Triple-negative breast cancer

Pathways to breast cancer recurrence

Breast cancer remains a deadly disease, even with all the recent technological advancements. Early intervention has made an impact, but an overwhelmingly large number of breast cancer patients still live under the fear of “recurrent” disease. Breast cancer recurrence is clinically a huge problem and one that is largely not well understood. Over the years, a number of factors have been studied with an overarching aim of being able to prognose recurrent disease. This paper attempts to provide an overview of our current knowledge of breast cancer recurrence and its associated challenges. Through a survey of the literature on cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), various signaling pathways such as Notch/Wnt/hedgehog, and microRNAs (miRNAs), we also examine the hypotheses that are currently under investigation for the prevention of breast cancer recurrence.

Promise of rapalogues versus mTOR kinase inhibitors in subset specific breast cancer: old targets new hope

The PI3K-AKT-mTOR network has been the major focus of attention for cancer researchers (both in the clinic and the laboratory) in the last decade. An incomplete knowledge of the molecular biology of this complex network has seen an expansion of first generation allosteric mTOR inhibitors, rapalogues, but also biomarker studies designed to identify the best responders of these agents. Currently, research in this pathway has focused on the dual nature of mTOR that is integrated by mTOR-RAPTOR complex (mTORC1) and mTOR-RICTOR complex (mTORC2). These two complexes are regulated by different upstream proteins and also regulated by multiple different compensatory feedback loops. The related advantage of feedback regulation of signaling systems is that it allows diversification in signal response. This deeper understanding has facilitated the development of a novel second generation of inhibitors that are able to affect both mTORC1 and mTORC2, and their downstream effectors, through inhibition of their catalytic activity (ATP competitive inhibitors, attacking the kinase domain of this protein) than binding to the FKBP12 regulatory proteins as for rapalogues. This article reviews the newest insight in the signaling network of the mTOR pathway, preclinical/clinical status of mTOR inhibitors (including second generation of kinase inhibitors) and then focuses on the development of a new wave of research related to combination therapies in subset specific breast tumors.

Synthetic lethal interactions between EGFR and PARP inhibition in human triple negative breast cancer cells

Few therapeutic options exist for the highly aggressive triple negative breast cancers (TNBCs). In this study, we report that a contextual synthetic lethality can be achieved both in vitro and in vivo with combined EGFR and PARP inhibition with lapatinib and ABT-888, respectively. The mechanism involves a transient DNA double strand break repair deficit induced by lapatinib and subsequent activation of the intrinsic pathway of apoptosis. Further dissection of the mechanism reveals that EGFR and BRCA1 can be found in the same protein complex, which is reduced by lapatinib. Interestingly, lapatinib also increases cytosolic BRCA1 and EGFR, away from their nuclear DNA repair substrates. Taken together, these results reveal a novel regulation of homologous recombination repair involving EGFR and BRCA1 interaction and alteration of subcellular localization. Additionally, a contextual synthetic lethality may exist between combined EGFR and PARP inhibitors.

Exploring molecular pathways of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype with a high rate of proliferation and metastasis, as well as poor prognosis for advanced-stage disease. Although TNBC was previously classified together with basal-like and BRCA1/2-related breast cancers, genomic profiling now shows that there is incomplete overlap, with important distinctions associated with each subtype. The biology of TNBC is still poorly understood; therefore, to define the relative contributions of major cellular pathways in TNBC, we have studied its molecular signature based on analysis of gene expression. Comparisons were then made with normal breast tissue. Our results suggest the existence of molecular networks in TNBC, characterized by explicit alterations in the cell cycle, DNA repair, nucleotide synthesis, metabolic pathways, NF-κB signaling, inflammatory response, and angiogenesis. Moreover, we also characterized TNBC as a cancer of mixed phenotypes, suggesting that TNBC extends beyond the basal-like molecular signature and may constitute an independent subtype of breast cancer. The data provide a new insight into the biology of TNBC.

Remodeling of central metabolism in invasive breast cancer compared to normal breast tissue - a GC-TOFMS based metabolomics study

Background

Changes in energy metabolism of the cells are common to many kinds of tumors and are considered a hallmark of cancer. Gas chromatography followed by time-of-flight mass spectrometry (GC-TOFMS) is a well-suited technique to investigate the small molecules in the central metabolic pathways. However, the metabolic changes between invasive carcinoma and normal breast tissues were not investigated in a large cohort of breast cancer samples so far.

Results

A cohort of 271 breast cancer and 98 normal tissue samples was investigated using GC-TOFMS-based metabolomics. A total number of 468 metabolite peaks could be detected; out of these 368 (79%) were significantly changed between cancer and normal tissues (p<0.05 in training and validation set). Furthermore, 13 tumor and 7 normal tissue markers were identified that separated cancer from normal tissues with a sensitivity and a specificity of >80%. Two-metabolite classifiers, constructed as ratios of the tumor and normal tissues markers, separated cancer from normal tissues with high sensitivity and specificity. Specifically, the cytidine-5-monophosphate / pentadecanoic acid metabolic ratio was the most significant discriminator between cancer and normal tissues and allowed detection of cancer with a sensitivity of 94.8% and a specificity of 93.9%.

Conclusions

For the first time, a comprehensive metabolic map of breast cancer was constructed by GC-TOF analysis of a large cohort of breast cancer and normal tissues. Furthermore, our results demonstrate that spectrometry-based approaches have the potential to contribute to the analysis of biopsies or clinical tissue samples complementary to histopathology.

Methylation profile of triple-negative breast carcinomas

Breast cancer is a group of clinically, histopathologically and molecularly heterogeneous diseases, with different outcomes and responses to treatment. Triple-negative (TN) breast cancers are defined as tumors that lack the expression of estrogen receptor, progesterone receptor and epidermal growth factor receptor 2. This subgroup accounts for 15% of all types of breast cancer and its prevalence is higher among young African, African-American and Latino women. The hypermethylation of CpG islands (CpGI) is a common epigenetic alteration for suppressing gene expression in breast cancer and has been shown to be a key factor in breast carcinogenesis. In this study we analyzed the hypermethylation of 110 CpGI within 69 cancer-related genes in TN tumors. For the methylation analysis, we used the methyl-specific multiplex-ligation probe amplification assay. We found that the number of methylated CpGI is similar between TN and non-TN tumors, but the methylated genes between the groups are different. The methylation profile of TN tumors is defined by the methylation of five genes (that is, CDKN2B, CD44, MGMT, RB and p73) plus the non-methylation of 11 genes (that is, GSTP1, PMS2, MSH2, MLH1, MSH3, MSH6, DLC1, CACNA1A, CACNA1G, TWIST1 and ID4). We conclude that TN tumors have a specific methylation profile. Our findings give new information for better understanding tumor etiology and encourage future studies on potential drug targets for triple-negative breast tumors, which now lack a specific treatment.

Overexpression of Cell Cycle Progression Inhibitor Geminin is Associated with Tumor Stem-Like Phenotype of Triple-Negative Breast Cancer

PURPOSE

Triple-negative breast cancer, has a significant clinical relevance being associated with a shorter median time to relapse and death and does not respond to endocrine therapy or other available targeted agents. For this reason, identifying the molecular pathways associated with increased aggressiveness, for example the presence of stem cell populations within the tumor and alteration of genes associated with cell cycle regulation represents an important objective in the clinical research into this neoplasm.

METHODS

To investigate the role of cell cycle progression inhibitor Geminin in triple-negative breast cancers and its potential correlation with stem-like phenotype of this neoplasm, we used tissue microarray technology to build a specific triple-negative breast cancer tissue micro-array. Geminin and cancer stem cell marker CD133 expression was further investigated at the mRNA level for selected breast tumor samples through realtime polymerase chain reaction quantification.

RESULTS

Our results showed that CD133 expression was significantly associated to high Geminin expression (p=0.017), a strong association between Ki-67 and tumor grade (p=0.020) and an inverse association between Geminin expression and lymphonode metastases (p=0.058), and a trend of statistically significance between Geminin marker expression and survival of triple-negative breast cancer patients (p=0.076).

CONCLUSION

The strong association between the expression of CD133 and Geminin could be useful in molecular stratification of breast tumors and in particular of triple-negative breast cancers.

A population-based study of Kurdish breast cancer in northern Iraq: hormone receptor and HER2 status. A comparison with Arabic women and United States SEER data

Background

Hormone receptor (HR) and HER2 expression predict the therapeutic response and prognosis of breast cancer. In the Middle-East, breast cancer is diagnosed at a young age, and Arabic women are reported to have a low frequency of HR positive tumors. This study investigates HR and HER2 expression among Kurdish and Arabic women.

Methods

During 2008–2010, the Sulaimaniyah Directorate of Health records identified 514 Sulaimaniyah Kurdish women, 227 Kurdish women of other Governates, and 83 Arabic women with a first diagnosis of breast cancer. The breast cancers of 432 women had immunohistochemistry (IHC) performed for estrogen and progesterone receptors (ER and PR) and HER2. Age specific and age standardized incidence rates were calculated for Sulaimaniyah Kurds. Results were compared with Egypt and with United States (US) SEER data.

Results

The median patient age was 46 years and 60.4% were < 50 years old. Tumors of 65.2% of women were ER+/HER2- with the rate increasing to 78.3% in patients ≥ 60 years old in proportions similar to US whites. The total annual age standardized incidence for breast cancer among Sulaimaniyah Kurds was 40.5/100,000 women, a rate similar to Egypt but much lower than the US. By HR/HER2 subtype, the highest age specific incidence rates were 16.4 and 45.4/100,000 for ER+/PR+/HER2- tumors in women < 50 or ≥ 50 years old, respectively (US whites: 37.7 and 226.1/100,000). Tumors of 20.4% of Sulaimaniyah women were HER2+ with annual incidence rates for ER-/PR-/HER2+ tumors of women <50 or ≥ 50 years old being 4.0 and 6.3/100,000 (US whites: 3.2 and 14.4/100,000). No significant differences in ER or HER2 status were found between Kurdish and Arabic patients.

Conclusions

Compared to the US, low age standardized and age specific breast cancer incidence rates were found in Kurdish women; nevertheless, the proportional expression of HR and HER2 for both Kurds and Arabs was comparable to that of US white women. The great majority of the breast cancer was ER+/HER2- and should respond to anti-estrogen therapy.

Targeting triple-negative breast cancer cells with the histone deacetylase inhibitor panobinostat

INTRODUCTION

Of the more than one million global cases of breast cancer diagnosed each year, approximately fifteen percent are characterized as triple-negative, lacking the estrogen, progesterone, and Her2/neu receptors. Lack of effective therapies, younger age at onset, and early metastatic spread have contributed to the poor prognoses and outcomes associated with these malignancies. Here, we investigate the ability of the histone deacetylase inhibitor panobinostat (LBH589) to selectively target triple-negative breast cancer (TNBC) cell proliferation and survival in vitro and tumorigenesis in vivo.

METHODS

TNBC cell lines MDA-MB-157, MDA-MB-231, MDA-MB-468, and BT-549 were treated with nanomolar (nM) quantities of panobinostat. Relevant histone acetylation was verified by flow cytometry and immunofluorescent imaging. Assays for trypan blue viability, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) proliferation, and DNA fragmentation were used to evaluate overall cellular toxicity. Changes in cell cycle progression were assessed with propidium iodide flow cytometry. Additionally, qPCR arrays were used to probe MDA-MB-231 cells for panobinostat-induced changes in cancer biomarkers and signaling pathways. Orthotopic MDA-MB-231 and BT-549 mouse xenograft models were used to assess the effects of panobinostat on tumorigenesis. Lastly, flow cytometry, ELISA, and immunohistochemical staining were applied to detect changes in cadherin-1, E-cadherin (CDH1) protein expression and the results paired with confocal microscopy in order to examine changes in cell morphology.

RESULTS

Panobinostat treatment increased histone acetylation, decreased cell proliferation and survival, and blocked cell cycle progression at G2/M with a concurrent decrease in S phase in all TNBC cell lines. Treatment also resulted in apoptosis induction at 24 hours in all lines except the MDA-MB-468 cell line. MDA-MB-231 and BT-549 tumor formation was significantly inhibited by panobinostat (10 mg/kg/day) in mice. Additionally, panobinostat up-regulated CDH1 protein in vitro and in vivo and induced cell morphology changes in MDA-MB-231 cells consistent with reversal of the mesenchymal phenotype.

CONCLUSIONS

This study revealed that panobinostat is overtly toxic to TNBC cells in vitro and decreases tumorigenesis in vivo. Additionally, treatment up-regulated anti-proliferative, tumor suppressor, and epithelial marker genes in MDA-MB-231 cells and initiated a partial reversal of the epithelial-to-mesenchymal transition. Our results demonstrate a potential therapeutic role of panobinostat in targeting aggressive triple-negative breast cancer cell types.

Synthesis of new 2-galactosylthiazolidine-4-carboxylic acid amides. Antitumor evaluation against melanoma and breast cancer cells

A set of 2-galactosylthiazolidine-4-carboxylic acid amides was synthesized with different length for the carbon chain amide moiety. The cytotoxicity of the molecules was evaluated against A375 melanoma and MCF7 breast cancer cell lines. For the derivatives tested, the one that contains a C(16) amide carbon chain is the most active with an IC(50) of 17.0 μM for A375 and 5.8 μM for MCF7. This compound also shows cytotoxicity in the triple negative cancer cell line HCC1806. The selectivity of the compounds was assessed by comparing the cytotoxicity in cancer cell line versus in a fibroblast cell line. Flow cytometry studies show the activation of apoptotic pathways and also DNA damages with blockage of the cell cycle in the S-phase and appearance of peaks in G0/G1-phase.

First indicators of relapse in breast cancer: evaluation of the follow-up program at our hospital

BACKGROUND

Guidelines for breast cancer patient follow-up have not been widely adopted in Japan. To assess our intensive follow-up program, we evaluated first relapse and its indicators in patients with breast cancer.

PATIENTS

Of 964 patients, 126 relapsed and 43 died in the median follow-up term of 45 months. Follow-ups were scheduled every 6-12 months for imaging and tumor marker (TM) evaluation.

RESULTS

Of 126 relapsed patients, 30 (23.8%) had symptoms of relapse. First indicators of relapse in 96 asymptomatic patients were physical examination in 24 patients (19%); imaging, 57 patients (45.3%); and TMs, 15 patients (11.9%). The most sensitive indicators were physical examination for local relapse, ultrasonography for regional lymph nodes, scintigraphy for bone, computed tomography for lung, and TMs for liver metastasis. During intensive follow-up, 43% of relapsed patients were identified by symptoms or physical examination. These patients had poor prognosis compare to patients identified by imaging or TMs in overall survival and post-relapse survival (p = 0.009 and 0.019, respectively). In all 964 patients, the relapse rates for stage I, IIA, IIB, and III tumors were 7.4, 7.9, 19.9, and 43.5%, respectively. The percentage of first relapse detected by imaging or TMs for stage I, IIA, IIB, and III were 4.7, 5.1, 11.8, and 19.8%, respectively. The cost of our follow-up program for 10 years was approximately 290,000 yen per patient.

CONCLUSION

A routine intensive follow-up program involving imaging and evaluation of TMs in all patients has low efficacy and high expenditure.

Patient survival and healthcare utilization costs after diagnosis of triple-negative breast cancer in a United States managed care cancer registry

BACKGROUND

Triple-negative breast cancer (TNBC) makes up 10-17% of all breast cancers and, due to lack of receptor expression, is unresponsive to therapies that target hormonal receptors or HER2. Unique in its tumor aggression and high rates of recurrence, TNBC is less likely to be detected by mammogram and has a poorer prognosis than other breast cancer subtypes (non-TNBC).

OBJECTIVES

To examine the survival, healthcare utilization, and healthcare cost for women with TNBC compared with non-TNBC breast cancer.

METHODS

The study population was derived from a US managed care cancer registry linked to health insurance claims and social security mortality data. Based on initial type and stage at diagnosis, patients were divided into two cohorts: patients with TNBC and those with non-TNBC. Records were analyzed from initial diagnosis until death, disenrollment, or end of observation period. Survival and annual healthcare utilization and costs were estimated and compared between cohorts after adjusting for baseline demographic characteristics, comorbidities, and prior resource use. Subgroup analyses were performed in patients diagnosed with stage I-III and IV breast cancer.

RESULTS

The study included women diagnosed with TNBC (n = 450) and non-TNBC (n = 1807). Median follow-up time for all patients was 716 days (688.5 and 733 days for TNBC and non-TNBC patients, respectively). After initial diagnosis, overall mortality risk for the TNBC cohort was twice as high as the non-TNBC cohort (HR = 2.02, p < 0.0001). Patients with TNBC had more annual hospitalizations, hospitalized days, and number of emergency room visits relative to non-TNBC. Despite similar annual total healthcare costs, adjusted inpatient costs for patients with non-TNBC averaged 77% higher ($8395 vs. $4745, p < 0.0001). Furthermore, payer reimbursements were higher for TNBC than non-TNBC patients ($8213 vs. $4486, p < 0.0001).

CONCLUSIONS

While it does not control for race or socioeconomic status, this study found that in a US managed care setting, patients with TNBC compared with non-TNBC have significantly shorter survival, accompanied by higher inpatient utilization and healthcare costs.

Small interfering RNA library screen identified polo-like kinase-1 (PLK1) as a potential therapeutic target for breast cancer that uniquely eliminates tumor-initiating cells

INTRODUCTION

Triple-negative breast cancer (TNBC) high rate of relapse is thought to be due to the presence of tumor-initiating cells (TICs), molecularly defined as being CD44high/CD24-/low. TICs are resilient to chemotherapy and radiation. However, no currently accepted molecular target exists against TNBC and, moreover, TICs. Therefore, we sought the identification of kinase targets that inhibit TNBC growth and eliminate TICs.

METHODS

A genome-wide human kinase small interfering RNA (siRNA) library (691 kinases) was screened against the TNBC cell line SUM149 for growth inhibition. Selected siRNAs were then tested on four different breast cancer cell lines to confirm the spectrum of activity. Their effect on the CD44high subpopulation and sorted CD44high/CD24-/low cells of SUM149 also was studied. Further studies were focused on polo-like kinase 1 (PLK1), including its expression in breast cancer cell lines, effect on the CD44high/CD24-/low TIC subpopulation, growth inhibition, mammosphere formation, and apoptosis, as well as the activity of the PLK1 inhibitor, BI 2536.

RESULTS

Of the 85 kinases identified in the screen, 28 of them were further silenced by siRNAs on MDA-MB-231 (TNBC), BT474-M1 (ER+/HER2+, a metastatic variant), and HR5 (ER+/HER2+, a trastuzumab-resistant model) cells and showed a broad spectrum of growth inhibition. Importantly, 12 of 28 kinases also reduced the CD44high subpopulation compared with control in SUM149. Further tests of these 12 kinases directly on a sorted CD44high/CD24-/low TIC subpopulation of SUM149 cells confirmed their effect. Blocking PLK1 had the greatest growth inhibition on breast cancer cells and TICs by about 80% to 90% after 72 hours. PLK1 was universally expressed in breast cancer cell lines, representing all of the breast cancer subtypes, and was positively correlated to CD44. The PLK1 inhibitor BI 2536 showed similar effects on growth, mammosphere formation, and apoptosis as did PLK1 siRNAs. Finally, whereas paclitaxel, doxorubicin, and 5-fluorouracil enriched the CD44high/CD24-/low population compared with control in SUM149, subsequent treatment with BI 2536 killed the emergent population, suggesting that it could potentially be used to prevent relapse.

CONCLUSION

Inhibiting PLK1 with siRNA or BI 2536 blocked growth of TNBCs including the CD44high/CD24-/low TIC subpopulation and mammosphere formation. Thus, PLK1 could be a potential therapeutic target for the treatment of TNBC as well as other subtypes of breast cancer.

ErbB2, EphrinB1, Src kinase and PTPN13 signaling complex regulates MAP kinase signaling in human cancers

In non-cancerous cells, phosphorylated proteins exist transiently, becoming de-phosphorylated by specific phosphatases that terminate propagation of signaling pathways. In cancers, compromised phosphatase activity and/or expression occur and contribute to tumor phenotype. The non-receptor phosphatase, PTPN13, has recently been dubbed a putative tumor suppressor. It decreased expression in breast cancer correlates with decreased overall survival. Here we show that PTPN13 regulates a new signaling complex in breast cancer consisting of ErbB2, Src, and EphrinB1. To our knowledge, this signaling complex has not been previously described. Co-immunoprecipitation and localization studies demonstrate that EphrinB1, a PTPN13 substrate, interacts with ErbB2. In addition, the oncogenic V660E ErbB2 mutation enhances this interaction, while Src kinase mediates EphrinB1 phosphorylation and subsequent MAP Kinase signaling. Decreased PTPN13 function further enhances signaling. The association of oncogene kinases (ErbB2, Src), a signaling transmembrane ligand (EphrinB1) and a phosphatase tumor suppressor (PTPN13) suggest that EphrinB1 may be a relevant therapeutic target in breast cancers harboring ErbB2-activating mutations and decreased PTPN13 expression.

Notch-1 and Notch-4 biomarker expression in triple-negative breast cancer

Triple-negative breast cancer (TNBC) demonstrates lack of expression of hormone receptors and human epidermal growth factor receptor. However, there is no targeted therapy for TNBC. The authors analyzed 29 TNBC cases for Notch-1 and Notch-4 biomarker expression and subcellular location, Ki67 proliferation rate, and relevant clinical/survival data. Results demonstrated an unfavorable Ki67 rate in 90% of cases, Notch-1 expression in tumor and endothelial cells in 100% of cases, and Notch-4 expression in tumor cells in 73% of cases and endothelial cells in 100% of cases. Additionally, subcellular localization of Notch-1 and Notch-4 was predominantly nuclear and cytoplasmic. In conclusion, (a) the majority of TNBCs are high-grade infiltrating ductal carcinomas with high Ki67 proliferation rate and (b) both Notch-1 and Notch-4 receptors are overexpressed in tumor and vascular endothelial cells with subcellular localization different from that of hormone-positive breast cancer. Targeting Notch signaling with gamma secretase inhibitors should to be explored to further improve the survival rate of TNBC patients.

DNA damage and breast cancer

Cancer is intimately related to the accumulation of DNA damage, and repair failures (including mutation prone repair and hyperactive repair systems). This article relates current clinical categories for breast cancer and their common DNA damage repair defects. Information is included on the potential for accumulation of DNA damage in the breast tissue of a woman during her lifetime and the role of DNA damage in breast cancer development. We then cover endogenous and exogenous sources of DNA damage, types of DNA damage repair and basic signal transduction pathways for three gene products involved in the DNA damage response system; namely BRCA1, BRIT1 and PARP-1. These genes are often considered tumor suppressors because of their roles in DNA damage response and some are under clinical investigation as likely sources for effective new drugs to treat breast cancers. Finally we discuss some of the problems of DNA damage repair systems in cancer and the conundrum of hyper-active repair systems which can introduce mutations and confer a survival advantage to certain types of cancer cells.

Overexpression of Hedgehog signaling molecules and its involvement in triple-negative breast cancer

The purpose of this study was to investigate the activation of Hedgehog (Hh) signaling molecules and its involvement in triple-negative breast cancer (TNBC). A total of 123 cases of paraffin blocks, including 83 cases of primary breast carcinoma, 30 cases of mammary hyperplasia and 10 cases of normal breast tissue, were immunohistochemically analyzed for Sonic Hedgehog (SHH), Patched-1 (PTCH1), Smoothened (SMO) and glioma-associated oncogene homoglog 1 (GLI1) expression. The expression of SMO and GLI1 in TNBC was significantly increased in comparison to non-triple-negative breast cancer (nTNBC). GLI1 expression manifested an inverse association with the estrogen receptor. The levels of GLI1 expression were increased in lymph node-positive cases. The expression of SHH and SMO was increased in high histological grades. Furthermore, the expression of SMO and GLI1 was correlated with superior tumor stage. The expression of SHH, SMO and GLI1 was significantly increased in breast cancer and mammary hyperplasia. PTCH1 expression was significantly decreased in breast cancer compared to mammary hyperplasia and normal breast tissue. For the first time, clinical evidence has been provided in support of significant roles of Hh signaling in TNBC. Hh signaling is involved in breast ductal changes and malignant transformation. Measures to inhibit Hh activity may improve the prognosis of TNBC patients.

'Triple negative' epithelial ovarian cancer and pathologic markers for prognosis

PURPOSE OF REVIEW

To summarize the recent evidence for 'triple negative' epithelial ovarian cancer (TNEOC), characterized by lack of expression of estrogen receptor, progesterone receptor and human epidermal growth factor receptor type 2 (HER2), and to discuss its potential pathologic markers for prognosis and targeted therapy.

RECENT FINDINGS

'Triple negative' phenotype is traditionally referred to as a specific subtype of breast cancer negative for estrogen receptor, progesterone receptor and HER2 expression. Recent studies have shown that such 'triple negative' phenotype also exists in ovarian and endometrial cancer. TNEOC accounts for about 15% of epithelial ovarian carcinoma. This specific subtype tends to exhibit more aggressive characteristics and a worse prognosis. The molecular features of TNEOC are similar to those of 'triple negative' breast cancer (TNBC), a widely studied histological subtype. Recently, a panel of specific pathologic biomarkers has been identified in TNBC. Currently, phase I and phase II trials to examine the safety and efficacy of a poly (ADP-ribose) polymerase inhibitor (olaparib) and angiogenesis inhibitors (sunitinib and bevacizumab) in TNBC are ongoing. These TNBC-associated pathologic markers could be used to screen for novel prognostic factors and therapeutic targets in TNEOC.

SUMMARY

'Triple negative' phenotype has important implications for clinical management of patients with ovarian cancer.

The indole-3-carbinol cyclic tetrameric derivative CTet inhibits cell proliferation via overexpression of p21/CDKN1A in both estrogen receptor-positive and triple-negative breast cancer cell lines

INTRODUCTION

Indole-3-carbinol (I3C), an autolysis product of glucosinolates present in cruciferous vegetables, and its dimeric derivative (3,3'-DIM) have been indicated as promising agents in preventing the development and progression of breast cancer. We have recently shown that I3C cyclic tetrameric derivative CTet formulated in γ-cyclodextrin (γ-CD) efficiently inhibited cellular proliferation in breast cancer cell lines. This study aims to analyze the mechanisms involved in the in vitro inhibition of cell proliferation and to evaluate the in vivo antitumor activity of CTet in a xenograft study.

METHODS

Estrogen receptor-positive MCF-7 and triple-negative MDA-MB-231 breast cancer cell lines were exposed to CTet to evaluate cell cycle perturbation (propidium iodide staining and cytofluorimetric acquisition), induction of autophagic morphological features (co-localization of LC3b autophagosome marker and LAMP2a lysosome marker by immunofluorescence) and changes in protein expression (immunoblot and microarray-based gene expression analyses). To test the in vivo efficacy of CTet, female athymic nude mice inoculated with MCF-7 cells were i.p. treated with 5 mg/kg/day of CTet for five days/week for two weeks and the tumor mass was externally monitored.

RESULTS

CTet induced accumulation in G2/M phase without evidence of apoptotic response induction in both cell lines tested. In triple-negative MDA-MB-231 the autophagic lysosomal activity was significantly up-regulated after exposure to 4 μM of CTet for 8 hours, while the highest CTet concentration was necessary to observe autophagic features in MCF-7 cells. The inhibition of Akt activity and p53-independent p21/CDKN1A and GADD45A overexpression were identified as the main molecular events responsible for CTet activity in MCF-7 and p53-mutant MDA-MB-231 cells. In vivo, CTet administration was able to significantly inhibit the growth of MCF-7 xenotransplanted into nude mice, without adverse effect on body weight or on haematological parameters.

CONCLUSIONS

Our data support CTet formulated with γ-CD as a promising and injectable anticancer agent for both hormone-responsive and triple-negative breast tumors.