Reliability of cyclin A assessment on tissue microarrays in breast cancer compared to conventional histological slides

Biopsy variability of lymphocytic infiltration in breast cancer subtypes and the ImmunoSkew score

The number of tumour biopsies required for a good representation of tumours has been controversial. An important factor to consider is intra-tumour heterogeneity, which can vary among cancer types and subtypes. Immune cells in particular often display complex infiltrative patterns, however, there is a lack of quantitative understanding of the spatial heterogeneity of immune cells and how this fundamental biological nature of human tumours influences biopsy variability and treatment resistance. We systematically investigate biopsy variability for the lymphocytic infiltrate in 998 breast tumours using a novel virtual biopsy method. Across all breast cancers, we observe a nonlinear increase in concordance between the biopsy and whole-tumour score of lymphocytic infiltrate with increasing number of biopsies, yet little improvement is gained with more than four biopsies. Interestingly, biopsy variability of lymphocytic infiltrate differs considerably among breast cancer subtypes, with the human epidermal growth factor receptor 2-positive (HER2+) subtype having the highest variability. We subsequently identify a quantitative measure of spatial variability that predicts disease-specific survival in HER2+ subtype independent of standard clinical variables (node status, tumour size and grade). Our study demonstrates how systematic methods provide new insights that can influence future study design based on a quantitative knowledge of tumour heterogeneity.

Pak1, adjuvant tamoxifen therapy, and breast cancer recurrence risk in a Danish population-based study

Background Adjuvant tamoxifen therapy approximately halves the risk of estrogen receptor-positive (ER+) breast cancer recurrence, but many women do not respond to therapy. Observational studies nested in clinical trial populations suggest that overexpression or nuclear localization of p21-activated kinase 1 (Pak1) in primary tumors predicts tamoxifen failure. Material and methods We measured the association between Pak1 expression and breast cancer recurrence in a Danish population-based case-control study. Pak1 cytoplasmic expression level and nuclear positivity were determined by immunohistochemical staining of primary breast tumors from recurrence cases and matched controls from two breast cancer populations; women diagnosed with ER-positive tumors who received at least one year of tamoxifen therapy (ER+/TAM+), and women diagnosed with ER-negative tumors who survived for at least one year (ER-/TAM-). Pak1 staining was assessed by a single, blinded pathologist, and associations were estimated with conditional logistic regression models. Results We included 541 recurrence cases and 1:1 matched controls from the ER+/TAM + group and 300 recurrence cases and 1:1 matched controls from the ER-/TAM - group. Pak1 cytoplasmic intensity was not associated with breast cancer recurrence in either group (ER+/TAM + ORadj for strong vs. no cytoplasmic staining = 0.91, 95% CI 0.57, 1.5; ER-/TAM - ORadj for strong vs. no cytoplasmic staining = 0.74, 95% CI 0.39, 1.4). Associations between Pak1 nuclear positivity and breast cancer recurrence were similarly near null in both groups. Conclusion Pak1 positivity in primary breast tumors was neither predictive nor prognostic in this prospective, population-based study.

A standardized method for quantifying proliferation by Ki-67 and cyclin A immunohistochemistry in breast cancer

Immunohistochemical analysis of proliferation markers such as Ki-67 and cyclin A is widely used in clinical evaluation as a prognostic factor in breast cancer. The proliferation status of tumors is guiding the decision of whether or not a patient should be treated with chemotherapy because low-proliferative tumors are less sensitive by such treatment. However, the lack of optimal cutoff points and selection of tumor areas hamper its use in clinical practice. This study was performed to compare the Ki-67 and cyclin A expression counted in hot-spot vs average counting based on 5 to 14 random tumor areas in 613 breast carcinomas. We correlated the findings with 10-year follow-up in order to standardize the evaluation of proliferation markers in clinical practice. A significant correlation was found between the percentage of positive cells estimated by Ki-67 and cyclin A both by hot-spot and by average counting. Both methods showed that high expression of Ki-67 and cyclin A is associated with more adverse tumor stage. The cutoff value for Ki-67 for distant metastases was set to 22% and to 15%, using hot-spot and average counting, respectively. For cyclin A, the values were set to 14% and 8% using the respective methods. Survival curves revealed that patients with a high hot-spot proliferation index had a significantly greater risk of shorter tumor-free survival. Our findings suggest that the determination of proliferation markers in breast cancer should be standardized to hot-spot counting and that specific cutoff values for proliferation could be useful as prognostic markers in clinical practice. Moreover, we suggest that expression levels of cyclin A could be used as a complementary marker to estimate the proliferation status in tumors, especially those with "borderline" expression levels of Ki-67, in order to more accurately estimate the proliferations status of the tumors.

Cyclin A2 and its associated kinase activity are required for optimal induction of progesterone receptor target genes in breast cancer cells

A role for the cell cycle protein cyclin A2 in regulating progesterone receptor (PR) activity is emerging. This study investigates the role of cyclin A2 in regulating endogenous PR activity in T47D breast cancer cells by depleting cyclin A2 expression and measuring PR target genes using q-RT-PCR. Targets examined included genes induced by the PR-B isoform more strongly than PR-A (SGK1, FKBP5), a gene induced predominantly by PR-A (HEF1), genes induced via PR tethering to other transcription factors (p21, p27), a gene induced in part via extra-nuclear PR signaling mechanisms (cyclin D1) and PR-repressed genes (DST, IL1R1). Progestin induction of target genes was reduced following cyclin A2 depletion. However, cyclin A2 depletion did not diminish progestin target gene repression. Furthermore, inhibition of the associated Cdk2 kinase activity of cyclin A2 also reduced progestin induction of target genes, while Cdk2 enhanced the interaction between PR and cyclin A2. These results demonstrate that cyclin A2 and its associated kinase activity are important for progestin-induced activation of endogenous PR target genes in breast cancer cells.

High proliferation is associated with inferior outcome in male breast cancer patients

Assessment of proliferation is important in female breast cancer and individual treatment decisions are based upon its results, especially in the luminal subgroups. Gene expression analyses fail to group male breast cancer into the intrinsic subgroups previously established in female breast cancer. Even though proliferation has been shown to divide male breast cancer into molecular subgroups with different prognoses, the clinical importance of proliferation markers has not yet been elucidated. Previous studies in male breast cancer have demonstrated contradictory results regarding the prognostic impact of histological grade and Ki-67, parameters strongly associated with proliferation. The aim of the present project was to study proliferation in male breast cancer by assessing other proliferation-related markers viz. cyclins A, B, D1 and mitotic count. A total of 197 male breast cancer cases with accessible paraffin-embedded material and outcome data were investigated. Immunohistochemical stainings were performed on tissue microarrays. Kaplan-Meier estimates and the Cox proportional regression models were used for survival analyses with breast cancer death as the event. The subset of patients with high expression of cyclin A (hazard ratio (HR) 3.7; P=0.001) and B (HR 2.7; P=0.02) demonstrated a poorer survival. Furthermore, high mitotic count was associated with an increased risk of breast cancer death (HR 2.5; P=0.01). In contrast, cyclin D1 overexpression was predictive of better breast cancer survival (HR 0.3; P=0.001). In conclusion, high levels of cyclin A and B expression and an elevated mitotic count result in a two to threefold higher risk for breast cancer death, whereas cyclin D1 overexpression halves the risk. The clinical utility of these proliferation markers needs further elucidation.

A practical guide to constructing and using tissue microarrays

Tissue microarray (TMA) technology is a robust "high throughput" method of tissue analysis, whereby a large number of patient samples can be examined in a short time using a minimum number of slides. In a TMA, cylinders of tissue are cored out of formalin-fixed, paraffin-embedded tissue blocks and slotted in a regular grid pattern into a blank recipient paraffin wax block. The TMA block is then cut using a standard laboratory microtome. Sections generated are suitable for all in situ techniques, such as immunohistochemistry (IHC) and in situ hybridisation, using essentially the same protocols as are used in conventional sections. The principle advantages of TMAs are that they save valuable biological material and ensure more reproducible reaction conditions while at the same time reducing re-agent costs and laboratory processing. Immunohistochemical studies designed to examine the prognostic utility of TMAs compared with large sections have generally found that they are comparable.

Tissue microarrays: one size does not fit all

BACKGROUND

Although tissue microarrays (TMAs) are commonly employed in clinical and basic-science research, there are no guidelines for evaluating the appropriateness of a TMA for a given biomarker and tumor type. Furthermore, TMA performance across multiple biomarkers has not been systematically explored.

METHODS

A simulated TMA with between 1 and 10 cores was designed to study tumor expression of 6 biomarkers with varied expression patterns (B7-H1, B7-H3, survivin, Ki-67, CAIX, and IMP3) using 100 patients with clear cell renal cell carcinoma (RCC). We evaluated agreement between whole tissue section and TMA immunohistochemical biomarker quantification to assess how many TMA cores are necessary to adequately represent RCC whole tissue section expression. Additionally, we evaluated associations of whole tissue section and TMA expression with RCC-specific death.

RESULTS

The number of simulated TMA cores necessary to adequately represent whole tissue section quantification is biomarker specific. Although 2-3 cores appeared adequate for B7-H3, Ki-67, CAIX, and IMP3, even as many as 10 cores resulted in poor agreement for B7-H1 and survivin compared to RCC whole tissue sections. While whole tissue section B7-H1 was significantly associated with RCC-specific death, no significant associations were detected using as many as 10 TMA cores, suggesting that TMAs can result in false-negative findings if the TMA is not optimally designed.

CONCLUSIONS

Prior to TMA analysis, the number of TMA cores necessary to accurately represent biomarker expression on whole tissue sections should be established as there is not a one-size-fits-all TMA. We illustrate the use of a simulated TMA as a cost-effective tool for this purpose.

Gene networks and microRNAs implicated in aggressive prostate cancer

Prostate cancer, a complex disease, can be relatively harmless or extremely aggressive. To identify candidate genes involved in causal pathways of aggressive prostate cancer, we implemented a systems biology approach by combining differential expression analysis and coexpression network analysis to evaluate transcriptional profiles using lymphoblastoid cell lines from 62 prostate cancer patients with aggressive phenotype (Gleason grade >or= 8) and 63 prostate cancer patients with nonaggressive phenotype (Gleason grade <or= 5). From 13,935 mRNA genes and 273 microRNAs (miRNA) tested, we identified significant differences in 1,100 mRNAs and 7 miRNAs with a false discovery rate (FDR) of <0.01. We also identified a coexpression module demonstrating significant association with the aggressive phenotype of prostate cancer (P = 3.67 x 10(-11)). The module of interest was characterized by overrepresentation of cell cycle-related genes (FDR = 3.50 x 10(-50)). From this module, we further defined 20 hub genes that were highly connected to other genes. Interestingly, 5 of the 7 differentially expressed miRNAs have been implicated in cell cycle regulation and 2 (miR-145 and miR-331-3p) are predicted to target 3 of the 20 hub genes. Ectopic expression of these two miRNAs reduced expression of target hub genes and subsequently resulted in cell growth inhibition and apoptosis. These results suggest that cell cycle is likely to be a molecular pathway causing aggressive phenotype of prostate cancer. Further characterization of cell cycle-related genes (particularly, the hub genes) and miRNAs that regulate these hub genes could facilitate identification of candidate genes responsible for the aggressive phenotype and lead to a better understanding of prostate cancer etiology and progression.

Cyclin A/cdk2 regulates adenomatous polyposis coli-dependent mitotic spindle anchoring

Mutations in adenomatous polyposis coli (APC) protein is a major contributor to tumor initiation and progression in several tumor types. These mutations affect APC function in the Wnt-beta-catenin signaling and influence mitotic spindle anchoring to the cell cortex and orientation. Here we report that the mitotic anchoring and orientation function of APC is regulated by cyclin A/cdk2. Knockdown of cyclin A and inhibition of cdk2 resulted in cells arrested in mitosis with activation of the spindle assembly checkpoint. The mitotic spindle was unable to form stable attachments to the cell cortex, and this resulted in the spindles failing to locate to the central position in the cells and undergo dramatic rotation. We have demonstrated that cyclin A/cdk2 specifically associates with APC in late G2 phase and phosphorylates it at Ser-1360, located in the mutation cluster region of APC. Mutation of APC Ser-1360 to Ala results in identical off-centered mitotic spindles. Thus, this cyclin A/cdk2-dependent phosphorylation of APC affects astral microtubule attachment to the cortical surface in mitosis.

High cyclin B1 expression is associated with poor survival in breast cancer

Cyclin B1 regulates the G₂-M transition of the cell cycle. Cyclin B1 expression is higher in premalignant and malignant than normal breast lesions. Correlation of cyclin B1 expression with other histopathological variables and prognostic role in breast cancer are not fully understood. Traditionally used prognostic criteria identify large subset of patients to receive adjuvant chemotherapy and to be exposed to adverse effects. A reliable and simple method helping prognostic evaluation in breast cancer is needed. We analysed cyclin B1 expression on 1348 invasive breast cancers and studied correlations with other histopathological variables and survival. High cyclin B1 correlated with high tumour grade, large tumour size and positive nodal status, oestrogen and progesterone receptor negativity, positive HER2 and p53 status, young age at diagnosis, and high cyclin E, cyclin A and Ki67 expression. Among patients not given adjuvant chemotherapy high cyclin B1 was a strong predictor of shorter overall and metastasis-free survival (RR 3.74, P<0.0005 and RR 3.51, P<0.0005, respectively), and remained as an independent prognostic factor also in multivariate analysis (RR 1.80, P=0.04 and RR 2.31, P=0.02, respectively). This study suggests high cyclin B1 associates with aggressive phenotype and is an independent prognostic factor in breast cancer.

Ki67 and cyclin A as prognostic factors in early breast cancer. What are the optimal cut-off values?

AIMS

To find the optimal cut-off values for cyclin A and Ki67 in early breast cancer tumours and to evaluate their prognostic values.

METHODS AND RESULTS

Tissue microarray (TMA) slides were constructed from 570 T1-4 N0-1 M0 breast cancer tumours. The TMA slides were stained for cyclin A and Ki67 using immunohistochemistry with commercial antibodies. To investigate the optimal cut-off values for cyclin A, Ki67 average and maximum values the material was split into two parts at cut-offs defined by dividing it into deciles. For each cut-off value the relative risk (RR) for metastasis-free survival (MFS) and overall survival (OS) was calculated comparing patients with high versus low cyclin A or Ki67 expression. When using a cut-off value around the seventh decile, cyclin A and Ki67 score correlated with the highest RR ratio for MFS in the chemotherapy-naïve subgroup. Among patients having received adjuvant chemotherapy, no statistically significant differences in MFS or OS were found.

CONCLUSIONS

The optimal cut-off value for cyclin A average is 8% and for cyclin A maximum value 11%; for Ki67 the corresponding values are 15% and 22%. Additional studies are needed to verify these results.

p27KIP-1, cyclin A and cyclin D1 protein expression in ductal carcinoma in situ of the breast: p27KIP-1 correlates with hormone receptor status but not with local recurrence

Using whole sections of formalin-fixed paraffin-embedded material the expression of p27(KIP-1), cyclin A and cyclin D1 was examined in 60 cases of ductal carcinoma in situ (DCIS) using routine immunohistochemistry with a median follow up of 95 months (range 10-139 months) to identify any association with disease recurrence. Fifty-six patients were treated by local excision and radiotherapy and four by mastectomy without radiotherapy. There was a highly significant positive association between p27(KIP-1) and estrogen receptor/progesterone receptor (ER/PR) status (P = 0.002, P = 0.02) and with p27(KIP-1) and cyclin D1 expression (P = 0.002). A trend between cyclin A and PR status (P = 0.08) was also identified. These findings mirror those described in invasive ductal carcinoma, but there were no associations of any biomarker with histological parameters such as nuclear grade or with local recurrence on univariate analysis, which was present in four of the 56 locally excised group (7.1%). Further examination of a larger cohort may be worthwhile to explore the possible role as adjunctive predictive markers to aid clinical decision making.