Differential roles of phosphoinositide-dependent protein kinase-1 and akt1 expression and phosphorylation in breast cancer cell resistance to Paclitaxel, Doxorubicin, and gemcitabine

Delivery of AKT1 phospho-forms to human cells reveals differential substrate selectivity

Protein kinase B (AKT1) is a serine/threonine kinase that regulates fundamental cellular processes, including cell survival, proliferation, and metabolism. AKT1 activity is controlled by two regulatory phosphorylation sites (Thr308, Ser473) that stimulate a downstream signaling cascade through phosphorylation of many target proteins. At either or both regulatory sites, hyperphosphorylation is associated with poor survival outcomes in many human cancers. Our previous biochemical and chemoproteomic studies showed that the phosphorylated forms of AKT1 have differential selectivity toward peptide substrates. Here, we investigated AKT1-dependent activity in human cells, using a cell-penetrating peptide (transactivator of transcription, TAT) to deliver inactive AKT1 or active phospho-variants to cells. We used enzyme engineering and genetic code expansion relying on a phosphoseryl-transfer RNA (tRNA) synthetase (SepRS) and tRNASep pair to produce TAT-tagged AKT1 with programmed phosphorylation at one or both key regulatory sites. We found that all TAT-tagged AKT1 variants were efficiently delivered into human embryonic kidney (HEK 293T) cells and that only the phosphorylated AKT1 (pAKT1) variants stimulated downstream signaling. All TAT-pAKT1 variants induced glycogen synthase kinase (GSK)-3α phosphorylation, as well as phosphorylation of ribosomal protein S6 at Ser240/244, demonstrating stimulation of downstream AKT1 signaling. Fascinatingly, only the AKT1 variants phosphorylated at S473 (TAT-pAKT1S473 or TAT-pAKT1T308,S473) were able to increase phospho-GSK-3β levels. Although each TAT-pAKT1 variant significantly stimulated cell proliferation, cells transduced with TAT-pAKT1T308 grew significantly faster than with the other pAKT1 variants. The data demonstrate differential activity of the AKT1 phospho-forms in modulating downstream signaling and proliferation in human cells.

The Landscape of PDK1 in Breast Cancer

Given that 3-phosphoinositide-dependent kinase 1 (PDK1) plays a crucial role in the malignant biological behaviors of a wide range of cancers, we review the influence of PDK1 in breast cancer (BC). First, we describe the power of PDK1 in cellular behaviors and characterize the interaction networks of PDK1. Then, we establish the roles of PDK1 in carcinogenesis, growth and survival, metastasis, and chemoresistance in BC cells. More importantly, we sort the current preclinical or clinical trials of PDK1-targeted therapy in BC and find that, even though no selective PDK1 inhibitor is currently available for BC therapy, the combination trials of PDK1-targeted therapy and other agents have provided some benefit. Thus, there is increasing anticipation that PDK1-targeted therapy will have its space in future therapeutic approaches related to BC, and we hope the novel approaches of targeted therapy will be conducive to ameliorating the dismal prognosis of BC patients.

AKT Isoforms as a Target in Cancer and Immunotherapy

Over the past years, targeted therapies have received tremendous attention in cancer therapy. One of the most frequently targeted pathways is the PI3K/AKT/mTOR signaling pathway that regulates crucial cellular processes including proliferation, survival, and migration. In a wide variety of cancer entities, the PI3K/AKT/mTOR signaling pathway was found to be a critical driver of disease progression, indicating a noteworthy target in cancer therapy. This chapter focuses on targeted therapies against AKT, which is a key enzyme within the PI3K/AKT/mTOR pathway. Although the three different isoforms of AKT, namely AKT1, AKT2, and AKT3, have a high homology, the isoforms exhibit different biological functions. Recently, direct inhibitors against all AKT isoforms as well as selective inhibitors against specific AKT isoforms have been extensively investigated in preclinical work as well as in clinical trials to attenuate proliferation of cancer cells. While no AKT inhibitor has been approved by the FDA for cancer therapy to date, AKT still plays a crucial role in a variety of treatment strategies including immune checkpoint inhibition. In this chapter, we summarize the status of AKT inhibitors either targeting all or specific AKT isoforms. Furthermore, we explain the role of AKT signaling in direct inhibition of tumor cell growth as well as in immune cells and immune checkpoint inhibition.

Ferroptosis: At the Crossroad of Gemcitabine Resistance and Tumorigenesis in Pancreatic Cancer

The overall five-year survival rate of pancreatic cancer has hardly changed in the past few decades (less than 10%) because of resistance to all known therapies, including chemotherapeutic drugs. In the past few decades, gemcitabine has been at the forefront of treatment for pancreatic ductal adenocarcinoma, but more strategies to combat drug resistance need to be explored. One promising possibility is ferroptosis, a form of a nonapoptotic cell death that depends on intracellular iron and occurs through the accumulation of lipid reactive oxygen species, which are significant in drug resistance. In this article, we reviewed gemcitabine-resistance mechanisms; assessed the relationship among ferroptosis, tumorigenesis and gemcitabine resistance, and explored a new treatment method for pancreatic cancer.

Emodin Interferes With AKT1-Mediated DNA Damage and Decreases Resistance of Breast Cancer Cells to Doxorubicin

Doxorubicin (DOX) is a cytotoxic drug used for the treatment of breast cancer (BC). However, the rapid emergence of resistance toward doxorubicin threatens its clinical application, thus the need for combination therapy. Here, we interrogate the role of Emodin, a chemical compound with tumor inhibitory properties, in the resistance of BC to Doxorubicin. We first evaluated the efficacy of Emodin in the treatment of BC cells. We then used γH2A to examine doxorubicin-induced DNA damage in BC cells, with or without Emodin. Data from CCK-8, flow cytometry, and tumor xenograft assays showed that Emodin suppresses the growth of BC cells. Further, we demonstrated that Emodin enhances γH2A levels in BC cells. Moreover, bioinformatics analysis and western blot assays indicated that Emodin down-regulates the AKT1 expression, and marginally decreases the levels of DNA damage proteins (XRCC1, PARP1, and RAD51) as well as increased p53 expression in BC cells. Taken together, our data demonstrates that Emodin affects cell proliferation, and DNA damage pathways in BC cells, thus increasing the sensitivity of BC cells to doxorubicin. Besides, we confirmed that Emodin confers sensitization of BC to doxorubicin through AKT1-mediated DNA.

Su(var)3-9, Enhancer of Zeste, and Trithorax Domain-Containing 5 Facilitates Tumor Growth and Pulmonary Metastasis through Up-Regulation of AKT1 Signaling in Breast Cancer

Several studies have confirmed the function of Su(var)3-9, Enhancer of zeste, and Trithorax (SET) domain-containing 5 (SETD5) in post-translational modifications of nonhistone proteins. Mutation of the SETD5 gene has been implicated in the progression of many human cancers, such as breast cancer (BC), but its functional role in BC progression is still unknown. The current article investigates the clinical significance and the functional role of SETD5 in BC. Our studies show that SETD5 expression in BC was related to poor clinical outcomes, including lymph node metastasis and advanced clinical stage. SETD5 expression positively correlated with tumor-associated macrophages. SETD5 was an independent predictor of poor overall survival in BC. Furthermore, these studies show that down-regulation of SETD5 significantly decreased BC cell proliferation, metastasis, and angiogenesis, and increased apoptosis of BC cells. The mechanistic analysis showed that SETD5 contributes BC progression by interacting with AKT1 pathway. Also, in vivo experiments show that blocking of SETD5 expression significantly inhibited tumor growth and pulmonary metastasis of BC cells. These findings indicate that SETD5 is a potential prognosis marker and facilitates tumor progression of BC.

Distinct functions of AKT isoforms in breast cancer: a comprehensive review

BACKGROUND

AKT, also known as protein kinase B, is a key element of the PI3K/AKT signaling pathway. Moreover, AKT regulates the hallmarks of cancer, e.g. tumor growth, survival and invasiveness of tumor cells. After AKT was discovered in the early 1990s, further studies revealed that there are three different AKT isoforms, namely AKT1, AKT2 and AKT3. Despite their high similarity of 80%, the distinct AKT isoforms exert non-redundant, partly even opposing effects under physiological and pathological conditions. Breast cancer as the most common cancer entity in women, frequently shows alterations of the PI3K/AKT signaling.

MAIN CONTENT

A plethora of studies addressed the impact of AKT isoforms on tumor growth, metastasis and angiogenesis of breast cancer as well as on therapy response and overall survival in patients. Therefore, this review aimed to give a comprehensive overview about the isoform-specific effects of AKT in breast cancer and to summarize known downstream and upstream mechanisms. Taking account of conflicting findings among the studies, the majority of the studies reported a tumor initiating role of AKT1, whereas AKT2 is mainly responsible for tumor progression and metastasis. In detail, AKT1 increases cell proliferation through cell cycle proteins like p21, p27 and cyclin D1 and impairs apoptosis e.g. via p53. On the downside AKT1 decreases migration of breast cancer cells, for instance by regulating TSC2, palladin and EMT-proteins. However, AKT2 promotes migration and invasion most notably through regulation of β-integrins, EMT-proteins and F-actin. Whilst AKT3 is associated with a negative ER-status, findings about the role of AKT3 in regulation of the key properties of breast cancer are sparse. Accordingly, AKT1 is mutated and AKT2 is amplified in some cases of breast cancer and AKT isoforms are associated with overall survival and therapy response in an isoform-specific manner.

CONCLUSIONS

Although there are several discussed hypotheses how isoform specificity is achieved, the mechanisms behind the isoform-specific effects remain mostly unrevealed. As a consequence, further effort is necessary to achieve deeper insights into an isoform-specific AKT signaling in breast cancer and the mechanism behind it.

Identification of Novel Breast Cancer Genes based on Gene Expression Profiles and PPI Data

Background:

Breast cancer is one of the most common malignancies, and a threat to female health all over the world. However, the molecular mechanism of breast cancer has not been fully discovered yet.

Objective:

It is crucial to identify breast cancer-related genes, which could provide new biomarker for breast cancer diagnosis as well as potential treatment targets.

Methods:

Here we used the minimum redundancy-maximum relevance (mRMR) method to select significant genes, then mapped the transcripts of the genes on the Protein-Protein Interaction (PPI) network and traced the shortest path between each pair of two proteins.

Results:

As a result, we identified 24 breast cancer-related genes whose betweenness were over 700. The GO enrichment analysis indicated that the transcription and oxygen level are very important in breast cancer. And the pathway analysis indicated that most of these 24 genes are enriched in prostate cancer, endocrine resistance, and pathways in cancer.

Conclusion:

We hope these 24 genes might be useful for diagnosis, prognosis and treatment for breast cancer.

URG4 expression in invasive breast carcinoma and its relation to clinicopathological characteristics

BACKGROUND

Upregulated gene 4 (URG4) is a recently described oncogene that upregulates cell proliferation. Its overexpression has been identified in many malignancies, and it is thought to be related to tumour progression, angiogenesis, metastasis and the recurrence of many cancers. This is the first study to show its expression in breast cancer patients and its association with clinicopathological characteristics in these patients.

METHODS

Fifty invasive ductal breast carcinoma cases and 25 control cases were included in the study. Tumourous tissues and control tissues were assessed molecularly for quantification of mRNA expression of URG4 and immunohistochemically for protein expression of URG4.

RESULTS

The mean ages of the patients and controls were 54.3 ± 11.3 and 38.9 ± 9.7 years, respectively. The expression levels of URG4 mRNA in tumour tissues were higher compared to control breast tissues (p = 0.023). An immunohistochemical assessment suggested that URG4 is strongly expressed in normal breast tissues and lower-grade (grades I and II) ductal carcinomas of the breast, but it is weakly expressed in high-grade (grade III) ductal breast carcinomas. Additionally, the immunohistochemical and molecular expression results of URG4 were relevant to most prognostic parameters (tumour size, oestrogen and progesterone receptor status, HER2 status and Ki67 proliferative index) for breast cancer. However, unlike the immunohistochemical studies, the molecular studies revealed that there was no significant difference in URG4 expression for different grades of tumour tissues.

CONCLUSION

The literature data suggest that URG4 overexpression is associated with poor prognosis in many types of cancer. Conversely, our results in breast cancer specimens indicate that URG4 overexpression in breast ductal carcinomas is significantly associated with good prognostic parameters. Nevertheless, these preliminary findings should be confirmed by further studies.

Targeting PDK1 for Chemosensitization of Cancer Cells

Despite the rapid development in the field of oncology, cancer remains the second cause of mortality worldwide, with the number of new cases expected to more than double in the coming years. Chemotherapy is widely used to decelerate or stop tumour development in combination with surgery or radiation therapy when appropriate, and in many cases this improves the symptomatology of the disease. Unfortunately though, chemotherapy is not applicable to all patients and even when it is, there are many cases where a successful initial treatment period is followed by chemotherapeutic drug resistance. This is caused by a number of reasons, ranging from the genetic background of the patient (innate resistance) to the formation of tumour-initiating cells (acquired resistance). In this review, we discuss the potential role of PDK1 in the development of chemoresistance in different types of malignancy, and the design and application of potent inhibitors which can promote chemosensitization.

Anti-tumor compound RY10-4 suppresses multidrug resistance in MCF-7/ADR cells by inhibiting PI3K/Akt/NF-κB signaling

RY10-4, an anti-tumor agent, exerts cytotoxicity to various human cancer cell lines. However, few studies reported the effect of combined application of RY10-4 and chemotherapeutic drugs against cancer cells with multidrug resistance (MDR). In this study, P-glycoprotein (P-gp), which is reported to mediate MDR to anti-cancer drugs, was proved to be overexpressed in the adriamycin (ADR)-resistant human breast cancer cells, namely MCF-7/ADR cells. Furthermore, RY10-4 application resulted in a downregulation of P-gp in MCF-7/ADR cells, thus leading to higher chemosensitivity to ADR. Our study further demonstrated that the MDR phenomenon was under the control of the PI3K/Akt/NF-κB pathway, which was suppressed by RY10-4, leading to MDR reversal effects in MCF-7/ADR cells. In vivo, MCF-7/ADR cells were effectively suppressed by the combined ADR/RY10-4 treatment compared with the ADR-alone treatment. Taken together, these results demonstrated that RY10-4 reverses the MDR phenotype in MCF-7/ADR cells by suppressing the PI3K/Akt/NF-κB pathway.

Effects of PI3K inhibitor NVP-BKM120 on overcoming drug resistance and eliminating cancer stem cells in human breast cancer cells

The multidrug resistance (MDR) phenotype often accompanies activation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway, which renders a survival signal to withstand cytotoxic anticancer drugs and enhances cancer stem cell (CSC) characteristics. As a result, PI3K/AKT-blocking approaches have been proposed as antineoplastic strategies, and inhibitors of PI3K/AKT are currently being trailed clinically in breast cancer patients. However, the effects of PI3K inhibitors on MDR breast cancers have not yet been elucidated. In the present study, the tumorigenic properties of three MDR breast cancer cell lines to a selective inhibitor of PI3K, NVP-BKM120 (BKM120), were assessed. We found that BKM120 showed a significant cytotoxic activity on MDR breast cancer cells both in vitro and in vivo. When doxorubicin (DOX) was combined with BKM120, strong synergistic antiproliferative effect was observed. BKM120 activity induced the blockage of PI3K/AKT signaling and NF-κB expression, which in turn led to activate caspase-3/7 and caspase-9 and changed the expression of several apoptosis-related gene expression. Furthermore, BKM120 effectively eliminated CSC subpopulation and reduced sphere formation of these drug-resistant cells. Our findings indicate that BKM120 partially overcomes the MDR phenotype in chemoresistant breast cancer through cell apoptosis induction and CSC abolishing, which appears to be mediated by the inhibition of the PI3K/AKT/NF-κB axis. This offers a strong rationale to explore the therapeutic strategy of using BKM120 alone or in combination for chemotherapy-nonresponsive breast cancer patients.

Gemcitabine resistance in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) ranks fourth among cancer related deaths. The disappointing 5-year survival rate of below 5% stems from drug resistance to all known therapies, as well as from disease presentation at a late stage when PDA is already metastatic. Gemcitabine has been the cornerstone of PDA treatment in all stages of the disease for the last two decades, but gemcitabine resistance develops within weeks of chemotherapy initiation. From a mechanistic perspective, gemcitabine resistance may result from alterations in drug metabolism until the point that the cytidine analog is incorporated into the DNA, or from mitigation of gemcitabine-induced apoptosis. Both of these drug resistance modalities can be either intrinsic to the cancer cell, or influenced by the cancer microenvironment. Mechanisms of intrinsic gemcitabine resistance are difficult to tackle, as many of the genes that drive the carcinogenic process itself also interfere with gemcitabine-induced apoptosis. In this regard, recent understanding of the involvement of microRNAs in gemcitabine resistance may offer new opportunities to overcome intrinsic gemcitabine resistance. The characteristically fibrotic and immune infiltrated stroma of PDA that accompanies tumor inception and expansion is a lush ground for treatments aimed at targeting tumor microenvironment-mediated drug resistance. In the last couple of years, drugs interfering with tumor microenvironment have matured to clinical trials. Although drugs inducing 'stromal depletion' have yet failed to improve survival, they have greatly increased our understanding of tumor microenvironment-mediated drug resistance. In this review we summarize the current knowledge on intrinsic and environment-mediated gemcitabine resistance, and discuss the impact of these pathways on patient screening, and on future treatments aimed to potentiate gemcitabine activity.

Clinical significance of pAkt and pErk1/2 expression in early-stage breast cancer patients treated with anthracycline-based adjuvant chemotherapy

The expression of phosphorylated Akt (pAkt) and phosphorylated extracellular-regulated kinase 1/2 (pErk1/2) proteins may result in breast cancer progression and drug resistance in vitro, however, compelling evidence regarding the clinical significance of pAkt and pErk1/2 in early-stage breast cancer is currently lacking. Thus, the aim of the present study was to determine the prognostic value of pAkt and pErk1/2 expression in early-stage breast cancer patients treated with anthracycline-based adjuvant chemotherapy. Tumor specimens were obtained from 256 patients with early-stage breast cancer who had been treated with anthracycline-based adjuvant chemotherapy, and pAkt and pErk1/2 protein expression was immunohistochemically determined. The interactions between pAkt, pErk1/2 and clinical characteristics were assessed by performing χ² tests, and survival functions were estimated using the Kaplan-Meier method. It was identified that pAkt and pErk1/2 were expressed in 38.7 and 33.6% of patients, respectively, and that pAkt protein expression was correlated with pErk1/2 protein expression (P<0.001). In addition, after a median follow-up period of 52.5 months, the patients with pAkt- and pErk1/2-negative tumors experienced a significantly longer disease-free survival (DFS) time compared with pAkt- or pErk1/2-positive patients (P=0.028). pErk1/2 expression was associated with the decreased DFS time of the patients (P=0.049), and pAkt and pErk1/2 expression were associated with the decreased DFS time in human epidermal growth factor receptor (HER2)-positive patients (P=0.002). pErk1/2 expression was associated with chemotherapy resistance (P=0.016). Thus, the coexpression of pAkt and pErk1/2 was an independent factor for a poor prognosis in early-stage and HER2-positive breast cancer patients. By contrast, pErk1/2 expression alone may be a poor predictor for determining the efficacy of anthracycline-based chemotherapy.

Gemcitabine resistance in breast cancer cells regulated by PI3K/AKT-mediated cellular proliferation exerts negative feedback via the MEK/MAPK and mTOR pathways

Chemoresistance is a major cause of cancer treatment failure and leads to a reduction in the survival rate of cancer patients. Phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) and mitogen-activated protein kinase (MAPK) pathways are aberrantly activated in many malignant tumors, including breast cancer, which may indicate an association with breast cancer chemoresistance. In this study, we generated a chemoresistant human breast cancer cell line, MDA-MB-231/gemcitabine (simplified hereafter as "231/Gem"), from MDA-MB-231 human breast cancer cells. Flow cytometry studies revealed that with the same treatment concentration of gemcitabine, 231/Gem cells displayed more robust resistance to gemcitabine, which was reflected by fewer apoptotic cells and enhanced percentage of S-phase cells. Through the use of inverted microscopy, Cell Counting Kit-8, and Transwell assays, we found that compared with parental 231 cells, 231/Gem cells displayed more morphologic projections, enhanced cell proliferative ability, and improved cell migration and invasion. Mechanistic studies revealed that the PI3K/AKT/mTOR and mitogen-activated protein kinase kinase (MEK)/MAPK signaling pathways were activated through elevated expression of phosphorylated (p)-extracellular signal-regulated kinase (ERK), p-AKT, mTOR, p-mTOR, p-P70S6K, and reduced expression of p-P38 and LC3-II (the marker of autophagy) in 231/Gem in comparison to control cells. However, there was no change in the expression of Cyclin D1 and p-adenosine monophosphate-activated protein kinase (AMPK). In culture, inhibitors of PI3K/AKT and mTOR, but not of MEK/MAPK, could reverse the enhanced proliferative ability of 231/Gem cells. Western blot analysis showed that treatment with a PI3K/AKT inhibitor decreased the expression levels of p-AKT, p-MEK, p-mTOR, and p-P70S6K; however, treatments with either MEK/MAPK or mTOR inhibitor significantly increased p-AKT expression. Thus, our data suggest that gemcitabine resistance in breast cancer cells is mainly mediated by activation of the PI3K/AKT signaling pathway. This occurs through elevated expression of p-AKT protein to promote cell proliferation and is negatively regulated by the MEK/MAPK and mTOR pathways.

Inhibition of phosphoinositide 3-kinase/Akt pathway decreases hypoxia inducible factor-1α expression and increases therapeutic efficacy of paclitaxel in human hypoxic gastric cancer cells

The phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway plays an important role in cell proliferation, transformation, apoptosis, tumor growth and angiogenesis. Paclitaxel is commonly used to treat multiple human malignancies; however, the underlying mechanisms of paclitaxel in gastric cancer (GC) have not been fully investigated. In the present study, specimens from 45 GC and 36 chronic gastritis patients were collected, and the correlations of PI3K, phosphorylated-Akt (p-Akt) and hypoxia-inducible factor-1α (HIF-1α) expression with the clinicopathological characteristics of GC were analyzed by immunohistochemistry. The human SGC-7901 GC cells under hypoxic conditions were pretreated with the PI3K inhibitor, LY294002 (40 μM), and paclitaxel (0.1 μM). The expression levels of PI3K, p-Akt and HIF-1α were detected by quantitative polymerase chain reaction and western blotting. Cell proliferative activity and apoptosis were evaluated by the Cell Counting Kit-8 assay and flow cytometry. As a result, the rates of positive expression of PI3K, p-Akt and HIF-1α were significantly higher in GC compared with chronic gastritis patients (each P<0.01), and were positively associated with the tumor-node-metastasis (TNM) staging, lymph node metastases, lymphatic infiltration and vascular infiltration (each P<0.01), but inversely correlated with tumor differentiation (P<0.01) in patients with GC. Under hypoxic conditions, the combined inhibition of the PI3K/Akt pathway with paclitaxel markedly reduced the proliferative activity and induced cell apoptosis in GC cells compared with the single treatment of PI3K inhibitor or paclitaxel (each P<0.01), and was accompanied by a decreased expression of HIF-1α. Overall, our findings indicate that the increased expression of the PI3K/Akt/HIF-1α pathway was closely correlated with tumor differentiation, TNM staging, lymph node metastases and lymphatic and vascular infiltration. The inhibition of the PI3K/Akt pathway enhanced the therapeutic efficacy of paclitaxel in GC cells under hypoxic conditions, suggesting that the PI3K/Akt/HIF-1α pathway may act as an important therapeutic target for paclitaxel treatment of GC.

Cancer development, progression, and therapy: an epigenetic overview

Carcinogenesis involves uncontrolled cell growth, which follows the activation of oncogenes and/or the deactivation of tumor suppression genes. Metastasis requires down-regulation of cell adhesion receptors necessary for tissue-specific, cell-cell attachment, as well as up-regulation of receptors that enhance cell motility. Epigenetic changes, including histone modifications, DNA methylation, and DNA hydroxymethylation, can modify these characteristics. Targets for these epigenetic changes include signaling pathways that regulate apoptosis and autophagy, as well as microRNA. We propose that predisposed normal cells convert to cancer progenitor cells that, after growing, undergo an epithelial-mesenchymal transition. This process, which is partially under epigenetic control, can create a metastatic form of both progenitor and full-fledged cancer cells, after which metastasis to a distant location may occur. Identification of epigenetic regulatory mechanisms has provided potential therapeutic avenues. In particular, epigenetic drugs appear to potentiate the action of traditional therapeutics, often by demethylating and re-expressing tumor suppressor genes to inhibit tumorigenesis. Epigenetic drugs may inhibit both the formation and growth of cancer progenitor cells, thus reducing the recurrence of cancer. Adopting epigenetic alteration as a new hallmark of cancer is a logical and necessary step that will further encourage the development of novel epigenetic biomarkers and therapeutics.

Silencing of PDK1 gene expression by RNA interference suppresses growth of esophageal cancer

The current study was conducted to explore the inhibitory effects of a small interfering RNA (siRNA) on 3-phosphoinositide-dependent protein kinase 1 (PDK1) expression in esophageal cancer 9706 (EC9706) cells and the influence on their biological behavior. After transfection of a synthesized PDK1 siRNA, PDK1 mRNA and protein expression and the phosphorylation level of the downstream Akt protein were assessed using RT-PCR and Western blot analysis. Proliferation, apoptosis, cell invasion and in vivo tumor formation capacity were also investigated using MTT, flow cytometry, Transwell invasion trials, and nude mouse tumor transplantation, respectively. PDK1 siRNA effectively suppressed PDK1 mRNA and protein expression, and down-regulated the phosphorylation level of the Akt protein in the EC9706 cells (P<0.05). It also inhibited cell proliferation and invasion, and promoted apoptosis; such effects were particularly obvious at 48 h and 72 h after transfection (P<0.05). Growth of transplanted tumors was inhibited in nude mice, with decreased PDK1 expression in tumor tissues. PDK1 may be closely correlated with proliferation, apoptosis and invasion of esophageal cancer cells and thus may serve as an effective target for gene therapy.

3-phosphoinositide-dependent kinase 1 controls breast tumor growth in a kinase-dependent but Akt-independent manner

3-phosphoinositide-dependent protein kinase 1 (PDK1) is the pivotal element of the phosphatidylinositol 3 kinase (PI3K) signaling pathway because it phosphorylates Akt/PKB through interactions with phosphatidylinositol 3,4,5 phosphate. Recent data indicate that PDK1 is overexpressed in many breast carcinomas and that alterations of PDK1 are critical in the context of oncogenic PI3K activation. However, the role of PDK1 in tumor progression is still controversial. Here, we show that PDK1 is required for anchorage-independent and xenograft growth of breast cancer cells harboring either PI3KCA or KRAS mutations. In fact, PDK1 silencing leads to increased anoikis, reduced soft agar growth, and pronounced apoptosis inside tumors. Interestingly, these phenotypes are reverted by PDK1 wild-type but not kinase-dead mutant, suggesting a relevant role of PDK1 kinase activity, even if PDK1 is not relevant for Akt activation here. Indeed, the expression of constitutively active forms of Akt in PDK1 knockdown cells is unable to rescue the anchorage-independent growth. In addition, Akt down-regulation and pharmacological inhibition do not inhibit the effects of PDK1 overexpression. In summary, these results suggest that PDK1 may contribute to breast cancer, even in the absence of PI3K oncogenic mutations and through both Akt-dependent and Akt-independent mechanisms.

MADD knock-down enhances doxorubicin and TRAIL induced apoptosis in breast cancer cells

The Map kinase Activating Death Domain containing protein (MADD) isoform of the IG20 gene is over-expressed in different types of cancer tissues and cell lines and it functions as a negative regulator of apoptosis. Therefore, we speculated that MADD might be over-expressed in human breast cancer tissues and that MADD knock-down might synergize with chemotherapeutic or TRAIL-induced apoptosis of breast cancer cells. Analyses of breast tissue microarrays revealed over-expression of MADD in ductal and invasive carcinomas relative to benign tissues. MADD knockdown resulted in enhanced spontaneous apoptosis in human breast cancer cell lines. Moreover, MADD knockdown followed by treatment with TRAIL or doxorubicin resulted in increased cell death compared to either treatment alone. Enhanced cell death was found to be secondary to increased caspase-8 activation. These data indicate that strategies to decrease MADD expression or function in breast cancer may be utilized to increase tumor cell sensitivity to TRAIL and doxorubicin induced apoptosis.

2-anilino-4-aryl-8H-purine derivatives as inhibitors of PDK1

A series of 2-anilino substituted 4-aryl-8H-purines were prepared as potent inhibitors of PDK1, a serine-threonine kinase thought to play a role in the PI3K/Akt signaling pathway, a key mediator of cancer cell growth, survival and tumorigenesis. The synthesis, SAR and ADME properties of this series of compounds are discussed culminating in the discovery of compound 6 which possessed sub-micromolar cell proliferation activity and 65% oral bioavailability in mice.

Innovative Therapies against Human Glioblastoma Multiforme

Glioblastoma multiforme is the most invasive and aggressive brain tumor in humans, and despite the latest chemical and radiative therapeutic approaches, it is still scarcely sensitive to these treatments and is generally considered an incurable disease. This paper will focus on the latest approaches to the treatment of this cancer, including the new chemicals such as proautophagic drugs and kinases inhibitors, and differentiating agents. In this field, there have been opening new perspectives as the discovery of possible specific targets such as the EGFRvIII, a truncated form of the EGF receptor. Antibodies against these targets can be used as proapoptotic agents and as possible carriers for chemicals, drugs, radioisotopes, and toxins. In this paper, we review the possible mechanism of action of these therapies, with particular attention to the combined use of toxic substances (for example, immunotoxins) and antiproliferative/differentiating compounds (i.e., ATRA, PPARγ agonists). All these aspects will be discussed in the view of progress clinical trials and of possible new approaches for directed drug formulations.

PPARδ activation acts cooperatively with 3-phosphoinositide-dependent protein kinase-1 to enhance mammary tumorigenesis

Peroxisome proliferator-activated receptorδ (PPARδ) is a transcription factor that is associated with metabolic gene regulation and inflammation. It has been implicated in tumor promotion and in the regulation of 3-phosphoinositide-dependent kinase-1 (PDK1). PDK1 is a key regulator of the AGC protein kinase family, which includes the proto-oncogene AKT/PKB implicated in several malignancies, including breast cancer. To assess the role of PDK1 in mammary tumorigenesis and its interaction with PPARδ, transgenic mice were generated in which PDK1 was expressed in mammary epithelium under the control of the MMTV enhancer/promoter region. Transgene expression increased pT308AKT and pS9GSK3β, but did not alter phosphorylation of mTOR, 4EBP1, ribosomal protein S6 and PKCα. The transgenic mammary gland also expressed higher levels of PPARδ and a gene expression profile resembling wild-type mice maintained on a diet containing the PPARδ agonist, GW501516. Both wild-type and transgenic mice treated with GW501516 exhibited accelerated rates of tumor formation that were more pronounced in transgenic animals. GW501516 treatment was accompanied by a distinct metabolic gene expression and metabolomic signature that was not present in untreated animals. GW501516-treated transgenic mice expressed higher levels of fatty acid and phospholipid metabolites than treated wild-type mice, suggesting the involvement of PDK1 in enhancing PPARδ-driven energy metabolism. These results reveal that PPARδ activation elicits a distinct metabolic and metabolomic profile in tumors that is in part related to PDK1 and AKT signaling.

Elesclomol, counteracted by Akt survival signaling, enhances the apoptotic effect of chemotherapy drugs in breast cancer cells

Elesclomol is a small-molecule investigational agent that selectively induces apoptosis in cancer cells by increasing oxidative stress. Elesclomol plus paclitaxel was shown to prolong progression-free survival compared with paclitaxel alone in a phase II clinical trial in patients with metastatic melanoma. However, the therapeutic potential of elesclomol in human breast cancer is unknown, and the signaling mechanism underlying the elesclomol effect is unclear. Here, we show that elesclomol alone modestly inhibited the growth of human breast cancer cells but not normal breast epithelial cells. Elesclomol potentiated doxorubicin- or paclitaxel-induced apoptosis and suppression of breast cancer cell growth. While both c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase were activated by elesclomol, elesclomol-induced apoptosis was only in part mediated by JNK1. The additive effect of elesclomol on chemotherapy drug-induced apoptosis was associated with increases in cleaved caspase-3, p21(Cip1), and p27(Kip1) and decreases in the Inhibitor of Apoptosis Protein levels and NF-kappaB activity. We also found that Akt/Hsp70 survival signaling was induced by elesclomol, which may reflect a cellular feedback mechanism. Blockade of Akt activation using a small-molecule inhibitor enhanced elesclomol-elicited apoptosis, while expression of a hyperactive Akt abolished the elesclomol effect. These data suggest that elesclomol's interaction with conventional chemotherapeutic and Akt-targeting agents may be exploited to induce apoptosis in breast cancer cells, and clinical trials of combined treatment of elesclomol and chemotherapy drugs or Akt-targeting agents in breast cancer patients, especially the estrogen receptor negative subgroup, may be warranted.

Stem cell and epithelial-mesenchymal transition markers are frequently overexpressed in circulating tumor cells of metastatic breast cancer patients

Introduction

The persistence of circulating tumor cells (CTC) in breast cancer patients might be associated with stem cell like tumor cells which have been suggested to be the active source of metastatic spread in primary tumors. Furthermore, these cells also may undergo phenotypic changes, known as epithelial-mesenchymal transition (EMT), which allows them to travel to the site of metastasis formation without getting affected by conventional treatment. Here we evaluated 226 blood samples of 39 metastatic breast cancer patients during a follow-up of palliative chemo-, antibody – or hormonal therapy for the expression of the stem cell marker ALDH1 and markers for EMT and correlated these findings with the presence of CTC and response to therapy.

Methods

2 × 5 ml blood was analyzed for CTC with the AdnaTest BreastCancer (AdnaGen AG) for the detection of EpCAM, MUC-1 and HER2 transcripts. The recovered c-DNA was additionally multiplex tested for three EMT markers [Twist1, Akt2, PI3Kα] and separately for the tumor stem-cell markers ALDH1. The identification of EMT markers was considered positive if at least one marker was detected in the sample.

Results

97% of 30 healthy donor samples investigated were negative for EMT and 95% for ALDH1 transcripts. CTC were detected in 69/226 (31%) cancer samples. In the CTC (+) group, 62% were positive for at least one of the EMT markers and 69% for ALDH1, respectively. In the CTC (-) group the percentages were 7% and 14%, respectively. In non-responders, EMT and ALDH1 expression was found in 62% and 44% of patients, in responders the rates were 10% and 5%, respectively.

Conclusions

Our data indicate that a major proportion of CTC of metastatic breast cancer patients shows EMT and tumor stem cell characteristics. Further studies are needed to prove whether these markers might serve as an indicator for therapy resistant tumor cell populations and, therefore, an inferior prognosis.

Down-regulation of 3-phosphoinositide-dependent protein kinase-1 levels inhibits migration and experimental metastasis of human breast cancer cells

High expression of 3-phosphoinositide-dependent protein kinase-1 (PDK1) has been detected in various invasive cancers. In the current study, we investigated its role in cancer cell migration and experimental metastasis. Down-regulation of PDK1 expression by small interference RNA markedly inhibited spontaneous migration and epidermal growth factor (EGF)-induced chemotaxis of human breast cancer cells. The defects were rescued by expressing wild-type PDK1. PDK1-depleted cells showed impaired EGF-induced actin polymerization and adhesion, probably due to a decrease in phosphorylation of LIM kinase/cofilin and integrin beta1. Confocal microscopy revealed that EGF induced cotranslocation of PDK1 with Akt and protein kinase Czeta (PKCzeta), regulators of LIM kinase, and integrin beta1. Furthermore, PDK1 depletion dampened EGF-induced phosphorylation and translocation of Akt and PKCzeta, suggesting that Akt and PKCzeta functioned downstream of PDK1 in the chemotactic signaling pathway. In severe combined immunodeficiency mice, PDK1-depleted human breast cancer cells formed more slowly growing tumors and were defective in extravasation to mouse lungs after i.v. injection. Our results indicate that PDK1 plays an important role in regulating the malignant behavior of breast cancer cells, including their motility, through activation of Akt and PKCzeta. Thus, PDK1, which increases its expression in cancer cells, can be used as a target for the development of novel therapies.

Requirement of 3-phosphoinositide-dependent protein kinase-1 for BDNF-mediated neuronal survival

Although PDK1 regulates several signaling pathways that respond to neurotrophins, direct evidence for its involvement in neurotrophin-mediated survival has not yet been reported. Here we show high neuronal expression of active PDK1 in the rat cortex and hippocampus at the developmental stages with pronounced dependence on extracellular survival signals. Also, in cultured cortical neurons from newborn rats, BDNF resulted in PDK1- and extracellular signal-regulated kinase-1/2 (ERK1/2)-mediated activation of their direct target, the p90 ribosomal S6 kinase 1/2 (RSK1/2). In trophic-deprived cortical neurons, knockdown of endogenous PDK1 attenuated the antiapoptotic survival response to 10 ng/ml BDNF, whereas an overexpressed active mutant form of PDK1 reduced apoptosis. The neuroprotection by BDNF or active PDK1 required RSK1/2. Conversely, PDK1 knockdown reversed the survival effects of combining the overexpressed RSK1 with a low, subprotective BDNF concentration of 2 ng/ml. Likewise, the protection by the overexpressed, active PDK1 was enhanced by coexpression of an active RSK1 mutant. Consistent with the observations that in BDNF-stimulated neurons RSK1/2 activation required both PDK1 and ERK1/2, ERK1/2 knockdown removed BDNF-mediated survival. Selective activation of ERK1/2 with an overexpressed active mutant form of MKK1 resulted in RSK1/2- and PDK1-dependent neuroprotection. Finally, at subprotective plasmid DNA dosage, overexpression of the active MKK1 and PDK1 mutants produced synergistic effect on survival. Our findings indicate a critical role for PDK1-RSK1/2 signaling in BDNF-mediated neuronal survival. Thus, the PDK1 is indispensable for the antiapoptotic effects of the ERK1/2 pathway offering previously unrecognized layer of survival signal processing and integration.

Phosphorylated EGFR and PI3K/Akt signaling kinases are expressed in circulating tumor cells of breast cancer patients

Introduction

The phosphoinositide-3 kinase (PI3K)/Akt pathway, operating downstream of epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor (HER)2, is implicated in cell migration and survival. EGFR and HER2 are expressed in circulating tumor cells, but the activation status of downstream signaling molecules has not yet been reported.

Methods

To investigate expression levels of EGFR, HER2, PI3K, and Akt in circulating tumor cells, we used peripheral blood mononuclear cells from 32 cytokeratin-19 mRNA-positive patients with early (n = 16) and metastatic (n = 16) breast cancer.

Peripheral blood mononuclear cell cytospins were double stained with cytokeratin antibody along with one of the following: EGFR, phospho-EGFR, HER2, phospho-PI3K, or phospho-Akt antibodies.

Results

EGFR and HER2 were expressed in circulating tumor cells of 38% and 50% patients with early and 44% and 63% patients with metastatic disease, respectively. Interestingly, phospho-PI3K and phospho-Akt expression levels were similar at 88% (14 out of 16) and 81% (13 out of 16), respectively, in circulating tumor cells of patients with early and metastatic disease. Phospho-EGFR was observed in circulating tumor cells of two (33%) early and six (86%) metastatic EGFR-positive patients. Immunomagnetic separation of peripheral blood mononuclear cells, using EpCAM antibody, and subsequent double-staining experiments of circulating tumor cells showed that EGFR was co-expressed with HER2, phospho-Akt and phospho-PI3K kinases, indicating activation of the corresponding survival signaling pathway.

Conclusions

Our findings demonstrate that circulating tumor cells express receptors and activated signaling kinases of the EGFR/HER2/PI3K/Akt pathway, which could be used as targets for their effective elimination.

Drug targets for tumorigenesis: insights from structural analysis of EGFR signaling network

Deciphering the complex network structure is crucial in drug target identification. This study presents a framework incorporating graph theoretic and network decomposition methods to analyze system-level properties of the comprehensive map of the epidermal growth factor receptor (EGFR) signaling, which is a good candidate model system to study the general mechanisms of signal transduction. The graph theoretic analysis of the EGFR network indicates that it has small-world characteristics with scale-free topology. The employment of network decomposition analysis enlightened the system-level properties, such as network cross-talk, specific molecules in each pathway and participation of molecules in the network. Participating in a significant fraction of the fundamental paths connecting the ligands to the phenotypes, cofactor GTP and complex Gbeta/Ggamma were identified as "housekeeping" molecules, through which all pathways of EGFR network are cross-talking. c-Src-Shc complex is identified as important due to its role in all fundamental paths through tumorigenesis and being specific to this phenotype. Inhibitors of this complex may be good anti-cancer agents having very little or no effect on other phenotypes.

Combined 3D-QSAR modeling and molecular docking study on indolinone derivatives as inhibitors of 3-phosphoinositide-dependent protein kinase-1

3-Phosphoinositide-dependent protein kinase-1 (PDK1) is a promising target for developing novel anticancer drugs. In order to understand the structure-activity correlation of indolinone-based PDK1 inhibitors, we have carried out a combined molecular docking and three-dimensional quantitative structure-activity relationship (3D-QSAR) modeling study. The study has resulted in two types of satisfactory 3D-QSAR models, including the CoMFA model (r(2)=0.907; q(2)=0.737) and CoMSIA model (r(2)=0.991; q(2)=0.824), for predicting the biological activity of new compounds. The detailed microscopic structures of PDK1 binding with inhibitors have been studied by molecular docking. We have also developed docking-based 3D-QSAR models (CoMFA with q(2)=0.729; CoMSIA with q(2)=0.79). The contour maps obtained from the 3D-QSAR models in combination with the docked binding structures help to better interpret the structure-activity relationship. All of the structural insights obtained from both the 3D-QSAR contour maps and molecular docking are consistent with the available experimental activity data. This is the first report on 3D-QSAR modeling of PDK1 inhibitors. The satisfactory results strongly suggest that the developed 3D-QSAR models and the obtained PDK1-inhibitor binding structures are reasonable for the prediction of the activity of new inhibitors and in future drug design.

A comprehensive analysis of transcript signatures of the phosphatidylinositol-3 kinase/protein kinase B signal-transduction pathway in prostate cancer

OBJECTIVE

To assess the gene activities of various important members of the phosphatidylinositol 3 kinase (PIK3)/protein kinase B (PKB/Akt) pathway (involved in the promotion and regulation of cellular metabolism, proliferation and apoptosis) for alterations in prostate carcinoma.

PATIENTS, SUBJECTS AND METHODS

Using quantitative real-time reverse-transcription polymerase chain reaction, we analysed the transcript levels of 12 genes involved in the PIK3/PKB pathway in microdissected tumour tissues from 20 patients with varying stages of prostate cancer, assessing differences from adjacent normal tissues and from a pool of prostate tissues from healthy controls.

RESULTS

In cancer samples with a high Gleason grade, the PIK3/PKB pathway was principally affected by marked decreases in expression over almost all the investigated stages of the pathway. These changes were in effectors of the pathway, especially PIK3 p85 alpha (PIK3R1) and integrin-linked kinase, and the pathway target fork-head box protein (FOXO)-1A, while the transcript quantities of regulators, e.g. phosphatase/tensin homologue (PTEN), were decreased in a smaller proportion of the patients. Transcript amounts of FOXO-1A and FOXO-3A were significantly higher in normal tumour-adjacent tissues than in the healthy controls.

CONCLUSIONS

Down-regulation of the PIK3/PKB pathway by repression of involved effector and regulator genes at all stages of the molecular pathway could represent a marker for the formation of highly de-differentiated prostate cancers from low-grade tumour foci. Also, parts of the pathway are deviant in normal tumour-adjacent tissue; this might represent a reaction to neighbouring tumours or be a sign of pre-cancerous biological alterations.

Proautophagic drugs: a novel means to combat apoptosis-resistant cancers, with a special emphasis on glioblastomas

The therapeutic goal of cancer treatment has been to trigger tumor-selective cell death. Although cell death can be achieved not only by apoptosis (type I programmed cell death) but also by necrosis, mitotic catastrophe, and autophagy, drugs inducing apoptosis remain the main chemotherapeutic agents in medical oncology. However, cancer cells in their relentless drive to survive, hijack cell processes, resulting in apoptosis resistance, which underlies not only tumorigenesis but also the inherent resistance of certain cancers to radiotherapy and chemotherapy. Unlike apoptosis, which is a caspase-dependent process characterized by nuclear condensation and fragmentation, autophagic cell death is a caspase-independent process characterized by the accumulation of autophagic vacuoles in the cytoplasm accompanied by extensive degradation of the Golgi apparatus, the polyribosomes, and the endoplasmic reticulum, which precedes the destruction of the nucleus. The most striking evidence for proautophagic chemotherapy to overcome apoptosis resistance in cancer cells comes from the use of temozolomide, a proautophagic cytotoxic drug, which has demonstrated real therapeutic benefits in glioblastoma patients and is in clinical trials for several types of apoptosis-resistant cancers. A number of potential common targets in autophagy and apoptosis resistance pathways, that is, mammalian target of rapamycin (mTOR), phosphatidylinositol 3' kinase (PI3K), and Akt have been identified. Thus, further success in certain devastating cancers might be achieved by the combination of proautophagic drugs such as temozolomide with mTOR, PI3K, or Akt inhibitors, or with endoplasmic reticulum stress inhibitors as adjuvant chemotherapies.

Expression patterns and predictive value of phosphorylated AKT in early-stage breast cancer

BACKGROUND

AKT phosphorylation is a critical step in the activation of growth factor receptors and can mediate tumor resistance to anthracyclines. We evaluated the expression patterns and predictive value of phosphorylated AKT (pAKT) in breast cancer tissues.

PATIENTS AND METHODS

pAKT expression was assessed by immunohistochemistry in 823 tumors from patients with early breast cancer enrolled in two randomized trials. The distribution of pAKT expression was correlated with HER2 and epidermal growth factor receptor (EGFR) expression. The predictive value of pAKT for the efficacy of adjuvant chemotherapy was determined by test for interaction.

RESULTS

pAKT, EGFR, and HER2 were expressed in 119 of 781 (15%), 118 of 758 (16%), and 99 of 775 (13%) assessable tumors. Staining was positive for pAKT in 28 of 99 (28%) and 90 of 676 (13%) HER2+ and HER2- tumors (P < 0.001). pAKT was expressed in 15 of 94 (16%) and 75 of 563 (13%) HER2-/EGFR+ and HER2-/EGFR- tumors, respectively (P = 0.49). A positive staining for pAKT did not correlate with prognosis (P = 0.94), and did not predict the resistance to anthracyclines (test for interaction, P = 0.70).

CONCLUSIONS

AKT phosphorylation is associated with HER2 expression but not EGFR expression in patients with early breast cancer. pAKT is not predictive for the efficacy of anthracycline-based adjuvant chemotherapy.

Correlation of TLK1B in Elevation and Recurrence in Doxorubicin-Treated Breast Cancer Patients with High eIF4E Overexpression

BACKGROUND

Tousled-like kinase 1B (TLK1B), a mammalian threonine kinase, facilitates the repair of DNA breaks. Eukaryotic initiation factor 4E (eIF4E) overexpression leads to the upregulation of TLK1B. Doxorubicin, commonly used in the adjuvant setting for breast cancer, causes DNA breaks. We hypothesized that the degree of TLK1B elevation is correlated with eIF4E overexpression and translates clinically to an increased risk for recurrence in breast cancer patients treated with doxorubicin-based adjuvant chemotherapy.

STUDY DESIGN

We prospectively accrued 152 patients with stage I to III breast cancer treated with a doxorubicin-based chemotherapy in an adjuvant setting. Standardized treatment and surveillance protocols were used. eIF4E and TLK1B protein levels were quantified using Western blots, and patients were divided into tertiles based on previously reported stratification of eIF4E and TLK1B levels. Primary end points were cancer recurrence and death. Statistical analysis included Spearman's correlation, Kaplan-Meier survival analysis, log rank test, and the Cox proportional hazard model.

RESULTS

The degree of TLK1B overexpression was highly correlated with the degree of eIF4E elevation (r=0.25, p=0.0025, Spearman rank correlation). Patients whose tumors were in the highest tertile for eIF4E overexpression had a higher risk for cancer recurrence and cancer death (p=0.015 and 0.049, respectively, log rank test). After adjusting for T-stage, nodal status, age, and estrogen receptor and progesterone receptor status, patients with tumors in the highest tertile of TLK1B overexpression treated with doxorubicin were 1.7-fold more likely to suffer recurrence than those in the low TLK1B group treated similarly (p=0.0078, CI, 1.17 to 2.75, Cox model).

CONCLUSIONS

TLK1B overexpression was highly correlated with the level of eIF4E elevation. High TLK1B in cancer specimens was associated with a higher risk for cancer recurrence in patients treated with doxorubicin-based adjuvant chemotherapy.