Overcoming acquired resistance to anticancer therapy: focus on the PI3K/AKT/mTOR pathway

Heat shock protein 47 promotes tumor survival and therapy resistance by modulating AKT signaling via PHLPP1 in colorectal cancer

Objective: Heat shock protein 47 (HSP47) is a collagen-specific molecular chaperone that facilitates collagen maturation. Its role in cancer remains largely unknown. In this study, we investigated the roles of HSP47 in colorectal cancer (CRC) and therapy resistance. Methods: Expression of HSP47 in CRC tissues was examined (1) in paired human CRC/adjacent normal tissues, using real time quantitative reverse transcription polymerase chain reaction (qRT-PCR), The Cancer Genome Atlas (TCGA) database, and 22 independent microarray databases (curated CRC). In vitro studies on several CRC cell lines (HCT116, RKO and CCL228) with modulated HSP47 expression were conducted to assess cell viability and apoptosis (TUNEL assay and caspase-3/-7) during exposure to chemotherapy. AKT signaling and co-immunoprecipitation studies were performed to examine HSP47 and PHLPP1 interaction. In vivo studies using tumor xenografts were conducted to assess the effects of HSP47 modulation on tumor growth and therapy response. Results: HSP47 was upregulated in CRC and was associated with poor prognosis in individuals with CRC. In vitro, HSP47 overexpression supported the survival of CRC cells, whereas its knockdown sensitized cells to 5-fluorouracil (5-FU). HSP47 promoted survival by inhibiting apoptosis, enhancing AKT phosphorylation, and decreasing expression of the AKT-specific phosphatase PHLPP1 when cells were exposed to chemotherapy. These effects were partly results of the interaction between HSP47 and PHLPP1, which decreased PHLPP1 stability and led to more persistent AKT activity. In vivo, HSP47 supported tumor growth despite 5-FU treatment. Conclusions: HSP47 supports the growth of CRC tumors and suppresses the efficacy of chemotherapy via modulation of AKT signaling.

LETM1 Promotes Gastric Cancer Cell Proliferation, Migration, and Invasion via the PI3K/Akt Signaling Pathway

Purpose

Globally, there is a high incidence of gastric cancer (GC). Leucine zipper-EF-hand containing transmembrane protein 1 (LETM1) is reported to play a vital role in several human malignancies. However, there is limited understanding of the role of LETM1 in GC. This study aims to investigate the effects of LETM1 on proliferation, migration, and invasion of GC cells.

Materials and Methods

The expression levels of LETM1 in the normal gastric mucosal epithelial cells (GES-1) and GC cells were analyzed by quantitative real-time polymerase chain reaction and western blotting. CCK-8, wound healing, and Transwell invasion assays were performed to evaluate the effect of LETM1 knockdown or overexpression on the proliferation, migration, and invasion of the GC cells, respectively. Additionally, the effect of LETM1 knockdown or overexpression on GC cell apoptosis was determined by flow cytometry. Furthermore, the effect of LETM1 knockdown or overexpression on the expression levels of PI3K/Akt signaling pathway-related proteins was evaluated by western blotting.

Results

The GC cells exhibited markedly higher mRNA and protein expression levels of LETM1 than the GES-1 cells. Additionally, the knockdown of LETM1 remarkably suppressed the GC cell proliferation, migration, and invasion, and promoted the apoptosis of GC cells, which were reversed upon LETM1 overexpression. Furthermore, the western blotting analysis indicated that LETM1 facilitates GC progression via the PI3K/Akt signaling pathway.

Conclusions

LETM1 acts as an oncogenic gene to promote GC cell proliferation, migration, and invasion via the PI3K/Akt signaling pathway. Therefore, LETM1 may be a potential target for GC diagnosis and treatment.

Systematic analysis of ovarian cancer platinum-resistance mechanisms via text mining

Background

Platinum resistance is an important cause of clinical recurrence and death for ovarian cancer. This study tries to systematically explore the molecular mechanisms for platinum resistance in ovarian cancer and identify regulatory genes and pathways via text mining and other methods.

Methods

Genes in abstracts of associated literatures were identified. Gene ontology and protein-protein interaction (PPI) network analysis were performed. Then co-occurrence between genes and ovarian cancer subtypes were carried out followed by cluster analysis.

Results

Genes with highest frequencies are mostly involved in DNA repair, apoptosis, metal transport and drug detoxification, which are closely related to platinum resistance. Gene ontology analysis confirms this result. Some proteins such as TP53, HSP90, ESR1, AKT1, BRCA1, EGFR and CTNNB1 work as hub nodes in PPI network. According to cluster analysis, specific genes were highlighted in each subtype of ovarian cancer, indicating that various subtypes may have different resistance mechanisms respectively.

Conclusions

Platinum resistance in ovarian cancer involves complicated signaling pathways and different subtypes may have specific mechanisms. Text mining, combined with other bio-information methods, is an effective way for systematic analysis.

Phosphorylation independent eIF4E translational reprogramming of selective mRNAs determines tamoxifen resistance in breast cancer

Eukaryotic translation initiation factor 4E (eIF4E) selectively promotes translation of mRNAs with atypically long and structured 5′-UTRs and has been implicated in drug resistance. Through genome-wide transcriptome and translatome analysis we revealed eIF4E overexpression could promote cellular activities mediated by ERα and FOXM1 signalling pathways. Whilst eIF4E overexpression could enhance the translation of both ERα and FOXM1, it also led to enhanced transcription of FOXM1. Polysome fractionation experiments confirmed eIF4E could modulate the translation of ERα and FOXM1 mRNA. The enhancement of FOXM1 transcription was contingent upon the presence of ERα, and it was the high levels of FOXM1 that conferred Tamoxifen resistance. Furthermore, tamoxifen resistance was conferred by phosphorylation independent eIF4E overexpression. Immunohistochemistry on 134 estrogen receptor (ER⁺) primary breast cancer samples confirmed that high eIF4E expression was significantly associated with increased ERα and FOXM1, and significantly associated with tamoxifen resistance. Our study uncovers a novel mechanism whereby phosphorylation independent eIF4E translational reprogramming in governing the protein synthesis of ERα and FOXM1 contributes to anti-estrogen insensitivity in ER⁺ breast cancer. In eIF4E overexpressing breast cancer, the increased ERα protein expression in turn enhances FOXM1 transcription, which together with its increased translation regulated by eIF4E, contributes to tamoxifen resistance. Coupled with eIF4E translational regulation, our study highlights an important mechanism conferring tamoxifen resistance via both ERα dependent and independent pathways.

Pristimerin inhibits the proliferation of HT1080 fibrosarcoma cells by inducing apoptosis

Fibrosarcoma is a soft tissue sarcoma that is classified as a rare cancer. Therefore, no standard anti-tumor drug therapy has been established for fibrosarcoma. Although pristimerin (PM) has been reported to exert an anti-tumor effect on various types of cancer, no studies have examined the therapeutic effect of PM on soft tissue sarcoma. The purpose of the current study was to investigate the anti-tumor effect of PM on human fibrosarcoma cells (HT1080). The present study examined the cell viability, IC50 values and ability to induce apoptosis of PM in HT1080 and normal human dermal fibroblast (aHDF) cells. The effect of PM on the following signaling pathways associated with cell proliferation was also evaluated: AKT and mitogen-activated protein kinase (MAPK). Using mice subcutaneously transplanted with fibrosarcoma cells, the effect of PM treatment was investigated on tumor growth inhibition, body weight and liver and renal function. The results revealed that PM administration reduced cell viability and induced apoptosis in a dose-dependent matter. In HT1080 cells, the IC50 value of PM was 0.16 µM at 24 h and 0.13 µM at 48 h. PM treatment also decreased the levels of phosphorylated AKT, mTOR, NF-κB and phosphorylated ERK in a dose-dependent manner. In the PM injection group, the increase in tumor volume was significantly reduced and the effect on weight loss and liver and renal function were revealed to be insignificant. PM exerted little effect on normal human dermal fibroblasts and was highly effective against human fibrosarcoma cells. The results indicated that PM may be used as a potential therapeutic agent against fibrosarcoma.

The Skp2 Pathway: A Critical Target for Cancer Therapy

Strictly regulated protein degradation by ubiquitin-proteasome system (UPS) is essential for various cellular processes whose dysregulation is linked to serious diseases including cancer. Skp2, a well characterized component of Skp2-SCF E3 ligase complex, is able to conjugate both K48-linked ubiquitin chains and K63-linked ubiquitin chains on its diverse substrates, inducing proteasome mediated proteolysis or modulating the function of tagged substrates respectively. Overexpression of Skp2 is observed in various human cancers associated with poor survival and adverse therapeutic outcomes, which in turn suggests that Skp2 engages in tumorigenic activity. To that end, the oncogenic properties of Skp2 are demonstrated by various genetic mouse models, highlighting the potential of Skp2 as a target for tackling cancer. In this article, we will describe the downstream substrates of Skp2 as well as upstream regulators for Skp2-SCF complex activity. We will further summarize the comprehensive oncogenic functions of Skp2 while describing diverse strategies and therapeutic platforms currently available for developing Skp2 inhibitors.

NSAID therapy for PIK3CA-Altered colorectal, breast, and head and neck cancer

Epidemiologic evidence indicates that regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) provides a protective effect against the development of colorectal, breast, and head and neck cancers. Genomic characterization of these cancers has lent considerable insight into the subpopulations of cancer patients who are most likely to benefit from NSAID therapy. The PIK3CA gene encodes the catalytic subunit of phosphatidylinositol 3-kinase (PI3K) and is among the most frequently mutated genes in solid tumor malignancies. Cancer-associated mutations in PIK3CA promote signaling via the PI3K pathway and stimulate tumor cell growth. In addition, activation of the PI3K pathway leads to induction of cyclooxygenase-2 (COX-2) enzyme and production of immunosuppressive prostaglandin E2 (PGE2). Notably, in both colorectal cancer and head and neck cancer the subpopulation of patients that benefit from NSAID use is restricted to those whose tumors exhibit PIK3CA genomic alterations. Preclinical studies, particularly in models of head and neck cancer, support the hypothesis that the chemopreventive impact of NSAIDs may be due, in part, to inhibition of COX-2 and reduction of PGE2 levels in the tumor microenvironment.

Cystatin SN Affects Cell Proliferation by Regulating the ERα/PI3K/AKT/ERα Loopback Pathway in Breast Cancer

Background

Cystatin SN (CST1) has been reported to act as an oncogene in cancers, but its underlying mechanism remains unclear.

Methods

We performed Western blotting analyses to observe protein expression and conducted transwell invasion, wound healing, and colony formation assays to assess cell invasion, migration, and proliferation, respectively. We also performed cell cycle analyses by flow cytometry to determine the role of CST1 in the cell cycle. In vivo experiments used subcutaneous tumor models in BALB/c-nu athymic female mice to evaluate the effect of CST1 on tumor growth.

Results

Western blotting analyses showed that CST1 was upregulated in ER+ breast cancer cells such as MCF7, T47D, and BT474. CST1 knockdown led to slower cell growth and inhibited the G1 to S phase transition in ER+ breast cancer cells. In vivo experiments showed that CST1 deletion inhibited tumor growth, and led to decreased expression of estrogen receptor α (ERα) and p-AKT. In vitro experiments showed that the over-expression of CST1 led to the upregulation of ERα, and inhibition of CST1 inhibited the expression of ERα. Western blotting analyses showed that CST1 regulated the activity of the PI3K/AKT signaling pathway in breast cancer cells. We confirmed that CST1 acted as an oncogene in ER+ breast cancer by regulating the ERα/PI3K/AKT/ERα loopback pathway.

Conclusion

CST1 acts as an oncogene in ER+ breast cancer, and CST1 contributes to cancer development by regulating the ERα/PI3K/AKT/ERα loopback pathway in ER+ breast cancer. Our findings indicate that CST1 could be a significant therapeutic target for ER+ breast cancer patients. Our discovery should inspire further studies on the role of CST1 in cancers.

Natural products targeting the PI3K-Akt-mTOR signaling pathway in cancer: A novel therapeutic strategy

The phosphatidylinositol 3-kinase (PI3K)-Akt and the mammalian target of rapamycin (mTOR) represent two vital intracellular signaling pathways, which are associated with various aspects of cellular functions. These functions play vital roles in quiescence, survival, and growth in normal physiological circumstances as well as in various pathological disorders, including cancer. These two pathways are so intimately connected to each other that in some instances these are considered as one unique pathway crucial for cell cycle regulation. The purpose of this review is to emphasize the role of PI3K-Akt-mTOR signaling pathway in different cancer conditions and the importance of natural products targeting the PI3K-Akt-mTOR signaling pathway. This review also aims to draw the attention of scientists and researchers to the assorted beneficial effects of the numerous classes of natural products for the development of new and safe drugs for possible cancer therapy. We also summarize and critically analyze various preclinical and clinical studies on bioactive compounds and constituents, which are derived from natural products, to target the PI3K-Akt-mTOR signaling pathway for cancer prevention and intervention.

Total saponins of Bolbostemma paniculatum (maxim.) Franquet exert antitumor activity against MDA-MB-231 human breast cancer cells via inhibiting PI3K/Akt/mTOR pathway

BACKGROUND

The aim of the present study was to examine the effects of the Bolbostemma paniculatum (Maxim.) Franquet (BP) active compound, BP total saponins (BPTS), on MDA-MB-231 cells, and investigate the underlying mechanism regarding BPTS-mediated attenuation of the PI3K/Akt/mTOR pathway.

METHODS

The effect of BPTS on cytotoxicity, induction of apoptosis and migration on MDA-MB-231 cells at three different concentrations was investigated. A CCK-8 assay, wound-healing assay and flow cytometry were used to demonstrate the effects of BPTS. Additionally, expression of the primary members of the PI3K/Akt/mTOR signaling pathway was assessed using western blotting. To verify the underlying mechanisms, a PI3K inhibitor and an mTOR inhibitor were used.

RESULTS

BPTS inhibited proliferation of MDA-MB-231 cells with an IC50 value of 10 μg/mL at 48 h. BPTS inhibited migration of MDA-MB-231 cells, and the western blot results demonstrated that BPTS reduced p-PI3K, p-Akt and p-mTOR protein expression levels in MDA-MB-231 cells. Additionally, the results were confirmed using a PI3K inhibitor and an mTOR inhibitor. BPTS decreased proliferation and migration of MDA-MB-231 cells possibly through inhibiting the PI3K/Akt/mTOR signaling pathway.

CONCLUSIONS

The results highlight the therapeutic potential of BPTS for treating patients with triple-negative breast cancer.

Synergistic Effect of Epigenetic Inhibitors Decitabine and Suberoylanilide Hydroxamic Acid on Colorectal Cancer In vitro

Background:

Colorectal Cancer (CRC) is a common cause of oncological deaths worldwide. Alterations of the epigenetic landscape constitute a well-documented hallmark of CRC phenotype. The accumulation of aberrant DNA methylation and histone acetylation plays a major role in altering gene activity and driving tumor onset, progression and metastasis.

Objective:

In this study, we evaluated the effect of Suberoylanilide Hydroxamic Acid (SAHA), a panhistone deacetylase inhibitor, and Decitabine (DAC), a DNA methyltransferase inhibitor, either alone or in combination, on Caco-2 human colon cancer cell line in vitro.

Results:

Our results showed that SAHA and DAC, separately, significantly decreased cell proliferation, induced apoptosis and cell cycle arrest of Caco-2 cell line. On the other hand, the sequential treatment of Caco-2 cells, first with DAC and then with SAHA, induced a synergistic anti-tumor effect with a significant enhancement of growth inhibition and apoptosis induction in Caco-2 cell line as compared to cells treated with either drug alone. Furthermore, the combination therapy upregulates protein expression levels of pro-apoptotic proteins Bax, p53 and cytochrome c, downregulates the expression of antiapoptotic Bcl-2 protein and increases the cleavage of procaspases 8 and 9; this suggests that the combination activates apoptosis via both the intrinsic and extrinsic pathways. Mechanistically, we demonstrated that the synergistic anti-neoplastic activity of combined SAHA and DAC involves an effect on PI3K/AKT and Wnt/β-catenin signaling.

Conclusion:

In conclusion, our results provide evidence for the profound anti-tumorigenic effect of sequentially combined SAHA and DAC in the CRC cell line and offer new insights into the corresponding underlined molecular mechanism.

Overexpression of CENPF correlates with poor prognosis and tumor bone metastasis in breast cancer

Background

Centromere Protein F (CENPF) associates with the centromere-kinetochore complex and influences cell proliferation and metastasis in several cancers. The role of CENPF in breast cancer (BC) bone metastasis remains unclear.

Methods

Using the ONCOMINE database, we compared the expression of CENPF in breast cancer and normal tissues. Findings were confirmed in 60 BC patients through immunohistochemical (IHC) staining. Microarray data from GEO and Kaplan-Meier plots were used analyze the overall survival (OS) and relapse free survival (RFS). Using the GEO databases, we compared the expression of CENPF in primary lesions, lung metastasis lesions and bone metastasis lesions, and validated our findings in BALB/C mouse 4T1 BC models. Based on gene set enrichment analysis (GSEA) and western blot, we predicted the mechanisms by which CENPF regulates BC bone metastasis.

Results

The ONCOMINE database and immunohistochemical (IHC) showed higher CENPF expression in BC tissue compared to normal tissue. Kaplan-Meier plots also revealed that high CENPF mRNA expression correlated to poor survival and shorter progression-free survival (RFS). From BALB/C mice 4T1 BC models and the GEO database, CENPF was overexpressed in primary lesions, other target organs, and in bone metastasis. Based on gene set enrichment analysis (GSEA) and western blot, we predicted that CENPF regulates the secretion of parathyroid hormone-related peptide (PTHrP) through its ability to activate PI3K-AKT-mTORC1.

Conclusion

CENPF promotes BC bone metastasis by activating PI3K-AKT-mTORC1 signaling and represents a novel therapeutic target for BC treatment.

PI3K/AKT/mTOR inhibitors for advanced or recurrent endometrial cancer

BACKGROUND

Endometrial cancer is one of the most common gynaecological cancers in developed countries. Treatment of advanced endometrial cancer usually involves radiotherapy, chemotherapy, endocrine therapy or a combination of these. However, survival outcomes are poor in advanced or metastatic disease. Better systemic treatment options are needed to improve survival and safety outcomes for these women. The PI3K/AKT/mTOR pathway is a frequently altered signalling pathway in endometrial cancer. Single-arm studies have reported some encouraging results of the PI3K/AKT/mTOR inhibition in advanced or recurrent endometrial cancer.

OBJECTIVES

To assess the efficacy and safety of PI3K/AKT/mTOR inhibitor-containing regimens in women with locally-advanced, metastatic or recurrent endometrial cancer.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials, MEDLINE and Embase to 16 January 2019; and the World Health Organization's International Clinical Trials Registry Platform (WHO ICTRP) and ClinicalTrials.gov in July 2018. We also reviewed reference lists from included studies and endometrial cancer guidelines.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing a regimen with a PI3K/AKT/mTOR inhibitor (either alone or in combination with other treatments, such as chemotherapy or hormonal therapy) versus a comparator regimen without a PI3K/AKT/mTOR inhibitor. There were no restrictions on which comparator(s) were included.

DATA COLLECTION AND ANALYSIS

We extracted data independently, and assessed risks of bias and the certainty of the evidence. The primary outcome measures were progression-free survival and toxicity (grade 3/4 where available). We derived hazard ratios (HRs) for time-to-event outcomes and risk ratios (RRs) for dichotomous outcomes. Secondary outcomes included overall survival, objective tumour response rate, quality of life and treatment-related death. We used GRADEproGDT to assess the certainty of the evidence for the most important outcomes (by first-line and second/third-line therapy for progression-free survival and overall survival).

MAIN RESULTS

We included two RCTs involving 361 women. One study assessed the effects of the mTOR inhibitor temsirolimus, in combination with carboplatin/paclitaxel versus carboplatin/paclitaxel and bevacizumab in treatment-naïve women with advanced or recurrent endometrial cancer. The second study compared the mTOR inhibitor ridaforolimus alone versus progestin or investigator choice of chemotherapy in women who had received prior treatment for metastatic or recurrent endometrial cancer. We identified five ongoing studies on the effects of PI3K and AKT inhibitors, metformin and dual mTOR inhibitors.For first-line therapy, an mTOR inhibitor-containing regimen may worsen progression-free survival (HR 1.43, 95% CI 1.06 to 1.93; 1 study, 231 participants; low-certainty evidence), while for second/third-line therapy, an mTOR inhibitor probably improves progression-free survival compared to chemotherapy or endocrine therapy (HR 0.53, 95% CI 0.31 to 0.91; 1 study, 95 participants; moderate-certainty evidence). Data on toxicity were available from both studies: administering an mTOR inhibitor regimen may increase the risk of grade 3/4 mucositis (RR 10.42, 95% CI 1.34 to 80.74; 2 studies, 357 participants; low-certainty evidence), but may result in little to no difference in risk of anaemia or interstitial pneumonitis (low-certainty evidence for both toxicities). Overall, event rates were low. For first-line therapy, an mTOR inhibitor-containing regimen may result in little to no difference in overall survival compared to chemotherapy (HR 1.32, 95% CI 0.98 to 1.781 study, 231 participants; low-certainty evidence). The finding was similar for second/third-line therapy (HR 1.06, 95% CI 0.70 to 1.61; 1 study, 130 participants; low-certainty evidence). Administering mTOR inhibitor-containing regimens may result in little to no difference in tumour response compared to chemotherapy or hormonal therapy in first-line or second/third-line therapy (first line: RR 0.93, 95% CI 0.75 to 1.17; 1 study, 231 participants; second/third line: RR 0.22, 95% CI 0.01 to 4.40; 1 study, 61 participants; low-certainty evidence).Neither study collected or reported quality-of-life data.

AUTHORS' CONCLUSIONS

Two RCTs have been reported to date, with low certainty of evidence. In a recurrent disease setting, mTOR inhibitors may result in improved progression-free survival, but we found no clear benefit in overall survival or tumour response rate. We await the publication of at least five ongoing studies investigating the role of PI3K/AKT/mTOR inhibitors in advanced or recurrent endometrial cancer before any conclusions can be drawn on their use.

Pantoprazole pretreatment elevates sensitivity to vincristine in drug-resistant oral epidermoid carcinoma in vitro and in vivo

Resistance to chemotherapeutic agents is a major cause of treatment failure in patients with oral cancer. Proton pump inhibitors (PPIs), essentially H⁺-K⁺-ATPase inhibitors which are currently used in the treatment of acid related diseases, have demonstrated promising antitumor and chemo-sensitizing efficacy. The main purpose of the present study was to investigate whether pantoprazole (PPZ, one of PPIs) could increase the sensitivity of chemoresistant oral epidermoid carcinoma cells (KB/V) to vincristine (VCR) and elucidate the underlying action mechanism. Results showed that combination treatment of PPZ and VCR synergistically inhibited the proliferation of KB/V cells in vitro and in vivo. Furthermore, administration of PPZ and VCR not only induce apoptosis and G2/M phase arrest in KB/V cells but also suppress the migration and invasion of KB/V cells. The mechanism underlying synergistic anti-tumor effect of PPZ and VCR was related to the inhibition of the function and expression of P-glycoprotein (P-gp) and the down-regulation of EGFR/MAPK and PI3K/Akt/mTOR signaling pathways in KB/V cells. Additionally, we observed that PPZ treatment induced an increase in lysosomal pH and inhibited the activity of lysosomal enzyme acid phosphatase in KB/V cells, which could functionally reduce the sequestration of VCR in lysosomes and sensitized KB/V cells to VCR. In conclusion, our study demonstrated that PPZ could be included in new combined therapy of human oral cancer (especially on VCR-resistant therapy) together with VCR.

The emergence of drug resistance to targeted cancer therapies: Clinical evidence

For many decades classical anti-tumor therapies included chemotherapy, radiation and surgery; however, in the last two decades, following the identification of the genomic drivers and main hallmarks of cancer, the introduction of therapies that target specific tumor-promoting oncogenic or non-oncogenic pathways, has revolutionized cancer therapeutics. Despite the significant progress in cancer therapy, clinical oncologists are often facing the primary impediment of anticancer drug resistance, as many cancer patients display either intrinsic chemoresistance from the very beginning of the therapy or after initial responses and upon repeated drug treatment cycles, acquired drug resistance develops and thus relapse emerges, resulting in increased mortality. Our attempts to understand the molecular basis underlying these drug resistance phenotypes in pre-clinical models and patient specimens revealed the extreme plasticity and adaptive pathways employed by tumor cells, being under sustained stress and extensive genomic/proteomic instability due to the applied therapeutic regimens. Subsequent efforts have yielded more effective inhibitors and combinatorial approaches (e.g. the use of specific pharmacologic inhibitors with immunotherapy) that exhibit synergistic effects against tumor cells, hence enhancing therapeutic indices. Furthermore, new advanced methodologies that allow for the early detection of genetic/epigenetic alterations that lead to drug chemoresistance and prospective validation of biomarkers which identify patients that will benefit from certain drug classes, have started to improve the clinical outcome. This review discusses emerging principles of drug resistance to cancer therapies targeting a wide array of oncogenic kinases, along with hedgehog pathway and the proteasome and apoptotic inducers, as well as epigenetic and metabolic modulators. We further discuss mechanisms of resistance to monoclonal antibodies, immunomodulators and immune checkpoint inhibitors, potential biomarkers of drug response/drug resistance, along with possible new therapeutic avenues for the clinicians to combat devastating drug resistant malignancies. It is foreseen that these topics will be major areas of focused multidisciplinary translational research in the years to come.

CapG promotes resistance to paclitaxel in breast cancer through transactivation of PIK3R1/P50

Background: Chemotherapy resistance is a major problem in breast cancer treatment and a leading cause of mortality in breast cancer patients. Biomarkers for chemotherapy resistance is under investigation.

Methods: Paclitaxel resistant cells were established and subjected to RNA sequencing. Analysis combined with two additional RNA-seq datasets was conducted. CapG expression in patients with adjuvant chemotherapy was studied in breast cancer resection specimens using IHC and related to pathological response and disease-free survival. Paclitaxel resistance was assessed by half-maximal inhibitory concentrations (IC50) and a mouse xenograft model.

Results: Increased expression of actin-binding protein CapG strongly correlated with the resistance to paclitaxel chemotherapy and decreased probability to achieve pathological complete response in breast cancer patients. Overexpressing CapG significantly enhanced paclitaxel resistance in breast cancer cells and xenograft tumors. High CapG level also significantly correlated with shorter relapse-free survival as well as hyper-activation of PI3K/Akt signaling in breast cancer patients. Mechanistically, CapG enhanced PIK3R1 expression which led to increased PI3K/Akt activation. Unexpectedly, CapG was found to bind to the variant-specific promoter of PIK3R1/P50 and directly enhance its transcription. We also identified p300/CBP as a transcriptional coregulator of CapG, which is recruited to PIK3R1 promoter through interaction with CapG, thereby increasing PIK3R1/P50 transcription by enhancing histone H3K27 acetylation. Consistently, inhibiting p300/CBP substantially decreased CapG-dependent upregulation of PIK3R1/P50 and subsequent PI3K/Akt activation, resulting in increased sensitivity to paclitaxel treatment in breast cancer cells.

Conclusion: High CapG levels may predict poor paclitaxel response in breast cancer patients. Targeting CapG-mediated hyperactivation of PI3K/Akt pathway may mitigate resistance to chemotherapy in breast cancer.

The antipsychotic agent flupentixol is a new PI3K inhibitor and potential anticancer drug for lung cancer

Background: The phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway is hyperactivated in lung cancer and regulates a broad range of cellular processes, including proliferation, survival, angiogenesis, and metastasis. Thus PI3K is considered a promising target for therapy. To date, PI3K inhibitors have not been approved for lung cancer. Recent studies showed that the antipsychotic agent flupentixol induced apoptosis of lung cancer cell, however the anti-tumor mechanism of flupentixol remains unclear.

Methods: (1) The idock software simulated the molecular docking between the PI3Kα protein and flupentixol. (2) Inhibition of PI3Kα by the flupentixol was examined by in vitro kinase assays. (3) The cytotoxicity of flupentixol on the NSCLC cell lines was tested by MTT assays. (4) We treated A549 and H661 cells with flupentixol and then measured the percentage of apoptotic cells by the Annexin V/PI analysis. (5) We investigated the effect of flupentixol on the expression of critical PI3K/AKT signaling pathway proteins, further analyzed on the cleavage of PARP and caspase-3 by Western blotting. (6) BALB/C nude mice were subcutaneously injected with A549 cells to evaluate the effect of flupentixol on the growth of lung carcinoma.

Results: Structural analysis of the predicted binding conformation suggested that flupentixol docks to the ATP binding pocket of PI3Kα. Kinase assays demonstrate that flupentixol indeed inhibited the PI3Kα kinase activity. Flupentixol exhibited cytotoxicity in lung cancer cell lines A549 and H661 in a dose- and time-dependent manner. Furthermore, flupentixol more strongly inhibited the phosphorylation of AKT (T308 and S473) and the expression of its downstream target gene Bcl-2 than two known PI3K inhibitors (BYL719 and BKM120). Flupentixol induced apoptosis as measured by PARP and caspase-3 cleavage. Finally, flupentixol significantly suppressed A549 xenograft growth in BALB/C nude mice.

Conclusions: Flupentixol could be docked to the PI3Kα protein and specifically inhibit the PI3K/AKT pathway and survival of lung cancer cells in vitro and in vivo. As an old drug, flupentixol is a new PI3K inhibitor that may be used for the treatment of lung cancers.

ALC1 knockdown enhances cisplatin cytotoxicity of esophageal squamous cell carcinoma cells by inhibition of glycolysis through PI3K/Akt pathway

AIMS

Amplified in liver cancer 1 gene (ALC1), a recently identified oncogene, was reported to be overexpressed in esophageal cancer cell lines and identified as a target oncogene in esophageal cancer pathogenesis. However, little literature is available to illustrate its significance in cisplatin resistance of esophageal squamous cell carcinoma (ESCC) cells. The aim of the current study was to investigate the effect of ALC1 on cisplatin cytotoxicity of ESCC cells and to study the potential mechanisms.

MAIN METHODS

ALC1 at mRNA and protein levels were detected by qRT-PCR and western blot, respectively. Cell viability was evaluated using CCK-8 assay. Apoptosis was assessed using caspase-3/7 activity assay and flow cytometry analysis. Glycolysis level was evaluated by measuring glucose consumption and lactate production. The protein levels of p-protein kinase B (Akt) and Akt were determined by western blot.

KEY FINDINGS

ALC1 was highly expressed in ESCC cells compared with human normal esophageal epithelial Het-1A cells. ALC1 knockdown suppressed the viability, induced apoptosis and enhanced cisplatin cytotoxicity in ESCC cells. In addition, ALC1 knockdown inhibited glycolysis and inactivated the phosphatidylinositol 3-kinase (PI3K)/Akt pathway in ESCC cells. Mechanistically, activation of the PI3K/Akt pathway by 740Y-P blocked the effects of ALC1 knockdown on cisplatin cytotoxicity and glycolysis in ESCC cells. In contrast, inhibition of the PI3K/Akt pathway by LY294002 or glycolysis by 2-deoxyglucose resisted the effect of ALC1 overexpression on cisplatin cytotoxicity in ESCC cells.

SIGNIFICANCE

ALC1 knockdown enhanced cisplatin cytotoxicity of ESCC cells by inhibition of glycolysis through inactivation of the PI3K/Akt pathway.

Targeting the phosphoinositide 3-kinase/AKT pathways by small molecules and natural compounds as a therapeutic approach for breast cancer cells

The phosphoinositide 3-kinase/AKT/mTOR (PI3K/AkT/mTOR) pathway plays a pivotal role in the uncontrolled growth, migration and development of human breast cancer. The elevated expression of TGF-β1 increases the PI3K/AkT/mTOR activity in human breast cancer tissue and potentially motivates tumor metastasis and resistance to chemotherapy. Here, we investigated whether treatment with PI3K/AkT/mTOR dual inhibitor NVP-BEZ235 alone or in combination with caffeic acid phenyl ester (CAPE) could prevent TGF-β1 effects on breast cancer cells. MCF-7 human breast cancer cells were exposed to TGF-β1 for 14 days and then were treated with/without NVP-BEZ235 and/or CAPE. Cell viability, apoptosis, CXCR4 surface expression and mRNA levels of CXCR4 and TWIST-1 were analyzed in all treated groups. We found that treatment of human breast cancer cells with a combination of NVP-BEZ235 and CAPE increased induction of cellular death. Although flow cytometry analysis demonstrated that NVP-BEZ235 alone treatment reduced CXCR4 expression while increasing CXCR4 mRNA level; when NVP-BEZ235 was combined with CAPE, inhibition of CXCR4 surface expression and enhancement of CXCR4 mRNA expression was diminished. In addition, TWIST-1 mRNA expression was down regulated in samples treated with both NVP-BEZ235 and CAPE. These altogether signified that NVP-BEZ235 in combination with CAPE showed improved therapeutic efficacy in breast cancer cells by decreasing apoptotic resistance and reduction of CXCR4 and TWIST-1 expression at mRNA level could be one of mechanism of action.

Inhibition of Phosphatidylinositol 3-kinase (PI3K) Signaling Synergistically Potentiates Antitumor Efficacy of Paclitaxel and Overcomes Paclitaxel-Mediated Resistance in Cervical Cancer

Acquired paclitaxel (PTX) resistance limits its effectiveness and results in advanced cancer progression. This review investigated whether the inhibition of phosphatidylinositol 3-kinase (PI3K) signaling overcomes paclitaxel resistance in cervical cancer. It was established paclitaxel-resistant cell lines (PTX-R ME180/PTX-R HeLa) and determined the combination index for paclitaxel and PI3K inhibitors (BYL-719/ LY294002) by tetrazolium dye assay. Flow cytometry was used to detect the cell cycle and apoptosis. Migration and invasion were explored by wound healing and transwell assays. Genes related to multiple pathways were assessed by a western blot. It was found that the PI3K pathway was significantly activated in paclitaxel-resistant HeLa and ME180 cells compared to parental cells. PTX + PI3K inhibitor combined therapy showed a synergistic effect by strengthening paclitaxel-induced S and G2M arrest in PTX-R cell sublines by the inactivation of cyclin A1, cyclin B1, cyclin E, and Cdc2 expression. Moreover, combination therapy significantly enhanced drug sensitivity and apoptosis through the activation of Bax, and cleavage of poly-(ADP-ribose) polymerase compared with paclitaxel alone. In addition, PI3K inhibition also suppressed tumor migration and invasion by targeting β-catenin and matrix metalloproteinase-2/9. The authors suggest that the combination of a PI3K inhibitor with paclitaxel may enhance antitumor activity through a cascade of PI3K signaling events.

microRNA-10b confers cisplatin resistance by activating AKT/mTOR/P70S6K signaling via targeting PPARγ in esophageal cancer

It is well known that the acquisition of chemoresistance is a major obstacle for the effective treatment of human cancers. It is reported that microRNAs (miRNAs) are implicated in chemotherapy resistance of various malignancies. miR-10b was previously proved as an oncogene in multiple malignancies, including esophageal cancer. However, its biological significance in regulating cisplatin (DDP) resistance in esophageal cancer is still elusive. Here, we observed that miR-10b expression was upregulated and peroxisome proliferator-activated receptor-γ (PPARγ) expression was downregulated in esophageal cancer tumor tissues and cells. PPARγ was proved as a functional target of miR-10b. Moreover, suppression of miR-10b enhanced the chemosensitivity of esophageal cancer cells to DDP in vitro and in vivo. In addition, PPARγ-mediated DDP sensitivity was weakened by miR-10b overexpression. Furthermore, miR-10b-activated AKT/mTOR/p70S6K signaling pathway through targeting PPARγ. Inactivation of AKT/mTOR/p70S6K by AKT inhibitor (GSK690693) attenuated miR-10b-induced DDP resistance in esophageal cancer cells. Taken together these observation, miRNA-10b-mediated PPARγ inhibition enhanced DDP resistance by activating the AKT/mTOR/P70S6K signaling in esophageal cancer, suggesting a potential target to improve therapeutic response of patients with esophageal cancer to DDP.

Safety and Tolerability of Phosphatidylinositol-3-Kinase (PI3K) Inhibitors in Oncology

Activation of phosphatidylinositol-3-kinase (PI3K) and downstream signalling by AKT/mammalian target of rapamycin (mTOR) modulates cellular processes such as increased cell growth, cell proliferation and increased cell migration as well as deregulated apoptosis and oncogenesis. The PI3K/AKT/mTOR pathway (particularly Class I PI3K isoforms) is frequently activated in a variety of solid tumours and haematological malignancies, making PI3K an attractive therapeutic target in oncology. Inhibitors of PI3K also have the potential to restore sensitivity to other modalities of treatments when administered as part of combination regimens. Although many PI3K inhibitors have reached different stages of clinical development, only two (idelalisib and copanlisib) have been currently approved for use in the treatment of B cell lymphoma and leukaemias. While these two agents are effective clinically, their use is associated with a number of serious class-related as well as drug-specific adverse effects. Some of these are immune-mediated and include cutaneous reactions, severe diarrhoea with or without colitis, hepatotoxicity and pneumonitis. They also induce various metabolic abnormalities such as hyperglycaemia and hypertriglyceridaemia. Not surprisingly, therefore, many new PI3K inhibitors with a varying degree of target selectivity have been synthesised in expectations of improved safety and efficacy, and are currently under clinical investigations for use in a variety of solid tumours as well as haematological malignancies. However, evidence from early clinical trials, reviewed herein, suggests that these newer agents are also associated not only with class-related but also other serious and unexpected adverse effects. Their risk/benefit evaluations have resulted in a number of them being discontinued from further development. Cumulative experience with the use of PI3K inhibitors under development suggests that, compared with their use as monotherapy, combining them with other anticancer therapies may be a more effective strategy in improving current standard-of-care and clinical outcomes in cancers beyond haematological cancers. For example, combination of alpelisib with fulvestrant has recently demonstrated unexpectedly superior efficacy compared to fulvestrant alone. Furthermore, the immunomodulatory activity of PI3Kδ and PI3Kγ inhibitors also provides unexpected opportunities for their use in cancer immunotherapy, as is currently being tested in several clinical trials.

Rotundic Acid Induces DNA Damage and Cell Death in Hepatocellular Carcinoma Through AKT/mTOR and MAPK Pathways

Hepatocellular carcinoma (HCC) is the fourth largest cause of cancer-related deaths worldwide with limited therapeutic interventions. Renewed interest in natural products as drug leads has resulted in a paradigm shift toward the rapid screening of medicinal plants for the discovery of new chemical entities. Rotundic acid (RA), a plant-derived triterpenoid, has been anecdotally reported to possess anti-inflammatory and cardio-protective abilities. The present study highlights the anti-cancer efficacy of RA on HCC in vitro and in vivo. The inhibitory effects of RA on HCC cell viability was determined by MTT. Soft agar colony formation and clonogenic assays also showed that RA inhibited HCC cell proliferation. Flow cytometry, confocal, and western blot results further indicated that RA induced cell cycle arrest, DNA damage, and apoptosis by modulating the AKT/mTOR and MAPK pathways. Besides the suppression of migration and invasion, tube formation and VEGF-ELISA revealed the anti-angiogenic abilities of RA on HCC. Moreover, RA also inhibited tumor growth in a HepG2 xenograft mouse model. To our best knowledge, this is the first extensive study of the anticancer activity of RA on HCC. The results demonstrate that RA could be a potential drug candidate for HCC treatment.

Immunotherapy Is Changing First-Line Treatment of Metastatic Renal-Cell Carcinoma

The incidence of renal-cell carcinoma has been increasing each year, with nearly one third of new cases diagnosed at advanced or metastatic stage. The advent of targeted therapies for metastatic renal-cell carcinoma (mRCC) has underscored the need to subtype tumors according to tumor-immune expression profiles that may more reliably predict treatment outcomes. Over the past 2 decades, several vascular endothelial growth factor (VEGF) and tyrosine kinase inhibitors have been the mainstay for first- and second-line treatment of mRCC. Very recently, immunotherapy checkpoint inhibitors have significantly changed the treatment landscape for patients with mRCC, particularly for first-line treatment of intermediate to poor risk mRCC patients. Now, combination immunotherapy as well as combinations of immunotherapy with targeted agents can significantly alter disease outcomes. The field of immuno-oncology for mRCC has unveiled a deeper understanding of the immunoreactivity inherent to these tumors, and as a result combination therapy is evolving as a first-line modality. This review provides a timeline of advances and controversies in first-line treatment of mRCC, describes recent advances in understanding the immunoreactivity of these tumors, and addresses the future of combination anti-VEGF and immunotherapeutic platforms.

Current Approaches and Challenges in the Molecular Therapeutic Targeting of Glioblastoma

Surgical resection continues to predominate as the primary treatment modality in glioblastoma (GBM). Effective chemotherapeutic/biologic agents capable of targeting GBM have yet to be developed in part because of the exceptionally heterogeneous nature and unique microenvironmental conditions associated with this malignant neoplasm. Temozolomide and bevacizumab represent the only U.S. Food and Drug Administration-approved agents for primary and recurrent GBM, respectively. Given the high therapeutic resistance of GBM to current therapies, as well as the failure of bevacizumab to prolong overall survival, new therapeutic agents are urgently warranted and are now in the preclinical and clinical phases of development. Accordingly, clinical trials evaluating the efficacy of immune checkpoint inhibition, chimeric antigen receptor T cell therapy, virotherapies, and tumor vaccination therapy are all under way in GBM. Herein, we review the application of current/novel therapeutics in GBM and in so doing attempt to highlight the most promising solutions to overcome current failures.

CACNA2D3 Enhances the Chemosensitivity of Esophageal Squamous Cell Carcinoma to Cisplatin via Inducing Ca2+-Mediated Apoptosis and Suppressing PI3K/Akt Pathways

Resistance to platinum-based combination chemotherapy is the main cause of poor prognosis in patients with advanced esophageal squamous cell carcinoma (ESCC). Previously, we showed that CACNA2D3 (voltage-dependent subunit alpha 2 delta 3 of a calcium channel complex) was significantly downregulated and functioned as a tumor suppressor in ESCC, but its role in the chemosensitivity of ESCC to cisplatin remained unknown. Here, we found that the expression of CACNA2D3 was significantly associated with poor platinum response in ESCC patients from the Gene Expression Omnibus database. Overexpression of CACNA2D3 increased sensitivity to cisplatin in ESCC in vitro, whereas knockdown of CACNA2D3 increased cisplatin resistance. CACNA2D3 promoted cisplatin-induced apoptosis by modulating intracellular Ca²⁺ stores. In vivo experiments further showed that overexpression of CACNA2D3 enhanced cisplatin anti-tumor effects in a xenograft mouse model. CACNA2D3 overexpression also resulted in the attenuation of PI3K and Akt phosphorylation. Treatment with the PI3K/Akt inhibitor LY294002 restored the chemosensitivity of CACAN2D3-knockdown cells to cisplatin. In conclusion, the results of the current study indicate that CACAN2D3 enhances the chemosensitivity of ESCC to cisplatin via inducing Ca²⁺-mediated apoptosis and suppressing PI3K/Akt pathways. Therefore, regulating the expression of CACNA2D3 is a potential new strategy to increase the efficacy of cisplatin in ESCC patients.

An overview of the multifaceted roles of miRNAs in gastric cancer: Spotlight on novel biomarkers and therapeutic targets

MicroRNAs (miRNAs) are a group of small non-coding RNAs that have displayed strong association with gastric cancer (GC). Through the repression of target mRNAs, miRNAs regulate many biological pathways that are involved in cell proliferation, apoptosis, migration, invasion, metastasis as well as drug resistance. The detection of miRNAs in tissues and in body fluids emerges as a promising method in the diagnosis and prognosis of GC, due to their unique expression pattern in correlation with GC. Notably, miRNAs are also identified as potential therapeutic targets for GC therapy. The present review is thus to highlight the multifaceted roles of miRNAs in GC and in GC therapies, which would give indications for future research.

Quantitative Measurement of Functional Activity of the PI3K Signaling Pathway in Cancer

The phosphoinositide 3-kinase (PI3K) growth factor signaling pathway plays an important role in embryonic development and in many physiological processes, for example the generation of an immune response. The pathway is frequently activated in cancer, driving cell division and influencing the activity of other signaling pathways, such as the MAPK, JAK-STAT and TGFβ pathways, to enhance tumor growth, metastasis, and therapy resistance. Drugs that inhibit the pathway at various locations, e.g., receptor tyrosine kinase (RTK), PI3K, AKT and mTOR inhibitors, are clinically available. To predict drug response versus resistance, tests that measure PI3K pathway activity in a patient sample, preferably in combination with measuring the activity of other signaling pathways to identify potential resistance pathways, are needed. However, tests for signaling pathway activity are lacking, hampering optimal clinical application of these drugs. We recently reported the development and biological validation of a test that provides a quantitative PI3K pathway activity score for individual cell and tissue samples across cancer types, based on measuring Forkhead Box O (FOXO) transcription factor target gene mRNA levels in combination with a Bayesian computational interpretation model. A similar approach has been used to develop tests for other signaling pathways (e.g., estrogen and androgen receptor, Hedgehog, TGFβ, Wnt and NFκB pathways). The potential utility of the test is discussed, e.g., to predict response and resistance to targeted drugs, immunotherapy, radiation and chemotherapy, as well as (pre-) clinical research and drug development.

Methylation-Mediated Silencing of MicroRNA-211 Decreases the Sensitivity of Melanoma Cells to Cisplatin

BACKGROUND Malignant melanoma is recalcitrant to most existing chemotherapies, and aberrant expression of miR-211 plays prominent roles in progression of melanoma. However, the trigger mechanism of aberrant miR-211 expression in melanoma is still elusive. MATERIAL AND METHODS We used qRT-PCR to test miR-211 expression. Cell viability assay and mouse xenograft assay were performed to examine the role of miR-211 on the sensitivity of melanoma cells to cisplatin. The epigenetic modification of miR-211 promoter was assess by DNA methylation analysis and DAC treatment. RESULTS In this study, decreased miR-211 expression was detected. Bisulfite sequencing PCR showed that DNA hypermethylation contributed to the downregulation of miR-211 in melanoma tissues. In melanoma cells, overexpressed 211 could enhance the anticancer effect of cisplatin and restoration of miR-211 rendered susceptibility to cisplatin in cisplatin-resistant cells. And the same result was showed in vivo by mouse xenograft assay. What is more, DAC treatment could increase miR-211 expression and EZH2 expression was increased in cisplatin-resistant cells. MiR-211 could be transcriptionally repressed by EZH2 mediated promoter methylation. CONCLUSIONS Taken together, our findings revealed that epigenetic modification of miR-211 governed melanoma cell chemosensitivity and were involved in the progression of tumorigenesis.

Knockdown of tripartite motif 59 (TRIM59) inhibits proliferation in cholangiocarcinoma via the PI3K/AKT/mTOR signalling pathway

AIM

We analysed multiple microarray datasets in the Cancer Genome Atlas (TCGA) database and Gene Expression Omnibus (GEO) DataSets for messenger RNAs (mRNAs) whose expression is apparently increased in human cholangiocarcinoma (CCA) samples, compared with that in the adjacent normal biliary epithelial tissue. The results revealed that the expression of tripartite motif-containing 59 (TRIM59) was significantly increased in the CCA tissue samples. TRIM59 is a member of the tripartite motif (TRIM) protein family, which contains a highly conserved N-terminal-an interesting new gene (RING) domain regulating transcriptional factors and tumorigenesis. In the present study, we investigated the effects of TRIM59 expression on tumour growth in CCA.

MATERIALS AND METHODS

After analyzing the microarray datasets from the TCGA database and GEO DataSets, we screened out 291 target genes, which are significantly overexpressed in CCA tissues, and TRIM59 was one of them. The quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), Western blotting, and immunohistochemistry were performed to determine the expression of TRIM59 in CCA tissues (n = 65) and cell lines. Kaplan-Meier survival analysis was conducted to assess the prognosis of TRIM59 in patients with CCA. A specific siRNA (siRNA-1008) was used to inhibit the expression of TRIM59 in HCCC9810 and HUCCT1 cell lines. The effects of TRIM59 silencing on cell proliferation were assessed by the CCK-8, colony-formation, and EDU incorporation assays. Furthermore, the effects of TRIM59 knockdown on cell apoptosis and cell cycle were determined by flow cytometry. The in vivo effects were evaluated using a mouse tumorigenic model. Western blotting was also performed to verify the relationship between knockdown of TRIM59 and activation of the PI3K/AKT/mTOR pathway.

RESULTS

TRIM59 was highly expressed in CCA tissues. The knockdown of TRIM59 obviously reduced the proliferation and colony formation abilities of CCA cells in vitro and in vivo. Furthermore, the cell apoptosis analysis results showed that TRIM59 silencing apparently promoted CCA cell apoptosis by the mitochondrial pathway. Our preliminary results indicate that the down-regulation of TRIM59 levels might restrict the PI3K/AKT/mTOR signalling pathway.

CONCLUSIONS

Our study revealed that TRIM59 is up-regulated in CCA tissues and cell lines and promoted CCA cell proliferation, possibly by affecting the PI3K/AKT/mTOR signalling pathway.

Auriculasin sensitizes primary prostate cancer cells to TRAIL-mediated apoptosis through up-regulation of the DR5-dependent pathway

Primary prostate cancer cells frequently develop resistance toward chemotherapy as well as most chemotherapeutics have been reported to induce undesirable cytotoxicity in normal cells. In this study, we performed sensitizing activity analysis of auriculasin (AC) to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in RC-58T/h/SA#4 primary prostate cancer cells without significant cytotoxicity in RWPE-1 prostate epithelial cells. Combined treatment with AC and TRAIL at optimal concentrations resulted in tumor-specific apoptotic cell death in RC-58T/h/SA#4 cells, characterized by DNA fragmentation, accumulation of apoptotic cell population, and nuclear condensation. Compared to single treatment with AC or TRAIL, co-treatment with AC and TRAIL significantly increased expression of Bax, cleaved PARP, AIF, endo G, and cytochrome c but decreased expression of phosphorylation of AKT and mammalian target of rapamycin (mTOR), phosphoinositide 3-kinase (PI3K), Bcl-2 and caspases-9, -8, -3, and -10. The sensitizing effect of AC to TRAIL was well correlated with inhibition of death receptor 5 (DR5) CHOP, and p53 expression. Moreover, pre-treatment with a chimeric blocking antibody for DR5 effectively reduced AC-TRAIL-induced cell death and apoptosis-related protein expression. These results suggest that non-toxic concentrations of AC sensitize TRAIL-resistant primary prostate cancer cells to TRAIL-mediated apoptosis via up-regulation of DR5 and downstream signaling pathways.

Ubenimex Reverses MDR in Gastric Cancer Cells by Activating Caspase-3-Mediated Apoptosis and Suppressing the Expression of Membrane Transport Proteins

Gastric cancer (GC) is one of the most malignant tumors, accounting for 10% of deaths caused by all cancers. Chemotherapy is often necessary for treatment of GC; the FOLFOX regimen is extensively applied. However, multidrug resistance (MDR) of GC cells prevents wider application of this treatment. Ubenimex, an inhibitor of CD13, is used as an immune adjuvant to treat hematological malignancies. Here, we demonstrate that CD13 expression positively correlates with MDR development in GC cells. Moreover, Ubenimex reverses the MDR of SGC7901/X and MKN45/X cells and enhances their sensitivity to FOLFOX, in part by decreasing CD13 expression, which is accompanied by downregulation of Bcl-xl, Bcl-2, and survivin expression; increased expression of Bax; and activation of the caspase-3-mediated apoptotic cascade. In addition, Ubenimex downregulates expression of membrane transport proteins, such as P-gp and MRP1, by inhibiting phosphorylation in the PI3K/AKT/mTOR pathway to increase intracellular accumulations of 5-fluorouracil and oxaliplatin, a process for which downregulation of CD13 expression is essential. Therefore, the present results reveal a previously uncharacterized function of CD13 in promoting MDR development in GC cells and suggest that Ubenimex is a candidate for reversing the MDR of GC cells.

Targeting PI3K Signaling in Acute Lymphoblastic Leukemia

Adhesion of acute lymphoblastic leukemia (ALL) cells to bone marrow stroma cells triggers intracellular signals regulating cell-adhesion-mediated drug resistance (CAM-DR). Stromal cell protection of ALL cells has been shown to require active AKT. In chronic lymphocytic leukemia (CLL), adhesion-mediated activation of the PI3K/AKT pathway is reported. A novel FDA-approved PI3Kδ inhibitor, CAL-101/idelalisib, leads to downregulation of p-AKT and increased apoptosis of CLL cells. Recently, two additional PI3K inhibitors have received FDA approval. As the PI3K/AKT pathway is also implicated in adhesion-mediated survival of ALL cells, PI3K inhibitors have been evaluated preclinically in ALL. However, PI3K inhibition has yet to be approved for clinical use in ALL. Here, we review the role of PI3K in normal hematopoietic cells, and in ALL. We focus on summarizing targeting strategies of PI3K in ALL.

Inhibition of AKT signalling by benzoxazine derivative LTUR6 through the modulation of downstream kinases

Many compounds structurally similar to chromones have been developed to enhance the sensitizing effect of cancer cells to chemotherapeutic agents. Most of these compounds have been shown to promote this sensitization by targeting the repair pathways. One such compound is LTUR6, which enhances the sensitization of doxorubicin to colon cancer cells HT29, by inhibiting the phosphorylation of the double stranded break (DSB) repair enzyme AKT. The downstream regulatory targets of AKT that enhance doxorubicin mediated cytotoxicity in the presence of LTUR6 remains elusive. In this study, we performed comparative analyses of 43 kinase phosphorylation sites using the human phospho-kinase array proteome profiler. Results revealed altered expression levels of multiple proteins that regulated apoptotic signalling pathways. Increased activation of mTOR, RSK1/2/3, p38α and PRAS40 after combination treatment with LTUR6 and doxorubicin over doxorubicin alone was observed. This study provides a deeper insight into the key proteins involved and presents a novel molecular pathway.

Retracted Article: Long non-coding RNA GACAT1 alleviates doxorubicin and vincristine resistance through a PTEN/AKT/mTOR/S6K1 regulatory pathway in gastric cancer

Gastric cancer (GC) is a major global health problem. Chemotherapy is a common therapeutic strategy for cancers including GC. However, chemoresistance strikingly limits the clinical applications of chemotherapeutic drugs. Long non-coding RNAs (lncRNAs) have been widely reported to be implicated in the pathogenesis and chemoresistance of cancers including GC. Our work aims to investigate the roles and molecular mechanisms of lncRNA gastric cancer-associated transcript 1 (GACAT1) in regulating doxorubicin (ADR) and vincristine (VCR) resistance in GC. In this text, RT-qPCR assay showed that GACAT1 expression was markedly reduced in ADR- or VCR-resistant GC (SGC7901/ADR or SGC7901/VCR) cells and GC tissues. CCK-8 assay and flow cytometry analysis revealed that GACAT1 overexpression alleviated the resistance of GC cells to ADR and VCR. RT-qPCR and western blot assay disclosed that GACAT1 deactivated the AKT/mTOR/S6K1 signaling pathway and promoted PTEN expression in SGC7901/ADR or SGC7901/VCR cells. Restoration experiments demonstrated that GACAT1 attenuated ADR or VCR resistance by regulating the PTEN/AKT/mTOR/S6K1 pathway in SGC7901/ADR or SGC7901/VCR cells. In vivo experiments demonstrated that GACAT1 overexpression inhibited tumor growth and enhanced ADR- or VCR-mediated anti-tumor effects in GC xenograft tumor models. Taken together, these data revealed that GACAT1 weakened the resistance of GC cells to ADR and VCR by the PTEN/AKT/mTOR/S6K1 regulatory pathway in vitro and in vivo, shedding new light on GACAT1 upregulation as a potential strategy to alleviate chemoresistance in GC.

Gastric cancer (GC) is a major global health problem.

TUG1 knockdown enhances adriamycin cytotoxicity by inhibiting glycolysis in adriamycin-resistant acute myeloid leukemia HL60/ADR cells

Taurine-upregulated gene 1 (TUG1) has been reported as an oncogenic long non-coding RNA (lncRNA) in acute myeloid leukemia (AML). Nevertheless, the roles and molecular mechanism of TUG1 in drug resistance of AML cells are still unclear. Glycolysis level was evaluated by detecting glucose consumption and lactate production. qRT-PCR and Western blot were performed to detect TUG1, hexokinase2 (HK2) and pyruvate kinase isoenzyme M2 (PKM2) expressions. Adriamycin (ADR) cytotoxicity and apoptosis were assessed by MTT assay and flow cytometry, respectively. The changes of the protein kinase B (Akt) pathway were determined by Western blot analysis of phosphorylated-Akt (p-Akt) (ser473) and Akt. Our results showed that glycolysis was increased in HL60/ADR cells, as evidenced by the elevated glucose consumption and lactate production, as well as the increased HK2 and PKM2 expressions at mRNA and protein levels. TUG1 was up-regulated in HL60/ADR cells and TUG knockdown inhibited glycolysis. TUG1 knockdown enhanced ADR-induced cytotoxicity and apoptosis in HL60/ADR cells. TUG1 knockdown inhibited the Akt pathway and activation of the Akt pathway by 740Y-P attenuated the effects of TUG1 knockdown on ADR-induced cytotoxicity and apoptosis, as well as glycolysis in HL60/ADR cells. Taken together, TUG1 knockdown enhances adriamycin cytotoxicity in HL60/ADR cells via inhibiting the glycolysis by inactivating the Akt pathway.

Taurine-upregulated gene 1 (TUG1) has been reported as an oncogenic long non-coding RNA (lncRNA) in acute myeloid leukemia (AML).

Endocrine Resistance in Hormone Receptor Positive Breast Cancer-From Mechanism to Therapy

The importance and role of the estrogen receptor (ER) pathway has been well-documented in both breast cancer (BC) development and progression. The treatment of choice in women with metastatic breast cancer (MBC) is classically divided into a variety of endocrine therapies, 3 of the most common being: selective estrogen receptor modulators (SERM), aromatase inhibitors (AI) and selective estrogen receptor down-regulators (SERD). In a proportion of patients, resistance develops to endocrine therapy due to a sophisticated and at times redundant interference, at the molecular level between the ER and growth factor. The progression to endocrine resistance is considered to be a gradual, step-wise process. Several mechanisms have been proposed but thus far none of them can be defined as the complete explanation behind the phenomenon of endocrine resistance. Although multiple cellular, molecular and immune mechanisms have been and are being extensively studied, their individual roles are often poorly understood. In this review, we summarize current progress in our understanding of ER biology and the molecular mechanisms that predispose and determine endocrine resistance in breast cancer patients.

EG-VEGF silencing inhibits cell proliferation and promotes cell apoptosis in pancreatic carcinoma via PI3K/AKT/mTOR signaling pathway

OBJECTIVE

Pancreatic carcinoma (PC), one of the most prevalent and malignant tumors, has a poor prognosis and a high mortality rate. EG-VEGF, a vascular endothelial growth factor from endocrine glands, also termed as PROK1, has a high positive expression rate in PC tissues and is involved in the pathogenesis of various tumors. However, the expression and potential role of EG-VEGF in PC has not been thoroughly explored. The aim of this study was to better clarify the expression and potential role of EG-VEGF in pancreatic carcinoma.

METHODS

Immunohistochemical staining, western blotting, and RT-qPCR analysis were performed to detect the EG-VEGF level in PC tissues and cells. Subsequently, two short hairpin RNA (shRNA) lentiviral expression vector, shPROK1-1/shPROK1-2, were transfected into PANC-1 and BxPC-3 PC cell lines. MTT assay was used to determine cell proliferation. Meanwhile, flow cytometry assay was conducted to measure cell cycle and cell apoptosis. The protein levels of PI3K/AKT/mTOR pathway-related genes were also determined by western blotting.

RESULTS

EG-VEGF was aberrantly expressed in PC samples, as compared with paracancerous samples. Knockdown of PROK1 notably decreased the protein level of EG-VEGF, indicating a successful downregulation model of EG-VEGF. EG-VEGF silencing remarkably attenuated cell proliferation, while also induced G0/G1 arrest and magnified the extent of cell apoptosis. Further, EG-VEGF knockdown significantly inhibited PI3K/AKT/mTOR signaling pathway by downregulating p-PI3K, p-AKT, and p-mTOR levels.

CONCLUSION

This study identified the high-expression of EG-VEGF in pancreatic carcinoma tissues and cells, and demonstrated that EG-VEGF silencing inhibits the proliferation of PC cells and promotes apoptosis via regulating PI3K/AKT/mTOR pathway. Thus, EG-VEGF may become an essential target for the therapy of pancreatic cancer in the future.

Synthesis of xanthone derivatives and anti-hepatocellular carcinoma potency evaluation: induced apoptosis

Twenty-one xanthone derivatives (XDs) were synthesized by a microwave-assisted technique. Their in vitro inhibition potency against the growth of four cancer cell lines was evaluated. XD-1 ∼ [6,9,10-trihydroxy-3,3-dimethyl-5-(2-methylbut-3-en-2-yl)-3H,7H-pyrano[2,3-c]xanthen-7-one] was confirmed as the most active agent against HepG2 cell line growth with IC₅₀ of 18.6 ± 2.31 μM. Apoptosis analysis indicated different contributions of early/late apoptosis and necrosis to cell death for XD-1. XD-1 arrested HepG2 cells on the G0/G1 phase, as indicated by the decreased expressions of cyclin D and CDK2 and the increased expressions of p21. Western blot implied that XD-1 regulated p53/MDM2 to a better healthier state. Moreover, XD-1-induced cell apoptosis was mitochondrion-mediated, as evidenced by caspase activation and involved the PI3K/AKT/mTOR signaling pathway. All the evidence supports that XD-1 is a significant anti-cancer agent for HCC.

Twenty-one xanthone derivatives (XDs) were synthesized by a microwave-assisted technique.

Challenges facing antiangiogenesis therapy: The significant role of hypoxia-inducible factor and MET in development of resistance to anti-vascular endothelial growth factor-targeted therapies

It is now fully recognized that along with multiple physiological functions, angiogenesis is also involved in the fundamental process and pathobiology of several disorders including cancer. Recent studies have fully established the role of angiogenesis in cancer progression as well as invasion and metastasis. Consequently, many therapeutic agents such as monoclonal antibodies targeting angiogenesis pathway have been introduced in clinic with the hope for improving the outcomes of cancer therapy. Bevacizumab (Avastin®) was the first anti-vascular endothelial growth factor (VEGF) targeting monoclonal antibody developed with this purpose and soon received its accelerated US Food and Drug Administration (FDA) approval for treatment of patients with metastatic breast cancer in 2008. However, the failure to meet expecting results in different follow-up studies, forced FDA to remove bevacizumab approval for metastatic breast cancer. Investigations have now revealed that while suppressing VEGF pathway initially decreases tumor progression rate and vasculature density, activation of several interrelated pathways and signaling molecules following VEGF blockade compensate the insufficiency of VEGF and initially blocked angiogenesis, explaining in part the failure observed with bevacizumab single therapy. In present review, we introduce some of the main pathways and signaling molecules involved in angiogenesis and then propose how their interconnection may result in development of resistance to bevacizumab.

Synergistic Anticancer Effects of Curcumin and Hinokitiol on Gefitinib Resistant Non-Small Cell Lung Cancer Cells

This study evaluated the synergistic effect of curcumin (diferuloylmethane) and hinokitiol (β-thujaplicin), natural product derived phytochemicals, on gefitinib (Iressa) resistant non-small cell lung cancer (NSCLC) cells. Gefitinib, a tyrosine kinase inhibitor targeting epidermal growth factor receptor (EGFR), is widely used for lung cancer treatment. However, gefitinib resistance is easily acquired by NSCLC and followed by the development of progressive disease. Curcumin and hinokitiol are well-known bioactive compounds demonstrating anti-inflammation, anti-bacteria and anticancer effects. However, the effects of co-treatment of curcumin and hinokitiol on cancer cells have not been reported. Here, we postulated, for the first time, the possibility of combination therapy with curcumin and hinokitiol for treatment of gefitinib resistant NSCLC via increment of apoptosis and lysosomal enlargement.

Therapeutic Potency of PI3K Pharmacological Inhibitors of Gastrointestinal Cancer

Therapeutic targeting of phosphatidyl-inositol 3-kinase (PI3K) is considered as a possible strategy in several types of cancer, including gastrointestinal ones. In vitro and in vivo studies indicated the significance of proapoptotic and antiproliferative inhibition of PI3K. Although there are many phase 1 and 2 clinical trials on PI3K inhibitors in patients with gastrointestinal cancer, the molecular mechanism of PI3K targeting PI3K/ mTOR pathway is not clear. Panclass I, isoformselective, and dual PI3K/mTOR inhibitors are under investigation. This review aimed to indicate PI3K-dependent targeting mechanisms in gastrointestinal cancer and the evaluation of related clinical data.

Resveratrol Brain Delivery for Neurological Disorders Prevention and Treatment

Resveratrol (RES) is a natural polyphenolic non-flavonoid compound present in grapes, mulberries, peanuts, rhubarb and in several other plants. Numerous health effects have been related with its intake, such as anti-carcinogenic, anti-inflammatory and brain protective effects. The neuroprotective effects of RES in neurological diseases, such as Alzheimer's (AD) and Parkinson's (PD) diseases, are related to the protection of neurons against oxidative damage and toxicity, and to the prevention of apoptotic neuronal death. In brain cancer, RES induces cell apoptotic death and inhibits angiogenesis and tumor invasion. Despite its great potential as therapeutic agent for the treatment of several diseases, RES exhibits some limitations. It has poor water solubility and it is chemically instable, being degraded by isomerization once exposed to high temperatures, pH changes, UV light, or certain types of enzymes. Thus, RES has low bioavailability, limiting its biological and pharmacological benefits. To overcome these limitations, RES can be delivered by nanocarriers. This field of nanomedicine studies how the drug administration, pharmacokinetics, and pharmacodynamics are affected by the use of nanosized materials. The role of nanotechnology, in the prevention and treatment of neurological diseases, arises from the necessity to mask the physicochemical properties of therapeutic drugs to prolong the half-life and to be able to cross the blood-brain barrier (BBB). This can be achieved by encapsulating the drug in a nanoparticle (NP), which can be made of different kinds of materials. An increasing trend to encapsulate and direct RES to the brain has been observed. RES has been encapsulated in many different types of nanosystems, as liposomes, lipid and polymeric NPs. Furthermore, some of these nanocarriers have been modified with targeting molecules able to recognize the brain areas. Then, this article aims to overview the RES benefits and limitations in the treatment of neurological diseases, as the different nanotechnology strategies to overcome these limitations.

Anticancer activity of 2'-hydroxyflavanone towards lung cancer

In previous studies, we found that 2'-hydroxyflavonone (2HF), a citrus flavonoid, inhibits the growth of renal cell carcinoma in a VHL-dependent manner. This was associated with the inhibition of glutathione S-transferases (GSTs), the first step enzyme of the mercapturic acid pathway that catalyzes formation of glutathione-electrophile conjugates (GS-E). We studied 2HF in small cell (SCLC) and non-small cell (NSCLC) lung cancer cell lines for sensitivity to 2HF antineoplastic activity and to determine the role of the GS-E transporter Rlip (Ral-interacting protein; RLIP76; RALBP1) in the mechanism of action of 2HF. Our results show that 2HF induced apoptosis in both histological types of lung cancer and inhibited proliferation and growth through suppression of CDK4, CCNB1, PIK3CA, AKT and RPS6KB1 (P70S6K) signaling. Increased E-cadherin and reduced fibronectin and vimentin indicated inhibition of epithelial-mesenchymal transition. Additionally, 2HF inhibited efflux of doxorubicin and increased its accumulation in the cells, but did not add to the transport inhibitory effect of anti-Rlip antibodies alone. Binding of Rlip to 2HF was evident from successful purification of Rlip by 2HF affinity chromatography. Consistent with increased drug accumulation, combined treatment with 1-chloro-2, 4-dinitrobenzene, reduced the GI50 of 2HF by an order of magnitude. Results of in-vivo nude mouse xenograft studies of SCLC and NSCLC, which showed that orally administered 2HF inhibited growth of both histological types of lung cancer, confirmed in-vitro study results. Our result suggest that Rlip inhibition is likely a mechanism of action. Our findings are basis of proposing 2HF as therapeutic or preventative drug for lung cancer.

The critical role of AMPK in driving Akt activation under stress, tumorigenesis and drug resistance

PI3K/Akt signaling is activated in cancers and governs tumor initiation and progression, but how Akt is activated under diverse stresses is poorly understood. Here we identify AMPK as an essential regulator for Akt activation by various stresses. Surprisingly, AMPK is also activated by growth factor EGF through Ca2+/Calmodulin-dependent kinase and is essential for EGF-mediated Akt activation and biological functions. AMPK phosphorylates Skp2 at S256 and promotes the integrity and E3 ligase activity of Skp2 SCF complex leading to K63-linked ubiquitination and activation of Akt and subsequent oncogenic processes. Importantly, AMPK-mediated Skp2 S256 phosphorylation promotes breast cancer progression in mouse tumor models, correlates with Akt and AMPK activation in breast cancer patients, and predicts poor survival outcomes. Finally, targeting AMPK-mediated Skp2 S256 phosphorylation sensitizes cells to anti-EGF receptor targeted therapy. Our study sheds light on how stress and EGF induce Akt activation and new mechanisms for AMPK-mediated oncogenesis and drug resistance.

How Akt pathway is activated under stress is poorly understood. Here, the authors demonstrate the crucial role of AMPK for cellular stresses and growth factors- mediated Akt activation through a mechanism involving the E3 ubiquitin ligase Skp2 and Cullin-1.

Genetic Profiles Associated with Chemoresistance in Patient-Derived Xenograft Models of Ovarian Cancer

PURPOSE

Recurrence and chemoresistance (CR) are the leading causes of death in patients with high-grade serous carcinoma (HGSC) of the ovary. The aim of this study was to identify genetic changes associated with CR mechanisms using a patient-derived xenograft (PDX) mouse model and genetic sequencing.

MATERIALS AND METHODS

To generate a CR HGSC PDX tumor, mice bearing subcutaneously implanted HGSC PDX tumors were treated with paclitaxel and carboplatin. We compared gene expression and mutations between chemosensitive (CS) and CR PDX tumors with whole exome and RNA sequencing and selected candidate genes. Correlations between candidate gene expression and clinicopathological variables were explored using the Cancer Genome Atlas (TCGA) database and the Human Protein Atlas (THPA).

RESULTS

Three CR and four CS HGSC PDX tumor models were successfully established. RNA sequencing analysis of the PDX tumors revealed that 146 genes were significantly up-regulated and 54 genes down-regulated in the CR group compared with the CS group. Whole exome sequencing analysis showed 39 mutation sites were identified which only occurred in CR group. Differential expression of SAP25, HLA-DPA1, AKT3, and PIK3R5 genes and mutation of TMEM205 and POLR2A may have important functions in the progression of ovarian cancer chemoresistance. According to TCGA data analysis, patients with high HLA-DPA1 expression were more resistant to initial chemotherapy (p=0.030; odds ratio, 1.845).

CONCLUSION

We successfully established CR ovarian cancer PDX mouse models. PDX-based genetic profiling study could be used to select some candidate genes that could be targeted to overcome chemoresistance of ovarian cancer.

RETRACTED: miR-539 enhances chemosensitivity to cisplatin in non-small cell lung cancer by targeting DCLK1

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. An Expression of Concern for this article was previously published while an investigation was conducted (see related editorial: https://doi.org/10.1016/j.biopha.2022.113812). This retraction notice supersedes the Expression of Concern published earlier. Concern was raised about the reliability of the flow cytometry data in Figures 2C, 3C and 6C, which appear to contain similar features as found in other publications, as detailed here: https://pubpeer.com/publications/96CACC6C7EAE327217D2319DC364C5; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. Examples of suspected image duplication were also identified in Figures 4A+B, 6E+F, 7C. The journal requested the corresponding author comment on these concerns and provide the associated raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.