PI3K/AKT/mTOR pathway activation in primary and corresponding metastatic breast tumors after adjuvant endocrine therapy

Functional activation of the AKT-mTOR signalling axis in a real-world metastatic breast cancer cohort

BACKGROUND

Mutations of the PIK3CA/AKT/mTOR axis are common events in metastatic breast cancers (MBCs). This study was designed to evaluate the extent to which genetic alterations of the PIK3CA/AKT/mTOR can predict protein activation of this signalling axis in MBCs.

METHODS

Molecular profiles were generated by CLIA-certified laboratories from a real-world evidence cohort of 171 MBC patients. Genetic alterations of the PIK3CA pathway were measured using next-generation sequencing. Activation levels of AKT and downstream signalling molecules were quantified using two orthogonal proteomic methods. Protein activity was correlated with underlying genomic profiles and response to CDK4/6 inhibition in combination with endocrine treatment (ET).

RESULTS

Oncogenic alterations of the PIK3CA/AKT/PTEN pathway were identified in 49.7% of cases. Genomic profiles emerged as poor predictors of protein activity (AUC:0.69), and AKT phosphorylation levels mimicked those of mutant lesions in 76.9% of wild-type tumours. High phosphorylation levels of the PI3K/AKT/mTOR downstream target p70S6 Kinase (T389) were associated with shorter PFS in patients treated with CDK4/6 inhibitors in combination with ET (HR:4.18 95%CI:1.19-14.63); this association was not seen when patients were classified by mutational status.

CONCLUSIONS

Phosphoprotein-based measurements of drug targets and downstream substrates should be captured along with genomic information to identify MBCs driven by the PI3K/AKT/mTOR signalling.

Unravelling the therapeutic potential of forkhead box proteins in breast cancer: An update (Review)

Breast cancer, a prominent cause of mortality among women, develops from abnormal growth of breast tissue, thereby rendering it one of the most commonly detected cancers in the female population. Although numerous treatment strategies are available for breast cancer, discordance in terms of effective treatment and response still exists. Recently, the potential of signaling pathways and transcription factors has gained substantial attention in the cancer community; therefore, understanding their role will assist researchers in comprehending the onset and advancement of breast cancer. Forkhead box (FOX) proteins, which are important transcription factors, are considered crucial regulators of various cellular activities, including cell division and proliferation. The present study explored several subclasses of FOX proteins and their possible role in breast carcinogenesis, followed by the interaction between microRNA (miRNA) and FOX proteins. This interaction is implicated in promoting cell infiltration into surrounding tissues, ultimately leading to metastasis. The various roles that FOX proteins play in breast cancer development, their intricate relationships with miRNA, and their involvement in therapeutic resistance highlight the complexity of breast cancer dynamics. Therefore, recognizing the progress and challenges in current treatments is crucial because, despite advancements, persistent disparities in treatment effectiveness underscore the need for ongoing research, with future studies emphasizing the necessity for targeted strategies that account for the multifaceted aspects of breast cancer.

The Prognostic and Therapeutic Implications of the Chemoresistance Gene BIRC5 in Triple-Negative Breast Cancer

Chemoresistance affects TNBC patient treatment responses. Therefore, identifying the chemoresistant gene provides a new approach to understanding chemoresistance in TNBC. BIRC5 was examined in the current study as a tool for predicting the prognosis of TNBC patients and assisting in developing alternative therapies using online database tools. According to the examined studies, BIRC5 was highly expressed in 45 to 90% of TNBC patients. BIRC5 is not only abundantly expressed but also contributes to resistance to chemotherapy, anti-HER2 therapy, and radiotherapy. Patients with increased expression of BIRC5 had a median survival of 31.2 months compared to 85.8 months in low-expression counterparts (HR, 1.73; CI, 1.4−2.13; p = 2.5 × 10−7). The overall survival, disease-free survival, relapse-free survival, distant metastasis-free survival, and the complete pathological response of TNBC patients with high expression of BIRC5 who received any chemotherapy (Taxane, Ixabepilone, FAC, CMF, FEC, Anthracycline) and anti-HER2 therapy (Trastuzumab, Lapatinib) did not differ significantly from those patients receiving any other treatment. Data obtained indicate that the BIRC5 promoter region was substantially methylated, and hypermethylation was associated with higher BIRC5 mRNA expression (p < 0.05). The findings of this study outline the role of BIRC5 in chemotherapy-induced resistance of TNBC, further indicating that BIRC5 may serve as a promising prognostic biomarker that contributes to chemoresistance and could be a possible therapeutic target. Meanwhile, several in vitro studies show that flavonoids were highly effective in inhibiting BIRC5 in genetically diverse TNBC cells. Therefore, flavonoids would be a promising strategy for preventing and treating TNBC patients with the BIRC5 molecule.

The Multi-Omic Landscape of Primary Breast Tumors and Their Metastases: Expanding the Efficacy of Actionable Therapeutic Targets

Breast cancer (BC) mortality is almost exclusively due to metastasis, which is the least understood aspect of cancer biology and represents a significant clinical challenge. Although we have witnessed tremendous advancements in the treatment for metastatic breast cancer (mBC), treatment resistance inevitably occurs in most patients. Recently, efforts in characterizing mBC revealed distinctive genomic, epigenomic and transcriptomic (multi-omic) landscapes to that of the primary tumor. Understanding of the molecular underpinnings of mBC is key to understanding resistance to therapy and the development of novel treatment options. This review summarizes the differential molecular landscapes of BC and mBC, provides insights into the genomic heterogeneity of mBC and highlights the therapeutically relevant, multi-omic features that may serve as novel therapeutic targets for mBC patients.

Utilizing the Hippo pathway as a therapeutic target for combating endocrine-resistant breast cancer

Drug resistance is always a great obstacle in any endocrine therapy of breast cancer. Although the combination of endocrine therapy and targeted therapy has been shown to significantly improve prognosis, refractory endocrine resistance is still common. Dysregulation of the Hippo pathway is often related to the occurrence and the development of many tumors. Targeted therapies of this pathway have played important roles in the study of triple negative breast cancer (TNBC). Targeting the Hippo pathway in combination with chemotherapy or other targeted therapies has been shown to significantly improve specific antitumor effects and reduce cancer antidrug resistance. Further exploration has shown that the Hippo pathway is closely related to endocrine resistance, and it plays a "co-correlation point" role in numerous pathways involving endocrine resistance, including related pathways in breast cancer stem cells (BCSCs). Agents and miRNAs targeting the components of the Hippo pathway are expected to significantly enhance the sensitivity of breast cancer cells to endocrine therapy. This review initially explains the possible mechanism of the Hippo pathway in combating endocrine resistance, and it concludes by recommending endocrine therapy in combination with therapies targeting the Hippo pathway in the study of endocrine-resistant breast cancers.

Estrogen Receptor on the move: Cistromic plasticity and its implications in breast cancer

Estrogen Receptor (ERα) is a hormone-driven transcription factor, critically involved in driving tumor cell proliferation in the vast majority of breast cancers (BCas). ERα binds the genome at cis-regulatory elements, dictating the expression of a large spectrum of responsive genes in 3D genomic space. While initial reports described a rather static ERα chromatin binding repertoire, we now know that ERα DNA interactions are highly versatile, altered in breast tumor development and progression, and deviate between tumors from patients with differential outcome. Multiple cellular signaling cascades are known to impinge on ERα genomic function, changing its cistrome to retarget the receptor to other regions of the genome and reprogram its impact on breast cell biology. This review describes the current state-of-the-art on which factors manipulate the ERα cistrome and how this alters the response to both endogenous and exogenous hormonal stimuli, ultimately impacting BCa cell progression and response to commonly used therapeutic interventions. Novel insights in ERα cistrome dynamics may pave the way for better patient diagnostics and the development of novel therapeutic interventions, ultimately improving cancer care and patient outcome.

Genomic landscape of metastatic breast cancer identifies preferentially dysregulated pathways and targets

Nearly all breast cancer deaths result from metastatic disease. Despite this, the genomic events that drive metastatic recurrence are poorly understood. We performed whole-exome and shallow whole-genome sequencing to identify genes and pathways preferentially mutated or copy-number altered in metastases compared with the paired primary tumors from which they arose. Seven genes were preferentially mutated in metastases - MYLK, PEAK1, SLC2A4RG, EVC2, XIRP2, PALB2, and ESR1 - 5 of which are not significantly mutated in any type of human primary cancer. Four regions were preferentially copy-number altered: loss of STK11 and CDKN2A/B, as well as gain of PTK6 and the membrane-bound progesterone receptor, PAQR8. PAQR8 gain was mutually exclusive with mutations in the nuclear estrogen and progesterone receptors, suggesting a role in treatment resistance. Several pathways were preferentially mutated or altered in metastases, including mTOR, CDK/RB, cAMP/PKA, WNT, HKMT, and focal adhesion. Immunohistochemical analyses revealed that metastases preferentially inactivate pRB, upregulate the mTORC1 and WNT signaling pathways, and exhibit nuclear localization of activated PKA. Our findings identify multiple therapeutic targets in metastatic recurrence that are not significantly mutated in primary cancers, implicate membrane progesterone signaling and nuclear PKA in metastatic recurrence, and provide genomic bases for the efficacy of mTORC1, CDK4/6, and PARP inhibitors in metastatic breast cancer.

Comparative Treatment Patterns and Outcomes of Fulvestrant versus Everolimus Plus Exemestane for Postmenopausal Metastatic Breast Cancer Resistant to Aromatase Inhibitors in Real-World Experience

Background

Fulvestrant (FUL) and the combination of everolimus and exemestane (EVE-EXE) were the options to treat hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2−) metastatic breast cancer (MBC) patients who were refractory to aromatase inhibitors (AIs). The practical knowledge of treatment patterns and outcomes between the two regimens is essential for improving treatment decisions.

Methods

HR+/HER2− MBC patients, who were refractory to AI, were treated with FUL or EVE-EXE from June 2013 to June 2016 were included. Treatment patterns, progression-free survival (PFS), overall survival (OS), and toxicity were reported. Propensity score matching (PSM) was used to minimize potential confounders.

Results

A total of 168 patients were enrolled. Of 168 patients, 124 patients were treated with FUL and 44 patients received EVE-EXE. Patients who were treated with EVE-EXE were younger, more likely to have visceral, liver, multiple sites of metastases, and had received more prior chemotherapy. After adjusting for propensity score matching (PSM), no significant difference in PFS was found between two groups (P=0.419). However, in the subgroup of multiple metastatic sites, the median PFS was significantly improved in the EVE-EXE arm compared with FUL arm (6.1 vs 3.2 months, respectively, P=0.012). More patients in EVE-EXE arm discontinued treatment due to adverse events than in the FUL arm.

Conclusion

A substantial difference in treatment patterns was observed between the two arms. Clinical outcomes were comparable after PSM.

Clinicaltrials.gov Identifier

NCT03695341 (May 14, 2018).

Contribution of the unfolded protein response to breast and prostate tissue homeostasis and its significance to cancer endocrine response

Resistant breast and prostate cancers remain a major clinical problem, new therapeutic approaches and better predictors of therapeutic response are clearly needed. Because of the involvement of the unfolded protein response (UPR) in cell proliferation and apoptosis evasion, an increasing number of publications support the hypothesis that impairments in this network trigger and/or exacerbate cancer. Moreover, UPR activation could contribute to the development of drug resistance phenotypes in both breast and prostate cancers. Therefore, targeting this pathway has recently emerged as a promising strategy in anticancer therapy. This review addresses the contribution of UPR to breast and prostate tissues homeostasis and its significance to cancer endocrine response with focus on the current progress on UPR research related to cancer biology, detection, prognosis and treatment.

PI3K/ Akt/ mTOR Pathway as a Therapeutic Target for Colorectal Cancer: A Review of Preclinical and Clinical Evidence

Background:

Phosphoinositide 3-kinase (PI3Ks) is a member of intracellular lipid kinases and involved in the regulation of cellular proliferation, differentiation and survival. Overexpression of the PI3K/Akt/mTOR signalling has been reported in various forms of cancers, especially in colorectal cancers (CRC). Due to their significant roles in the initiation and progression events of colorectal cancer, they are recognized as a striking therapeutic target.

Objective:

The present review is aimed to provide a detailed outline on the role of PI3K/Akt/mTOR pathway in the initiation and progression events of colorectal cancers as well as its function in drug resistance. Further, the role of PI3K/Akt/mTOR inhibitors alone and in combination with other chemotherapeutic drugs, in alleviating colorectal cancer is also discussed. The review contains preclinical and clinical evidence as well as patent literature of the pathway inhibitors which are natural and synthetic in origin.

Methods:

The data were obtained from PubMed/Medline databases, Scopus and Google patent literature.

Results:

PI3K/Akt/mTOR signalling is an important event in colorectal carcinogenesis. In addition, it plays significant roles in acquiring drug resistance as well as metastatic initiation events of CRCs. Several small molecules of natural and synthetic origin have been found to be potent inhibitors of CRCs by effectively downregulating the pathway. Data from various clinical studies also support these pathway inhibitors and several among them are patented.

Conclusion:

Inhibitors of the PI3K/mTOR pathway have been successful for the treatment of primary and metastatic colorectal cancers, rendering the pathway as a promising clinical cancer therapeutic target.

Melatonin: An important anticancer agent in colorectal cancer

Colorectal cancer is one of the most common cancers among the elderly, which is also seen in the forms of hereditary syndromes occurring in younger individuals. Numerous studies have been conducted to understand the molecular and cellular pathobiology underlying colorectal cancer. These studies have found that cellular signaling pathways are at the core of colorectal cancer pathology. Because of this, new agents have been proposed as possible candidates to accompany routine therapy regimens. One of these agents is melatonin, a neuro-hormone known best for its essential role in upholding the circadian rhythm and orchestrating the many physiologic changes it accompanies. Melatonin is shown to be able to modulate many signaling pathways involved in many essential cell functions, which if deregulated cause an accelerated pace towards cancer. More so, melatonin is involved in the regulation of immune function, tumor microenvironment, and acts as an antioxidant agent. Many studies have focused on the beneficial effects of melatonin in colorectal cancers, such as induction of apoptosis, increased sensitivity to chemotherapy agents and radiotherapy, limiting cellular proliferation, migration, and invasion. The present review aims to illustrate the known significance of melatonin in colorectal cancer and to address possible clinical use.

PI3K/Akt/mTOR signalling pathway activation in patients with ER-positive, metachronous, contralateral breast cancer treated with hormone therapy

Oestrogen receptor (ER)-positive, metachronous, contralateral breast cancer (MCBC) sometimes develops during or soon after completion of hormone therapy (HT), but it is uncertain whether it is HT-resistant. We examined the association between ER-positive second cancer and activation of the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase (MAPK) pathways, which are associated with HT resistance. We examined the treatment-free interval (time after completion of HT for initial cancer) in 41 patients with ER-positive MCBC with a history of adjuvant HT for initial cancer (HT group), and initial-to-second period duration (time after operation of initial cancer to onset of second cancer) in 17 patients with ER-positive MCBC in whom adjuvant HT was not applied to the initial tumour (control group or no HT group). Phosphorylated S6 (pS6) and phosphorylated MAPK (pMAPK) were used as indicators of PI3K/Akt/mTOR and MAPK pathway activity, respectively. Tumours were classified as showing negative, positive or strongly positive staining, and the correlation between staining and treatment-free interval or initial-to-second period duration was evaluated using the Spearman's rank correlation coefficient (ρ). Treatment-free interval and pS6 staining showed a negative correlation (ρ=-0.5355; P=0.0003) in the HT group. There was no correlation between initial-to-second period duration and pS6 staining in the no HT group (ρ=-0.0814; P=0.756). There was no correlation between pMAPK signalling and the treatment-free interval in the HT group (ρ=-0.1560; P=0.330) or the initial-to-second period duration in the no HT group (ρ=-0.0116; P=0.965). Development of a second ER-positive cancer during or soon after completion of HT for the initial cancer may be associated with activation of the PI3K/Akt/mTOR pathway. Care should be taken during follow-up and when selecting adjuvant therapy for second cancer.

Ceramide Metabolism Balance, a Multifaceted Factor in Critical Steps of Breast Cancer Development

Ceramides are key lipids in energetic-metabolic pathways and signaling cascades, modulating critical physiological functions in cells. While synthesis of ceramides is performed in endoplasmic reticulum (ER), which is altered under overnutrition conditions, proteins associated with ceramide metabolism are located on membrane arrangement of mitochondria and ER (MAMs). However, ceramide accumulation in meta-inflammation, condition that associates obesity with a chronic low-grade inflammatory state, favors the deregulation of pathways such as insulin signaling, and induces structural rearrangements on mitochondrial membrane, modifying its permeability and altering the flux of ions and other molecules. Considering the wide biological processes in which sphingolipids are implicated, they have been associated with diseases that present abnormalities in their energetic metabolism, such as breast cancer. In this sense, sphingolipids could modulate various cell features, such as growth, proliferation, survival, senescence, and apoptosis in cancer progression; moreover, ceramide metabolism is associated to chemotherapy resistance, and regulation of metastasis. Cell–cell communication mediated by exosomes and lipoproteins has become relevant in the transport of several sphingolipids. Therefore, in this work we performed a comprehensive analysis of the state of the art about the multifaceted roles of ceramides, specifically the deregulation of ceramide metabolism pathways, being a key factor that could modulate neoplastic processes development. Under specific conditions, sphingolipids perform important functions in several cellular processes, and depending on the preponderant species and cellular and/or tissue status can inhibit or promote the development of metabolic and potentially breast cancer disease.

Significance and prognostic role of human epidermal growth factor receptor 2 and RAB1A expression in gastric cancer

Human epidermal growth factor receptor 2 (HER-2) has an important clinical role in various cancers. However, the prognostic impact of HER-2 in gastric cancer (GC) is controversial. RAB1A is an important small molecule in the mechanistic target of rapamycin signalling pathway, which is one of the downstream signalling pathways of the epidermal growth factor receptor family. In recent years, the aberrant expression of RAB1A has been reported in a number of tumours, but its regulation in GC has not been extensively examined. Therefore, the present study investigated the expression pattern and prognostic significance of HER-2 and RAB1A in gastric adenocarcinoma (CAG). A comprehensive analysis was performed to examine the expression level of HER-2 and RAB1A in 280 cases of paired paraffin-embedded GAC tissues and an additional 120 archived GAC tissue samples. HER-2 and RAB1A protein expression was assessed by immunohistochemistry and cases with a 2+ score for HER-2 expression levels were subjected to fluorescence in situ hybridization to determine the HER-2 amplification status. Furthermore, HER-2 and RAB1A mRNA expression was quantified by reverse transcription-quantitative polymerase chain reaction. The comparison of continuous data between two groups was performed using a paired-samples t-test. Clinical correlations were determined using Pearson's Chi-square and Fisher's exact tests. Kaplan-Meier survival curves were used to estimate overall survival (OS). Cox proportional hazards models were used to determine associations between HER-2 and RAB1A expression and outcomes. Regression analyses were performed to detect the correlation between the mRNA levels of HER-2 and RAB1A in GAC tissues. It was observed that RAB1A was significantly overexpressed in GAC tissues compared with normal tissues (P<0.001). Approximately 12.86% of the 280 GAC patients had HER-2 amplification. Additionally, RAB1A expression was significantly associated with a short OS (P<0.001) but there were no significant differences in survival between the HER-2 high-expression group and the HER-2 low-expression group. Additionally, the co-expression of HER-2 and RAB1A indicated poorer OS than the overexpression of each protein (P=0.001), and the two factors were significantly positively correlated in GAC (P=0.012). These findings may be used to further explore the molecular mechanisms and regulatory associations among signalling pathways in GC.

Regulatory effects of antitumor agent matrine on FOXO and PI3K-AKT pathway in castration-resistant prostate cancer cells

We previously demonstrated that matrine could inhibit the proliferating, migrating, as well as invading processes of both PC-3 and DU145 cells. However, the underlying molecular mechanisms have not yet been clearly defined. In this study, using various techniques such as high throughput sequencing technology, bioinformatics, quantitative real-time PCR, and immunoblot analysis, we aimed to understand whether matrine serves as a novel regulator of FOXO and PI3K-AKT signaling pathway. DU145 and PC-3 cell lines were cultured for 24 h in vitro. Cells were treated with either matrine or control serum for 48 h, followed by extraction of total RNA. The RNA was sequenced using HiSeq 2500 high-throughput sequencing platform (Illumina). A gene library was established and quality analysis of read data carried out. Integrated database from the website DAVID was used to analyze Gene Ontology (GO), and Kyoto encyclopedia of genes and genomes (KEGG) pathway of differential genes was used for pathway analysis, screening for fold differences of more than two times. The FOXO and PI3K-AKT signaling pathways were screened, and expression levels of mRNA and core protein detected by real-time PCR and immunoblotting, respectively. High throughput sequencing and GO analysis revealed that differentially expressed genes before and after treatment played an important role in cell metabolic process, growth process, anatomical structure formation, cellular component organization, and biological regulation. KEGG signal pathway analysis revealed that FOXO and PI3K-AKT signal pathways had a significant difference between before and after matrine-treated androgen-independent prostate cancer cells PC-3 and DU145. Real-time PCR showed that matrine treatment led to a significant increase in the expression levels of FOXO1A, FOXO3A, FOXO4, and FOXO6 in DU145 and PC-3 cells (P<0.01 or P<0.05), whereas the PI3K expression levels decreased (P<0.01). Similarly, immunoblotting revealed a significant increase (P<0.05) in the expression levels of FOXO1A FOXO3A, FOXO4, and FOXO6 in both PC-3 and DU145 cells, whereas PI3K expression levels decreased (P<0.05). Matrine had a broad regulating effect on the mRNA expression profiles of both PC-3 and DU145 cells. Matrine may inhibit cell proliferation, migration, as well as invasion, and induce apoptosis in both PC-3 and DU145 cells through FOXO and PI3K-AKT signaling pathways. Matrine could therefore be used as a complementary drug to present chemotherapeutic agents, for treating androgen-independent prostate cancer.

Increased MAPK1/3 Phosphorylation in Luminal Breast Cancer Related with PIK3CA Hotspot Mutations and Prognosis

INTRODUCTION: While mutations in PIK3CA are most frequently (45%) detected in luminal breast cancer, downstream PI3K/AKT/mTOR pathway activation is predominantly observed in the basal subtype. The aim was to identify proteins activated in PIK3CA mutated luminal breast cancer and the clinical relevance of such a protein in breast cancer patients. MATERIALS AND METHODS: Expression levels of 171 signaling pathway (phospho-)proteins established by The Cancer Genome Atlas (TCGA) using reverse phase protein arrays (RPPA) were in silico examined in 361 breast cancers for their relation with PIK3CA status. MAPK1/3 phosphorylation was evaluated with immunohistochemistry on tissue microarrays (TMA) containing 721 primary breast cancer core biopsies to explore the relationship with metastasis-free survival. RESULTS: In silico analyses revealed increased phosphorylation of MAPK1/3, p38 and YAP, and decreased expression of p70S6K and 4E–BP1 in PIK3CA mutated compared to wild-type luminal breast cancer. Augmented MAPK1/3 phosphorylation was most significant, i.e. in luminal A for both PIK3CA exon 9 and 20 mutations and in luminal B for exon 9 mutations. In 290 adjuvant systemic therapy naïve lymph node negative (LNN) breast cancer patients with luminal cancer, high MAPK phosphorylation in nuclei (HR = 0.49; 95% CI, 0.25–0.95; P = .036) and in tumor cells (HR = 0.37; 95% CI, 0.18–0.79; P = .010) was related with favorable metastasis-free survival in multivariate analyses including traditional prognostic factors. CONCLUSION: Enhanced MAPK1/3 phosphorylation in luminal breast cancer is related to PIK3CA exon-specific mutations and correlated with favorable prognosis especially when located in the nuclei of tumor cells.

Decreasing Eukaryotic Initiation Factor 3C (EIF3C) Suppresses Proliferation and Stimulates Apoptosis in Breast Cancer Cell Lines Through Mammalian Target of Rapamycin (mTOR) Pathway

Background

Translation initiation is the rate limiting step of protein synthesis and is highly regulated. Eukaryotic initiation factor 3C (EIF3C), an oncogene overexpressed in several human cancers, plays an important role in tumorigenesis and cell proliferation.

Material/Methods

Immunohistochemistry was used to determine the expression of EIF3C in breast cancer tissues from 42 patients. We investigated whether EIF3C silencing decreases breast cancer cell proliferation as assessed by colony formation assay, and whether EIF3C gene knockdown induces apoptosis as assessed by flow cytometry analysis. We utilized the stress and apoptosis signaling antibody array kit, while p-ERK1/2, p-Akt, p-Smad2, p-p38 MAPK, cleaved caspase-3, and cleaved caspase-7 were explored between EIF3C-siRNA and controls. Furthermore, the effects of EIF3C gene knockdown in mTOR pathway were analyzed by western blotting for different cell lines.

Results

In EIF3C-positive tumors, 32 out of 42 showed significantly higher frequencies of high grade group by immunoreactivity (p=0.0016). BrdU incorporation after four days of cell plating was significantly suppressed in MDA-MB-231 cells by EIF3C knockdown compared with controls, with average changes of 7.8-fold (p<0.01). Clone number was significantly suppressed in MDA-MB-231 cells by EIF3C knockdown compared with controls (p<0.05). Cell apoptosis was significantly increased in the EIF3C-siRNA group when compared with the cells that were transfected with scrambled siRNA (3.51±0.0842 versus 13.24±0.2307, p<0.01). The mTOR signaling pathway was involved in decreasing EIF3C translational efficiency.

Conclusions

Unveiling the mechanisms of EIF3 action in tumorigenesis may help identify attractive targets for cancer therapy.

Enrichment of PI3K-AKT-mTOR Pathway Activation in Hepatic Metastases from Breast Cancer

Purpose: Little is known about the molecular signatures associated with specific metastatic sites in breast cancer. Using comprehensive multi-omic molecular profiling, we assessed whether alterations or activation of the PI3K-AKT-mTOR pathway is associated with specific sites of breast cancer metastasis.Experimental Design: Next-generation sequencing-based whole-exome sequencing was coupled with reverse-phase protein microarray (RPPA) functional signaling network analysis to explore the PI3K-AKT-mTOR axis in 32 pretreated breast cancer metastases. RPPA-based signaling data were further validated in an independent cohort of 154 metastatic lesions from breast cancer and 101 unmatched primary breast tumors. The proportion of cases with PI3K-AKT-mTOR genomic alterations or signaling network activation were compared between hepatic and nonhepatic lesions.Results:PIK3CA mutation and activation of AKT (S473) and p70S6K (T389) were detected more frequently among liver metastases than nonhepatic lesions (P < 0.01, P = 0.056, and P = 0.053, respectively). However, PIK3CA mutations alone were insufficient in predicting protein activation (P = 0.32 and P = 0.19 for activated AKT and p70S6K, respectively). RPPA analysis of an independent cohort of 154 tumors confirmed the relationship between pathway activation and hepatic metastasis [AKT (S473), mTOR (S2448), and 4EBP1 (S65); P < 0.01, P = 0.02, and P = 0.01, respectively]. Similar results were also seen between liver metastases and primary breast tumors [AKT (S473) P < 0.01, mTOR (S2448) P < 0.01, 4EBP1 (S65) P = 0.01]. This signature was lost when primary tumors were compared with all metastatic sites combined.Conclusions: Breast cancer patients with liver metastasis may represent a molecularly homogenized cohort with increased incidence of PIK3CA mutations and activation of the PI3K-AKT-mTOR signaling network. Clin Cancer Res; 23(16); 4919-28. ©2017 AACR.

Identification of Personalized Chemoresistance Genes in Subtypes of Basal-Like Breast Cancer Based on Functional Differences Using Pathway Analysis

Breast cancer is a highly heterogeneous disease that is clinically classified into several subtypes. Among these subtypes, basal-like breast cancer largely overlaps with triple-negative breast cancer (TNBC), and these two groups are generally studied together as a single entity. Differences in the molecular makeup of breast cancers can result in different treatment strategies and prognoses for patients with different breast cancer subtypes. Compared with other subtypes, basal-like and other ER+ breast cancer subtypes exhibit marked differences in etiologic factors, clinical characteristics and therapeutic potential. Anthracycline drugs are typically used as the first-line clinical treatment for basal-like breast cancer subtypes. However, certain patients develop drug resistance following chemotherapy, which can lead to disease relapse and death. Even among patients with basal-like breast cancer, there can be significant molecular differences, and it is difficult to identify specific drug resistance proteins in any given patient using conventional variance testing methods. Therefore, we designed a new method for identifying drug resistance genes. Subgroups, personalized biomarkers, and therapy targets were identified using cluster analysis of differentially expressed genes. We found that basal-like breast cancer could be further divided into at least four distinct subgroups, including two groups at risk for drug resistance and two groups characterized by sensitivity to pharmacotherapy. Based on functional differences among these subgroups, we identified nine biomarkers related to drug resistance: SYK, LCK, GAB2, PAWR, PPARG, MDFI, ZAP70, CIITA and ACTA1. Finally, based on the deviation scores of the examined pathways, 16 pathways were shown to exhibit varying degrees of abnormality in the various subgroups, indicating that patients with different subtypes of basal-like breast cancer can be characterized by differences in the functional status of these pathways. Therefore, these nine differentially expressed genes and their associated functional pathways should provide the basis for novel personalized clinical treatments of basal-like breast cancer.

FOXP1 regulation via the PI3K/Akt/p70S6K signaling pathway in breast cancer cells

Loss of Forkhead box P1 (FOXP1) protein expression confers a poor prognosis in sporadic and familial breast cancer patients, and the FOXP1 gene maps to a tumor suppressor locus at chromosome 3p14. Although correlation studies have indicated that FOXP1 has a role in tumor suppression, determination of the regulatory mechanism of FOXP1 is required to establish its function in breast cancer. It has previously been identified that FOXP1 is regulated by estrogen in breast cancer and that treatment with bisphenol A is effective for regulating the transformation of the normal human breast epithelial cell line, MCF-10F. In addition, FOXO-regulated activation of FOXP1 inhibits the apoptosis of MCF-10F cells following tamoxifen and Akt inhibitor VIII administration. The present study indicates that FOXP1 regulation occurs via a PI3K/Akt/p70S6 kinase (p70S6K) signaling pathway. Following treatment with wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3K)/Akt, MCF7 and MDA-MB-231 breast cancer cells demonstrated decreased FOXP1 protein expression levels; this result was also observed in the small interfering (si)RNA silencing of Akt. By contrast, overexpression of Akt resulted in increased FOXP1 protein expression levels in the MDA-MB-231 cells compared with the control cell lysates. Furthermore, treatment with rapamycin, a specific inhibitor of the mammalian target of rapamycin/p70S6K cascade, resulted in decreased FOXP1 expression in the MCF7 cells, but not in the MDA-MB-231 cells, which were resistant to rapamycin-induced inhibition. In addition, silencing of p70S6K using siRNA produced a marked decrease in FOXP1 expression. These data indicate that FOXP1 protein expression is regulated by a PI3K/Akt/p70S6K signaling cascade in breast cancer.

Slit/Robo pathway: a promising therapeutic target for cancer

Axon guidance molecules, slit glycoprotein (Slit) and Roundabout receptor (Robo), have implications in the regulation of physiological processes. Recent studies indicate that Slit and Robo also have important roles in tumorigenesis, cancer progression and metastasis. The Slit/Robo pathway can be considered a master regulator for multiple oncogenic signaling pathways. Herein, we provide a comprehensive review on the role of these molecules and their associated signaling pathways in cancer progression and metastasis. Overall, the current available data suggest that the Slit/Robo pathway could be a promising target for development of anticancer drugs.