Elevated PI3K signaling drives multiple breast cancer subtypes

LncRNAs signatures associated with cuproptosis predict the prognosis of endometrial cancer

Background: Endometrial cancer (UCEC) is the sixth most common cancer in women, and although surgery can provide a good prognosis for early-stage patients, the 5-year overall survival rate for women with metastatic disease is as low as 16%. Long non-coding RNAs (LncRNAs) are thought to play an important role in tumor progression. Cuproptosis is a recently discovered form of cell death in which copper binds directly to the lipoacylated component of the tricarboxylic acid (TCA) cycle. The aggregation of these copper-bound listed mitochondrial proteins and the loss of Fe-S cluster proteins trigger proteotoxic stress, which leads to cell death. Therefore, the aim of this work was to investigate the role of Cuproptosis-related LncRNAs signaling in clinical prognostic prediction and immunotherapy, as well as the relationship between tumor mutation burden. Methods: Genomic, clinical and mutational data of endometrial cancer patients were presented in the TCGA database, and cuproptosis-related genes obtained from related studies. Coexpression analysis and Cox regression analysis were used to construct prognostic features. Patients were divided into high risk group and low risk group, and then ROC, survival rate, risk curve, principal component analysis, independent prognostic analysis and clinical subgroup model validation were performed to observe the prognostic value of characteristics. Subsequently, the GO and genomic KEGG enrichment and immune-related functions of LncRNAs as well as the tumor mutation burden were analyzed. Results: In 548 UCEC case data, we identified five associated LncRNAs co-expressed with cuproptosis genes, and we found that high-risk patients had poorer overall survival (OS), progression-free survival (PFS), and higher mortality. Independent prognostic analysis, ROC showed that the LncRNAs associated with cuproptosis could accurately predict the prognosis of patients. Enrichment analysis revealed that the biological functions of LncRNAs were related to tumorigenesis. We also discovered suppression of immune-related functions in high-risk patients with oncogene mutations, higher tumor mutation burden in low-risk patients, and longer overall survival in patients with higher tumor mutation burden. Conclusion: The identification of five LncRNAs associated with cuproptosis can accurately predict the prognosis of patients with endometrial cancer, and may provide a new perspective for clinical application and immunotherapy.

The current staging and classification systems of breast cancer and their pitfalls: Is it possible to integrate the complexity of this neoplasm into a unified staging system?

Breast cancer is one of the leading causes of cancer death in women worldwide due to its variable aggressiveness and high propensity to develop distant metastases. The staging can be performed clinically or pathologically, generating the stage stratification by the TNM (T - tumor size; N- lymph node metastasis; M - distant organ metastasis) system. However, cancers with virtually identical TNM characteristics can present highly contrasting behaviors due to the divergence of molecular profiles. This review focuses on the histopathological nuances and molecular understanding of breast cancer through the profiling of gene and protein expression, culminating in improvements promoted by the integration of this information into the traditional staging system. As a culminating point, it will highlight predictive statistical tools for genomic risks and decision algorithms as a possible solution to integrate the various systems because they have the potential to reduce the indications for such tests, serving as a funnel in association with staging and previous classification.

Gene expression profiling of giant fibroadenomas of the breast

INTRODUCTION

Fibroadenomas of the breast present as two phenotypic variants. The usual variety is 5 cm or less in diameter and there is another large variant called giant fibroadenoma which is greater than 5 cm in diameter. Despite of its large size, it is not malignant. The aim of our study is to determine whether this large variant is different from the usual fibroadenoma in terms of its biological pathways and biomarkers.

METHODS

mRNA was extracted from 44 fibroadenomas and 36 giant fibroadenomas, and transcriptomic profiling was performed to identify up- and down-regulated genes in the giant fibroadenomas as compared to the fibroadenomas.

RESULTS

A total of 40 genes were significantly up-regulated and 18 genes were significantly down-regulated in the giant fibroadenomas as compared to the fibroadenomas of the breast. The top 5 up-regulated genes were FN1, IL3, CDC6, FGF8 and BMP8A. The top 5 down-regulated genes were TNR, CDKN2A, COL5A1, THBS4 and BMPR1B. The differentially expressed genes (DEGs) were found to be associated with 5 major canonical pathways involved in cell growth (PI3K-AKT, cell cycle regulation, WNT, and RAS signalling) and immune response (JAK-STAT signalling). Further analyses using 3 supervised learning algorithms identified an 8-gene signature (FN1, CDC6, IL23A, CCNA1, MCM4, FLT1, FGF22 and COL5A1) that could distinguish giant fibroadenomas from fibroadenomas with high predictive accuracy.

CONCLUSION

Our findings demonstrated that the giant fibroadenomas are biologically distinct to fibroadenomas of the breast with overexpression of genes involved in the regulation of cell growth and immune response.

Ginsenoside Rg3 enhances the anticancer effect of 5‑FU in colon cancer cells via the PI3K/AKT pathway

Chemotherapy is one of the most commonly used treatments for patients with advanced colon cancer, yet the toxicity of chemotherapy agents, such as 5-fluorouracil (5-FU), limits the effectiveness of chemotherapy. Ginsenoside Rg3 (Rg3) is an active ingredient isolated from ginseng. Rg3 has been shown to display anticancer effects on a variety of malignancies. Yet, whether Rg3 synergizes the effect of 5-FU to inhibit the growth of human colon cancer remains unknown. The present study was designed to ascertain whether Rg3 is able to enhance the anti-colon cancer effect of 5-FU. The results revealed that combined treatment of Rg3 and 5-FU significantly enhanced the inhibition of the proliferation, colony formation, invasion and migration of human colon cancer cells (SW620 and LOVO) in vitro. We also found that combined treatment of Rg3 and 5-FU significantly enhanced the apoptosis of colon cancer cells by activating the Apaf1/caspase 9/caspase 3 pathway and arrested the cell cycle of the colon cancer cells in G0/G1 by promoting the expression of Cyclin D1, CDK2 and CDK4. In addition, the PI3K/AKT signaling pathway in colon cancer cells was suppressed by Rg3 and 5-FU. In vivo, Rg3 synergized the effect of 5-FU to inhibit the growth of human colon cancer xenografts in nude mice. Similarly, combined treatment of Rg3 and 5-FU altered the expression of colon cancer protein in vivo and in vitro. Collectively, the present study demonstrated that ginsenoside Rg3 enhances the anticancer effect of 5-FU in colon cancer cells via the PI3K/AKT pathway.

Expression of Bioinformatically Candidate miRNAs including, miR-576-5p, miR-501-3p and miR-3143, Targeting PI3K Pathway in Triple-Negative Breast Cancer

Background

Triple-negative breast cancer (TNBC) is an invasive and lethal form of breast cancer. PI3K pathway, which often activated in TNBC patients, can be a target of miRNAs. The purpose of this study was bioinformatic prediction of miRNAs targeting the key genes of this pathway and evaluation of the expression of them and their targets in TNBC.

Materials and Methods

We predicted miRNAs targeting PIK3CA and AKT1 genes using bioinformatics tools. Extraction of total RNA, synthesis of cDNA and quantitative real-time polymerase chain reaction were performed from 18 TNBC samples and normal adjacent tissues and cell lines.

Results

Our results demonstrated that miR-576-5p, miR-501-3p and miR-3143 were predicted to target PIK3CA, AKT1 and both of these mRNAs, respectively and were down-regulated while their target mRNAs were up-regulated in clinical samples and cell lines. The analysis of the receiver operating characteristic curve was done for the evaluation of the diagnostic value of predicted miRNAs in TNBC patients.

Conclusion

The findings of our study demonstrated the reverse correlation between miRNAs and their target genes and therefore the possibility of these miRNAs to be proposed as new candidates for TNBC targeted therapies.

The relation between PI3K/AKT signalling pathway and cancer

Phosphatidylinositol 3-kinases (PI3Ks) are crucial coordinators of intracellular signalling in response to the extracellular stimulators. Hyperactivation of PI3K signalling cascades is one among the most ordinary events in human cancers. Focusing on the PI3K pathway remains both a chance and a challenge for cancer therapy. The high recurrence of phosphoinositide 3-kinase (PI3K) pathway adjustments in cancer has led to a surge in the progression of PI3K inhibitors. Recent developments incorporate a re-assessment of the oncogenic mechanisms behind PI3K pathway modifications. Receptor tyrosine kinases upstream of PI3K, the p110a catalytic fractional unit of PI3K, the downstream kinase, AKT, and therefore the negative regulator, PTEN, are all often altered in cancer. In this review, we consider about the phosphoinositide 3-kinases family and mechanisms of PI3K-Akt stimulation in cancer.

Enhanced ZnR/GPR39 Activity in Breast Cancer, an Alternative Trigger of Signaling Leading to Cell Growth

Acquired resistance to the estrogen receptor (ER) antagonist tamoxifen, is a major obstacle in treatment of breast cancer. Changes in Zn2+ accumulation and distribution are associated with tamoxifen-resistance and breast cancer progression. The Zn2+-sensing G-protein coupled receptor, ZnR/GPR39, triggers signaling leading to cell growth, but a role for this receptor in breast cancer in unknown. Using fluorescence imaging, we found Zn2+-dependent Ca2+ release, mediated by ZnR/GPR39 activity, in TAMR tamoxifen-resistant cells derived from MCF-7 cells, but not in ER-expressing MCF-7 or T47D cells. Furthermore, ZnR/GPR39 signaling was monitored in ER negative BT20, MDA-MB-453 and JIMT-1 cells. Expression of ZnR/GPR39 was increased in grade 3 human breast cancer biopsies compared to grade 2. Consistently, analysis of two breast cancer patient cohorts, GDS4057 and TCGA, indicated that in ER-negative tumors higher ZnR/GPR39 mRNA levels are associated with more aggressive tumors. Activation of ZnR/GPR39 in TAMR cells triggered MAPK, mTOR and PI3K signaling. Importantly, enhanced cell growth and invasiveness was observed in the ER negative breast cancer cells, TAMR, MDA-MB-453 and BT20 cells but not in the ER expressing MCF-7 cells. Thus, we suggest ZnR/GPR39 as a potential therapeutic target for combination treatment in breast cancer, particularly relevant in ER negative tumors.

Relationship Between PIK3CA Amplification and P110α and CD34 Tissue Expression as Angiogenesis Markers in Iranian Women with Sporadic Breast Cancer

BACKGROUND AND OBJECTIVE

The PI3K/AKT/mTOR pathway is known to play an important role in regulating angiogenesis both in normal and breast cancer (BC) tissues. PIK3CA amplification was reported in various malignancies, including approximately 10% of BC cases. The aim of this study was to identify the frequency of PIK3CA amplification in Iranian female patients suffering from BC. Additionally, possible association between PIK3CA amplification and P110α expression with microvascular density (MVD) was examined.

METHODS

DNA samples were extracted from paraffin embedded tumor tissue blocks and copy number changes were evaluated by MLPA Technique. The results were analyzed by coffalyzer software. The tissue expression of P110α and CD34 was assessed using immunohistochemistry.

RESULTS

Ten out of 40 samples (17.5%) showed amplification in PIK3CA gene and 22 out of 40 samples (55%) showed overexpression in P110α. For CD34, from 40 samples, 20 (50%), 15 (37.5%) and 5 (12.5%) had scores 1+, 2+ and 3+, respectively.

CONCLUSION

No significant association was detected between gain of PIK3CA copy number and P110α or CD34 tissue expression.

Histological subtypes of mouse mammary tumors reveal conserved relationships to human cancers

Human breast cancer has been characterized by extensive transcriptional heterogeneity, with dominant patterns reflected in the intrinsic subtypes. Mouse models of breast cancer also have heterogeneous transcriptomes and we noted that specific histological subtypes were associated with particular subsets. We hypothesized that unique sets of genes define each tumor histological type across mouse models of breast cancer. Using mouse models that contained both gene expression data and expert pathologist classification of tumor histology on a sample by sample basis, we predicted and validated gene expression signatures for Papillary, EMT, Microacinar and other histological subtypes. These signatures predict known histological events across murine breast cancer models and identify counterparts of mouse mammary tumor types in subtypes of human breast cancer. Importantly, the EMT, Adenomyoepithelial, and Solid signatures were predictive of clinical events in human breast cancer. In addition, a pan-cancer comparison revealed that the histological signatures were active in a variety of human cancers such as lung, oral, and esophageal squamous tumors. Finally, the differentiation status and transcriptional activity implicit within these signatures was identified. These data reveal that within tumor histology groups are unique gene expression profiles of differentiation and pathway activity that stretch well beyond the transgenic initiating events and that have clear applicability to human cancers. As a result, our work provides a predictive resource and insights into possible mechanisms that govern tumor heterogeneity.

Cryptotanshinone inhibition of mammalian target of rapamycin pathway is dependent on oestrogen receptor alpha in breast cancer

Cryptotanshinone (CPT) has been demonstrated to inhibit proliferation and mammalian target of rapamycin (mTOR) pathway in MCF-7 breast cancer cells. However, the same results are unable to be repeated in MDA-MB-231 cells. Given the main difference of oestrogen receptor α (ERα) between two types of breast cancer cells, It is possibly suggested that CPT inhibits mTOR pathway dependent on ERα in breast cancer. CPT could significantly inhibit cell proliferation of ERα-positive cancer cells, whereas ERα-negative cancer cells are insensitive to CPT. The molecular docking results indicated that CPT has a high affinity with ERα, and the oestrogen receptor element luciferase reporter verified CPT distinct anti-oestrogen effect. Furthermore, CPT inhibits mTOR signalling in MCF-7 cells, but not in MDA-MB-231 cells, which is independent on binding to the FKBP12 and disrupting the mTOR complex. Meanwhile, increased expression of phosphorylation AKT and insulin receptor substrate (IRS1) induced by insulin-like growth factor 1 (IGF-1) was antagonized by CPT, but other molecules of IGF-1/AKT/mTOR signalling pathway such as phosphatase and tensin homolog (PTEN) and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) were negatively affected. Finally, the MCF-7 cells transfected with shERα for silencing ERα show resistant to CPT, and p-AKT, phosphorylation of p70 S6 kinase 1 (p-S6K1) and eukaryotic initiation factor 4E binding protein 1 (4E-BP1) were partially recovered, suggesting ERα is required for CPT inhibition of mTOR signalling. Overall, CPT inhibition of mTOR is dependent on ERα in breast cancer and should be a potential anti-oestrogen agent and a natural adjuvant for application in endocrine resistance therapy.

Common and distinct features of mammary tumors driven by Pten-deletion or activating Pik3ca mutation

PTEN loss and PIK3CA activation both promote the accumulation of phosphatidylinositol (3, 4, 5)-trisphosphate (PIP3). While these proteins also have distinct biochemical functions, beyond the regulation of PIP3, little is known about the consequences of these differences in vivo. Here, we directly compared cancer signalling in mammary tumors from MMTV-Cre:Pten^f/f and MMTV-Cre:Pik3ca^LSL-H1047R mice. Using unsupervised hierarchical clustering we found that whereas MMTV-Cre:Pik3ca^LSL-H1047R-derived tumors fall into two separate groups, designated squamous-like^Ex and class14^Ex, MMTV-Cre:Pten^f/f tumors cluster as one group together with PIK3CA^H1047R class14^Ex, exhibiting a ‘luminal’ expression profile. Gene Set Enrichment Analysis (GSEA) of Pten^Δ and PIK3CA^H1047R class14^Ex tumors revealed very similar profiles of signalling pathways as well as some interesting differences. Analysis of 18 signalling signatures revealed that PI3K signalling is significantly induced whereas EGFR signalling is significantly reduced in Pten^Δ versus PIK3CA^H1047R tumors. Thus, Pten^Δ and PIK3CA^H1047R tumors exhibit discernable differences that may impact tumorigenesis and response to therapy.

Mutation of genes of the PI3K/AKT pathway in breast cancer supports their potential importance as biomarker for breast cancer aggressiveness

Deregulation of phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway is closely associated with cancer development and cancer progression. PIK3CA, AKT1, and PTEN are the fundamental molecules of the PI3K/AKT pathway with increased mutation rates in cancer cases leading to aberrant regulation of the pathway. Even though molecular alterations of the PI3K/AKT pathway have been studied in breast cancer, correlations between specific molecular alterations and clinicopathological features remain contradictory. In this study, we examined mutations of the PI3K/AKT pathway in 75 breast carcinomas using high-resolution melting analysis and pyrosequencing, in parallel with analysis of relative expression of PIK3CA and AKT2 genes. Mutations of PIK3CA were found in our cohort in 21 cases (28 %), 10 (13 %) in exon 9 and 11(15 %) in exon 20. Mutation frequency of AKT1 and PTEN genes was 4 and 3 %, respectively. Overall, alterations in the PI3K/AKT signaling cascade were detected in 35 % of the cases. Furthermore, comparison of 50 breast carcinomas with adjacent normal tissues showed elevated PIK3CA messenger RNA (mRNA) levels in 18 % of tumor cases and elevated AKT2 mRNA levels in 14 %. Our findings, along with those of previous studies, underline the importance of the PI3K/AKT pathway components as potential biomarkers for breast carcinogenesis.

Investigating the Inhibitory Effect of Wortmannin in the Hotspot Mutation at Codon 1047 of PIK3CA Kinase Domain: A Molecular Docking and Molecular Dynamics Approach

Oncogenic mutations in phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) are the most frequently reported in association with various forms of cancer. Several studies have reported the significance of hotspot mutations in a catalytic subunit of PIK3CA in association with breast cancer. Mutations are frequently observed in the highly conserved region of the kinase domain (797-1068 amino acids) of PIK3CA are activating or gain-of-function mutations. Mutation in codon 1047 occurs in the C-terminal region of the kinase domain with histidine (H) replaced by arginine (R), lysine (L), and tyrosine (Y). Pathogenicity and protein stability predictors PhD-SNP, Align GVGD, HANSA, iStable, and MUpro classified H1047R as highly deleterious when compared to H1047L and H1047Y. To explore the inhibitory activity of Wortmannin toward PIK3CA, the three-dimensional structure of the mutant protein was determined using homology modeling followed by molecular docking and molecular dynamics analysis. Docking studies were performed for the three mutants and native with Wortmannin to measure the differences in their binding pattern. Comparative docking study revealed that H1047R-Wortmannin complex has a higher number of hydrogen bonds as well as the best binding affinity next to the native protein. Furthermore, 100 ns molecular dynamics simulation was initiated with the docked complexes to understand the various changes induced by the mutation. Though Wortmannin was found to nullify the effect of H1047R over the protein, further studies are required for designing a better compound. As SNPs are major genetic variations observed in disease condition, personalized medicine would provide enhanced drug therapy.

Ras Signaling Is a Key Determinant for Metastatic Dissemination and Poor Survival of Luminal Breast Cancer Patients

Breast cancer is associated with alterations in a number of growth factor and hormone-regulated signaling pathways. Mouse models of metastatic breast cancer typically feature mutated oncoproteins that activate PI3K, Stat3, and Ras signaling, but the individual and combined roles of these pathways in breast cancer progression are poorly understood. In this study, we examined the relationship between oncogenic pathway activation and breast cancer subtype by analyzing mouse mammary tumor formation in which each pathway was activated singly or pairwise. All three oncogenes showed cooperation during primary tumor formation, but efficient dissemination was only dependent on Ras. In addition, transcriptional profiling demonstrated that Ras induced adenocarcinomas with molecular characteristics related to human basal-like and HER2(+) tumors. In contrast, Ras combined with PIK3CA(H1047R), an oncogenic mutant linked to ERα(+)/luminal breast cancer in humans, induced metastatic luminal B-like tumors. Consistent with these data, elevated Ras signaling was associated with basal-like and HER2(+) subtype tumors in humans and showed a statistically significant negative association with estrogen receptor (ER) signaling across all breast cancer. Despite this, there are luminal tumors with elevated Ras signaling. Importantly, when considered as a continuous variable, Ras pathway activation was strongly linked to reduced survival of patients with ERα(+) disease independent of PI3K or Stat3 activation. Therefore, our studies suggest that Ras activation is a key determinant for dissemination and poor prognosis of ERα(+)/luminal breast cancer in humans, and hormone therapy supplemented with Ras-targeting agents may be beneficial for treating this aggressive subtype.

Deregulation of the EGFR/PI3K/PTEN/Akt/mTORC1 pathway in breast cancer: possibilities for therapeutic intervention

The EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance and metastasis. The expression of this pathway is frequently altered in breast cancer due to mutations at or aberrant expression of: HER2, ERalpha, BRCA1, BRCA2, EGFR1, PIK3CA, PTEN, TP53, RB as well as other oncogenes and tumor suppressor genes. In some breast cancer cases, mutations at certain components of this pathway (e.g., PIK3CA) are associated with a better prognosis than breast cancers lacking these mutations. The expression of this pathway and upstream HER2 has been associated with breast cancer initiating cells (CICs) and in some cases resistance to treatment. The anti-diabetes drug metformin can suppress the growth of breast CICs and herceptin-resistant HER2+ cells. This review will discuss the importance of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway primarily in breast cancer but will also include relevant examples from other cancer types. The targeting of this pathway will be discussed as well as clinical trials with novel small molecule inhibitors. The targeting of the hormone receptor, HER2 and EGFR1 in breast cancer will be reviewed in association with suppression of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway.

Force engages vinculin and promotes tumor progression by enhancing PI3K activation of phosphatidylinositol (3,4,5)-triphosphate

Extracellular matrix (ECM) stiffness induces focal adhesion assembly to drive malignant transformation and tumor metastasis. Nevertheless, how force alters focal adhesions to promote tumor progression remains unclear. Here, we explored the role of the focal adhesion protein vinculin, a force-activated mechanotransducer, in mammary epithelial tissue transformation and invasion. We found that ECM stiffness stabilizes the assembly of a vinculin-talin-actin scaffolding complex that facilitates PI3K-mediated phosphatidylinositol (3,4,5)-triphosphate phosphorylation. Using defined two- and three-dimensional matrices, a mouse model of mammary tumorigenesis with vinculin mutants, and a novel super resolution imaging approach, we established that ECM stiffness, per se, promotes the malignant progression of a mammary epithelium by activating and stabilizing vinculin and enhancing Akt signaling at focal adhesions. Our studies also revealed that vinculin strongly colocalizes with activated Akt at the invasive border of human breast tumors, where the ECM is stiffest, and we detected elevated mechanosignaling. Thus, ECM stiffness could induce tumor progression by promoting the assembly of signaling scaffolds, a conclusion underscored by the significant association we observed between highly expressed focal adhesion plaque proteins and malignant transformation across multiple types of solid cancer. See all articles in this Cancer Research section, "Physics in Cancer Research."

GSK-3 as potential target for therapeutic intervention in cancer

The serine/threonine kinase glycogen synthase kinase-3 (GSK-3) was initially identified and studied in the regulation of glycogen synthesis. GSK-3 functions in a wide range of cellular processes. Aberrant activity of GSK-3 has been implicated in many human pathologies including: bipolar depression, Alzheimer's disease, Parkinson's disease, cancer, non-insulin-dependent diabetes mellitus (NIDDM) and others. In some cases, suppression of GSK-3 activity by phosphorylation by Akt and other kinases has been associated with cancer progression. In these cases, GSK-3 has tumor suppressor functions. In other cases, GSK-3 has been associated with tumor progression by stabilizing components of the beta-catenin complex. In these situations, GSK-3 has oncogenic properties. While many inhibitors to GSK-3 have been developed, their use remains controversial because of the ambiguous role of GSK-3 in cancer development. In this review, we will focus on the diverse roles that GSK-3 plays in various human cancers, in particular in solid tumors. Recently, GSK-3 has also been implicated in the generation of cancer stem cells in various cell types. We will also discuss how this pivotal kinase interacts with multiple signaling pathways such as: PI3K/PTEN/Akt/mTORC1, Ras/Raf/MEK/ERK, Wnt/beta-catenin, Hedgehog, Notch and others.

Translational studies within the TAMRAD randomized GINECO trial: evidence for mTORC1 activation marker as a predictive factor for everolimus efficacy in advanced breast cancer

BACKGROUND

Everolimus is an agent frequently associated with specific toxicities. Predictive markers of efficacy are needed to help define which patients could benefit from it. The goal of this exploratory study was to identify potential predictive biomarkers in the mammalian target of rapamycin (mTOR) complex 1 (mTORC1) activation pathway using primary tumor samples collected during the phase II tamoxifen plus everolimus (TAMRAD) trial.

PATIENTS AND METHODS

Tumor tissues were collected retrospectively from the TAMRAD trial. Immunohistochemistry was carried out using specific antibodies directed toward proteins that result in mTORC1 activation [canonical phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mTOR or alternative pathways]. DNA was extracted from the tumor tissue; mutation screening in the PIK3CA gene (exons 9 and 20) and the KRAS gene (exons 2 and 3) was first carried out using Sanger direct sequencing, and then completed by next-generation sequencing for PIK3CA. An exploratory analysis of everolimus efficacy in terms of a time-to-progression (TTP) increase was carried out in each biomarker subgroup (high versus low expression referring to the median percentage of marked cells).

RESULTS

A total of 55 primary tumor samples from the TAMRAD trial—25 from the tamoxifen-alone group and 30 from the tamoxifen/everolimus group—were evaluated for biomarkers. The subgroups most likely to have an improvement in TTP with tamoxifen/everolimus therapy, compared with tamoxifen alone, were patients with high p4EBP1, low 4EBP1, low liver kinase B1, low pAkt, and low PI3K. Among the 45 samples screened for mutation status, nine samples (20%; 95% CI 9.6-34.6) had a PIK3CA mutation. KRAS mutation was observed in one patient.

CONCLUSIONS

A positive correlation between late effectors of mTORC1 activation, a positive correlation between Akt-independent mTORC1 activation, and an inverse correlation between canonical PI3K/Akt/mTOR pathway and everolimus efficacy were observed in this exploratory analysis. However, these correlations need to be validated in larger studies before applying the findings to routine clinical practice.

Combined deletion of Pten and p53 in mammary epithelium accelerates triple-negative breast cancer with dependency on eEF2K

The tumor suppressors Pten and p53 are frequently lost in breast cancer, yet the consequences of their combined inactivation are poorly understood. Here, we show that mammary-specific deletion of Pten via WAP-Cre, which targets alveolar progenitors, induced tumors with shortened latency compared to those induced by MMTV-Cre, which targets basal/luminal progenitors. Combined Pten-p53 mutations accelerated formation of claudin-low, triple-negative-like breast cancer (TNBC) that exhibited hyper-activated AKT signaling and more mesenchymal features relative to Pten or p53 single-mutant tumors. Twenty-four genes that were significantly and differentially expressed between WAP-Cre:Pten/p53 and MMTV-Cre:Pten/p53 tumors predicted poor survival for claudin-low patients. Kinome screens identified eukaryotic elongation factor-2 kinase (eEF2K) inhibitors as more potent than PI3K/AKT/mTOR inhibitors on both mouse and human Pten/p53-deficient TNBC cells. Sensitivity to eEF2K inhibition correlated with AKT pathway activity. eEF2K monotherapy suppressed growth of Pten/p53-deficient TNBC xenografts in vivo and cooperated with doxorubicin to efficiently kill tumor cells in vitro. Our results identify a prognostic signature for claudin-low patients and provide a rationale for using eEF2K inhibitors for treatment of TNBC with elevated AKT signaling.

PI3K/Akt-mediated regulation of p53 in cancer

Mutations activating the PI3K (phosphoinositide 3-kinase)/Akt signalling pathway and inactivating the TP53 tumour-suppressor gene are common mechanisms that cancer cells require to proliferate and escape pre-programmed cell death. In a well-described mechanism, Akt mediates negative control of p53 levels through enhancing MDM2 (murine double minute 2)-mediated targeting of p53 for degradation. Accumulating evidence is beginning to suggest that, in certain circumstances, PTEN (phosphatase and tensin homologue deleted on chromosome 10)/PI3K/Akt also promotes p53 translation and protein stability, suggesting that additional mechanisms may be involved in the Akt-mediated regulation of p53 in tumours. In the present article, we discuss these aspects in the light of clinical PI3K/Akt inhibitors, where information regarding the effect on p53 activity will be a crucial factor that will undoubtedly influence therapeutic efficacy.

A Tumor initiating cell-enriched prognostic signature for HER2+:ERα- breast cancer; rationale, new features, controversies and future directions

The high intra- and inter-tumor heterogeneity of many types of cancers, including breast cancer (BC), poses great challenge to development of subtype-specific prognosis. In BC, the classification of tumors as either ERα⁺ (Luminal A and Luminal B), HER2⁺ (ERα⁺ or ERα⁻) or triple-negative (TNBC)(Basal-like, claudin-low) guides both prognostication and therapy. Indeed, prognostic signatures for ERα⁺ BC are being incorporated into clinical use. However, these signatures distinguish between luminal A (low risk) and Luminal B (high risk) BC; signatures that identify low/high risk patients with luminal B BC are yet to be developed. Likewise, no signature is in clinical use for HER2⁺ or TNBC. The major obstacles to development of robust signatures stem from diversity of BC, clonal evolution and heterogeneity within each subtype. We have recently generated a prognostic signature for HER2⁺:ERα⁻ BC based on the identification of genes that were differentially expressed in a tumor-initiating cell (TIC)-enriched fraction versus non-TIC fraction from a mouse model of HER2⁺ BC (MMTV-Hers/Neu). Here we describe the rationale behind development of this prognosticator, and present new features of the signature, including elevated PI3K pathway activity and low TNFalpha and IFNgamma signaling in high-risk tumors. In addition, we address controversies in the field such as whether random gene expression signatures significantly associate with cancer outcome. Finally, we suggest a guideline for development of prognostic signatures and discuss future directions.

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.

FAM83B-mediated activation of PI3K/AKT and MAPK signaling cooperates to promote epithelial cell transformation and resistance to targeted therapies

Therapies targeting MAPK and AKT/mTOR signaling are currently being evaluated in clinical trials for several tumor types. However, recent studies suggest that these therapies may be limited due to acquired cancer cell resistance and a small therapeutic index between normal and cancer cells. The identification of novel proteins that are involved in MAPK or AKT/mTOR signaling and differentially expressed between normal and cancer cells will provide mechanistically distinct therapeutic targets with the potential to inhibit these key cancer-associated pathways. We recently identified FAM83B as a novel, previously uncharacterized oncogene capable of hyperactivating MAPK and mTOR signaling and driving the tumorigenicity of immortalized human mammary epithelial cells (HMEC). We show here that elevated FAM83B expression also activates the PI3K/AKT signaling pathway and confers a decreased sensitivity to PI3K, AKT, and mTOR inhibitors. FAM83B co-precipitated with the p85α and p110α subunits of PI3K, as well as AKT, and increased p110α and AKT membrane localization, consistent with elevated PI3K/AKT signaling. In tumor-derived cells harboring elevated FAM83B expression, ablation of FAM83B decreased p110α and AKT membrane localization, suppressed AKT phosphorylation, and diminished proliferation, AIG, and tumorigenicity in vivo. We propose that the level of FAM83B expression may be an important factor to consider when combined therapies targeting MAPK and AKT/mTOR signaling are used. Moreover, the identification of FAM83B as a novel oncogene and its integral involvement in activating PI3K/AKT and MAPK provides a foundation for future therapies aimed at targeting FAM83B in order to suppress the growth of PI3K/AKT- and MAPK-driven cancers.

Inhibition of GSK-3β activity can result in drug and hormonal resistance and alter sensitivity to targeted therapy in MCF-7 breast cancer cells

The PI3K/Akt/mTORC1 pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance, and metastasis. One molecule regulated by this pathway is GSK-3β. GSK-3β is phosphorylated by Akt on S9, which leads to its inactivation; however, GSK-3β also can regulate the activity of the PI3K/Akt/mTORC1 pathway by phosphorylating molecules such as PTEN, TSC2, p70S6K, and 4E-BP1. To further elucidate the roles of GSK-3β in chemotherapeutic drug and hormonal resistance of MCF-7 breast cancer cells, we transfected MCF-7 breast cancer cells with wild-type (WT), kinase-dead (KD), and constitutively activated (A9) forms of GSK-3β. MCF-7/GSK-3β(KD) cells were more resistant to doxorubicin and tamoxifen compared with either MCF-7/GSK-3β(WT) or MCF-7/GSK-3β(A9) cells. In the presence and absence of doxorubicin, the MCF-7/GSK-3β(KD) cells formed more colonies in soft agar compared with MCF-7/GSK-3β(WT) or MCF-7/GSK-3β(A9) cells. In contrast, MCF-7/GSK-3β(KD) cells displayed an elevated sensitivity to the mTORC1 blocker rapamycin compared with MCF-7/GSK-3β(WT) or MCF-7/GSK-3β(A9) cells, while no differences between the 3 cell types were observed upon treatment with a MEK inhibitor by itself. However, resistance to doxorubicin and tamoxifen were alleviated in MCF-7/GSK-3β(KD) cells upon co-treatment with an MEK inhibitor, indicating regulation of this resistance by the Raf/MEK/ERK pathway. Treatment of MCF-7 and MCF-7/GSK-3β(WT) cells with doxorubicin eliminated the detection of S9-phosphorylated GSK-3β, while total GSK-3β was still detected. In contrast, S9-phosphorylated GSK-3β was still detected in MCF-7/GSK-3β(KD) and MCF-7/GSK-3β(A9) cells, indicating that one of the effects of doxorubicin on MCF-7 cells was suppression of S9-phosphorylated GSK-3β, which could result in increased GSK-3β activity. Taken together, these results demonstrate that introduction of GSK-3β(KD) into MCF-7 breast cancer cells promotes resistance to doxorubicin and tamoxifen, but sensitizes the cells to mTORC1 blockade by rapamycin. Therefore GSK-3β is a key regulatory molecule in sensitivity of breast cancer cells to chemo-, hormonal, and targeted therapy.

Effects of epidermal growth factor receptor and phosphatase and tensin homologue gene expression on the inhibition of U87MG glioblastoma cell proliferation induced by protein kinase inhibitors

The aim of the present study was to analyse the antiproliferative effects and mechanisms of action of protein kinase inhibitors (PKIs) in human glioblastoma multiforme (GBM) cells with different epidermal growth factor receptor (EGFR) and phosphatase and tensin homologue (PTEN) status. The GBM cell models were established by transfection of plasmids carrying wild-type EGFR, mutated EGFRvIII or PTEN and clonal selection in U87MG cells. Phosphatidylinositol 3-kinase (PI3-K)/AKT pathway-focused gene profiles were examined by real-time polymerase chain reaction-based assays, protein expression was evaluated by western blotting and the antiproliferative effects of PKI treatment were determined by the 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay in GBM cells. The cell model with intact PTEN and low EGFR levels was the most sensitive to treatment with the EGFR inhibitor erlotinib, whereas the model with EGFRvIII was the most resistant to treatment with the mitogen-activated protein kinase kinase inhibitor U0126. The dual PI3-K and mammalian target of rapamycin (mTOR) inhibitor PI103 had the most potent antiproliferative effects against all GBM cells tested. Following simultaneous stimulation of AKT and extracellular signal-regulated kinase, rapamycin concentrations > 0.5 nmol/L failed to exhibit a further growth inhibitory effect. Concurrent inhibition of mTOR and ribosomal protein s6 activity may underlie the inhibition of GBM proliferation by PKI. In conclusion, overexpression of EGFR or EGFRvIII, accompanied by a loss of PTEN, contributed to the activation of multiple intracellular signalling pathways in GBM cells. Rigorous examination of biomarkers in tumour tissues before and after treatment may be necessary to determine the efficacy of PKI therapy in patients with GBM.

CDK4/6-inhibiting drug substitutes for p21 and p16 in senescence: duration of cell cycle arrest and MTOR activity determine geroconversion

CDKN1A (p21) and CDKN2A (p16) inhibit CDK4/6, initiating senescence. According to our view on senescence, the role of p21 and p16 is to cause cell cycle arrest, whereas MTOR (mechanistic target of rapamycin) drives geroconversion to senescence. Recently we demonstrated that one of the markers of p21- and p16-initiated senescence is MEK-dependent hyper-elevation of cyclin D1. We noticed that a synthetic inhibitor of CDK 4/6 (PD0332991) also induced cyclin D1-positive senescence. We demonstrated that PD0332991 and p21 caused almost identical senescence phenotypes. p21, p16, and PD0332991 do not inhibit MTOR, and rapamycin decelerates geroconversion caused by all 3 molecules. Like p21, PD0332991 initiated senescence at any concentration that inhibited cell proliferation. This confirms the notion that a mere arrest in the presence of active MTOR may lead to senescence.

Autophagy-related gene 12 (ATG12) is a novel determinant of primary resistance to HER2-targeted therapies: utility of transcriptome analysis of the autophagy interactome to guide breast cancer treatment

The autophagic process, which can facilitate breast cancer resistance to endocrine, cytotoxic, and molecularly targeted agents, is mainly regulated at the post-translational level. Although recent studies have suggested a possible transcriptome regulation of the autophagic genes, little is known about either the analysis tools that can be applied or the functional importance of putative candidate genes emerging from autophagy-dedicated transcriptome studies. In this context, we evaluated whether the constitutive activation of the autophagy machinery, as revealed by a transcriptome analysis using an autophagy-focused polymerase chain reaction (PCR) array, might allow for the identification of novel autophagy-specific biomarkers for intrinsic (primary) resistance to HER2-targeted therapies. Quantitative real-time PCR (qRT-PCR)-based profiling of 84 genes involved in autophagy revealed that, when compared to trastuzumab-sensitive SKBR3 cells, the positive regulator of autophagic vesicle formation ATG12 (autophagy-related gene 12) was the most differentially up-regulated gene in JIMT1 cells, a model of intrinsic cross-resistance to trastuzumab and other HER1/2-targeting drugs. An analysis of the transcriptional status of ATG12 in > 50 breast cancer cell lines suggested that the ATG12 transcript is commonly upregulated in trastuzumab-unresponsive HER2-overexpressing breast cancer cells. A lentiviral-delivered small hairpin RNA stable knockdown of the ATG12 gene fully suppressed the refractoriness of JIMT1 cells to trastuzumab, erlotinib, gefitinib, and lapatinib in vitro. ATG12 silencing significantly reduced JIMT1 tumor growth induced by subcutaneous injection in nude mice. Remarkably, the outgrowth of trastuzumab-unresponsive tumors was prevented completely when trastuzumab treatment was administered in an ATG12-silenced genetic background. We demonstrate for the first time the usefulness of low-density, autophagy-dedicated qRT-PCR-based platforms for monitoring primary resistance to HER2-targeted therapies by transcriptionally screening the autophagy interactome. The degree of predictive accuracy warrants further investigation in the clinical situation.

Common drugs and treatments for cancer and age-related diseases: revitalizing answers to NCI's provocative questions

In 2011, The National Cancer Institute (NCI) has announced 24 provocative questions on cancer. Some of these questions have been already answered in “NCI's provocative questions on cancer: some answers to ignite discussion” (published in Oncotarget, 2011, 2: 1352.) The questions included “Why do many cancer cells die when suddenly deprived of a protein encoded by an oncogene?” “Can we extend patient survival by using approaches that keep tumors static?” “Why are some disseminated cancers cured by chemotherapy alone?” “Can we develop methods to rapidly test interventions for cancer treatment or prevention?” “Can we use our knowledge of aging to enhance prevention or treatment of cancer?” “What is the mechanism by which some drugs commonly and chronically used for other indications protect against cancer?” “How does obesity contribute to cancer risk?” I devoted a single subchapter to each the answer. As expected, the provocative questions were very diverse and numerous. Now I choose and combine, as a single problem, only three last questions, all related to common mechanisms and treatment of age-related diseases including obesity and cancer. Can we use common existing drugs for cancer prevention and treatment? Can we use some targeted “cancer-selective” agents for other diseases and … aging itself.

PIK3CA mutations in advanced cancers: characteristics and outcomes

PIK3CA mutations are frequently diagnosed in diverse cancers and may predict response to PI3K/AKT/mTOR inhibitors. It remains unclear whether they are associated with other characteristics. We analyzed characteristics and outcome of 90 consecutive patients with diverse advanced tumors and PIK3CA mutations and 180 wild-type PIK3CA controls matched by tumor type, gender, and age referred to the Clinical Center for Targeted Therapy. PIK3CA and MAPK mutations (KRAS, NRAS, and BRAF) were analyzed using polymerase chain reaction-based DNA sequencing. The most frequent PIK3CA mutations were E545K (31/90, 34%), E542K (16/90, 18%) in exon 9, and H1047R (20/90, 22%) in exon 20. PIK3CA mutations compared to wild-type PIK3CA were associated with simultaneous KRAS (p=0.047) and MAPK mutations (p=0.03), but only MAPK mutations were confirmed as having an independent association in multivariate analysis. Rates of lung, bone, liver and brain metastases were similar in PIK3CA-mutant and wild-type patients. Patients with PIK3CA mutations treated on trials with PI3K/AKT/mTOR inhibitors had a higher partial/complete response (PR/CR) rate than wild-type PIK3CA patients treated with their best phase I therapy (10/56, 18% vs. 12/152, 8%; p=0.045), but not a prolonged progression-free survival. Patients with H1047R PIK3CA mutations had higher PR/CR rate with PI3K/AKT/mTOR inhibitors compared to wild-type PIK3CA patients treated with their best phase I therapy (6/16, 38% vs. 12/152, 8%; p=0.003). In conclusion, PIK3CA mutations in diverse cancers were not associated with clinical characteristics, but were correlated with MAPK mutations. PIK3CA mutations, especially, H1047R, were associated with attaining a PR/CR to PI3K/AKT/mTOR pathway inhibitors.

Answering the ultimate question "what is the proximal cause of aging?"

Recent discoveries suggest that aging is neither driven by accumulation of molecular damage of any cause, nor by random damage of any kind. Some predictions of a new theory, quasi-programmed hyperfunction, have already been confirmed and a clinically-available drug slows aging and delays diseases in animals. The relationship between diseases and aging becomes easily apparent. Yet, the essence of aging turns out to be so startling that the theory cannot be instantly accepted and any possible arguments are raised for its disposal. I discuss that these arguments actually support a new theory. Are any questions remaining? And might accumulation of molecular damage still play a peculiar role in aging?

Recent discoveries in the cycling, growing and aging of the p53 field

The P53 gene and it product p53 protein is the most studied tumor suppressor, which was considered as oncogene for two decades until 1990. More than 60 thousand papers on the topic of p53 has been abstracted in Pubmed. What yet could be discovered about its role in cell death, growth arrest and apoptosis, as well as a mediator of the therapeutic effect of anticancer drugs. Still during recent few years even more amazing discoveries have been done. Here we review such topics as suppression of epigenetic silencing of a large number of non-coding RNAs, role of p53 in suppression of the senescence phenotype, inhibition of oncogenic metabolism, protection of normal cells from chemotherapy and even tumor suppression without apoptosis and cell cycle arrest.

pRb controls estrogen receptor alpha protein stability and activity

A cross talk between the Estrogen Receptor (ESR1) and the Retinoblastoma (pRb) pathway has been demonstrated to influence the therapeutic response of breast cancer patients but the full mechanism remains poorly understood. Here we show that the N-terminal domain of pRb interacts with the CD domain of ESR1 to allow for the assembly of intermediate complex chaperone proteins HSP90 and p23. We demonstrated that a loss of pRb in human/mouse breast cells decreases the expression of the ESR1 protein through the proteasome pathway. Our work reveals a novel regulatory mechanism of ESR1 basal turnover and activity and an unanticipated relationship with the pRb tumor suppressor.

Ectopic NGAL expression can alter sensitivity of breast cancer cells to EGFR, Bcl-2, CaM-K inhibitors and the plant natural product berberine

Neutrophil gelatinase-associated lipocalin (NGAL, a.k.a Lnc2) is a member of the lipocalin family and has diverse roles. NGAL can stabilize matrix metalloproteinase-9 from autodegradation. NGAL is considered as a siderocalin that is important in the transport of iron. NGAL expression has also been associated with certain neoplasias and is implicated in the metastasis of breast cancer. In a previous study, we examined whether ectopic NGAL expression would alter the sensitivity of breast epithelial, breast and colorectal cancer cells to the effects of the chemotherapeutic drug doxorubicin. While abundant NGAL expression was detected in all the cells infected with a retrovirus encoding NGAL, this expression did not alter the sensitivity of these cells to doxorubicin as compared with empty vector-transduced cells. We were also interested in determining the effects of ectopic NGAL expression on the sensitivity to small-molecule inhibitors targeting key signaling molecules. Ectopic NGAL expression increased the sensitivity of MCF-7 breast cancer cells to EGFR, Bcl-2 and calmodulin kinase inhibitors as well as the natural plant product berberine. Furthermore, when suboptimal concentrations of certain inhibitors were combined with doxorubicin, a reduction in the doxorubicin IC 50 was frequently observed. An exception was observed when doxorubicin was combined with rapamycin, as doxorubicin suppressed the sensitivity of the NGAL-transduced MCF-7 cells to rapamycin when compared with the empty vector controls. In contrast, changes in the sensitivities of the NGAL-transduced HT-29 colorectal cancer cell line and the breast epithelial MCF-10A cell line were not detected compared with empty vector-transduced cells. Doxorubicin-resistant MCF-7/Dox (R) cells were examined in these experiments as a control drug-resistant line; it displayed increased sensitivity to EGFR and Bcl-2 inhibitors compared with empty vector transduced MCF-7 cells. These results indicate that NGAL expression can alter the sensitivity of certain cancer cells to small-molecule inhibitors, suggesting that patients whose tumors exhibit elevated NGAL expression or have become drug-resistant may display altered responses to certain small-molecule inhibitors.

Advances in targeting signal transduction pathways

Over the past few years, significant advances have occurred in both our understanding of the complexity of signal transduction pathways as well as the isolation of specific inhibitors which target key components in those pathways. Furthermore critical information is being accrued regarding how genetic mutations can affect the sensitivity of various types of patients to targeted therapy. Finally, genetic mechanisms responsible for the development of resistance after targeted therapy are being discovered which may allow the creation of alternative therapies to overcome resistance. This review will discuss some of the highlights over the past few years on the roles of key signaling pathways in various diseases, the targeting of signal transduction pathways and the genetic mechanisms governing sensitivity and resistance to targeted therapies.

Mechanistic or mammalian target of rapamycin (mTOR) may determine robustness in young male mice at the cost of accelerated aging

Males, who are bigger and stronger than females, live shorter in most species from flies to mammals including humans. Cellular mass growth is driven in part by mTOR (Target of Rapamycin). When developmental growth is completed, then, instead of growth, mTOR drives aging, manifested by increased cellular functions, such as hyper-secretion by fibroblasts, thus altering homeostasis, leading to age-related diseases and death. We hypothesize that MTOR activity is elevated in male mice compared with females. Noteworthy, 6 months old males were 28 % heavier than females. Also levels of phosphorylated S6 (pS6) and phospho-AKT (p-AKT, Ser 473), markers of the mTOR activity, were higher in male organs tested. Levels of pS6 were highly variable among mice and correlated with body weight and p-AKT. With age, the difference between levels of pS6 between sexes tended to minimize, albeit males still had hyperactive mTOR. Unlike fasting, the intraperitoneal (i.p.) administration of rapamycin eliminated pS6 in all organs of all females measured by immunoblotting and immunohistochemistry without affecting p-AKT and blood insulin. Although i.p. rapamycin dramatically decreased levels of pS6 in males too, it was still detectable by immunoblotting upon longer exposure. Our study demonstrated that both tissue p-AKT and pS6 were higher in young male mice and were associated with increased body weight and insulin. These data can explain bigger body size and faster aging in males. Our data suggest higher efficacy of rapamycin compared to fasting. Higher sensitivity of females to rapamycin may explain more pronounced life extension by rapamycin observed in females compared to males in several studies.

Two hits are better than one: targeting both phosphatidylinositol 3-kinase and mammalian target of rapamycin as a therapeutic strategy for acute leukemia treatment

Phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) are two key components of the PI3K/Akt/mTOR signaling pathway. This signal transduction cascade regulates a wide range of physiological cell processes, that include differentiation, proliferation, apoptosis, autophagy, metabolism, motility, and exocytosis. However, constitutively active PI3K/Akt/mTOR signaling characterizes many types of tumors where it negatively influences response to therapeutic treatments. Hence, targeting PI3K/Akt/mTOR signaling with small molecule inhibitors may improve cancer patient outcome. The PI3K/Akt/mTOR signaling cascade is overactive in acute leukemias, where it correlates with enhanced drug-resistance and poor prognosis. The catalytic sites of PI3K and mTOR share a high degree of sequence homology. This feature has allowed the synthesis of ATP-competitive compounds targeting the catalytic site of both kinases. In preclinical models, dual PI3K/mTOR inhibitors displayed a much stronger cytotoxicity against acute leukemia cells than either PI3K inhibitors or allosteric mTOR inhibitors, such as rapamycin. At variance with rapamycin, dual PI3K/mTOR inhibitors targeted both mTOR complex 1 and mTOR complex 2, and inhibited the rapamycin-resistant phosphorylation of eukaryotic initiation factor 4E-binding protein 1, resulting in a marked inhibition of oncogenic protein translation. Therefore, they strongly reduced cell proliferation and induced an important apoptotic response. Here, we reviewed the evidence documenting that dual PI3K/mTOR inhibitors may represent a promising option for future targeted therapies of acute leukemia patients.

Mutations and deregulation of Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades which alter therapy response

The Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades are often activated by genetic alterations in upstream signaling molecules such as receptor tyrosine kinases (RTK). Certain components of these pathways, RAS, NF1, BRAF, MEK1, DUSP5, PP2A, PIK3CA, PIK3R1, PIK3R4, PIK3R5, IRS4, AKT, NFKB1, MTOR, PTEN, TSC1, and TSC2 may also be activated/inactivated by mutations or epigenetic silencing. Upstream mutations in one signaling pathway or even in downstream components of the same pathway can alter the sensitivity of the cells to certain small molecule inhibitors. These pathways have profound effects on proliferative, apoptotic and differentiation pathways. Dysregulation of components of these cascades can contribute to: resistance to other pathway inhibitors, chemotherapeutic drug resistance, premature aging as well as other diseases. This review will first describe these pathways and discuss how genetic mutations and epigenetic alterations can result in resistance to various inhibitors.

Involvement of Akt-1 and mTOR in sensitivity of breast cancer to targeted therapy

Elucidating the response of breast cancer cells to chemotherapeutic and hormonal based drugs is clearly important as these are frequently used therapeutic approaches. A signaling pathway often involved in chemo- and hormonal-resistance is the Ras/PI3K/PTEN/Akt/mTOR cascades. In the studies presented in this report, we have examined the effects of constitutive activation of Akt on the sensitivity of MCF-7 breast cancer cells to chemotherapeutic- and hormonal-based drugs as well as mTOR inhibitors. MCF-7 cells which expressed a constitutively-activated Akt-1 gene [∆Akt-1(CA)] were more resistant to doxorubicin, etoposide and 4-OH-tamoxifen (4HT) than cells lacking ∆Akt-1(CA). Cells which expressed ∆Akt-1(CA) were hypersensitive to the mTOR inhibitor rapamycin. Furthermore, rapamycin lowered the IC50s for doxorubicin, etoposide and 4HT in the cells which expressed ∆Akt-1(CA), demonstrating a potential improved method for treating certain breast cancers which have deregulated PI3K/PTEN/Akt/mTOR signaling. Understanding how breast cancers respond to chemo- and hormonal-based therapies and the mechanisms by which they can become drug resistant may enhance our ability to treat breast cancer. These results also document the potential importance of knowledge of the mutations present in certain cancers which may permit more effective therapies.

Cooperative effects of Akt-1 and Raf-1 on the induction of cellular senescence in doxorubicin or tamoxifen treated breast cancer cells

Escape from cellular senescence induction is a potent mechanism for chemoresistance. Cellular senescence can be induced in breast cancer cell lines by the removal of estrogen signaling with tamoxifen or by the accumulation of DNA damage induced by the chemotherapeutic drug doxorubicin. Long term culturing of the hormone-sensitive breast cancer cell line MCF-7 in doxorubicin (MCF-7/DoxR) reduced the ability of doxorubicin, but not tamoxifen, to induce senescence. Two pathways that are often upregulated in chemo- and hormonal-resistance are the PI3K/PTEN/Akt/mTOR and Ras/Raf/MEK/ERK pathways. To determine if active Akt-1 and Raf-1 can influence drug-induced senescence, we stably introduced activated ΔAkt-1(CA) and ΔRaf-1(CA) into drug-sensitive and doxorubicin-resistant cells. Expression of a constitutively-active Raf-1 construct resulted in higher baseline senescence, indicating these cells possessed the ability to undergo oncogene-induced-senescence. Constitutive activation of the Akt pathway significantly decreased drug-induced senescence in response to doxorubicin but not tamoxifen in MCF-7 cells. However, constitutive Akt-1 activation in drug-resistant cells containing high levels of active ERK completely escaped cellular senescence induced by doxorubicin and tamoxifen. These results indicate that up regulation of the Ras/PI3K/PTEN/Akt/mTOR pathway in the presence of elevated Ras/Raf/MEK/ERK signaling together can contribute to drug-resistance by diminishing cell senescence in response to chemotherapy. Understanding how breast cancers containing certain oncogenic mutations escape cell senescence in response to chemotherapy and hormonal based therapies may provide insights into the design of more effective drug combinations for the treatment of breast cancer.

The prognostic impact of Akt isoforms, PI3K and PTEN related to female steroid hormone receptors in soft tissue sarcomas

Background

The PI3K/Akt pathway is involved in cellular survival pathways by inhibiting apoptotic processes and stimulating cell growth and proliferation. Its negative prognostic value has been proven in many types of cancer. In soft tissue sarcomas, the expression profiles of the PI3K/Akt pathway components are poorly defined and their significance uncertain. We aimed to investigate the prognostic impact of Akt (Akt1) phosphorylated at threonine³⁰⁸ and serine⁴⁷³, Akt2, Akt3, PI3K and PTEN, alone and in coexpression with ER and PgR in non-gastrointestinal stromal tumor soft tissue sarcomas (non-GIST STSs).

Patients and methods

Tumor samples and clinical data from 249 patients with non-GIST STS were obtained, and tissue microarrays (TMAs) were constructed. Immunohistochemistry (IHC) was used to evaluate marker expression in tumor cells.

Results

In univariate analyses, the expression levels of p-Akt Thr³⁰⁸ (P = 0.002), Akt2 (P = 0.008) and PI3K (P < 0.001) were significant prognostic factors. In the multivariate analysis, high PI3K expression was an independent negative prognosticator (HR = 1.5, 95% CI = 1.0-2.2, P = 0.042) in addition to advanced age, tumor depth, high malignancy grade, metastasis at diagnosis, surgery and positive resection margins. p-Akt Thr³⁰⁸ expression had strong unfavorable effect in men only (P = 0.009). In contrast, p-Akt Ser⁴⁷³ expression had strong unfavorable impact in women (P = 0.023). PgR-/p-Akt Ser⁴⁷³+ phenotype tended to have less favorable impact in women (P = 0.087), but was the most favorable one in men (P = 0.010).

Conclusion

Expression of PI3K was significantly associated with aggressive behavior and shorter DSS in non-GIST STSs. The site of Akt phosphorylation seems to have gender-dependent impact on survival in STS patients.

Order and disorder in large multi-site docking proteins of the Gab family--implications for signalling complex formation and inhibitor design strategies

Large multi-site docking (LMD) proteins of the Gab, IRS, FRS, DOK and Cas families consist of one or two folded N-terminal domains, followed by a predominantly disordered C-terminal extension. Their primary function is to provide a docking platform for signalling molecules (including PI3K, PLC, Grb2, Crk, RasGAP, SHP2) in intracellular signal transmission from activated cell-surface receptors, to which they become coupled. A detailed analysis of the structural nature and intrinsic disorder propensity of LMD proteins, with Gab proteins as specific examples, is presented. By primary sequence analysis and literature review the varying levels of disorder and hidden order are predicted, revealing properties and a physical architecture that help to explain their biological function and characteristics, common for network hub proteins. The virulence factor, CagA, from Helicobacter pylori is able to mimic Gab function once injected by this human pathogen into stomach epithelial cells. Its predicted differential structure is compared to Gab1 with respect to its functional mimicry. Lastly, we discuss how LMD proteins, in particular Gab1 and Gab2, and their protein partners, such as SH2 and SH3 domain-containing adaptors like Grb2, might qualify for future anti-cancer strategies in developing protein-protein interaction (PPI) inhibitors towards binary interactors consisting of an intrinsically disordered epitope and a structured domain surface.

Involvement of Akt and mTOR in chemotherapeutic- and hormonal-based drug resistance and response to radiation in breast cancer cells

Elucidating the response of breast cancer cells to chemotherapeutic and hormonal based drugs and radiation is clearly important as these are common treatment approaches. Signaling cascades often involved in chemo-, hormonal- and radiation resistance are the Ras/PI3K/PTEN/Akt/mTOR, Ras/Raf/MEK/ERK and p53 pathways. In the following studies we have examined the effects of activation of the Ras/PI3K/PTEN/Akt/mTOR cascade in the response of MCF-7 breast cancer cells to chemotherapeutic- and hormonal-based drugs and radiation. Activation of Akt by introduction of conditionally-activated Akt-1 gene could result in resistance to chemotherapeutic and hormonal based drugs as well as radiation. We have determined that chemotherapeutic drugs such as doxorubicin or the hormone based drug tamoxifen, both used to treat breast cancer, resulted in the activation of the Raf/MEK/ERK pathway which is often associated with a pro-proliferative, anti-apoptotic response. In drug sensitive MCF-7 cells which have wild-type p53; ERK, p53 and downstream p21 (Cip-1 ) were induced upon exposure to doxorubicin. In contrast, in the drug resistant cells which expressed activated Akt-1, much lower levels of p53 and p21 (Cip1) were induced upon exposure to doxorubicin. These results indicate the involvement of the Ras/PI3K/PTEN/Akt/mTOR, Ras/Raf/MEK/ERK and p53 pathways in the response to chemotherapeutic and hormonal based drugs. Understanding how breast cancers respond to chemo- and hormonal-based therapies and radiation may enhance the ability to treat breast cancer more effectively.