biomarkers involved in the immunologic portrait of tumors was seen. Compared with TN3BKE- tumors, BLBC was positively associated with BRCA1 mutation status and showed a unique pattern of distant metastasis, better response to chemotherapy, and shorter survival. CONCLUSION: TN breast cancers encompass a remarkably heterogeneous group of tumors. Expression of basal markers identifies a biologically and clinically distinct subgroup of TN tumors, justifying the use of basal markers (in TN tumors) to define BLBC.

C-terminal Tensin-like (CTEN) is an oncogene which alters cell motility possibly through repression of E-cadherin in colorectal cancer.

The Tensin gene family encodes proteins thought to modulate integrin function. C-terminal Tensin-like (CTEN) is a member of the Tensin gene family which lacks the N-terminus actin-binding domain. Cten is reported to have both oncogenic and tumour-suppressor functions. We investigated the role that Cten may play in colorectal cancer (CRC). By quantitative RT-PCR CTEN is up-regulated (i.e. > two-fold increase) in 62% of cell lines and 69% of tumours compared with normal mucosa, consistent with CTEN being a possible oncogene. Stable transfection of HCT116 and SW480 (CRC cell lines with low endogenous Cten expression) with a Cten expression vector gave identical results in both cell lines. Forced Cten expression did not cause change in cell numbers, although it did confer resistance to staurosporine-induced apoptosis (p < 0.005). Cten also induced epithelial-mesenchymal transition (EMT) in tumour cells accompanied by a significant increase in both cell migration (transwell migration and cell wounding assays, p < 0.001 and p < 0.05, respectively) and cell invasion (invasion through Matrigel, p < 0.001). Given the observed EMT, we investigated the levels of E-cadherin. Cten induction was associated with a reduction in E-cadherin protein expression but not levels of E-cadherin mRNA. These data suggest that CTEN is an oncogene in CRC which stimulates EMT, cell migration and invasion and may therefore have a role in tumour invasion/spread. Furthermore, Cten induction is associated with post-transcriptional repression of E-cadherin.