Dysregulated PTEN-PKB and negative receptor status in human breast cancer

Navigating the complexity of PI3K/AKT pathway in HER-2 negative breast cancer: biomarkers and beyond

The results of the SOLAR-1 and CAPItello-291, highlight the benefit of the ɑ-selective phosphoinositide 3-Kinase Pathway inhibitor (PI3Ki) alpelisib and the AKT inhibitor (AKTi) capivasertib in patients with hormone receptor-positive (HR+)/Human Epidermal Growth Factor Receptor 2 (HER2)- negative metastatic breast cancer (mBC) that have PIK3CA/AKT1/PTEN tumour alterations. Although effective, these drugs are associated with significant toxicities, which often limit their use, particularly in frail patients. Following the recent incorporation of these agents into clinical practice, and with many others currently in development, significant challenges have emerged, particularly those regarding biomarkers for patient selection. This review will discuss biomarkers of response and their resistance to PI3K/AKT inhibitors (PI3K/AKTis) in HR+/HER- BC in early and advanced settings to ascertain which populations will most benefit from these drugs. Of the biomarkers that were analysed, such as PIK3CA, AKT, PTEN mutations, insulin levels, 18 F-FDG-PET/TC, only the PIK3CA-mutations (PIK3CA-mut) and the AKT pathway alterations seem to have a predictive value for treatments with alpelisib and capivasertib. However, due to the retrospective and exploratory nature of the study, the data did not provide conclusive results. In addition, the different methods used to detect PIK3CA/AKT1/PTEN alterations underline the fact that the optimal diagnostic companion has yet to be established. We have summarised the clinical data on the approved and discontinued agents targeting this pathway and have assessed the drugs development, successes, and failures. Finally, because of tumour heterogeneity, we emphasise the importance of reassessing the mutational status of PI3KCA in both metastatic tissue and blood at the time of disease progression to better tailor treatment for patients.

Current State and Future Challenges for PI3K Inhibitors in Cancer Therapy

The phosphoinositide 3 kinase (PI3K)-protein kinase B (PKB/AKT)-mammalian target of the rapamycin (mTOR) axis is a key signal transduction system that links oncogenes and multiple receptor classes which are involved in many essential cellular functions. Aberrant PI3K signalling is one of the most commonly mutated pathways in cancer. Consequently, more than 40 compounds targeting key components of this signalling network have been tested in clinical trials among various types of cancer. As the oncogenic activation of the PI3K/AKT/mTOR pathway often occurs alongside mutations in other signalling networks, combination therapy should be considered. In this review, we highlight recent advances in the knowledge of the PI3K pathway and discuss the current state and future challenges of targeting this pathway in clinical practice.

Targeting PI3K/Akt signal transduction for cancer therapy

The phosphatidylinositol 3-kinase (PI3K)/Akt pathway plays a crucial role in various cellular processes and is aberrantly activated in cancers, contributing to the occurrence and progression of tumors. Examining the upstream and downstream nodes of this pathway could allow full elucidation of its function. Based on accumulating evidence, strategies targeting major components of the pathway might provide new insights for cancer drug discovery. Researchers have explored the use of some inhibitors targeting this pathway to block survival pathways. However, because oncogenic PI3K pathway activation occurs through various mechanisms, the clinical efficacies of these inhibitors are limited. Moreover, pathway activation is accompanied by the development of therapeutic resistance. Therefore, strategies involving pathway inhibitors and other cancer treatments in combination might solve the therapeutic dilemma. In this review, we discuss the roles of the PI3K/Akt pathway in various cancer phenotypes, review the current statuses of different PI3K/Akt inhibitors, and introduce combination therapies consisting of signaling inhibitors and conventional cancer therapies. The information presented herein suggests that cascading inhibitors of the PI3K/Akt signaling pathway, either alone or in combination with other therapies, are the most effective treatment strategy for cancer.

Correlation Between Onco-suppressors PTEN and NM23 and Clinical Outcome in Patients With T1 Breast Cancer

BACKGROUND

The aim of the present work was to evaluate the prognostic significance in patients with T1 breast cancer of tissue expression of the two oncosuppressors phosphatase and tensin homolog (PTEN) and non-metastatic clone 23 (NM23) as detected by immunohistochemistry.

MATERIALS AND METHODS

We prospectively analyzed 62 patients who underwent surgery for a T1 stage breast cancer. Expression of PTEN and NM23 was tested for correlation with clinical characteristics and clinical outcome.

RESULTS

Of the 62 patients considered for our study, 16 underwent mastectomy and 46 underwent conservative surgical treatment. The surgery was considered radical (R0) in all cases described. PTEN and NM23 expression was higher in patients with no lymph node metastases and no recurrent cancer at a mean follow-up of 36 months (range=6-48 months). This correlation was more evident when both PTNE and NM23 expression were highly expressed (p<0.0001).

CONCLUSION

Low or lack of PTEN and NM23 immunohistochemical expression in cancer tissue is a risk factor for lymph node involvement and recurrent disease. It may represent a valid prognostic factor in planning therapy in patients who had surgery for T1 breast cancer.

Nexus between PI3K/AKT and Estrogen Receptor Signaling in Breast Cancer

Signaling from estrogen receptor alpha (ERα) and its ligand estradiol (E2) is critical for growth of ≈70% of breast cancers. Therefore, several drugs that inhibit ERα functions have been in clinical use for decades and new classes of anti-estrogens are continuously being developed. Although a significant number of ERα+ breast cancers respond to anti-estrogen therapy, ≈30% of these breast cancers recur, sometimes even after 20 years of initial diagnosis. Mechanism of resistance to anti-estrogens is one of the intensely studied disciplines in breast cancer. Several mechanisms have been proposed including mutations in ESR1, crosstalk between growth factor and ERα signaling, and interplay between cell cycle machinery and ERα signaling. ESR1 mutations as well as crosstalk with other signaling networks lead to ligand independent activation of ERα thus rendering anti-estrogens ineffective, particularly when treatment involved anti-estrogens that do not degrade ERα. As a result of these studies, several therapies that combine anti-estrogens that degrade ERα with PI3K/AKT/mTOR inhibitors targeting growth factor signaling or CDK4/6 inhibitors targeting cell cycle machinery are used clinically to treat recurrent ERα+ breast cancers. In this review, we discuss the nexus between ERα-PI3K/AKT/mTOR pathways and how understanding of this nexus has helped to develop combination therapies.

Exploring Dysregulated Signaling Pathways in Cancer

Cancer cell biology takes advantage of identifying diverse cellular signaling pathways that are disrupted in cancer. Signaling pathways are an important means of communication from the exterior of cell to intracellular mediators, as well as intracellular interactions that govern diverse cellular processes. Oncogenic mutations or abnormal expression of signaling components disrupt the regulatory networks that govern cell function, thus enabling tumor cells to undergo dysregulated mitogenesis, to resist apoptosis, and to promote invasion to neighboring tissues. Unraveling of dysregulated signaling pathways may advance the understanding of tumor pathophysiology and lead to the improvement of targeted tumor therapy. In this review article, different signaling pathways and how their dysregulation contributes to the development of tumors have been discussed.

Neuroprotective effect of pharmacological postconditioning on cerebral ischaemia-reperfusion-induced injury in mice

OBJECTIVES

To investigate the mechanism of neuroprotection rendered via pharmacological postconditioning in cerebral ischaemia-reperfusion-induced injury in mice.

METHODS

Pharmacological postconditioning is strategy which either involves hindering deleterious pathway or inducing modest stress level which triggers intracellular defence pathway to sustain more vigorous insult leading to conditioning. Hence, in current research we explored the potentiality of CGS21680 (0.5 mg/kg; i.p), an adenosine A₂ A receptor agonist and PTEN inhibitor, SF1670 (3 mg/kg; i.p.) to trigger postconditioning after inducing cerebral global ischaemia (17 min) and reperfusion (24 h)-induced injury via occlusion of both carotid arteries. Mice were also given treatment with LY294002 (1.5 mg/kg; i.p.), a PI3K inhibitor and adenosine A₂ A receptor antagonist, Istradefylline (2 mg/kg; i.p.), to establish the precise mechanism of postconditioning. Various biochemical and behavioural parameters were assessed to examine the effect of pharmacological postconditioning.

KEY FINDINGS

Pharmacological postconditioning induced with CGS21680 and SF1670 attenuated the infarction along with improved behavioural and biochemical parameters in comparison with ischaemia-reperfusion control group. The outcome of postconditioning with CGS21680 and SF1670 was significantly reversed by LY294002 and Istradefylline, respectively.

CONCLUSIONS

The neuroprotective effects of CGS21680 and SF1670 postconditioning on cerebral ischaemia-reperfusion injury may be due to PI3K/Akt pathway activation.

DJ-1 promotes survival of human colon cancer cells under hypoxia by modulating HIF-1α expression through the PI3K-AKT pathway

Background

Protein/nucleic acid deglycase (DJ-1) and hypoxia-inducible factor-1α (HIF-1α) play significant roles in the progression of various types of cancer and are associated with the phosphatidylinositol 3-kinase (PI3K) pathway. However, their functions in colorectal cancer (CRC) have not been identified. The aim of this study was to analyze the putative signaling pathway encompassing DJ-1, PI3K, and HIF-1α in a series of CRC tissues and cell lines.

Purpose

This study aimed at exploring the expression status of DJ-1 in colon cancer and its role in survival of cancer cell lines.

Methods

The expression and localization of DJ-1, PI3K-p110α, phosphorylated Akt (p-AKT), and HIF-1α were determined by immunohistochemistry in 73 resected CRC tissues. The effect of DJ-1 on cell activity was explored by in vitro knockdown and overexpression experiments in SW480 and HT-29 cells. The cells were treated with a PI3K inhibitor (LY294002 or wortmannin), and p-AKT and HIF-1α protein expression were then analyzed. Apoptosis was analyzed by flow cytometry. The expression levels of several HIF-1 target genes were assessed under hypoxic conditions by reverse transcription-PCR and Western blot. Xenograft tumor growth studies were conducted in DJ-1 knockdown or overexpression cells.

Results

High DJ-1 expression was found in 68.49% (50/73) of CRC tissues and associated with larger tumor size and advanced clinical stages. DJ-1 expression was positively associated with PI3K-p110α, p-AKT, and HIF-1α expression in CRC. HIF-1α and p-AKT protein levels were lower in SW480 and HT-29 cells with stable DJ-1 knockdown than in those with DJ-1 overexpression. PI3K inhibitors almost completely blocked DJ-1-induced AKT phosphorylation. However, the expression of HIF-1α was partially preserved after treatment with PI3K inhibitors. We also show that DJ-1 is necessary for the transcriptional ability of HIF-1α and CRC cell survival after hypoxic stress. Moreover, DJ-1 promoted the growth of established tumor xenografts in nude mice.

Conclusion

Our findings are the first to show that DJ-1 is overexpressed in CRC. We suggest a model in which DJ-1 mediates CRC cell survival by regulating the PI3K-AKT-HIF-1α pathway.

Regulation of Signal Transduction by DJ-1

The ability of DJ-1 to modulate signal transduction has significant effects on how the cell regulates normal processes such as growth, senescence, apoptosis, and autophagy to adapt to changing environmental stimuli and stresses. Perturbations of DJ-1 levels or function can disrupt the equilibrium of homeostatic signaling networks and set off cascades that play a role in the pathogenesis of conditions such as cancer and Parkinson's disease.DJ-1 plays a major role in various pathways. It mediates cell survival and proliferation by activating the extracellular signal-regulated kinase (ERK1/2) pathway and the phosphatidylinositol-3-kinase (PI3K)/Akt pathway. It attenuates cell death signaling by inhibiting apoptosis signal-regulating kinase 1 (ASK1) activation as well as by inhibiting mitogen-activated protein kinase kinase kinase 1 (MEKK1/MAP3K1) activation of downstream apoptotic cascades. It also modulates autophagy through the ERK, Akt, or the JNK/Beclin1 pathways. In addition, DJ-1 regulates the transcription of genes essential for male reproductive function, such as spermatogenesis, by relaying nuclear receptor androgen receptor (AR) signaling. In this chapter, we summarize the ways that DJ-1 regulates these pathways, focusing on how its role in signal transduction contributes to cellular homeostasis and the pathologic states that result from dysregulation.

Insulin growth factor receptor-1 expression and loss of PTEN protein predict early recurrence in triple-negative breast cancer

AIMS

Insulin-like growth factor receptor-1 (IGFR-1) and its signalling axis promote tumorigenesis, metastasis, and resistance to existing forms of cancer therapy, and have become a major focus for the development of anticancer drugs. As oncological management options for triple-negative breast cancers (TNBCs) are limited, there is potential for the rapid development of novel selective anticancer agents specifically targeting components of the PTEN-phosphoinositide 3-kinase-AKT pathway, including the phosphorylated form of AKT (pAKT) and the tumour suppressor molecule PTEN. The aim of this study was to conduct immunohistochemical analyses to examine the levels of PTEN, IGFR-1 and pAKT expression in TNBCs, and determine whether these levels correlated with poor prognosis in this subset of aggressive breast cancers.

METHODS AND RESULTS

Immunohistochemistry was performed on paraffin-embedded tumour tissues from a consecutive cohort of 144 female patients diagnosed with TNBC. Associations of IGFR-1, PTEN and pAKT expression with clinicopathological parameters, disease-free survival (DFS) and overall survival (OS) were evaluated. There were significant increases in IGFR-1 expression (99%) and pAKT expression (92%) with concomitant loss of PTEN expression in the majority of cases (63%). Increased IGFR-1 expression and loss of PTEN expression were associated with reduced OS and DFS, respectively. pAKT expression showed a strong correlation with basal-like expression. Combinatorial immunophenotypic analyses showed that loss of PTEN expression with concomitant IGFR-1 expression correlated with poor DFS.

CONCLUSION

A high percentage of PTEN loss with overexpression of IGFR-1 and pAKT in TNBC indicates the potential of these molecules for predicting early recurrence and/or as targets in the formulation of effective alternative therapy regimens.

A study on promoter methylation of PTEN in sporadic breast cancer patients from North India

BACKGROUND

Epigenetic silencing of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) through DNA methylation has been implicated in the pathogenesis of breast cancer. Present study investigates the contribution of PTEN promoter methylation and its associated protein expression in sporadic breast cancer patients from North India.

METHODS

A total of 360 paired breast carcinoma and adjacent normal tissue samples from 180 sporadic breast cancer patients were included in the present study and examined for PTEN promoter methylation status by methylation-specific polymerase chain reaction. Immunohistochemistry method was used for determining PTEN protein expression. Molecular findings were statistically correlated with various clinicopathological parameters to identify associations of clinical relevance.

RESULTS

Presence of PTEN promoter methylation (39.44 %) significantly correlated with its expression downregulation (45.56 %) in breast tumors (P = 0.0001). Furthermore, their interaction with various clinical parameters was evidenced in stratified analysis. Correlation of PTEN promoter methylation with histologically more malignant grade and PTEN expression loss with triple negative tumor status remained significant even after Bonferroni correction (P < 0.003).

CONCLUSIONS

Results implicate promoter methylation to be a mechanism partially responsible for PTEN silencing in sporadic breast cancer for North Indian women. Besides, methylation and expression loss of PTEN exhibited promising potential as candidate biomarkers of risk assessment in subcategorized breast tumors with critical pathologic parameters.

A Novel Inhibitor of AKT1-PDPK1 Interaction Efficiently Suppresses the Activity of AKT Pathway and Restricts Tumor Growth In Vivo

The serine/threonine kinase AKT/PKB has a critical role in the regulation of cell proliferation. Because AKT signaling is deregulated in numerous human malignancies, it has become an attractive anticancer drug target. A number of small molecule AKT kinase inhibitors have been developed; however, severe side effects have prevented their use in clinical trials. To find inhibitors of AKT1 signaling with principally novel mechanism of action, we carried out a live cell-based screen for small molecule inhibitors of physical interaction between AKT1 and its primary activator PDPK1. The screen revealed one molecule-NSC156529, which downregulated AKT1 signaling, efficiently decreased the proliferation of human cancer cells in vitro, and substantially inhibited the growth of prostate tumor xenografts in vivo. Interestingly, the treated tumor xenografts exhibited higher expression level of normal prostate differentiation markers but did not show augmented cell death, suggesting that the identified compound primarily enhances the differentiation of malignant cells toward normal prostate epithelium and thus poses as an attractive lead compound for developing novel antitumor agents with less cytotoxic side effects.

Effect of DJ-1 overexpression on the proliferation, apoptosis, invasion and migration of laryngeal squamous cell carcinoma SNU-46 cells through PI3K/AKT/mTOR

The aim of the present study was to explore the effect of DJ-1-mediated PI3K/AKT/mTOR pathway on the proliferation, apoptosis, invasion, migration and other tumor biological characteristics of laryngeal squamous cell SNU-46, through stable transfection and overexpression of the DJ-1 gene. Retrovirus carrying DJ-1 gene was used to stabilize transfected human laryngeal squamous carcinoma SNU-46 cell line, and monoclonal cell line of stably overexpressed DJ-1 protein was screened out by G418. DJ-1 protein expression was determined by western blotting, and changes of p-AKT, p-mTOR and PTEN protein content were detected, followed by the detection of changes in proliferation, apoptosis, invasion, migration and other tumor biological characteristics of laryngeal squamous carcinoma cell line with stably transfected DJ-1 protein overexpression by flow cytometry, CCK-8 method and Transwell. We successfully constructed a laryngeal squamous carcinoma cell line of stably overexpressed DJ-1 protein and termed it SNU-46-DJ-1. After overexpression of DJ-1 protein, the levels of PTEN expression in laryngeal squamous cell SNU-46 decreased and p-AKT and p-mTOR protein expression levels increased. Compared to the untreated SNU-46 cells, the proliferation rate of SNU-46-DJ-1 cells increased (0.834±0.336 vs. 0.676±0.112; p<0.001); invasiveness was enhanced (165.7±13.6 vs. 100.0±17.4; p=0.001), the migration ability was enhanced (207.3±13.1 vs. 175.3±13.3; p=0.036), and the apoptosis rate decreased (3.533±5.167 vs. 16.397±5.447%; p=0.019). The overexpression of DJ-1 protein in laryngeal squamous carcinoma SNU-46 cells can accelerate proliferation rate, increase the invasion and migration capacity, and reduce apoptosis, by activating the PI3K/AKT/mTOR pathway.

Expression of the Androgen Receptor, pAkt, and pPTEN in Breast Cancer and Their Potential in Prognostication

BACKGROUND

Importance of androgen receptor (AR) as an independent prognostic marker in Pakistani women with breast cancer (BCa) remains unexplored. Our aim was to identify the expression and potential prognostic value of AR, its upstream regulator (pAkt) and target gene (pPTEN) in invasive BCa.

METHODS

This study used a cohort of 200 Pakistani women with invasive BCa diagnosed during 2002-2011. Expression of AR, pAkt and pPTEN was determined on formalin fixed paraffin embedded tissue sections by immunohistochemistry. The association of AR, pAkt and pPTEN with clinicopathological parameters was determined. Survival analyses were undertaken on patients with ≥5years of follow-up (n=82).

RESULTS

Expression of AR, pAkt and pPTEN was observed in 47.5%, 81.3% and 50.6% of patients, respectively. AR-expressing tumors were low or intermediate in grade (P<.001) and expressed ER (P=.002) and PR (P=.001). Patients with AR+ tumors had significantly higher OS (Mean OS=10.2±0.465years) compared to patients with AR- tumors (Mean OS=5.8±0.348years) (P=.047). Furthermore, AR-positivity was associated with improved OS in patients receiving endocrine therapy (P=.020). Patients with AR+ /pAkt+ /pPTEN- tumors, had increased OS (Mean OS=7.1±0.535years) compared to patients with AR-/pAkt+/pPTEN- tumors (Mean OS=5.1±0.738years).

CONCLUSION

AR-expressing tumors are frequently characterized by low or intermediate grade tumors, expressing ER and PR. In addition, expression of AR, pAkt and pPTEN, could be considered in prognostication of patients with invasive BCa.

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.

Tumorigenesis role and clinical significance of DJ-1, a negative regulator of PTEN, in supraglottic squamous cell carcinoma

Background

DJ-1 can induce the tumor cell proliferation and invasion via down-regulating PTEN in many malignant tumors, and correlated to prognostic significance. However, the tumorigenesis role and clinical significance of DJ-1 in supraglottic squamous cell carcinoma (SSCC) is unclear. We aimed to evaluate the DJ-1 the relationship between DJ-1 and clinicopathological data including patient survival.

Methods

The expression of DJ-1 and PTEN in SSCCs (52) and adjacent non-cancerous tissues (42) was assessed by immunohistochemistry (IHC), and the relationship between DJ-1 and clinicopathological data was analyzed.

Results

DJ-1 was detected mainly in SSCCs (88.5%) and less frequently in adjacent non-cancerous tissues (21.0%). PTEN expression was detected in 46.2% of SSCCs and in 90.5% of adjacent non-cancerous tissues. DJ-1 expression was linked to nodal status (P = 0.009), a highly significant association of DJ-1 expression with shortened patient overall survival (5-year survival rate 88.0% versus 53.9%; P = 0.007; log rank test) was demonstrated.

Conclusions

Our data suggested that DJ-1 over-expression was linked to nodal status, and might be an independent prognostic marker for patients with SSCC.

Analysis of PTEN expression in large intestine polyps and its relation to the recognized histopathological and clinical risk factors for cancer development in this location

AIM OF THE STUDY

PTEN is an important gene whose protein product is double specific phosphatase holding key regulatory functions in sending signals from membrane receptors for growth factors into the cell downstreams. Its participation, mainly by PI3K/AKT signaling pathway in the pathomechanism of many malignant cancers was unambiguously confirmed. The PTEN function gets disturbed on many levels and for various reasons. Disorders of PTEN protein expression seem to be even more common in many carcinomas. The aim of the study is to enquire the meaning of PTEN expression in the cancer transformation process in large intestine glandular polyps.

MATERIAL AND METHODS

The group includes 40 patients, 21 men and 19 women, age median 64 years (51-83) qualified to endoscopic removal of large intestine polyp. Tissue material obtained during polyp removal endoscopy was immediately fixed in 4% buffered formalin solution with the mixture of phosphatase activity inhibitors (PhosStop Roche). Time of fixation 24-48 h. After fixation, the material was embedded in paraffin. PTEN visualization was based on specific rabbit monoclonal antibodies (Cell Signaling). The expression of PTEN protein in large intestine and rectum polyps was marked by a semi-quantitative method and an attempt to correlate the results with the acknowledged clinical and histopathological malignancy risk factors was undertaken.

RESULTS

Loss or weakening of protein expression was found in 45% cases. Moreover, the relationship between polyp diameter and a loss of PTEN expression was proved. The received results can indicate a significant participation of PTEN gene in early oncogenesis stages of large intestine cancer.

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.

Contributions of the Epstein-Barr virus EBNA1 protein to gastric carcinoma

Approximately 10% of gastric carcinomas (GC) are comprised of cells latently infected with Epstein-Barr virus (EBV); however, the mechanism by which EBV contributes to the development of this malignancy is unclear. We have investigated the cellular effects of the only EBV nuclear protein expressed in GC, EBNA1, focusing on promyelocytic leukemia (PML) nuclear bodies (NBs), which play important roles in apoptosis, p53 activation, and tumor suppression. AGS GC cells infected with EBV were found to contain fewer PML NBs and less PML protein than the parental EBV-negative AGS cells, and these levels were restored by silencing EBNA1. Conversely, EBNA1 expression was sufficient to induce the loss of PML NBs and proteins in AGS cells. Consistent with PML functions, EBNA1 expression decreased p53 activation and apoptosis in response to DNA damage and resulted in increased cell survival. In addition, EBNA1 mutants unable to bind CK2 kinase or ubiquitin-specific protease 7 had decreased ability to induce PML loss and to interfere with p53 activation. PML levels in EBV-positive and EBV-negative GC biopsy specimens were then compared by immunohistochemistry. Consistent with the results in the AGS cells, EBV-positive tumors had significantly lower PML levels than EBV-negative tumors. The results indicate that EBV infection of GC cells leads to loss of PML NBs through the action of EBNA1, resulting in impaired responses to DNA damage and promotion of cell survival. Therefore, PML disruption by EBNA1 is one mechanism by which EBV may contribute to the development of gastric cancer.

Evidence for PTEN-independent Akt activation and Akt-independent p27(Kip1) expression in advanced bladder cancer

In the treatment of advanced bladder cancer (BC), attention has recently focused on small molecule therapy concerning EGFR and the downstream Akt signalling pathway. Cellular deregulation processes are poorly understood, and biological determinants for the selection of therapy and monitoring are currently not available. The proteins PTEN, p-Akt and p27(Kip1) are suggested to be potentially significant biomarkers of Akt signalling. In this study, we investigated the expression of these proteins in advanced BC. PTEN, p-Akt and p27(Kip1) expression was determined immunohistochemically in 86 T2-4 BC specimens using a tissue microarray technique. Staining was documented with regard to intensity, cellular frequency and a multiplied staining score. Staining characteristics of the three proteins were correlated by regression analysis with the parameters of tumour stage and grade. A positive correlation was observed in the expression scores of PTEN and p-Akt, p-Akt and p27(Kip1) as well as PTEN and p27(Kip1) (p<0.02 for all combinations). The positive correlation between PTEN and p-Akt resulted mainly due to the strong correlation of PTEN intensity with p-Akt (p=0.0003 and p=0.0006 to p-Akt frequency and intensity, respectively). A positive correlation between p-Akt and p27(Kip1) was noted for p-Akt frequency as well as intensity (p<0.05 for all combinations). The positive correlation between PTEN and p27(Kip1) resulted due to the correlation of PTEN intensity alone with p27(Kip1) (p<0.03 for p27(Kip1) frequency and intensity), whereas no significance was noted for PTEN frequency. No correlation was found between T or G and expression of the proteins. However, activation of Akt in BC is known to occur independently of PTEN protein loss and appears not to cause a decrease of p27(Kip1). However, a direct regulatory impact of PTEN on p27(Kip1) was found. PTEN intensity, rather than frequency, appears to be a superior biomarker. These results may provide information to support research into protein profiling-predicted targeted therapy for BC. Correlations to benign urothelium, superficial BC specimens and follow-up data remain to be investigated.

MicroRNA-301 mediates proliferation and invasion in human breast cancer

Several microRNAs have been implicated in human breast cancer but none to date have been validated or utilized consistently in clinical management. MicroRNA-301 (miR-301) overexpression has been implicated as a negative prognostic indicator in lymph node negative (LNN) invasive ductal breast cancer, but its potential functional impact has not been determined. Here we report that in breast cancer cells, miR-301 attenuation decreased cell proliferation, clonogenicity, migration, invasion, tamoxifen resistance, tumor growth, and microvessel density, establishing an important oncogenic role for this gene. Algorithm-based and experimental strategies identified FOXF2, BBC3, PTEN, and COL2A1 as candidate miR-301 targets, all of which were verified as direct targets through luciferase reporter assays. We noted that miR-301 is located in an intron of the SKA2 gene which is responsible for kinetochore assembly, and both genes were found to be coexpressed in primary breast cancer samples. In summary, our findings define miR-301 as a crucial oncogene in human breast cancer that acts through multiple pathways and mechanisms to promote nodal or distant relapses.

Significance and relationship between DJ-1 gene and surviving gene expression in laryngeal carcinoma

This study aimed at exploring the correlation between DJ-1 gene and survivin gene in laryngeal squamous cell carcinoma by analyzing their gene expression levels and their relationship with clinicopathologic parameters. The expression of DJ-1 gene and survivin gene in 82 laryngeal carcinoma tissues from patients and 82 negative surgical margin tissue samples were detected by immunohistochemistry, respectively. The correlation of their expression levels and patients' clinical parameters were then analyzed by Pearson correlation analysis. The positive detection rates of DJ-1 and survivin in laryngeal carcinoma tissues were 71.95% and 60.98%, which were higher than those of the normal control that were 29.27% and 0.00%, respectively (P<0.01). The positive detection rates of DJ-1 and survivin were found associated with tumor stages (P<0.05), but not with lymph node metastasis. The DJ-1 gene expression level was related to cell differentiation (P<0.05). Finally, a positive correlation between DJ-1 and survivin gene expression in laryngeal carcinoma was found. The overall survival rate of patients was 51.2%, and disease-free survival (DFS) was 39.0%. DFS in DJ-1 negative-expression group was 87.0%, and 20.3% in DJ-1 positive-expression group. The negative expression of DJ-1 was associated with a shorter mean patient DFS time (44.643±1.417 months), whereas positive expression of DJ-1 was associated with a longer mean DSF time (25.943±;1.297 months). DJ-1 and survivin play a vital role in the occurrence and development of laryngeal carcinoma. DJ-1 may promote the carcinogenesis of laryngeal cells by up-regulating the survivin gene expression.

Clinical significance of progesterone receptor and HER2 status in estrogen receptor-positive, operable breast cancer with adjuvant tamoxifen

PURPOSE

To evaluate prognostic factors in estrogen receptor (ER)-positive, operable breast cancer focusing on the progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2).

PATIENTS AND METHODS

A total of 819 patients with ER-positive, operable breast cancer were enrolled. All patients received upfront adjuvant tamoxifen, as stipulated by eligibility criteria. Prognostic values of the PR status and HER2 status were evaluated using Cox regression.

RESULTS

Of all patients enrolled, 72% were PR positive and 20% were HER2 positive. PR and HER2 status were inversely correlated (P = 0.014). PR-negative tumors were associated with older age over 50 years (P < 0.001) and higher histologic grade (P = 0.024). HER2 overexpression correlated with older age over 50 years (P = 0.007), higher T stage (P = 0.010), and higher histologic grade (P = 0.047). For recurrence, PR negativity was a poor prognostic factor before 5 years postsurgery (hazard ratio = 1.57; P = 0.049) and HER2 overexpression was a consistent poor prognostic factor over all time periods (hazard ratio = 1.93; P = 0.001) in the multivariate model adjusted by age, T/N stage, and histologic grade.

CONCLUSIONS

In ER-positive, operable breast cancer, PR negativity may provide additional information on poor prognosis or tamoxifen resistance during adjuvant tamoxifen therapy within 5 years postsurgery. HER2 overexpression was a poor prognostic factor consistently throughout time. This suggests that an alternative adjuvant strategy, possibly incorporating prolonged HER2-targeted therapy, needs to be evaluated for HER2-overexpressing tumors.

t-DARPP regulates phosphatidylinositol-3-kinase-dependent cell growth in breast cancer

Background

Recent reports have shown that t-DARPP (truncated isoform of DARPP-32) can mediate trastuzumab resistance in breast cancer cell models. In this study, we evaluated expression of t-DARPP in human primary breast tumors, and investigated the role of t-DARPP in regulating growth and proliferation in breast cancer cells.

Results

Quantitative real time RT-PCR analysis using primers specific for t-DARPP demonstrated overexpression of t-DARPP in 36% of breast cancers (13/36) as opposed to absent to very low t-DARPP expression in normal breast tissue (p < 0.05). The mRNA overexpression of t-DARPP was overwhelmingly observed in ductal carcinomas, including invasive ductal carcinomas and intraductal carcinomas, rather than other types of breast cancers. The immunohistochemistry analysis of DARPP-32/t-DARPP protein(s) expression in breast cancer tissue microarray that contained 59 tumors and matched normal tissues when available indicated overexpression in 35.5% of primary breast tumors that were more frequent in invasive ductal carcinomas (43.7%; 21/48). In vitro studies showed that stable overexpression of t-DARPP in MCF-7 cells positively regulated proliferation and anchorage-dependent and -independent growth. Furthermore, this effect was concomitant with induction of phosphorylation of AKT^ser473 and its downstream target phospho^ser9 GSK3β, and increased Cyclin D1 and C-Myc protein levels. The knockdown of endogenous t-DARPP in HCC1569 cells led to a marked decrease in phosphorylation of AKTs^ser473 and GSK3β^ser9. The use of PI3K inhibitor LY294002 or Akt siRNA abrogated the t-DARPP-mediated phosphorylation of AKT^ser473 and led to a significant reduction in cell growth.

Conclusions

Our findings underscore the potential role of t-DARPP in regulating cell growth and proliferation through PI3 kinase-dependent mechanism.

Clinicopathologic and molecular significance of phospho-Akt expression in early invasive breast cancer

Akt/PKB serine/threonine kinase is a leading signalling modulator for several cellular processes including metabolism, growth, proliferation and survival. However, complexity and diversity in the upstream/downstream arms of Akt pathway, as recent genetic studies reported, challenge considerably the evolvement of effective targeted therapies. The aim was to study the expression of phospho-Akt1 (pAkt) in breast cancer (BC), with respect to different component proteins upstream/downstream of Akt pathway activation, clinicopathologic parameters and patients' outcome. pAkt (Ser473) was evaluated by immunohistochemistry, on tissue microarrays containing 1,202 early invasive BC with long-term clinical follow-up. Seventy-six percent of the studied tumours overexpressed pAkt, where it was associated with expression of oestrogen and androgen receptors, PIK3CA, cytokeratin (CK)18, CK19 and PTEN. Loss of pAkt was correlated with high grade, CK5/6, p53 and high Ki67 labelling index. Higher proportions of luminal tumours were pAkt positive relative to triple negative/basal subtypes. However, pAkt overexpression was not associated with breast cancer specific (BCSS) or metastasis-free survival (MFS). Four tumour phenotypes were identified based on PIK3CA and pAkt expression, with substantial proportions being PIK3CA⁻/pAkt⁺ or PIK3CA⁺/pAkt⁻. These four combinatorial phenotypes were significantly associated with BCSS (p = 0.001) and MFS (p = 0.002). Although pAKT is an oncogene correlated with poor prognostic variables, it was not a prognostic marker. Combinatorial phenotypic groups of PIK3CA/pAkt denoted functional complexity, at translational level, within the upstream and downstream arms of Akt activation with significant impact on patients' outcome. These findings may help development more adequate therapeutic regimens for specific subgroups of this key cancer pathway.

Targeting mTOR in cancer: renal cell is just a beginning

The mammalian target of rapamycin (mTOR) is a key regulator of cell growth and proliferation. The mTOR pathway integrates signals from nutrients, energy status and extracellular growth factors to regulate many processes, including cell cycle progression, angiogenesis, ribosome biogenesis, and metabolism. Growth factors such as insulin-like growth factor, epidermal growth factor and vascular endothelial growth factor bind to and activate their corresponding tyrosine kinase receptors (TKR) located on the cell surface, to induce signal transduction to the nucleus. TKR induces intracellular signaling cascades via the phosphorylation of the phosphatidylinositol 3-kinase, which in turn phosphorylates Akt. Of particular interest among the Akt targets is the downstream effect on mTOR, which is responsible for protein synthesis of molecules necessary for nutrient uptake, angiogenesis, ribosome biogenesis, cell growth, and proliferation. Growing evidence suggests that mTOR deregulation is associated with many types of human cancer. The importance of mTOR signaling in tumor biology is now widely accepted. Consequently, a number of agents that selectively target mTOR are being developed for cancer treatment and currently temsirolimus and everolimus are approved for the treatment of advanced renal cell cancer. However, the therapeutic benefit of mTOR inhibitors in the clinic may vary depending on the activation state of the different components of the mTOR pathway in a given case. Therefore it seems clear that predicting sensitivity to rapamycins in different cancers will likely require assessing multiple molecular markers related to mTOR signaling pathway, such as phosphatase and tensin homolog (PTEN), phospho-Akt, cytoplasmic p27, and phospho-S6 kinase.

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.

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.

Dysregulated PI3K/Akt/PTEN pathway is a marker of a short disease-free survival in node-negative breast carcinoma

The phosphoinositide 3-kinase/Akt pathway is involved in the pathogenesis of several human cancers. In this study, the biological and prognostic value of phosphoinositide 3-kinase/Akt pathway dysregulation was assessed by immunohistochemistry in a well-characterized series of 72 patients with node-negative breast cancer with a long-term follow-up. Phosphorylated Akt and PTEN expression was reduced in 32% and 12.5% of the tumors, respectively. Phosphorylated Akt or PTEN status was not associated with the main clinicopathologic and biological parameters, whereas their expression was tightly related to their downstream targets cyclin D1 and p27(Kip1) which are involved in cell proliferation. Survival analysis showed a strong association between a shorter disease-free survival and the dysregulated expression of phosphorylated Akt (P = .036), PTEN (P = .003), p27(Kip1) (P = .008), and Ki67 (P = .0007), or the distinct subtypes of breast tumors (luminal, HER2 overexpressing, and basal-like; P = .03). Moreover, multivariate analysis using the Cox proportional-hazards regression model showed that PTEN and Ki67 were independent predictive factors of disease recurrence and that their simultaneous dysregulation strongly increased the hazards ratio of the patients with node-negative breast cancer (hazards ratio, 38.30; P = .0014). In conclusion, our results show that the dysregulation of the phosphoinositide 3-kinase/Akt/PTEN pathway is relevant to the prognosis in node-negative breast carcinoma and that the evaluation of key components of this pathway might be a useful tool to identify the patients with node-negative breast cancer at high-risk of disease recurrence.

Tenets of PTEN tumor suppression

Since its discovery as the elusive tumor suppressor gene at the frequently mutated 10q23 locus, PTEN has been identified as lost or mutated in several sporadic and heritable tumor types. A decade of work has established that PTEN is a nonredundant phosphatase that is essential for regulating the highly oncogenic prosurvival PI3K/AKT signaling pathway. This review discusses emerging modes of PTEN function and regulation, and speculates about how manipulation of PTEN function could be used for cancer therapy.

Analysis of complex protein kinase B signalling pathways in human prostate cancer samples

OBJECTIVE

To provide a rational basis for targeted treatment approaches in prostate cancer deregulation of the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (PKB/Akt) system was analysed.

PATIENTS AND METHODS

In all, 45 patients with primary localized prostate cancer that underwent radical prostatectomy were included in the present study. Upon scoring of the pathological grade, expression and phosphorylation levels of PKB/Akt and relevant downstream targets were determined in tissue specimens by immunohistochemistry using specific antibodies against PTEN, PKB/Akt, its downstream targets, and the respective phosphorylated proteins.

RESULTS

Most patients (>90%) had up-regulated expression and/or phosphorylation of PKB/Akt in the malignant tissue compared with the surrounding benign tissue, with a higher prevalence of increased phosphorylated PKB/Akt in patients with Gleason scores of > or =6 (100%) compared with those with Gleason scores of 4-5 (five of 13 patients), and in particular in patients with clinical progression. Up-regulated phosphorylation of PKB/Akt occurred either in association with loss or inactivation of PTEN or in a PTEN-independent manner. Enhanced phosphorylation levels of the PKB/Akt substrates glycogen synthase kinase 3, the mammalian target of rapamycin or the forkhead transcription factor like 1 (FKHRL1) were found in 29%, 42% and 40% of the tumours, respectively. Of these, only increased phosphorylated-FKHRL1 levels correlated with clinical progression. Interestingly, 80% of patients had a notable overexpression but not phosphorylation of the eucaryotic initiation factor 4E binding protein.

CONCLUSION

Deregulation of p-PKB/Akt is common in localized prostate cancer and has a putative value as predictive marker for disease progression and as therapeutic target. However, as a consequence of the substantial heterogeneity in the expression and phosphorylation levels of relevant PKB/Akt effector pathways, for a rational use of specified inhibitors of the PI3K/PKB system a complex pattern testing of expression and activity of the respective target proteins for prediction of efficacy and prognosis seems mandatory.

Clinicopathological significance of PTEN loss and the phosphoinositide 3-kinase/Akt pathway in sporadic colorectal neoplasms: is PTEN loss predictor of local recurrence?

BACKGROUND

PTEN is a tumor-suppressor gene located on chromosome 10. Deficient PTEN expression leads to activation of the phosphoinositide 3-kinase (PI3K)/Akt (pAkt) signaling pathway, which may contribute to multiple human cancers. The relation between PTEN expression and Akt activation is still unclear in colorectal cancers and adenomatous polyps. Moreover, PTEN and pAkt expression in relation to demographic, tumoral, and outcome variables remains to be elucidated.

METHODS

PTEN and pAkt expression were evaluated in 76 primary colorectal cancers and 25 adenomatous colorectal polyp tissues using immunohistochemical staining on paraffin-embedded sections. PTEN and pAkt expression were compared with clinicopathologic features of colorectal cancers. The relationship between PTEN and pAkt expression was also investigated.

RESULTS

In colorectal cancers, pAkt expression was found to be significantly higher than polyps (P = .007). On the other hand, PTEN expression was significantly lower in polyps (P <.0001). In colorectal cancer patients, PTEN expression showed a negative correlation with young age, female sex, and left-sided (distal) tumors. On multivariate analysis, low PTEN expression (PTEN loss) was noted as an independent parameter for local recurrence (P = .024). There was significant association between pAkt expression and stage (P = .008), and preoperative serum carcinoembryonic antigen (CEA) levels (P = .017) in colorectal cancers. A negative correlation between PTEN and pAkt expression was found in colon cancer patients (P = .010), whereas no significiant association was found in adenomatous polyps (P = .403). No correlation of PTEN expression or pAkt expression was observed in Kaplan-Meier survival statistics and multivariate analyses for disease-free and overall survival.

CONCLUSIONS

The current study suggests that the PTEN loss-PI3K/pAkt pathway may play an important role in sporadic colon carcinogenesis and that reduced PTEN expression may predict relapse in colorectal cancer patients.

Minireview: nuclear receptors and breast cancer

Until recently, the study of nuclear receptor (NR) function in breast cancer biology has been largely limited to estrogen and progesterone receptors. The development of reliable gene expression arrays, real-time quantitative RT-PCR, and immunohistochemical techniques for studying NR superfamily members in primary human breast cancers has now revealed the presence and potential importance of several additional NRs in the biology of breast cancer. These include receptors for steroid hormones (including androgens and corticosteroids), fat-soluble vitamins A and D, fatty acids, and xenobiotic lipids derived from diet. It is now clear that after NR activation, both genomic and nongenomic NR pathways can coordinately activate growth factor signaling pathways. Advances in our understanding of both NR functional networks and epithelial cell growth factor signaling pathways have revealed a frequent interplay between NR and epithelial cell growth factor family signaling that is clinically relevant to breast cancer. Understanding how growth factor receptors and their downstream kinases are activated by NRs (and vice-versa) is a central goal for maximizing treatment opportunities in breast cancer. In addition to the estrogen receptor, it is predicted that modulating the activity of other NRs will soon provide novel prevention and treatment approaches for breast cancer patients.

t-Darpp promotes cancer cell survival by up-regulation of Bcl2 through Akt-dependent mechanism

t-Darpp is a cancer-related truncated isoform of Darpp-32 (dopamine and cyclic-AMP-regulated phosphoprotein of M(r) 32,000). We detected overexpression of t-Darpp mRNA in two thirds of gastric cancers compared with normal samples (P = 0.004). Using 20 micromol/L ceramide treatment as a model for induction of apoptosis in AGS cancer cells, we found that expression of t-Darpp led to an increase in Bcl2 protein levels and blocked the activation of caspase-3 and caspase-9. The MitoCapture mitochondrial apoptosis and cytochrome c release assays indicated that t-Darpp expression enforces the mitochondrial transmembrane potential and protects against ceramide-induced apoptosis. Interestingly, the expression of t-Darpp in AGS cells led to >or=2-fold increase in Akt kinase activity with an increase in protein levels of p-Ser(473) Akt and p-Ser(9) GSK3 beta. These findings were further confirmed using tetracycline-inducible AGS cells stably expressing t-Darpp. We also showed transcriptional up-regulation of Bcl2 using the luciferase assay with Bcl2 reporter containing P1 full promoter, quantitative reverse transcription-PCR, and t-Darpp small interfering RNA. The Bcl2 promoter contains binding sites for cyclic AMP-responsive element binding protein CREB/ATF1 transcription factors and using the electrophoretic mobility shift assay with a CREB response element, we detected a stronger binding in t-Darpp-expressing cells. The t-Darpp expression led to an increase in expression and phosphorylation of CREB and ATF-1 transcription factors that were required for up-regulating Bcl2 levels. Indeed, knockdown of Akt, CREB, or ATF1 in t-Darpp-expressing cells reduced Bcl2 protein levels. In conclusion, the t-Darpp/Akt axis underscores a novel oncogenic potential of t-Darpp in gastric carcinogenesis and resistance to drug-induced apoptosis.

Overcoming endocrine resistance in breast cancer: are signal transduction inhibitors the answer?

Endocrine therapy is probably the most important systemic therapy for hormone receptor positive breast cancer. Hormonal manipulation was the first targeted treatment employed in breast cancer therapy even before the role of the estrogen (ER) and progesterone receptors (PR) had been elucidated. Unfortunately, a substantial proportion of patients, despite being ER and/or PR positive, are either primarily resistant to hormone therapies or will develop hormone resistance during the course of their disease. Signaling through complex growth factor receptor pathways, which activate the ER are emerging as important causes of endocrine resistance. Targeted therapies, such as signal transduction inhibitors (STIs), are being explored as agents to be able to potentially overcome this crosstalk and thus, resistance to hormone treatment. This article reviews the biology of the ER, the proposed mechanisms of endocrine resistance, and ongoing clinical trials with STIs in combination with hormonal manipulation as a means to overcome endocrine resistance.

EGFR signaling pathway in breast cancers: from traditional signal transduction to direct nuclear translocalization

Aberrant epidermal growth factor receptor (EGFR) signaling is a major characteristic of many human malignancies including breast cancer. Since the discovery of EGF in 1960's and its receptor in 1980's, our understanding of the EGF/EGFR pathway has been significantly advanced and consequently, EGFR is considered as a major oncogenic factor and an attractive therapeutic target. The well-established traditional function of EGFR is known to transmit extra-cellular mitogenic signals, such as EGF and transforming growth factor-alpha (TGF-alpha), through activating a number of downstream signaling cascades. These include signaling modules that involve phospholipase C-gamma, Ras, and phosphatidylinositol-3 kinase (PI-3K). In cancer cells, the common outcomes following the activation of the EGFR-mediated downstream pathways are altered gene activities, leading to un-controlled tumor proliferation and apoptosis. Interestingly, emerging evidences suggest the existence of a direct mode of the EGFR pathway that is distinct from the traditional transduction pathway. This new mode of EGFR signaling involves cellular transport of EGFR from the cell-surface to the cell nucleus, association of nuclear EGFR complex with gene promoters, and transcriptional regulation of the target genes. Although the nature and pathological consequences of the nuclear EGFR pathway remain elusive, accumulating evidences suggest its association with increased tumor cell proliferation and poor survival rate in breast cancer patients. While several anti-EGFR agents are being tested in breast cancer patients clinically and others under pre-clinical development, a better understanding of the traditional and the nuclear EGFR pathways will facilitate the identification of patients that are likely to respond to these agents as well as future development of more effective anti-EGFR therapeutic interventions.

Clinical significance of CK5/6 and PTEN protein expression in patients with bilateral breast carcinoma

AIMS

To assess the expression of cytokeratin (CK) 5/6 in bilateral breast cancers and to assess the relationship between its expression and other prognostic variables, as well as between CK5/6 expression and patients' survival.

METHODS AND RESULTS

The expression of CK5/6, PTEN protein, oestrogen receptor, progesterone receptor, p53 and c-erbB-2 protein were evaluated by immunohistochemistry in 88 primary breast cancers diagnosed in 44 women. To assess the prognostic value of studied factors, Cox regression analysis was performed. Expression of CK5/6 was found in 23 of 88 primary breast carcinomas (23/88; 26%). The hazard ratio of development of distant metastasis in patients in whom at least one cancer was CK5/6+ was 99.8 (P=0.037) and in patients with at least one carcinoma with reduced PTEN expression it was 10.8 (P=0.044). CK5/6 expression was correlated with absence of oestrogen (P<0.0001) and progesterone receptors (P<0.0001) and very strong expression of p53 (P<0.05). Reduced PTEN expression was correlated with presence of axillary metastases (P<0.01), with very strong expression of c-erbB-2 (P<0.05) and with reduced expression of oestrogen receptor (P<0.05).

CONCLUSIONS

Analysis of expression of CK5/6 and PTEN protein in bilateral breast carcinomas may be of value in clinical practice and warrant further studies.

Coexistence of the loss of heterozygosity at the PTEN locus and HER2 overexpression enhances the Akt activity thus leading to a negative progesterone receptor expression in breast carcinoma

Serine/threonine kinase Akt/PKB is known to regulate divergent cellular processes, including apoptosis, proliferation, differentiation, and metabolism. Akt is activated by a variety of stimuli, through such growth factor receptors as HER2, in phosphoinositide-3-OH kinase (PI3K)-dependent manner. A loss of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) function also activates Akt. It has recently been shown that Akt activation is associated with a worse outcome among endocrine treated breast cancer patients and that it also inhibits the progesterone receptor (PR) expression via the PI3K/Akt pathway in breast cancer cells. Therefore, the PI3K/Akt signaling pathway has recently attracted considerable attention as a new target for effective therapeutic strategies. In the present study, we investigated the relationship between Akt activation and either HER2 overexpression or PTEN gene alteration, as well as the PR expression. We analyzed the incidence of LOH at the PTEN locus in 138 breast cancer patients, using our new system for microsatellite analysis, called high-resolution fluorescent microsatellite analysis (HRFMA). We showed Akt activation to significantly correlate with HER2 overexpression or LOH at the PTEN gene locus while inversely correlating with the PR expression. In addition, when LOH at the PTEN gene locus and HER2 overexpression occurred simultaneously, the incidence of Akt activation and reduced PR expression was significant. The association between Akt activation and PR negative expression was observed even in the ER-positive cases. Our results suggest that simultaneous PTEN LOH and HER2 overexpression enhances Akt activation and may thus lead to a negative PR expression.

Progesterone receptor loss correlates with human epidermal growth factor receptor 2 overexpression in estrogen receptor-positive breast cancer

Response to endocrine therapy in breast cancer correlates with estrogen receptor (ER) and progesterone receptor (PR) status. It was originally hypothesized that the ability of PR to predict response to endocrine therapy was due to the fact that PR is an estrogen-regulated gene and that its levels represented a marker of functional ER activity. However, it is now known that loss of PR can occur via multiple mechanisms, many of which do not include ER function, e.g., hypermethylation of the PR promoter and loss of heterozygosity of the PR gene. We have shown that growth factor signaling pathways can directly down-regulate PR levels via the phosphatidylinositol 3'-kinase (PI3K)/Akt/mTOR pathway, and that this can occur independent of ER. For example, overexpression of myr-Akt in MCF-7 cells causes complete loss of PR protein and mRNA but does not reduce ER levels or activity, thus generating ER+/PR- MCF-7 cells. Therefore, the absence of PR may not simply reflect a lack of ER activity but rather may reflect hyperactive cross-talk between ER and growth factor signaling pathways. Consistent with this hypothesis, several recent clinical studies have found that ER+/PR- breast cancers overexpress human epidermal growth factor receptor (HER) 1 and HER2 compared with ER+/PR+ breast cancers. Although HER receptors can lower ER levels, one study showed that loss of PR correlated with high HER2 levels in a multivariate analysis. Furthermore, loss of PTEN, a negative regulator of the PI3K/Akt signaling pathway, has been shown to be associated with specific loss of PR and no change in ER levels. Given the well-recognized resistance of ER+/PR- breast cancer to antiestrogens, more studies are needed to better understand the etiology of ER+/PR- breast cancer, particularly the analysis of other growth factor receptors and their downstream signaling intermediates with respect to PR status.

Beyond PTEN mutations: the PI3K pathway as an integrator of multiple inputs during tumorigenesis

The tumour-suppressor phosphatase with tensin homology (PTEN) is the most important negative regulator of the cell-survival signalling pathway initiated by phosphatidylinositol 3-kinase (PI3K). Although PTEN is mutated or deleted in many tumours, deregulation of the PI3K-PTEN network also occurs through other mechanisms. Crosstalk between the PI3K pathways and other tumorigenic signalling pathways, such as those that involve Ras, p53, TOR (target of rapamycin) or DJ1, can contribute to this deregulation. How does the PI3K pathway integrate signals from numerous sources, and how can this information be used in the rational design of cancer therapies?

Biology of progesterone receptor loss in breast cancer and its implications for endocrine therapy

The response to endocrine therapy in breast cancer correlates with estrogen receptor (ER) and progesterone receptor (PR) status. ER-positive/PR-negative breast cancers respond less well to selective ER modulator (SERM) therapy than ER-positive/PR-positive tumors. The predictive value of PR has long been attributed to the dependence of PR expression on ER activity, with the absence of PR reflecting a nonfunctional ER and resistance to hormonal therapy. However, recent clinical and laboratory evidence suggests that ER-positive/PR-negative breast cancers may be specifically resistant to SERMs, whereas they may be less resistant to estrogen withdrawal therapy with aromatase inhibitors, which is a result inconsistent with the nonfunctional ER theory. Novel alternative molecular mechanisms potentially explaining SERM resistance in ER-positive/PR-negative tumors have been suggested by recent experimental indications that growth factors may downregulate PR levels. Thus, the absence of PR may not simply indicate a lack of ER activity, but rather may reflect hyperactive cross talk between ER and growth factor signaling pathways that downregulate PR even as they activate other ER functions. Therefore, ER-positive/PR-negative breast tumors might best be treated by completely blocking ER action via estrogen withdrawal with aromatase inhibitors, by targeted ER degradation, or by combined therapy targeting both ER and growth factor signaling pathways. In this review, we will discuss the biology and etiology of ER-positive/PR-negative breast cancer, highlighting recent data on molecular cross talk between ER and growth factor signaling pathways and demonstrating how PR might be a useful marker of these activities. Finally, we will consider the clinical implications of these observations.

Activation of AKT kinases in cancer: implications for therapeutic targeting

The AKT1, AKT2, and AKT3 kinases have emerged as critical mediators of signal transduction pathways downstream of activated tyrosine kinases and phosphatidylinositol 3-kinase. An ever-increasing list of AKT substrates has precisely defined the multiple functions of this kinase family in normal physiology and disease states. Cellular processes regulated by AKT include cell proliferation and survival, cell size and response to nutrient availability, intermediary metabolism, angiogenesis, and tissue invasion. All these processes represent hallmarks of cancer, and a burgeoning literature has defined the importance of AKT alterations in human cancer and experimental models of tumorigenesis, continuing the legacy represented by the original identification of v-Akt as the transforming oncogene of a murine retrovirus. Many oncoproteins and tumor suppressors intersect in the AKT pathway, finely regulating cellular functions at the interface of signal transduction and classical metabolic regulation. This careful balance is altered in human cancer by a variety of activating and inactivating mechanisms that target both AKT and interrelated proteins. Reprogramming of this altered circuitry by pharmacologic modulation of the AKT pathway represents a powerful strategy for rational cancer therapy. In this review, we summarize a large body of data, from many types of cancer, indicating that AKT activation is one of the most common molecular alterations in human malignancy. We also review mechanisms of activation of AKT kinases, examples of therapeutic modulation of the AKT pathway in animal models, and the current status of efforts to target molecular components of the AKT pathway for cancer therapy and, possibly, cancer prevention.

Reduced Expression of PTEN Protein and Its Prognostic Implications in Invasive Ductal Carcinoma of the Breast

OBJECTIVE

The PTEN tumor suppressor gene has been demonstrated to be inactivated in a variety of human tumors. In breast cancer, the PTEN gene mutation is not commonly found whereas loss of heterozygosity affecting the PTEN locus is frequently found. The aim of this study was to analyze PTEN protein expression in breast cancer and to evaluate the prognostic significance of PTEN protein expression.

METHODS

Paraffin-embedded sections ofinvasive ductal carcinoma of the breast were immunohistochemically stained for PTEN protein expression in 236 breast cancers. The immunohistochemical expression of breast cancer cells was judged to be either normal or reduced compared with the PTEN protein expression of the normal mammary gland.

RESULTS

The expression of PTEN protein was found to have decreased in 67 (28%) of 236 breast cancers. The reduced expression correlated with lymph node metastasis (p = 0.0371), but not with tumor size, nuclear grade, MIB-1 counts or p53 protein expression. Univariate analysis indicated that patients with a reduced PTEN expression had a shorter disease-free survival (DFS) than those with a normal PTEN expression (p = 0.0174). Univariate analyses also determined tumor size, lymph node metastases, nuclear grade, MIB-1 counts, p53 protein as well as PTEN protein expression to be significant factors for DFS, while multivariate analysis determined lymph node metastases and the MIB-1 counts to be independent significant factors for DFS.

CONCLUSIONS

The inactivation of PTEN, demonstrated by a reduced expression of PTEN protein by immunohistochemistry, was found in about one third of all breast cancers. The reduced expression of PTEN protein correlated with lymph node metastases and a worse prognosis in the patients with breast cancer.

The S100A7-c-Jun Activation Domain Binding Protein 1 Pathway Enhances Prosurvival Pathways in Breast Cancer

S100A7 is among the most highly expressed genes in preinvasive breast cancer, is a marker of poor survival when expressed in invasive disease, and promotes breast tumor progression in experimental models. To explore the mechanism of action, we examined the role of S100A7 in cell survival and found that overexpression of S100A7 in MDA-MB-231 cell lines promotes survival under conditions of anchorage-independent growth. This effect is paralleled by increased activity of nuclear factor-κB (3-fold) and phospho-Akt (4-fold), which are known to mediate prosurvival pathways. S100A7 and phospho-Akt are also correlated in breast tumors examined by immunohistochemistry (n = 142; P &lt; 0.0001; r = 0.34). To explore the underlying mechanism, we examined the role of a putative c-Jun activation domain-binding protein 1 (Jab1)–binding domain within S100A7 using a panel of MDA-MB-231 breast cell lines stably transfected with either S100A7 or S100A7 mutated at the Jab1 domain. Structural analysis by three-dimensional protein modeling, immunoprecipitation, and yeast two-hybrid assay and functional analysis using transfected reporter gene and Western blot assays revealed that the in vitro effects of S100A7 on phospho-Akt and the nuclear factor-κB pathway are dependent on the Jab1-binding site and the interaction with Jab1. Enhanced epidermal growth factor receptor signaling was also found to correlate with the increased phospho-Akt. Furthermore, the Jab1-binding domain is also necessary for the enhanced tumorigenicity conferred by S100A7 expression in murine xenograft tumors in vivo. We conclude that the S100A7-Jab1 pathway acts to enhance survival under conditions of cellular stress, such as anoikis, which may promote progression of breast cancer.

Estrogen receptor positivity in mammary tumors of Wnt-1 transgenic mice is influenced by collaborating oncogenic mutations

The majority (75%) of human breast cancers express estrogen receptor (ER). Although ER-positive tumors usually respond to antiestrogen therapies, 30% of them do not. It is not known what controls the ER status of breast cancers or their responsiveness to antihormone interventions. In this report, we document that transgenic (TG) expression of Wnt-1 in mice induces ER-positive tumors. Loss of Pten or gain of Ras mutations during the evolution of tumors in Wnt-1 TG mice has no effect on the expression of ER, but overexpression of Neu or loss of p53 leads to ER-negative tumors. Thus, our results provide compelling evidence that expression of ER in breast cancer may be influenced by specific genetic changes that promote cancer progression. These findings constitute a first step to explore the molecular mechanisms leading to ER-positive or ER-negative mammary tumors. In addition, we find that ER-positive tumors arising in Wnt-1 TG mice are refractory to both ovariectomy and the ER antagonist tamoxifen, but lose ER expression with tamoxifen, suggesting that antiestrogen selects for ER-negative tumor cells and that the ER-positive cell fraction is dispensable for growth of these tumors. This is a first report of a mouse model of antiestrogen-resistant ER-positive breast cancers, and could provide a powerful tool to study the molecular mechanisms that control antiestrogen resistance.

DJ-1, a novel regulator of the tumor suppressor PTEN

The phosphatidylinositol 3' kinase (PI3'K) pathway, which regulates cell survival, is antagonized by the PTEN tumor suppressor. The regulation of PTEN is unclear. A genetic screen of Drosophila gain-of-function mutants identified DJ-1 as a suppressor of PTEN function. In mammalian cells, DJ-1 underexpression results in decreased phosphorylation of PKB/Akt, while DJ-1 overexpression leads to hyperphosphorylation of PKB/Akt and increased cell survival. In primary breast cancer samples, DJ-1 expression correlates negatively with PTEN immunoreactivity and positively with PKB/Akt hyperphosphorylation. In 19/23 primary non-small cell lung carcinoma samples, DJ-1 expression was increased compared to paired nonneoplastic lung tissue, and correlated positively with relapse incidence. DJ-1 is thus a key negative regulator of PTEN that may be a useful prognostic marker for cancer.

Tumor cell sensitization to apoptotic stimuli by selective inhibition of specific Akt/PKB family members

Recent studies indicate that dysregulation of the Akt/PKB family of serine/threonine kinases is a prominent feature of many human cancers. The Akt/PKB family is composed of three members termed Akt1/PKBα, Akt2/PKBβ, and Akt3/PKBγ. It is currently not known to what extent there is functional overlap between these family members. We have recently identified small molecule inhibitors of Akt. These compounds have pleckstrin homology domain-dependent, isozyme-specific activity. In this report, we present data showing the relative contribution that inhibition of the different isozymes has on the apoptotic response of tumor cells to a variety of chemotherapies. In multiple cell backgrounds, maximal induction of caspase-3 activity is achieved when both Akt1 and Akt2 are inhibited. This induction is not reversed by overexpression of functionally active Akt3. The level of caspase-3 activation achieved under these conditions is equivalent to that observed with the phosphatidylinositol-3-kinase inhibitor LY294002. We also show that in different tumor cell backgrounds inhibition of mammalian target of rapamycin, a downstream substrate of Akt, is less effective in inducing caspase-3 activity than inhibition of Akt1 and Akt2. This shows that the survival phenotype conferred by Akt can be mediated by signaling pathways independent of mammalian target of rapamycin in some tumor cell backgrounds. Finally, we show that inhibition of both Akt1 and Akt2 selectively sensitizes tumor cells, but not normal cells, to apoptotic stimuli.