Allelic loss of the PTEN region (10q23) in breast carcinomas of poor pathophenotype

Progression from ductal carcinoma in situ to invasive breast cancer: molecular features and clinical significance

Ductal carcinoma in situ (DCIS) represents pre-invasive breast carcinoma. In untreated cases, 25-60% DCIS progress to invasive ductal carcinoma (IDC). The challenge lies in distinguishing between non-progressive and progressive DCIS, often resulting in over- or under-treatment in many cases. With increasing screen-detected DCIS in these years, the nature of DCIS has aroused worldwide attention. A deeper understanding of the biological nature of DCIS and the molecular journey of the DCIS-IDC transition is crucial for more effective clinical management. Here, we reviewed the key signaling pathways in breast cancer that may contribute to DCIS initiation and progression. We also explored the molecular features of DCIS and IDC, shedding light on the progression of DCIS through both inherent changes within tumor cells and alterations in the tumor microenvironment. In addition, valuable research tools utilized in studying DCIS including preclinical models and newer advanced technologies such as single-cell sequencing, spatial transcriptomics and artificial intelligence, have been systematically summarized. Further, we thoroughly discussed the clinical advancements in DCIS and IDC, including prognostic biomarkers and clinical managements, with the aim of facilitating more personalized treatment strategies in the future. Research on DCIS has already yielded significant insights into breast carcinogenesis and will continue to pave the way for practical clinical applications.

The interplay of PTEN and AKT nexus in breast cancer: a molecular perspective

BACKGROUND

Breast cancer is a highly prevalent and life-threatening ailment that is commonly detected among the females. The downregulation of PTEN in breast cancer is associated with a poor prognosis, aggressive tumor type, and metastasis to lymph nodes, as it activates the pro-survival pathway PI3K/AKT, which is considered the ultimate proliferative pathway.

MATERIAL AND METHODS

The mRNA expression of PTEN and AKT genes was investigated using RT-qPCR and TaqMan primer probe chemistry. Moreover DNA was also isolated from the same tissue samples and exonic regions of both genes were amplified for mutational analysis. The proteins expression of PTEN and AKT from seven human breast cancer cell lines was checked through western blot experiments.

RESULT

The study revealed a decrease in PTEN expression in 73.3% of the samples, whereas an increase in AKT expression in 40% of samples was observed when compared to the distant normal breast tissue. Conversely, the remaining 60% of samples exhibited a decrease in AKT mRNA expression. There was no observed alteration in the genetic sequence of AKT and PTEN within the targeted amplified regions of breast cancer samples. The high levels of PTEN protein in T-47D and MDA-MB-453 resulted in a lower p-AKT. Two cell lines ZR-75-1 and MDA-MB-468 appeared to be PTEN negative on western blot but mRNA was detected on RT-qPCR.

CONCLUSION

In breast cancer the status/expression of PTEN & AKT at mRNA and protein level might be obliging in forecasting the path of disease progression, treatment and prognosis.

An Immunohistochemical Study of the PTEN/AKT Pathway Involvement in Canine and Feline Mammary Tumors

Simple Summary

The PTEN/AKT pathway is involved in several human and animal tumors’ pathogenesis. This study investigates the PTEN/AKT pathway’s biological and prognostic values in canine and feline mammary tumors. PTEN, phospho-AKT (p-AKT) and Rictor expression was determined by immunohistochemistry in canine mammary adenomas and carcinomas and feline mammary carcinomas. In mammary tumors of both species p-Akt was inversely correlated with PTEN expression and positively with Rictor expression; p-Akt and Rictor expression correlated with poorer prognosis. This data could provide a rationale for further studies of this pathway in veterinary oncology due to prognostic and therapeutic implications.

Abstract

Phosphatase and tensin homolog deleted on chromosome10 (PTEN), phospho-v-Akt murine thymoma viral oncogene homolog (AKT), and the Rapamycin-Insensitive Companion of mTOR (Rictor) expression was investigated by immunohistochemistry in 10 canine mammary adenomas (CMAs), 40 canine mammary carcinomas (CMCs), and 30 feline mammary carcinomas (FMCs). All the CMAs, 25 of 40 CMCs (63%) and 7 of 30 FMCs (23%), were PTEN-positive. In dogs, no CMAs and 15 of 25 CMCs (37%) expressed phospho-AKT (p-AKT), while 24 of 30 FMCs (82%) were p-AKT-positive. One of 10 CMAs (10%), 24 of 40 CMCs (60%) and 20 of 30 FMCs (67%) were Rictor-positive. In the dog, PTEN expression correlated with less aggressive tumors, absence of lymphatic invasion, and longer survival. P-AKT expression correlated with more aggressive subtype, lymphatic invasion, and poorer survival and Rictor expression with lymphatic invasion. In cats, PTEN correlated with less aggressive carcinomas, absence of lymphatic invasion, and better survival. P-AKT and Rictor expression correlated with poorer survival. PTEN expression was inversely correlated with p-AKT and Rictor in both species, while p-AKT positively correlated with Rictor expression. A strong PTEN/AKT pathway involvement in behavior worsening of CMT and FMTs is demonstrated, providing a rationale for further studies of this pathway in veterinary oncology.

Targeting Loss of Heterozygosity: A Novel Paradigm for Cancer Therapy

Loss of heterozygosity (LOH) is a common genetic event in the development of cancer. In certain tumor types, LOH can affect more than 20% of the genome, entailing loss of allelic variation in thousands of genes. This reduction of heterozygosity creates genetic differences between tumor and normal cells, providing opportunities for development of novel cancer therapies. Here, we review and summarize (1) mutations associated with LOH on chromosomes which have been shown to be promising biomarkers of cancer risk or the prediction of clinical outcomes in certain types of tumors; (2) loci undergoing LOH that can be targeted for development of novel anticancer drugs as well as (3) LOH in tumors provides up-and-coming possibilities to understand the underlying mechanisms of cancer evolution and to discover novel cancer vulnerabilities which are worth a further investigation in the near future.

Hormone Receptor Loss in Breast Cancer: Molecular Mechanisms, Clinical Settings, and Therapeutic Implications

Hormone receptor-positive breast cancer (HR+ BC) accounts for approximately 75% of new BC diagnoses. Despite the undisputable progresses obtained in the treatment of HR+ BC in recent years, primary or acquired resistance to endocrine therapies still represents a clinically relevant issue, and is largely responsible for disease recurrence after curative surgery, as well as for disease progression in the metastatic setting. Among the mechanisms causing primary or acquired resistance to endocrine therapies is the loss of estrogen/progesterone receptor expression, which could make BC cells independent of estrogen stimulation and, consequently, resistant to estrogen deprivation or the pharmacological inhibition of estrogen receptors. This review aims at discussing the molecular mechanisms and the clinical implications of HR loss as a result of the therapies used in the neoadjuvant setting or for the treatment of advanced disease in HR+ BC patients.

The frequency of PTEN germline mutations in Chinese breast cancer patients: The PTEN gene may not be closely associated with breast cancer in the Chinese population

BACKGROUND

PTEN is a tumour suppressor gene that has been proven to be related to breast cancer incidence and tumour progression. The aim of this study was to investigate the frequency of PTEN mutations in breast carcinomas in China and the relationships of PTEN mutations with clinicopathological parameters and clinical outcomes.

MATERIAL AND METHODS

Trimmomatic, Burrows-Wheeler Aligner (BWA), ANNOVAR, SAMtools, and Sanger sequencing were used to analyse PTEN mutations and identify variants in Chinese breast cancer. The frequency of PTEN mutations and the relationships of PTEN mutations with clinicopathological parameters and clinical outcomes were evaluated in breast carcinomas in China.

RESULTS

The rate of PTEN germline mutation was 0.23% (n = 9) among 3955 unselected primary breast cancer patients. Of these 9 patients, 2 carried pathogenic mutations, and both were identified as having infiltrative carcinoma. One patient had a family history. The other 7 patients carried only PTEN germline variants that were not identified as pathogenic mutations.

CONCLUSIONS

We studied the frequency of PTEN germline mutations in a sequential cohort of Chinese breast carcinoma patients. Based on these data, we hypothesize that the germline mutation of the PTEN gene is not closely related to the occurrence of breast cancer in the Chinese population. In the clinic, the PTEN germline mutation cannot be used as the basis for the detection of breast cancer.

PTEN Tumor-Suppressor: The Dam of Stemness in Cancer

PTEN is one of the most frequently inactivated tumor suppressor genes in cancer. Loss or variation in PTEN gene/protein levels is commonly observed in a broad spectrum of human cancers, while germline PTEN mutations cause inherited syndromes that lead to increased risk of tumors. PTEN restrains tumorigenesis through different mechanisms ranging from phosphatase-dependent and independent activities, subcellular localization and protein interaction, modulating a broad array of cellular functions including growth, proliferation, survival, DNA repair, and cell motility. The main target of PTEN phosphatase activity is one of the most significant cell growth and pro-survival signaling pathway in cancer: PI3K/AKT/mTOR. Several shreds of evidence shed light on the critical role of PTEN in normal and cancer stem cells (CSCs) homeostasis, with its loss fostering the CSC compartment in both solid and hematologic malignancies. CSCs are responsible for tumor propagation, metastatic spread, resistance to therapy, and relapse. Thus, understanding how alterations of PTEN levels affect CSC hallmarks could be crucial for the development of successful therapeutic approaches. Here, we discuss the most significant findings on PTEN-mediated control of CSC state. We aim to unravel the role of PTEN in the regulation of key mechanisms specific for CSCs, such as self-renewal, quiescence/cell cycle, Epithelial-to-Mesenchymal-Transition (EMT), with a particular focus on PTEN-based therapy resistance mechanisms and their exploitation for novel therapeutic approaches in cancer treatment.

Targeting the PI3-kinase pathway in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is characterised by poor outcomes and a historical lack of targeted therapies. Dysregulation of signalling through the phosphoinositide 3 (PI3)-kinase and AKT signalling pathway is one of the most frequent oncogenic aberrations of TNBC. Although mutations in individual genes occur relatively rarely, combined activating mutations in PIK3CA and AKT1, with inactivating mutations in phosphatase and tensin homologue, occur in ∼25%‒30% of advanced TNBC. Recent randomised trials suggest improved progression-free survival (PFS) with AKT-inhibitors in combination with first-line chemotherapy for patients with TNBC and pathway genetic aberrations. We review the evidence for PI3K pathway activation in TNBC, and clinical trial data for PI3K, AKT and mammalian target of rapamycin inhibitors in TNBC. We discuss uncertainty over defining which cancers have pathway activation and the future overlap between immunotherapy and pathway targeting.

Mechanisms of PTEN loss in cancer: It's all about diversity

PTEN is a phosphatase which metabolises PIP₃, the lipid product of PI 3-Kinase, directly opposing the activation of the oncogenic PI3K/AKT/mTOR signalling network. Accordingly, loss of function of the PTEN tumour suppressor is one of the most common events observed in many types of cancer. Although the mechanisms by which PTEN function is disrupted are diverse, the most frequently observed events are deletion of a single gene copy of PTEN and gene silencing, usually observed in tumours with little or no PTEN protein detectable by immunohistochemistry. Accordingly, with the exceptions of glioblastoma and endometrial cancer, mutations of the PTEN coding sequence are uncommon (<10%) in most types of cancer. Here we review the data relating to PTEN loss in seven common tumour types and discuss mechanisms of PTEN regulation, some of which appear to contribute to reduced PTEN protein levels in cancers.

PTEN Genetic and Epigenetic Alterations Define Distinct Subgroups in North Indian Breast Cancer Patients

Background:

Breast cancer is a heterogeneous disease that can be subdivided on the basis of histopathological features, genetic alterations, and gene-expression profiles. PTEN gene is considered an established tumor suppressor gene in different types of cancer including breast cancer. However, the role of PTEN alterations in north Indian breast cancer has not been explored especially in defining a group with distinct histological factors.

Methodology:

181 sporadic breast cancer and their adjacent normal tissues were included in the present study. We analyzed methylation and LOH through MS-PCR and microsatellite markers respectively. While, for PTEN protein expression, we used immunohistochemistry. All the molecular findings were correlated with the clinicopathological parameters of the patients to underline clinical relevance.

Results:

We found that LOH and methylation of the PTEN promoter were significantly associated with loss of PTEN protein expression, while, PTEN mutation was a rare event. Furthermore, out of 46 double hit cases (i.e., having both methylation and LOH), 70% (32/46) cases showed complete loss of PTEN expression (P= 0.0249). Both LOH and PTEN promoter methylation were associated significantly with age and clinical stage, while, methylation and loss of PTEN expression were associated with high grade and Her-2 negativity. In addition, a quadruple (ER/PR/Her-2 and PTEN) negative group with distinct features was found.

Conclusion:

The pattern of PTEN expression and its correlation with the clinical parameters indicates that loss of PTEN expression defines a clinical group with distinct features. Hence, PTEN expression provides differential therapeutic strategies for north Indian breast cancer.

The next generation of PI3K-Akt-mTOR pathway inhibitors in breast cancer cohorts

The PI3K/Akt/mTOR pathway plays a role in various oncogenic processes in breast cancer and key pathway aberrations have been identified which drive the different molecular subtypes. Early drugs developed targeting this pathway produced some clinical success but were hampered by pharmacokinetics, tolerability and efficacy problems. This created a need for new PI3K pathway-inhibiting drugs, which would produce more robust results allowing incorporation into treatment regimens for breast cancer patients. In this review, the most promising candidates from the new generation of PI3K-pathway inhibitors is explored, presenting evidence from preclinical and early clinical research, as well as ongoing trials utilising these drugs in breast cancer cohorts. The problems hindering the development of drugs targeting the PI3K pathway are examined, which have created problems for their use as monotherapies. PI3K pathway inhibitor combinations therefore remains a dynamic research area, and their role in combination with immunotherapies and epigenetic therapies is also inspected.

Phosphoinositide 3-Kinase Signalling Pathways in Tumor Progression, Invasion and Angiogenesis

Aims and background

The PI3 kinase signalling pathway is now accepted as being at least as important as the ras-MAP kinase pathway in cell survival and proliferation, and hence its potential role in cancer is of great interest1. The purpose of this review is briefly to examine evidence for an involvement of PI3K in human cancers, discuss the mechanisms by which its activation promotes tumor progression, and consider its utility as a novel target for anticancer therapy.

Methods and study design

A Medline review of recent literature concerning the role of PI3 kinase in tumor progression -mechanisms of action and clinical implications.

Results

Evidence is presented that misregulation of the PI3 kinase pathway is a feature of many common cancers, either by loss of the suppressor protein PTEN, or by constitutive activation of PI3 kinase isoforms or downstream elements such as AKT and mTOR. This activation potentiates not only cell survival and proliferation, but also cytoskeletal deformability and motility; key elements in tumor invasion. In addition the PI3K pathway is implicated in many aspects of angiogenesis, including upregulation of angiogenic cytokines due to tumor hypoxia or oncogene activation and endothelial cell responses to them. These cytokines signal though receptors such as VEGF-R, FGF-R and Tie-2 and potentiate processes essential for neoangiogenesis including cell proliferation, migration, differentiation into tubules and “invasion” of these capillary sprouts into extracellular matrix (ECM).

Conclusions

A more complete understanding of the role of the PI3 kinase pathway in cancer will lead the way to the development of more potent and selective inhibitors which should be a useful adjunct to conventional therapies, potentially interfering with tumor progression at several pivotal points; in particular cell survival, invasion and angiogenesis.

The Role of Chromosome Deletions in Human Cancers

Chromosome deletions are a hallmark of human cancers. These chromosome abnormalities have been observed for over than a century and frequently associated with poor prognosis. However, their functions and potential underlying mechanisms remain elusive until recently. Recent technique breakthroughs, including cancer genomics, high throughput library screening and genome editing, opened a new era in the mechanistic studying of chromosome deletions in human cancer. In this chapter, we will focus on the latest studies on the functions of chromosome deletions in human cancers, especially hematopoietic malignancies and try to persuade the readers that these chromosome alterations could play significant roles in the genesis and drug responses of human cancers.

Molecular genetics complexity impeding research progress in breast and ovarian cancers

Breast and ovarian cancer are heterogeneous diseases. While breast cancer accounts for 25% of cancers worldwide, ovarian cancer accounts for 3.5% of all cancers and it is considered to be the most lethal type of cancer among women. In Oman, breast cancer accounts for 25% and ovarian cancer for 4.5% of all cancer cases. Various risk factors, including variable biological and clinical traits, are involved in the onset of breast and ovarian cancer. Although highly developed diagnostic and therapeutic methods have paved the way for better management, targeted therapy against specific biomarkers has not yet shown any significant improvement, particularly in triple-negative breast cancer and epithelial ovarian cancer, which are associated with high mortality rates. Thus, elucidating the mechanisms underlying the pathology of these diseases is expected to improve their prevention, prognosis and management. The aim of the present study was to provide a comprehensive review and updated information on genomics and proteomics alterations associated with cancer pathogenesis, as reported by several research groups worldwide. Furthermore, molecular research in our laboratory, aimed at identifying new pathways involved in the pathogenesis of breast and ovarian cancer using microarray and chromatin immunoprecipitation (ChIP), is discussed. Relevant candidate genes were found to be either up- or downregulated in a cohort of breast cancer cases. Similarly, ChIP analysis revealed that relevant candidate genes were regulated by the E2F5 transcription factor in ovarian cancer tissue. An ongoing study aims to validate these genes with a putative role as biological markers that may contribute to the development of targeted therapies for breast and ovarian cancer.

Combined PI3K and CDK2 inhibition induces cell death and enhances in vivo antitumour activity in colorectal cancer

BACKGROUND

The phosphatidylinositol-3-kinase/mammalian target of rapamycin (PI3K/mTOR) pathway is commonly deregulated in human cancer, hence many PI3K and mTOR inhibitors have been developed and have now reached clinical trials. Similarly, CDKs have been investigated as cancer drug targets.

METHODS

We have synthesised and characterised a series of 6-aminopyrimidines identified from a kinase screen that inhibit PI3K and/or mTOR and/or CDK2. Kinase inhibition, tumour cell growth, cell cycle distribution, cytotoxicity and signalling experiments were undertaken in HCT116 and HT29 colorectal cancer cell lines, and in vivo HT29 efficacy studies.

RESULTS

2,6-Diaminopyrimidines with an O(4)-cyclohexylmethyl substituent and a C-5-nitroso or cyano group (1,2,5) induced cell cycle phase alterations and were growth inhibitory (GI50<20 μM). Compound 1, but not 2 or 5, potently inhibits CDK2 (IC50=0.1 nM) as well as PI3K, and was cytotoxic at growth inhibitory concentrations. Consistent with kinase inhibition data, compound 1 reduced phospho-Rb and phospho-rS6 at GI50 concentrations. Combination of NU6102 (CDK2 inhibitor) and pictilisib (GDC-0941; pan-PI3K inhibitor) resulted in synergistic growth inhibition, and enhanced cytotoxicity in HT29 cells in vitro and HT29 tumour growth inhibition in vivo.

CONCLUSIONS

These studies identified a novel series of mixed CDK2/PI3K inhibitors and demonstrate that dual targeting of CDK2 and PI3K can result in enhanced antitumour activity.

Feedbacks, Bifurcations, and Cell Fate Decision-Making in the p53 System

The p53 transcription factor is a regulator of key cellular processes including DNA repair, cell cycle arrest, and apoptosis. In this theoretical study, we investigate how the complex circuitry of the p53 network allows for stochastic yet unambiguous cell fate decision-making. The proposed Markov chain model consists of the regulatory core and two subordinated bistable modules responsible for cell cycle arrest and apoptosis. The regulatory core is controlled by two negative feedback loops (regulated by Mdm2 and Wip1) responsible for oscillations, and two antagonistic positive feedback loops (regulated by phosphatases Wip1 and PTEN) responsible for bistability. By means of bifurcation analysis of the deterministic approximation we capture the recurrent solutions (i.e., steady states and limit cycles) that delineate temporal responses of the stochastic system. Direct switching from the limit-cycle oscillations to the “apoptotic” steady state is enabled by the existence of a subcritical Neimark—Sacker bifurcation in which the limit cycle loses its stability by merging with an unstable invariant torus. Our analysis provides an explanation why cancer cell lines known to have vastly diverse expression levels of Wip1 and PTEN exhibit a broad spectrum of responses to DNA damage: from a fast transition to a high level of p53 killer (a p53 phosphoform which promotes commitment to apoptosis) in cells characterized by high PTEN and low Wip1 levels to long-lasting p53 level oscillations in cells having PTEN promoter methylated (as in, e.g., MCF-7 cell line).

Cancers are diseases of signaling networks. Transcription factor p53 is a pivotal node of a network that integrates a variety of stress signals and governs critical processes of DNA repair, cell cycle arrest, and apoptosis. Somewhat paradoxically, despite the fact that carcinogenesis is prevalently caused by p53 network malfunction, most of our knowledge about p53 signaling is based on cancer or immortalized cell lines. In this paper, we construct a mathematical model of intact p53 network to understand dynamics of non-cancerous cells and then dynamics of cancerous cells by introducing perturbations to the regulatory system. Cell fate decisions are enabled by the presence of interlinked feedback loops which give rise to a rich repertoire of behaviors. We explain and analyze by means of numerical simulations how the dynamical structure of the regulatory system allows for generating unambiguous single-cell fate decisions, also in the case when the cell population splits into an apoptotic and a surviving subpopulation. Perturbation analysis provides an explanation why cancer cell lines known to have vastly diverse expression levels of p53 regulators can exhibit a broad spectrum of responses to DNA damage.

Partial PTEN deletion is linked to poor prognosis in breast cancer

BACKGROUND

Deletions of chromosome 10q23, including the PTEN (phosphatase and tensin homolog) locus, are known to occur in breast cancer, but systematic analyses of its clinical relevance are lacking.

METHODS

We thus analyzed a tissue microarray (TMA) with 2,197 breast cancers by fluorescence in-situ hybridization (FISH) using a PTEN-specific probe.

RESULTS

PTEN deletions were detected in 19% of no special type, 9% of lobular, 4% of tubular cancers and 46% in carcinomas with medullary features. 98.7% of deletions were heterozygous and only 1.3% were homozygous. PTEN deletion was significantly linked to advanced tumor stage (p=0.0054), high-grade (p<0.0001), high tumor cell proliferation (Ki67 Labeling Index; p<0.0001), and shortened overall survival (p=0.0090). PTEN deletions were inversely associated with features of luminal type breast cancers (ER/PR positivity; p<0.0001 each, and CCND1 amplification; p=0.0020). PTEN deletions were also strongly linked to amplification of genes involved in the PTEN/AKT pathway such as MYC (p=0.0430) and HER2 (p=0.0065). Remarkably the combined analysis of MYC, HER2, CCND1 and PTEN aberrations suggested that aberrations of multiple PTEN/AKT pathway genes have a strong additive effect on breast cancer prognosis. While cancers with one of these aberrations behaved only marginally different from cancers with none, disease outcome was markedly worse in cancers with two or more aberrations as compared to those with only one aberration (p=0.0002). In addition, the particularly poor prognosis of patients with HER2 amplification and PTEN deletions challenges the concept of PTEN deletions interfering with trastuzumab therapy.

CONCLUSION

PTEN deletion occurs in a relevant fraction of breast cancers, and is linked to aggressive tumor behavior. Reduced PTEN function cooperates with MYC and HER2 activation in conferring aggressive phenotype to cancer cells.

Expression of MHC Class I on breast cancer cells correlates inversely with HER2 expression

HER2 is a promising target for immunotherapeutic interventions with T cell-based approaches since it is amplified and overexpressed in 20–30% of breast cancers. However, several previous studies including ours showed that HER2-overexpressing tumors may escape cytotoxic T lymphocyte-mediated lysis by downregulating MHC Class I and components of the antigen-processing machinery. The aims of the present study were to analyze the relationship between HER2 and MHC Class I expression and to elucidate the mechanisms underlying MHC Class I downregulation in breast cancer. We explored expression of HER2, MHC Class I, PTEN, Ki67, estrogen and progesterone expression in 70 breast cancer patients by immunohistochemistry (IHC) and analyzed their correlation. We also explored the components of the signal transduction pathway that are involved in the regulation of MHC Class I expression using small-interfering RNAs targeting HER2 as well as an inhibitor of HER2 signaling. HER2 expression in breast cancers correlated inversely with MHC Class I expression analyzed by IHC. HER2 depletion by small-interfering RNAs resulted in MHC Class I upregulation. Moreover, MHC Class I expression on breast cancer cell lines was upregulated by PD98059, an inhibitor of mitogen-associated protein kinases, in a dose-dependent manner. Thus, agents that target the MAPK signaling pathway may increase MHC Class I expression in breast cancer cells.

The PTEN/PI3K/Akt and Wnt/β-catenin signaling pathways are involved in the inhibitory effect of resveratrol on human colon cancer cell proliferation

Colon cancer is one of the most common malignancies and the treatments for colon cancer have been developed substantially in the last decades, but there is still a great clinical need to explore new treatment regimens due to the undesirable prognosis. In this investigation, we demonstrated the anti-proliferative and apoptosis-inducing activities of resveratrol (Res) in human colon cancer cells, and the possible mechanisms underlying these effects. We used crystal violet staining, flow cytometry and western blotting to validate the anti-proliferative and apoptosis-inducing effects of Res on HCT116 cells. A xenograft tumor model was used to confirm the anti-proliferative effects of Res. We employed polymerase chain reaction, western blotting, recombinant adenovirus and luciferase reporter assay to explore the possible mechanism(s) of action. We found that Res inhibits significantly the proliferation and promotes apoptosis in HCT116 cells, as well as inhibits the xenograft tumor growth of colon cancer. Res upregulates the expression of phosphatase and tensin homolog (PTEN) and decreases the phosphorylation of Akt1/2. The exogenous expression of PTEN inhibits the PI3K/Akt signal and promotes the anti-proliferative effects of Res in HCT116 cells, while knockdown of PTEN increases PI3K/Akt signal but reduces the anti-proliferative function of Res. The protein and mRNA expression of β-catenin are all decreased by Res concentration-dependently. Thus, our findings strongly suggest that the anti-proliferative effects of Res in human colon cancer cells may be mediated by regulating separately the PTEN/PI3K/Akt and Wnt/β-catenin signaling.

Targeting the PI3K/AKT/mTOR pathway in estrogen receptor-positive breast cancer

Approximately 70-75% of breast cancers express the estrogen receptor (ER), indicating a level of dependence on estrogen for growth. Endocrine therapy is an important class of target-directed therapy that blocks the growth-promoting effects of estrogen via ER. Although endocrine therapy continues to be the cornerstone of effective treatment of ER-positive (ER+) breast cancer, many patients with advanced ER+ breast cancer encounter de novo or acquired resistance and require more aggressive treatment such as chemotherapy. Novel approaches are needed to augment the benefit of existing endocrine therapies by prolonging time to disease progression, preventing or overcoming resistance, and delaying the use of chemotherapy. The phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway is a key intracellular signaling system that drives cellular growth and survival; hyperactivation of this pathway is implicated in the tumorigenesis of ER+ breast cancer and in resistance to endocrine therapy. Moreover, preclinical and clinical evidence show that PI3K/AKT/mTOR pathway inhibition can augment the benefit of endocrine therapy in ER+ breast cancer, from the first-line setting and beyond. This article will review the fundamental role of the PI3K/AKT/mTOR pathway in driving ER+ breast tumors, and its inherent interdependence with ER signaling. In addition, ongoing strategies to combine PI3K/AKT/mTOR pathway inhibitors with endocrine therapy for improved clinical outcomes, and methods to identify patient populations that would benefit most from inhibition of the PI3K/AKT/mTOR pathway, will be evaluated.

Radiation-associated small cell neuroendocrine carcinoma of the thyroid: a case report with molecular analyses

BACKGROUND

Neuroendocrine tumor (NET) of the thyroid other than medullary carcinoma is extremely rare. We describe here a case of calcitonin-negative small cell neuroendocrine carcinoma (SCNEC), which occurred in a thyroid gland that had previously been irradiated at high dose (60 Gy) for pharyngeal cancer, with molecular analyses for follicular cell origin.

PATIENT FINDINGS

The tumor cells were small with fine chromatin, inconspicuous nucleoli, and inapparent cytoplasm, and showed neuroendocrine architectures such as palisading, rosettes, and trabeculae. Mitotic figures were numerous exceeding 10 mitoses per 10 high-power fields. The tumor cells invaded into several vessels and metastasized to regional lymph nodes. Immunohistochemically, the tumor cells were strongly positive for neuroendocrine markers and thyroglobulin (Tg), a marker of thyroid follicular cells but negative for calcitonin and carcinoembryonic antigen (CEA). Expression of Tg and thyrotropin receptor (TSHR) were confirmed by quantitative real-time polymerase chain reaction (RT-PCR). Ki-67 labeling index was more than 70% in the tumor cells. Taken together, the tumor was diagnosed as SCNEC of the thyroid. Genetic analyses also revealed microsatellite abnormalities of the phosphatase and tensin homolog (PTEN) gene, suggesting that functional loss of PTEN contributes to carcinogenesis.

CONCLUSIONS

This is the first report describing a SCNEC of the thyroid with molecular analyses that provide evidence for a follicular epithelial origin.

Overview of diagnostic/targeted treatment combinations in personalized medicine for breast cancer patients

Breast cancer includes a body of molecularly distinct subgroups, characterized by different presentation, prognosis, and sensitivity to treatments. Significant advances in our understanding of the complex architecture of this pathology have been achieved in the last few decades, thanks to new biotechnologies that have recently come into the research field and the clinical practice, giving oncologists new instruments that are based on biomarkers and allowing them to set up a personalized approach for each individual patient. Here we review the main treatments available or in preclinical development, the biomolecular diagnostic and prognostic approaches that changed our perspective about breast cancer, giving an overview of targeted therapies that represent the current standard of care for these patients. Finally, we report some examples of how new technologies in clinical practice can set in motion the development of new drugs.

Recent progress in mouse models for tumor suppressor genes and its implications in human cancer

Gain-of-function mutations in oncogenes and loss-of-function mutations in tumor suppressor genes (TSG) lead to cancer. In most human cancers, these mutations occur in somatic tissues. However, hereditary forms of cancer exist for which individuals are heterozygous for a germline mutation in a TSG locus at birth. The second allele is frequently inactivated by gene deletion, point mutation, or promoter methylation in classical TSGs that meet Knudson's two-hit hypothesis. Conversely, the second allele remains as wild-type, even in tumors in which the gene is haplo-insufficient for tumor suppression. This article highlights the importance of PTEN, APC, and other tumor suppressors for counteracting aberrant PI3K, β-catenin, and other oncogenic signaling pathways. We discuss the use of gene-engineered mouse models (GEMM) of human cancer focusing on Pten and Apc knockout mice that recapitulate key genetic events involved in initiation and progression of human neoplasia. Finally, the therapeutic potential of targeting these tumor suppressor and oncogene signaling networks is discussed.

PTEN mutation, methylation and expression in breast cancer patients

The tumor suppressor gene, PTEN, has previously been demonstrated to be involved in breast tumorigenesis and tumor progression. The aim of the present study was to investigate the expression and significance of PTEN in breast carcinomas, to detect the mutation frequency of PTEN in sporadic breast carcinoma tissues and to determine the association between PTEN promoter methylation and gene expression. Immunohistochemical methods were used to analyze the expression of the PTEN gene in 146 cases of breast carcinoma and 10 cases of normal breast tissue closely adjacent to the carcinoma. Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis was used to analyze conformation polymorphisms in 45 breast carcinoma and 10 normal breast tissues. Point mutations of abnormal single stranded conformation were detected by DNA sequencing. The methylation of the PTEN promoter was analyzed by methylation-specific PCR. Expression of PTEN was detected in 57.5% (84/146) of patients with breast carcinoma. By contrast, PTEN expression was detected in 100% of normal samples. Expression of PTEN was found to negatively correlate with the tumor size, the pathological stage and the expression of the estrogen receptor (ER) and the progesterone receptor (PR) in breast cancer. The 2-year disease-free survival of patients with a high expression of PTEN was higher compared with those with low PTEN expression (P<0.05). Missense mutations in exon 2 of PTEN were identified in 1/45 breast cancer cases. PTEN promoter methylation was detected in 31.1% (14/45) of breast carcinomas, of which 64.3% (9/14) were associated with a loss of PTEN expression. The tumor suppressor gene, PTEN, was abnormally expressed in the breast carcinomas. The number of PTEN mutations were low (1/45) in the sporadic breast cancer cases analyzed in the present study and PTEN promoter methylation may have been the main mechanism leading to the decreased expression of PTEN. These results indicate that PTEN is important for the tumorigenesis, development and prognosis of breast cancer.

Phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin pathway inhibition: a breakthrough in the management of luminal (ER+/HER2-) breast cancers?

PURPOSE OF REVIEW

Recent data from clinical trials evaluating mammalian target of rapamycin (mTOR) inhibitors in the setting of endocrine resistance in luminal (estrogen receptor-positive, human epidermal growth factor receptor 2-negative) breast cancers have validated this pathway as a bona-fide therapeutic target in this setting. There are currently many agents under clinical investigation that inhibit the phosphatidylinositol 3-kinase (PI3K) pathway. We review these findings in the context of the preclinical data and the current status of biomarker development in this field.

RECENT FINDINGS

Clinical trials in the neoadjuvant (RAD2222) and metastatic setting (TAMRAD, BOLERO-2) have reported improved clinical outcome of patients with unselected luminal breast cancer through the addition of mTOR inhibitors to standard endocrine treatment. PI3K molecular aberrations are frequently found in luminal breast cancer, yet the role of these in defining patients' prognosis and response to PI3K/AKT/mTOR inhibitors remains to be determined.

SUMMARY

Therapeutic targeting of the PI3K pathway promises improved clinical outcome for patients with luminal breast cancer. Correspondingly, agents that target this pathway are entering the clinic at an unprecedented rate. Future clinical trials that incorporate correlative translational research will help us decipher important information critical for successful development of these agents in breast cancer: which part of the pathway should be targeted and in which clinical scenario; and which patients are more likely to benefit from these drugs, particularly in the adjuvant setting.

Germline and somatic KLLN alterations in breast cancer dysregulate G2 arrest

PTEN is a well-described predisposition gene for Cowden syndrome (CS), a familial cancer syndrome characterized by a high risk of breast and other cancers. KLLN, which shares a bidirectional promoter with PTEN, causes cell cycle arrest and apoptosis. We previously identified germline hypermethylation of the KLLN promoter in 37% of PTEN mutation-negative CS/CS-like (CSL) patients. Patients with germline KLLN hypermethylation have an increased prevalence of breast and renal cancers when compared with PTEN mutation carriers. We have consequently sought to identify and characterize germline KLLN variants/mutations in CS/CSL and in apparently sporadic breast cancer patients. KLLN variants in CS/CSL patients are rare (1 of 136, 0.007%). Interestingly, among 438 breast cancer patients, 13 (3%) have germline KLLN variants when compared with none in 128 controls (P = 0.049). Patients with KLLN variants have a family history of breast cancer when compared with those without (P = 0.02). We demonstrate that germline KLLN variants dysregulate the cell cycle at G2. Of 24 breast carcinomas analyzed, 3 (13%) have somatic KLLN hemizygous deletions, with somatic loss of the wild-type allele in a patient with germline KLLN p.Leu119Leu. Of 452 breast carcinomas in The Cancer Genome Atlas project, 93 (21%) have KLLN hemizygous or homozygous deletions. This is the first study to associate germline KLLN variants with sporadic breast cancer and to recognize somatic KLLN deletions in breast carcinomas. Our observations suggest that KLLN may be a low penetrance susceptibility factor for apparently sporadic breast cancer.

Molecular mapping the presence of druggable targets in preinvasive and precursor breast lesions: a comprehensive review of biomarkers related to therapeutic interventions

The analysis of clinical breast samples using biomarkers is integral to current breast cancer management. Currently, a limited number of targeted therapies are standard of care in breast cancer treatment. However, these targeted therapies are only suitable for a subset of patients and resistance may occur. Strategies to prevent the occurrence of invasive lesions are required to reduce the morbidity and mortality associated with the development of cancer. In theory, application of targeted therapies to pre-invasive lesions will prevent their progression to invasive lesions with full malignant potential. The diagnostic challenge for pathologists is to make interpretative decisions on early detected pre-invasive lesions. Overall, only a small proportion of these pre-invasive lesions will progress to invasive carcinoma and morphological assessment is an imprecise and subjective means to differentiate histologically identical lesions with varying malignant potential. Therefore differential biomarker analysis in pre-invasive lesions may prevent overtreatment with surgery and provide a predictive indicator of response to therapy. There follows a review of established and emerging potential druggable targets in pre-invasive lesions and correlation with lesion morphology.

Targeting the PI3K/Akt/mTOR pathway for breast cancer therapy

Recent advances in genetics and genomics have revealed new pathways that are aberrantly activated in many breast cancers. Chief among these genetic changes are somatic mutations and/or gains and losses of key genes within the phosphoinositide 3-kinase (PI3K) pathway. Since breast cancer cell growth and progression is often dependent upon activation of the PI3K pathway, there has been intense research interest in finding therapeutic agents that can selectively inhibit one or more constituents of this signaling cascade. Here we review key molecules involved with aberrant PI3K pathway activation in breast cancers and current efforts to target these components for therapeutic gain.

The impact of PTEN tumor suppressor gene on acquiring resistance to tamoxifen treatment in breast cancer patients

Tamoxifen is a standard therapeutical treatment in patients with estrogen receptor positive breast carcinoma. However, less than 50% of estrogen receptor positive breast cancers do not respond to tamoxifen treatment whereas 40% of tumors that initially respond to treatment develop resistance over time. The underlying mechanisms for tamoxifen resistance are probably multifactorial but remain largely unknown. The primary aim of this study was to investigate the impact of PTEN tumor suppressor gene on acquiring resistance to tamoxifen by analyzing loss of heterozygosity (LOH) and immunohystochemical expression of PTEN in 49 primary breast carcinomas of patients treated with tamoxifen as the only adjuvant therapy. The effect of PTEN inactivation on breast cancer progression and disease outcome was also analyzed. Reduced or completely lost PTEN expression was observed in 55.1% of samples, while 63.3% of samples displayed LOH of PTEN gene. Inactivation of PTEN immunoexpression significantly correlated with the PTEN loss of heterozygosity, suggesting LOH as the most important genetic mechanism for the reduction or complete loss of PTEN expression in primary breast carcinoma. Most importantly, LOH of PTEN and consequential reduction of its immunoexpression showed significant correlation with the recurrence of the disease. Besides, our study revealed that LOH of PTEN tumor suppressor was significantly associated with shorter disease free survival, breast cancer specific survival and overall survival. In summary, our results imply that LOH of PTEN could be used as a good prognostic characteristic for the outcome of breast cancer patients treated with tamoxifen.

Inhibition of phosphoinositide 3-kinase enhances the cytotoxicity of AG1478, an epidermal growth factor receptor inhibitor, in breast cancer cells

Aberrant activation and dysfunction of the EGFR/PI3K/Akt signaling pathways are commonly reported in breast cancer. Constitutive activation of the PI3K/Akt pathway by the lack of PTEN regulation is associated with resistance to novel targeted therapies including EGFR inhibitors. We aimed to study whether Ly294002, an inhibitor of PI3K, could enhance the cytotoxicity of AG1478, an inhibitor of EGFR, on breast cancer cells. We tested these agents in the MDA-MB-468 and MCF-7 breast cancer cell lines with different EGFR and PTEN profiles (MDA-MB-468: high expression of EGFR and PTEN mutation; MCF-7: low expression of EGFR and PTEN wild type). Simultaneous inhibition of EGFR and PI3K in MDA-MB-468 cells with combined Ly294002 and AG1478 treatment had a greater anti-proliferative effect and increased mitotic death than either treatment alone. In addition, more apoptosis and increased induction of cell arrest at G0/G1 phase were observed in MDA-MB-468 cells with the combined treatment. Phosphor-EGFR and its downstream signal transducer, phosphor-Akt, were fully attenuated only by simultaneous treatment with Ly294002 and AG1478. These data suggest that the inhibition of PI3K could enhance the cytotoxicity of EGFR inhibitors on breast cancer cells and tumors which overexpress EGFR and demonstrate mutated PTEN. This dual inhibition treatment protocol may have important therapeutic implication in the treatment of a subset of breast cancer patients with high expression of EGFR and deficient function of PTEN.

SGK3 is associated with estrogen receptor expression in breast cancer

While breast cancer mortality rate has seen a steady decline in the last few decades, advances in better treatment and diagnostic tools remain important as we come into the age of personalized therapy. In this report, we describe our studies of SGK3's role in breast cancer. SGK3 (also known as CISK) is a member of the AGC family of kinases. Our previous work indicates that SGK3 functions downstream of the PI 3-kinase cascade and shares molecular and biochemical similarities with Akt. Here, we show that SGK3 expression is linked to estrogen receptor (ER) both in breast caner cell lines and in primary tumor samples. Our analysis also indicated a positive correlation between SGK3 expression and tumor prognosis. Importantly, our immunochemistry analysis of human tumor samples established a clinical link between SGK3 expression and ER+ tumors. These findings implicate SGK3 as an additional component to a complex and heterogeneous disease, and point to the potential benefits of incorporating SGK3 into the process of breast cancer diagnosis and treatment.

Targeting the PI3K signaling pathway in cancer therapy

INTRODUCTION

The PI3K signaling pathway is involved in the regulation of cancer cell growth, motility, survival and metabolism. The pathway is frequently active in many different types of cancer-e.g., breast, bladder, prostate, thyroid, ovarian and NSCLC. Targetable genetic aberrations in this pathway give us many opportunities for development of targeted therapies for different types of cancer.

AREAS COVERED

The genetic alterations in the PI3K/mammalian target of rapamycin (mTOR)/Akt pathway, as well as the drugs that target this pathway, either alone, in combination with other targeted agents or in chemotherapy. Targeted inhibitors of the PI3K pathway currently being tested in clinical trials in different types of human cancer.

EXPERT OPINION

Small-molecule inhibitors targeting the PI3K/Akt/mTOR pathway show some success with these agents in current clinical trials. For further improvement in response, molecular correlates that can be used for patient selection, need to be determined. A more efficient and effective way to screen for patients to determine which patients are most likely to benefit from PI3K pathway inhibitors is also needed.

Evaluation of cell-free tumour DNA and RNA in patients with breast cancer and benign breast disease

High levels of DNA and RNA released by apoptotic and necrotic cells circulate in the blood of cancer patients. In the present study we determined the applicability of the quantification of nucleic acids and their genetic alterations as minimally invasive tool for breast cancer screening. The relative concentrations of DNA and RNA were determined in preoperative serum of 102 breast cancer patients, 32 patients with benign breast disease and 53 healthy women. The mean follow-up time of the cancer patients was 6.2 years. Loss of heterozygosity (LOH) at four polymorphic markers (D13S159, D13S280, D13S282 at region 13q31-33 and D10S1765 at PTEN region 10q23.31) was analyzed by PCR-based fluorescence microsatellite analyses using cell-free DNA. The serum levels of DNA (p = 0.016) and RNA (p = 0.001) could differentiate between healthy women and cancer patients, but could not discriminate malignant from benign breast lesions. A significant correlation of serum DNA with RNA levels was observed in all groups (p = 0.018). Increased serum DNA levels (but not RNA levels) in cancer patients were associated with a poorer overall (p = 0.021) and disease-free survival (p = 0.025). The occurrence of LOH at all markers significantly correlated with lymph node status (p = 0.026). In addition, the LOH frequency at D13S280 (p = 0.047) and D13S159 (p = 0.046) associated with overall and disease-free survival, respectively. In conclusion, the quantification of cell-free tumour DNA had diagnostic and prognostic values in breast cancer patients, and DNA loss at the region 13q31-33 may be an indication of lymphatic tumour cell spread.

Elevated PI3K signaling drives multiple breast cancer subtypes

Most human breast tumors have mutations that elevate signaling through a key metabolic pathway that is induced by insulin and a number of growth factors. This pathway serves to activate an enzyme known as phosphatidylinositol 3' kinase (PI3K) as well as to regulate proteins that signal in response to lipid products of PI3K. The specific mutations that activate this pathway in breast cancer can occur in genes coding for tyrosine kinase receptors, adaptor proteins linked to PI3K, catalytic and regulatory subunits of PI3K, serine/threonine kinases that function downstream of PI3K, and also phosphatidylinositol 3' phosphatase tumor suppressors that function to antagonize this pathway. While each genetic change results in net elevation of PI3K pathway signaling, and all major breast cancer subtypes show pathway activation, the specific mutation(s) involved in any one tumor may play an important role in defining tumor subtype, prognosis and even sensitivity to therapy. Here, we describe mouse models of breast cancer with elevated PI3K signaling, and how they may be used to guide development of novel therapeutics.

Treatment strategy for HER2-positive breast cancer

HER2-positive tumors account for approximately 18-20% of all breast cancers. These tumors tend to be more aggressive than HER2-negative tumors and are associated with a poorer prognosis. HER2 overexpression, as determined by either 3+ immunohistochemical staining for HER2 protein or HER2 gene amplification by fluorescence in situ hybridization, should be used to select patients for anti-HER2 therapy. Trastuzumab-containing regimens as first-line therapy should be recommended to women with HER2-positive metastatic breast cancer. The continuation of trastuzumab plus capecitabine provided a significant clinical benefit compared with capecitabine alone in women who experienced progression during trastuzumab treatment. An adjuvant trastuzumab-containing regimen should be also recommended to all intermediate- or high-risk women with HER2-positive early breast cancer. Cardiac function should be serially monitored during this treatment. Many anti-HER2 drugs against breast cancer are being developed. The basic mechanisms of their action and resistance emergence are being clarified step by step. Over the mid- or long term, clinical trials comparing these drugs will be conducted until drugs that are clinically effective and easy to use in the true sense survive. Biomarkers are being aggressively searched for concerning individual drugs under development. A position of the "proper drug for the proper patient" will be more firmly established.

Proteomic and transcriptomic profiling reveals a link between the PI3K pathway and lower estrogen-receptor (ER) levels and activity in ER+ breast cancer

INTRODUCTION

Accumulating evidence suggests that both levels and activity of the estrogen receptor (ER) and the progesterone receptor (PR) are dramatically influenced by growth-factor receptor (GFR) signaling pathways, and that this crosstalk is a major determinant of both breast cancer progression and response to therapy. The phosphatidylinositol 3-kinase (PI3K) pathway, a key mediator of GFR signaling, is one of the most altered pathways in breast cancer. We thus examined whether deregulated PI3K signaling in luminal ER+ breast tumors is associated with ER level and activity and intrinsic molecular subtype.

METHODS

We defined two independent molecular signatures of the PI3K pathway: a proteomic (reverse-phase proteomic array) PI3K signature, based on protein measurement for PI3K signaling intermediates, and a PI3K transcriptional (mRNA) signature based on the set of genes either induced or repressed by PI3K inhibitors. By using these signatures, we scored each ER+ breast tumor represented in multiple independent expression-profiling datasets (four mRNA, n = 915; one protein, n = 429) for activation of the PI3K pathway. Effects of PI3K inhibitor BEZ-235 on ER expression and activity levels and cell growth were tested by quantitative real-time PCR and cell proliferation assays.

RESULTS

Within ER+ tumors, ER levels were negatively correlated with the PI3K activation scores, both at the proteomic and transcriptional levels, in all datasets examined. PI3K signature scores were also higher in ER+ tumors and cell lines of the more aggressive luminal B molecular subtype versus those of the less aggressive luminal A subtype. Notably, BEZ-235 treatment in four different ER+ cell lines increased expression of ER and ER target genes including PR, and treatment with IGF-I (which signals via PI3K) decreased expression of ER and target genes, thus further establishing an inverse functional relation between ER and PI3K. BEZ-235 had an additional effect on tamoxifen in inhibiting the growth of a number of ER+ cell lines.

CONCLUSIONS

Our data suggest that luminal B tumors have hyperactive GFR/PI3K signaling associated with lower ER levels, which has been correlated with resistance to endocrine therapy. Targeting PI3K in these tumors might reverse loss of ER expression and signaling and restore hormonal sensitivity.

Faithfull modeling of PTEN loss driven diseases in the mouse

A decade of work has indisputably defined PTEN as a pivotal player in human health and disease. Above all, PTEN has been identified as one of the most commonly lost or mutated tumor suppressor genes in human cancers. For this reason, the generation of a multitude of mouse models has been an invaluable strategy to dissect the function and consequences-of-loss of this essential, evolutionary conserved lipid phosphatase in tumor initiation and progression.In this chapter, we will summarize the mouse models that have allowed us to faithfully recapitulate features of human cancers and to highlight the network of connections between the PTEN signaling cascade and other oncogenic or tumor suppressive pathways.Notably, PTEN represents one of the most extensively modeled genes involved in human cancer and exemplifies the strength of genetic mouse modeling as an approach to gain information aimed to improve our understanding of and ability to alleviate human disease.

Deletion of PTEN promotes tumorigenic signaling, resistance to anoikis, and altered response to chemotherapeutic agents in human mammary epithelial cells

Many cancers, including breast cancer, harbor loss-of-function mutations in the catalytic domain of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) or have reduced PTEN expression through loss of heterozygosity and/or epigenetic silencing mechanisms. However, specific phenotypic effects of PTEN inactivation in human cancer cells remain poorly defined without a direct causal connection between the loss of PTEN function and the development or progression of cancer. To evaluate the biological and clinical relevance of reduced or deleted PTEN expression, a novel in vitro model system was generated using human somatic cell knockout technologies. Targeted homologous recombination allowed for a single and double allelic deletion, which resulted in reduced and deleted PTEN expression, respectively. We determined that heterozygous loss of PTEN in the nontumorigenic human mammary epithelial cell line MCF-10A was sufficient for activation of the phosphoinositide 3-kinase/AKT and mitogen-activated protein kinase pathways, whereas the homozygous absence of PTEN expression led to a further increased activation of both pathways. The deletion of PTEN was able to confer growth factor-independent proliferation, which was confirmed by the resistance of the PTEN(-/-) MCF-10A cells to small-molecule inhibitors of the epidermal growth factor receptor. However, neither heterozygous nor homozygous loss of PTEN expression was sufficient to promote anchorage-independent growth, but the loss of PTEN did confer apoptotic resistance to cell rounding and matrix detachment. Finally, MCF-10A cells with the reduction or loss of PTEN showed increased susceptibility to the chemotherapeutic drug doxorubicin but not paclitaxel.

Trastuzumab versus lapatinib: the cardiac side of the story

HER2 gene plays a pivotal role in the pathogenesis of 20% of breast cancer patients. At the same time, it is one of the main cardiac survival pathways when subjected to bio-mechanical stress including exposure to anthracyclines. With the emergence of the anti-HER2 targeting agents, concerns raised regarding the potential cardiac toxicities of these drugs. In the early clinical trials with trastuzumab, it was evident that it has a significant cardiac toxicity. The incidence of symptomatic heart failure ranged from 4% to 7% with trastuzumab alone, and 27% when administered concurrently with doxorubicin. On the other hand, available data suggest that lapatinib is much less cardiotoxic. The incidence of symptomatic heart failure has been constantly reported to be less than 0.5%. In this review, we discuss the possible theories behind the differences in the cardiac profile of both agents. We emphasize on the role of cardiac bioenergetics and the effects of trastuzumab and lapatinib on ATP production through the different effects they exert on the cardiac mitochondria.

Simultaneous loss of the DLC1 and PTEN tumor suppressors enhances breast cancer cell migration

The phosphatase and tensin homolog (PTEN) gene is a tumor suppressor frequently deleted or mutated in sporadic tumors of the breast, prostate, endometrium and brain. The protein acts as a dual specificity phosphatase for lipids and proteins. PTEN loss confers a growth advantage to cells, protects from apoptosis and favors cell migration. The deleted in liver cancer 1 (DLC1) gene has emerged as a novel tumor suppressor downregulated in a variety of tumor types including those of the breast. DLC1 contains a Rho GTPase activating domain that is involved in the inhibition of cell proliferation, migration and invasion. To investigate how simultaneous loss of PTEN and DLC1 contributes to cell transformation, we downregulated both proteins by RNA interference in the non-invasive MCF7 breast carcinoma cell line. Joint depletion of PTEN and DLC1 resulted in enhanced cell migration in wounding and chemotactic transwell assays. Interestingly, both proteins were found to colocalize at the plasma membrane and interacted physically in biochemical pulldowns and coimmunoprecipitations. We therefore postulate that the concerted local inactivation of signaling pathways downstream of PTEN and DLC1, respectively, is required for the tight control of cell migration.

PTEN deficiency in a luminal ErbB-2 mouse model results in dramatic acceleration of mammary tumorigenesis and metastasis

Overexpression and/or amplification of the ErbB-2 oncogene as well as inactivation of the PTEN tumor suppressor are two important genetic events in human breast carcinogenesis. To address the biological impact of conditional inactivation of PTEN on ErbB-2-induced mammary tumorigenesis, we generated a novel transgenic mouse model that utilizes the murine mammary tumor virus (MMTV) promoter to directly couple expression of activated ErbB-2 and Cre recombinase to the same mammary epithelial cell (MMTV-NIC). Disruption of PTEN in the mammary epithelium of the MMTV-NIC model system dramatically accelerated the formation of multifocal and highly metastatic mammary tumors, which exhibited homogenous pathology. PTEN-deficient/NIC-induced tumorigenesis was associated with an increase in angiogenesis. Moreover, inactivation of PTEN in the MMTV-NIC mouse model resulted in hyperactivation of the phosphatidylinositol 3'-kinase/Akt signaling pathway. However, like the parental strain, tumors obtained from PTEN-deficient/NIC mice displayed histopathological and molecular features of the luminal subtype of primary human breast cancer. Taken together, our findings provide important implications in understanding the molecular determinants of mammary tumorigenesis driven by PTEN deficiency and ErbB-2 activation and could provide a valuable tool for testing the efficacy of therapeutic strategies that target these critical signaling pathways.

Reduced PTEN protein expression and its prognostic implications in canine and feline mammary tumors

Phosphatase and tensin homolog (PTEN) belongs to the group of gatekeeper tumor suppressor genes and is involved in multiple mechanisms leading to cellular defense against neoplastic transformation and progression. Twenty-four dogs and 17 cats were submitted to a 2-year follow-up study, and clinicopathologic features were recorded and compared with immunohistochemical PTEN staining. PTEN-negative status occurred in 33% of canine and 76% of feline mammary carcinomas. In canine mammary carcinomas, there was a significant (P < .05) correlation between loss of PTEN protein expression and simple carcinoma histotype, lymphatic vessel invasion, lymph node metastases, distant organ metastases, tumor dedifferentiation, tumor recurrence, and shorter overall survival. In feline mammary tumors, a significant correlation between loss of PTEN protein expression and lymphatic vessel invasion was found. Loss of PTEN expression could be a useful prognostic marker in canine mammary carcinomas.

A chemical screen in diverse breast cancer cell lines reveals genetic enhancers and suppressors of sensitivity to PI3K isoform-selective inhibition

The PI3K (phosphoinositide 3-kinase) pathway regulates cell proliferation, survival and migration and is consequently of great interest for targeted cancer therapy. Using a panel of small-molecule PI3K isoform-selective inhibitors in a diverse set of breast cancer cell lines, we have demonstrated that the biochemical and biological responses were highly variable and dependent on the genetic alterations present. p110alpha inhibitors were generally effective in inhibiting the phosphorylation of PKB (protein kinase B)/Akt and S6, two downstream components of PI3K signalling, in most cell lines examined. In contrast, p110beta-selective inhibitors only reduced PKB/Akt phosphorylation in PTEN (phosphatase and tensin homologue deleted on chromosome 10) mutant cell lines, and was associated with a lesser decrease in S6 phosphorylation. PI3K inhibitors reduced cell viability by causing cell-cycle arrest in the G(1) phase, with multi-targeted inhibitors causing the most potent effects. Cells expressing mutant Ras were resistant to the cell-cycle effects of PI3K inhibition, which could be reversed using inhibitors of Ras signalling pathways. Taken together, our data indicate that these compounds, alone or in suitable combinations, may be useful as breast cancer therapeutics, when used in appropriate genetic contexts.

Genomic instability and the development of metastatic lymph node tumors

BACKGROUND

Although recent data suggest that cells with metastatic potential disseminate from the primary breast tumor early in tumor development, the mechanism by which disseminated breast cancer cells proliferate within foreign tissues is not well understood. Here, we examined levels and patterns of allelic imbalance (AI) in metastatic lymph node (LN) tumors to identify molecular signals that promote the survival and growth of disseminated breast tumor cells.

METHODS

DNA from 106 metastatic LN tumors from 25 patients was isolated after laser microdissection of pure tumor cell populations. AI was assessed at 26 chromosomal regions frequently altered in breast cancer. Tumor burden was calculated by dividing the area of the metastatic tumor in the node by the area of the entire LN.

RESULTS

Metastatic tumor burden ranged from focal to complete replacement of the LN with tumor. Grouping the nodes as < 25% tumor, 25-50% tumor, 50-75% tumor, and > or = 75% tumor replacement revealed the average frequency of AI ranged from 0.13 (+/-0.11) in the < 25% group to 0.17 (+/-0.13) in LNs with > or = 75% tumor burden. The range of AI in both the < 25% and > 75% replacement group was 0.00-0.48. Allelic losses at chromosomal regions 1p36.1-36.2, 5q21.1-21.3, 6q15, 10q23.31-23.33, and 17p13.1 were significantly higher in metastatic LNs with > 75% compared with < 25% tumor burden.

CONCLUSIONS

In metastatic LNs, levels of AI were not associated with tumor burden, suggesting that accumulation of genetic changes is not coincidental with tumor growth; rather the accumulation of specific genetic changes is a prerequisite to the transformation of disseminated breast cells into metastatic LN tumors.

The phosphatidyl inositol 3-kinase signaling network: implications for human breast cancer

The phosphatidyl inositol 3-kinase (PI3K)/Akt pathway is activated downstream of a variety of extracellular signals and activation of this signaling pathway impacts a number of cellular processes including cell growth, proliferation and survival. The alteration of components of this pathway, through either activation of oncogenes or inactivation of tumor suppressors, disrupts a signaling equilibrium and can thus lead to cellular transformation. The frequent dysregulation of the PI3K/Akt pathway in human cancer has made components of this pathway attractive for therapeutic targeting; however, a more comprehensive understanding of the signaling intricacies is necessary to develop pharmacological agents to target not only specific molecules, but also specific functions. Here, we review a series of experiments examining the contribution of molecules of this signaling network including PI3K, phosphatase and tensin homolog deleted on chromosome 10, integrin-linked kinase and Akt and address the significance to human breast cancer.

Proteasome inhibitor bortezomib increases PTEN expression and enhances trastuzumab-induced growth inhibition in trastuzumab-resistant cells

PTEN (phosphatase and tension homolog deleted on chromosome 10) has been shown to be inactivated in a wide range of cancers and the role of this gene product is associated with the suppression of the phosphatidylinositol-3-kinase (PI3K)/Akt pathway in many cancers. Recently, some reports demonstrated that the degree of PTEN expression could predict trastuzumab chemosensitivity in ErbB2-overexpressing breast cancer. Here, we demonstrate the possible involvement of a proteasome inhibitor (PS341) in PTEN expression and elucidate the influence of PI3K/Akt, one of the main cascades of the ErbB2 downstream pathway, and discuss the role of the proteasome inhibitors in trastuzumab resistance. ErbB2-overexpressing SKBR3 human breast cancer cells and trastuzumab-resistant SKBR3/R cells were analyzed in this study. We show that the expression of phosphorylated Akt was highly increased in trastuzumab-resistant cells, although the expression of PI3K, phosphorylated PI3K and non-phosphorylated Akt was unchanged in comparison with wild-type SKBR3 cells. However, following treatment with PS341, the level of phosphorylated Akt was decreased in a dose-dependent manner. Conversely, the level of PTEN was increased in the same fashion. PS341 showed sufficient cytotoxicity in resistant cells in combination with trastuzumab and the efficacy of trastuzumab was inclined to be better in resistant cells under PS341 treatment. Remarkable activity of Akt was observed in trastuzumab-resistant SKBR3 breast cancer cells and this phenomenon could be associated with the decreased expression of PTEN. The proteasome inhibitor PS341 could increase the level of PTEN and inhibit the downstream pathway of ErbB2, interfering with phosphorylation of Akt.