Lactate Decreases Bortezomib Sensitivity and Predicts Poor Clinical Outcomes of Multiple Myeloma

OBJECTIVE

Metabolic disorders are regarded as hallmarks of multiple myeloma (MM) and are responsible for rapid cancer cell proliferation and tumor growth. However, the exact biological roles of metabolites in MM cells have not been fully explored. This study aimed to explore the feasibility and clinical significance of lactate for MM and investigate the molecular mechanism of lactic acid (Lac) in the proliferation of myeloma cells and cell sensitivity to bortezomib (BTZ).

METHODS

Metabolomic analysis of the serum was carried out to obtain metabolites expression and clinical characteristics in MM patients. The CCK8 assay and flow cytometry were used to detect cell proliferation, apoptosis, and cell cycle changes. Western blotting was used to detect the potential mechanism and apoptosis- and cycle-related protein changes.

RESULTS

Lactate was highly expressed in both the peripheral blood and bone marrow of MM patients. It was significantly correlated with Durie-Salmon Staging (DS Staging) and the International Staging System (ISS Staging) and the serum and urinary involved/uninvolved free light chain ratios. Patients with relatively high lactate levels had a poor treatment response. Moreover, in vitro experiments showed that Lac could promote the proliferation of tumor cells and decrease the proportion of G0/G1-phase cells, which was accompanied by an increased proportion of S-phase cells. In addition, Lac could decrease tumor sensitivity to BTZ by disrupting the expression of nuclear factor kappa B subunit 2 (NFkB2) and RelB.

CONCLUSION

Metabolic changes are important in MM cell proliferation and treatment response; lactate could be used as a biomarker in MM and as a therapeutic target to overcome cell resistance to BTZ.

Cancer Antigen 125 Expression Enhances the Gemcitabine/Cisplatin-Resistant Tumor Microenvironment in Bladder Cancer

Cancer antigen 125 (CA125) is one of the mucin family proteins and is a serum tumor marker for various tumors, such as ovarian cancer, endometrial cancer, pancreatic cancer, and bladder cancer. CA125 is used to distinguish between benign and malignant tumors, monitor the response to chemotherapy, and detect relapse after initial treatment. Recently, CA125 was reported to be involved in chemoresistance through the physical characteristics of mucin or by modifying the immune tumor-microenvironment. However, the relationship between CA125 expression and chemoresistance in bladder cancer is still unclear. In this study, the clinicopathologic features of bladder cancer with CA125 expression and the status of the tumor-microenvironment related to gemcitabine/cisplatin resistance were investigated using publicly available data sets (Cancer Genome Atlas Expression, GSE169455 data set) from the cBioPortal website, the National Center for Biotechnology Information website, and an in-house case collection of bladder cancer. The cases with CA125 expression had poorer disease-free and overall survival rates than those without CA125 expression. A mucinous area surrounding cancer cells was frequently detected in cases with CA125 expression (81%; 13/16 cases). CA125 expression was also related to the immunosuppressive tumor-microenvironment through the infiltration of immunosuppressive immune cells, such as regulatory T cells and M2 macrophages. These results suggest that the status of tumor-microenvironment associated with CA125 is involved in gemcitabine/cisplatin resistance in bladder cancer.

Tumor Cell-Intrinsic CD96 Mediates Chemoresistance and Cancer Stemness by Regulating Mitochondrial Fatty Acid β-Oxidation

Targeting CD96 that originates in immune cells has shown potential for cancer therapy. However, the role of intrinsic CD96 in solid tumor cells remains unknown. Here, it is found that CD96 is frequently expressed in tumor cells from clinical breast cancer samples and is correlated with poor long-term prognosis in these patients. The CD96⁺ cancer cell subpopulations exhibit features of both breast cancer stem cells and chemoresistance. In vivo inhibition of cancer cell-intrinsic CD96 enhances the chemotherapeutic response in a patient-derived tumor xenograft model. Mechanistically, CD96 enhances mitochondrial fatty acid β-oxidation via the CD155-CD96-Src-Stat3-Opa1 pathway, which subsequently promotes chemoresistance in breast cancer stem cells. A previously unknown role is identified for tumor cell-intrinsic CD96 and an attractive target in improving the chemotherapeutic response.

Chitosan-Gelatin-EGCG Nanoparticle-Meditated LncRNA TMEM44-AS1 Silencing to Activate the P53 Signaling Pathway for the Synergistic Reversal of 5-FU Resistance in Gastric Cancer

Chemoresistance is one of the leading causes of therapeutic failure in gastric cancer (GC) treatment. Recent studies have shown lncRNAs play pivotal roles in regulating GC chemoresistance. Nanocarriers delivery of small interfering RNAs (siRNAs) to silence cancer-related genes has become a novel approach to cancer treatment research. However, finding target genes and developing nanosystems capable of selectively delivering siRNAs for disease treatment remains a challenge. In this study, a novel lncRNA TMEM44-AS1 that is related to 5-FU resistance is identified. TMEM44-AS1 has the ability to bind to and sponge miR-2355-5p, resulting in the upregulated PPP1R13L expression and P53 pathway inhibition. Next, a new nanocarrier called chitosan-gelatin-EGCG (CGE) is developed, which has a higher gene silencing efficiency than lipo2000, to aid in the delivery of a si-TMEM44-AS1 can efficiently silence TMEM44-AS1 expression to synergistically reverse 5-FU resistance in GC, leading to a markedly enhanced 5-FU therapeutic effect in a xenograft mouse model of GC. These findings indicate that TMEM44-AS1 may estimate 5-FU therapy outcome among GC cases, and that systemic si-TMEM44-AS1 delivery combined with 5-FU therapy is significant in the treatment of patients with recurrent GC.

Natural Products in Preventing Tumor Drug Resistance and Related Signaling Pathways

Drug resistance is still an obstacle in cancer therapy, leading to the failure of tumor treatment. The emergence of tumor drug resistance has always been a main concern of oncologists. Therefore, overcoming tumor drug resistance and looking for new strategies for tumor treatment is a major focus in the field of tumor research. Natural products serve as effective substances against drug resistance because of their diverse chemical structures and pharmacological effects. We reviewed the signaling pathways involved in the development of tumor drug resistance, including Epidermal growth factor receptor (EGFR), Renin-angiotensin system (Ras), Phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), Wnt, Notch, Transforming growth factor-beta (TGF-β), and their specific signaling pathway inhibitors derived from natural products. This can provide new ideas for the prevention of drug resistance in cancer therapy.

Endothelial p130cas confers resistance to anti-angiogenesis therapy

Anti-angiogenic therapies, such as anti-VEGF antibodies (AVAs), have shown promise in clinical settings. However, adaptive resistance to such therapies occurs frequently. We use orthotopic ovarian cancer models with AVA-adaptive resistance to investigate the underlying mechanisms. Genomic profiling of AVA-resistant tumors guides us to endothelial p130cas. We find that bevacizumab induces cleavage of VEGFR2 in endothelial cells by caspase-10 and that VEGFR2 fragments internalize into the nucleus and autophagosomes. Nuclear VEGFR2 and p130cas fragments, together with TNKS1BP1 (tankyrase-1-binding protein), initiate endothelial cell death. Blockade of autophagy in AVA-resistant endothelial cells retains VEGFR2 at the membrane with bevacizumab treatment. Targeting host p130cas with RGD (Arg-Gly-Asp)-tagged nanoparticles or genomic ablation of vascular p130cas in p130casflox/floxTie2Cre mice significantly extends the survival of mice with AVA-resistant ovarian tumors. Higher vascular p130cas is associated with shorter survival of individuals with ovarian cancer. Our findings identify opportunities for new strategies to overcome adaptive resistance to AVA therapy.

KHDRBS3 promotes paclitaxel resistance and induces glycolysis through modulated MIR17HG/CLDN6 signaling in epithelial ovarian cancer

Paclitaxel (PTX) resistance contributes to mortality in epithelial ovarian cancer (EOC). Aerobic glycolysis is elevated in the tumor environment and may influence resistance to PTX in EOC. KH domain-containing, RNA-binding signal transduction-associated protein 3 (KHDRBS3) is an RNA binding protein that is up-regulated in EOC, but its underlying mechanism in EOC is unclear. Here, we investigate the role of KHDRBS3 in glycolysis and increased resistance to PTX. Expression of KHDRBS3 and Claudin (CLDN6) were measured in EOC tissue and cells by quantitative real-time PCR, western blotting and immunohistochemistry. The biological functions of KHDRBS3, MIR17HG and CLDN6 were examined using MTT, colony formation, apoptosis and seahorse assays in vitro. For in vivo experiments, a xenograft model was used to investigate the effects of KHDRBS3 and MIR17HG in EOC. Here, we investigate the role of KHDRBS3 in glycolysis and increased resistance to PTX. The expression of KHDRBS3 was up-regulated in PTX-resistant cells. KHDRBS3 knockdown restrained the IC₅₀ of PTX, cell proliferation, colony formation and glycolysis in SKOV3-R and A2780-R cells in vitro and enhanced PTX sensitivity in a xenograft mouse model in vivo. KHDRBS3 interacts with lncRNA MIR17HG, which is down-regulated in EOC tissue and cells. The effect of KHDRBS3 overexpression on PTX resistance and glycolysis was rescued by MIR17HG overexpression. Additionally, MIR17HG interacts with the 3'UTR of CLDN6 and negatively regulates CLDN6 expression. MIR17HG overexpression suppressed the IC₅₀ of PTX and glycolysis by targeting CLDN6. Our results reveal a KHDRBS3-MIR17HG-CLDN6 regulatory axis that contributes to enhanced glycolysis in EOC and represents a potential target for therapy.

Emerging roles of CD133 in the treatment of gastric cancer, a novel stem cell biomarker and beyond

Gastric cancer (GC) is an aggressive disease with one of the highest mortality rates in the world. In the early stage, most patients are asymptomatic and early diagnosis is difficult. Recently, cancer stem cells (CSCs) have been highlighted as crucial emerging factors in the initiation or invasiveness of solid tumors. CD133, a CSC marker, is highly expressed in various tumors including gastric cancer. CD133-positive cells showed elevated malignant biological behaviors and CD133 upregulation is related to chemoresistance, cancer relapse, and poor prognosis. CD133 also plays an important role in the progression of tumors and metastasis. This review summarizes the current knowledge of the role of CD133 expression in GC and aims to contribute at identifying promising new strategies for treatment and management of gastric cancer.

A review of research progress on mechanisms and overcoming strategies of acquired osimertinib resistance

Targeted therapy with epidermal growth factor receptor tyrosine kinase inhibitors(EGFR-TKIs) is the standard first-line treatment for advanced EGFR-mutated non-small cell lung cancer (NSCLC). Third-generation EGFR-TKIs, represented by osimertinib, have been approved to overcome the EGFR T790M mutation in patients who are resistant to first- or second-generation TKIs, which brings more survival benefits for patients with advanced NSCLC. However, resistance to the third generation of EGFR-TKIs is still inevitable. Acquired drug resistance is the main reason for limiting the long-term effectiveness of targeted therapy in EGFR-mutated NSCLC patients. The mechanism of EGFR-TKI resistance of the third generation has become a focus of research in the field of targeted therapy. In this review, we summarize the research progress in resistance mechanisms of advanced NSCLC to osimertinib and the potential overcoming strategies and hope to provide a clinical basis and ideas for precision treatment of NSCLC.

Warburg and pasteur phenotypes modulate cancer behavior and therapy

Energetic pathways combine in the heart of metabolism. These essential routes supply energy for biochemical processes through glycolysis and oxidative phosphorylation. Moreover, they support the synthesis of various biomolecules employed in growth and survival over branching pathways. Yet, cellular energetics are often misguided in cancers as a result of the mutations and altered signaling. As nontransformed and Pasteur-like cells metabolize glucose through oxidative respiration when only oxygen is sufficient, some cancer cells bypass this metabolic switch and run glycolysis at higher rates even in the presence of oxygen. The phenomenon is called aerobic glycolysis or the Warburg effect. An increasing number of studies indicate that both Warburg and Pasteur phenotypes are recognized in the cancer microenvironment and take vital roles in the regulation of drug resistance mechanisms such as redox homeostasis, apoptosis and autophagy. Therefore, the different phenotypes call for different therapeutic approaches. Combined therapies targeting energy metabolism grant new opportunities to overcome the challenges. Nevertheless, new biomarkers emerge to classify the energetic subtypes, thereby the cancer therapy, as our knowledge in coupling energy metabolism with cancer behavior grows.

Circular RNA circ-RNF121 contributes to cisplatin (DDP) resistance of non-small-cell lung cancer cells by regulating the miR-646/SOX4 axis

Chemo-resistance is considered a major obstacle in the clinical treatment of non-small-cell lung cancer (NSCLC). Circular RNA (circRNA) circ-RNF121 (hsa_circ_0023404) has been identified to be related to the cisplatin (DDP) resistance. However, the role and mechanism of circ-RNF121 in the DDP resistance in NSCLC are still unknown. Real-time quantitative PCR (RT-qPCR) was applied to detect the levels of circ-RNF121, microRNA-646 (miR-646) and SRY-related HMG box transcription factor 4 (SOX4). Cell viability, proliferation, apoptosis, migration, invasion and cell cycle progression were assessed by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT), colony formation, flow cytometry, wound-healing, transwell and flow cytometry assays, severally. The binding relationship between miR-646 and circ-RNF121 or SOX4 was predicted by the circular RNA interactome or Target Scan Human7.2 and then verified by a dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. SOX4 protein level was measured by western blot assay. The biological role of circ-RNF121 on NSCLC tumor growth and drug resistance was examined by the xenograft tumor model in vivo. Circ-RNF121 and SOX4 were increased, and miR-646 was declined in DDP-resistant NSCLC tissues and cells. Furthermore, the circ-RNF121 deficiency could enhance DDP sensitivity by inhibiting cell proliferation, migration, invasion, cell cycle progression and promoting apoptosis in DDP-resistant NSCLC cells in vitro. Mechanically, circ-RNF121 served as a sponge of miR-646 to increase SOX4 expression. Circ-RNF121 knockdown improved the drug sensitivity of NSCLC in vivo. Circ-RNF121 silencing could reduce the DDP resistance of NSCLC cells by regulating SOX4 expression via miR-646. These findings hinted at a promising therapeutic target for NSCLC treatment.

Targeting AKT in ER-Positive HER2-Negative Metastatic Breast Cancer: From Molecular Promises to Real Life Pitfalls?

The AKT protein kinase plays a central role in several interconnected molecular pathways involved in growth, apoptosis, angiogenesis, and cell metabolism. It thereby represents a therapeutic target, especially in hormone receptor-positive (HR) breast cancers, where the PI3K/AKT signaling pathway is largely hyperactivated. Moreover, resistance to therapeutic classes, including endocrine therapy, is associated with the constitutive activation of the PI3K/AKT pathway. Improved knowledge on the molecular mechanisms underlying resistance to endocrine therapy has led to the diversification of the therapeutic arsenal, notably with the development of PI3K and mTOR inhibitors, which are currently approved for the treatment of advanced HR-positive breast cancer patients. AKT itself constitutes a novel pharmacological target for which AKT inhibitors have been developed and tested in clinical trials. However, despite its pivotal role in cell survival and anti-apoptotic mechanisms, as well as in endocrine therapy resistance, few drugs have been developed and are available for clinical practice. The scope of the present review is to focus on the pivotal role of AKT in metastatic breast cancer through the analysis of its molecular features and to discuss clinical implications and remaining challenges in the treatment of HR-positive metastatic breast cancer.

Exploring the clinical value of tumor microenvironment in platinum-resistant ovarian cancer

Platinum resistance in epithelial ovarian cancer (OvCa) is rising at an alarming rate, with recurrence of chemo-resistant high grade serous OvCa (HGSC) in roughly 75 % of all patients. Additionally, HGSC has an abysmal five-year survival rate, standing at 39 % and 17 % for FIGO stages III and IV, respectively. Herein we review the crucial cellular interactions between HGSC cells and the cellular and non-cellular components of the unique peritoneal tumor microenvironment (TME). We highlight the role of the extracellular matrix (ECM), ascitic fluid as well as the mesothelial cells, tumor associated macrophages, neutrophils, adipocytes and fibroblasts in platinum-resistance. Moreover, we underscore the importance of other immune-cell players in conferring resistance, including natural killer cells, myeloid-derived suppressive cells (MDSCs) and T-regulatory cells. We show the clinical relevance of the key platinum-resistant markers and their correlation with the major pathways perturbed in OvCa. In parallel, we discuss the effect of immunotherapies in re-sensitizing platinum-resistant patients to platinum-based drugs. Through detailed analysis of platinum-resistance in HGSC, we hope to advance the development of more effective therapy options for this aggressive disease.

Overcoming Microenvironment-Mediated Chemoprotection through Stromal Galectin-3 Inhibition in Acute Lymphoblastic Leukemia

Environmentally-mediated drug resistance in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) significantly contributes to relapse. Stromal cells in the bone marrow environment protect leukemia cells by secretion of chemokines as cues for BCP-ALL migration towards, and adhesion to, stroma. Stromal cells and BCP-ALL cells communicate through stromal galectin-3. Here, we investigated the significance of stromal galectin-3 to BCP-ALL cells. We used CRISPR/Cas9 genome editing to ablate galectin-3 in stromal cells and found that galectin-3 is dispensable for steady-state BCP-ALL proliferation and viability. However, efficient leukemia migration and adhesion to stromal cells are significantly dependent on stromal galectin-3. Importantly, the loss of stromal galectin-3 production sensitized BCP-ALL cells to conventional chemotherapy. We therefore tested novel carbohydrate-based small molecule compounds (Cpd14 and Cpd17) with high specificity for galectin-3. Consistent with results obtained using galectin-3-knockout stromal cells, treatment of stromal-BCP-ALL co-cultures inhibited BCP-ALL migration and adhesion. Moreover, these compounds induced anti-leukemic responses in BCP-ALL cells, including a dose-dependent reduction of viability and proliferation, the induction of apoptosis and, importantly, the inhibition of drug resistance. Collectively, these findings indicate galectin-3 regulates BCP-ALL cell responses to chemotherapy through the interactions between leukemia cells and the stroma, and show that a combination of galectin-3 inhibition with conventional drugs can sensitize the leukemia cells to chemotherapy.

Addressing Resistance to Targeted Therapies in Metastatic Colorectal Cancer

Metastatic colorectal cancer (mCRC) is the second most common cause of cancer-related death worldwide. In the mid-1980s, the median overall survival (OS) for patients with mCRC ranged from 10 to 12 months from the time of initial diagnosis. In more recent studies, this median has more than doubled and is commonly reported at more than 25 to 30 months. These improvements are due, in large part, to the introduction of multiple novel agents during the last 3 decades. Despite these improvements, however, nearly all patients treated with palliative chemotherapy will eventually develop resistance and ultimately succumb to progression of metastatic disease. Understanding the mechanisms by which malignant cells evade treatment could unlock novel therapeutic strategies that overcome resistance and improve survival. In this review, we will discuss some of the drivers of therapeutic resistance in patients with mCRC and present some novel strategies to overcome resistance.

Role of PI3K-AKT-mTOR Pathway as a Pro-Survival Signaling and Resistance-Mediating Mechanism to Therapy of Prostate Cancer

Androgen deprivation therapy (ADT) and androgen receptor (AR)-targeted therapy are the gold standard options for treating prostate cancer (PCa). These are initially effective, as localized and the early stage of metastatic disease are androgen- and castration-sensitive. The tumor strongly relies on systemic/circulating androgens for activating AR signaling to stimulate growth and progression. However, after a certain point, the tumor will eventually develop a resistant stage, where ADT and AR antagonists are no longer effective. Mechanistically, it seems that the tumor becomes more aggressive through adaptive responses, relies more on alternative activated pathways, and is less dependent on AR signaling. This includes hyperactivation of PI3K-AKT-mTOR pathway, which is a central signal that regulates cell pro-survival/anti-apoptotic pathways, thus, compensating the blockade of AR signaling. The PI3K-AKT-mTOR pathway is well-documented for its crosstalk between genomic and non-genomic AR signaling, as well as other signaling cascades. Such a reciprocal feedback loop makes it more complicated to target individual factor/signaling for treating PCa. Here, we highlight the role of PI3K-AKT-mTOR signaling as a resistance mechanism for PCa therapy and illustrate the transition of prostate tumor from AR signaling-dependent to PI3K-AKT-mTOR pathway-dependent. Moreover, therapeutic strategies with inhibitors targeting the PI3K-AKT-mTOR signal used in clinic and ongoing clinical trials are discussed.

Exosomal miR-27a-3p derived from tumor-associated macrophage suppresses propranolol sensitivity in infantile hemangioma

Propranolol is the first-line drug for infantile hemangioma (IH) therapy, whereas propranolol resistance is clinically observed. Tumor-associated macrophages (TAMs)-derived exosomes may deliver biological molecules to promote tumor progression. Here, we aimed to investigate the relationship between TAMs-derived exosomal miR-27a-3p and propranolol sensitivity in IH. Human peripheral blood monocytes (PBMCs) were cultured with macrophage colony-stimulating factor (M-CSF) for 7 days to get unactivated macrophages (Un-Mac), which were further treated with IL-4 and IL-13 to induce M2 polarized macrophages. Exosomes were isolated from the conditioned medium of M2 macrophage, followed by identification. Cell co-culture and/or transfection were performed to explore whether M2 polarized macrophage-derived exosomes (M2-exos) could mediate the crosstalk between TAMs-derived miR-27a-3p and hemangioma stem cells (HemSCs). In addition, nude mice were subcutaneously transplanted with HemSCs pretreated with or without M2-Exos to examine the effects of M2-Exos on IH in vivo. M2 polarized macrophages inhibited propranolol sensitivity of HemSCs, as shown by the increased cell viability and decreased apoptosis. miR-27a-3p was upregulated in M2 polarized macrophages and M2-Exos. Moreover, M2-exos delivered miR-27a-3p from macrophages to HemSCs and subsequently reduced propranolol sensitivity. Luciferase reporter and biotin-RNA pulldown assay proved that dickkopf-related protein 2 (DKK2) was the direct target of miR-27a-3p. These results demonstrate that M2-exos could deliver miR-27a-3p from macrophages to HemSCs to reduce the sensitivity of HemSCs to propranolol by down-regulating DKK2 expression, and exosomal miR-27a-3p and DKK2 in HemSCs could be considered as treatment targets.

Effect of EPA on Hsp90 and GRα protein expression in multiple myeloma drug-resistant cells

BACKGROUND

Approximately 20% of MM patients harbor glucocorticoid (GC) resistance and are not responsive to therapeutic effect. Chaperoneheat-shock proteins Hsp90 is needed for ligand docking, The imbalance of Hsp90/GRα (glucocorticoid receptor α) may be an important cause of GC resistance. Recent studies have indicated that EPA could repress cancer cell growth by regulating critical influential factors in progression of cancer, consisting of resistance to drugs, chemosensitivity. The aim of the present study was to test the cytotoxic effects of EPA alone or EPA + Dexamethasone in dexamethasone-resistant MM cell (MM.1R) and investigate whether DHA can induce apoptosis and reverse acquired glucocorticoid resistance in dexamethasone-resistant MM cell (MM.1R).

METHODS

Cell Counting Kit-8 (CCK-8) was used to detect the proliferation of MM.1R cells after treating with EPA alone and EPA combined with DEX. Mitochondrial membrane potential was measured by flow cytometry and GRα and Hsp90 protein expression were assessed by western blot analysis.

RESULTS

EPA alone was able to inhibit cell proliferation as evidenced by CCK-8 assay and the tumor growth was remarkably suppressed by EPA + Dexamethasone, Cell apoptosis after EPA treatment was obviously observed by Flow cytometry analysis of the mitochondrial membrane potential. Analysis of Hsp90 and GRα proteins in MM.1R cells incubated with EPA revealed down-regulation of Hsp90 and up-regulation of GRα. Accordingly, the Hsp90/GRα ratio was significantly decreased with the increase of EPA concentration.

CONCLUSIONS

EPA might be used as a new effective treatment for reversal of glucocorticoid-resistance in multiple myeloma.

Fatty acid oxidation and autophagy promote endoxifen resistance and counter the effect of AKT inhibition in ER-positive breast cancer cells

Tamoxifen (TAM) is the first-line endocrine therapy for estrogen receptor-positive (ER+) breast cancer (BC). However, acquired resistance occurs in ∼50% cases. Meanwhile, although the PI3K/AKT/mTOR pathway is a viable target for treatment of endocrine therapy-refractory patients, complex signaling feedback loops exist, which can counter the effectiveness of inhibitors of this pathway. Here, we analyzed signaling pathways and metabolism in ER+ MCF7 BC cell line and their TAM-resistant derivatives that are co-resistant to endoxifen using immunoblotting, quantitative polymerase chain reaction, and the Agilent Seahorse XF Analyzer. We found that activation of AKT and the energy-sensing kinase AMPK was increased in TAM and endoxifen-resistant cells. Furthermore, ERRα/PGC-1β and their target genes MCAD and CPT-1 were increased and regulated by AMPK, which coincided with increased fatty acid oxidation (FAO) and autophagy in TAM-resistant cells. Inhibition of AKT feedback-activates AMPK and ERRα/PGC-1β-MCAD/CPT-1 with a consequent increase in FAO and autophagy that counters the therapeutic effect of endoxifen and AKT inhibitors. Therefore, our results indicate increased activation of AKT and AMPK with metabolic reprogramming and increased autophagy in TAM-resistant cells. Simultaneous inhibition of AKT and FAO/autophagy is necessary to fully sensitize resistant cells to endoxifen.

Drug resistance in pituitary tumours: from cell membrane to intracellular signalling

The pharmacological treatment of pituitary tumours is based on the use of stable analogues of somatostatin and dopamine. The analogues bind to somatostatin receptor types 2 and 5 (SST2 and SST5) and dopamine receptor type 2 (DRD2), respectively, and generate signal transduction cascades in cancerous pituitary cells that culminate in the inhibition of hormone secretion, cell growth and invasion. Drug resistance occurs in a subset of patients and can involve different steps at different stages, such as following receptor activation by the agonist or during the final biological responses. Although the expression of somatostatin and dopamine receptors in cancer cells is a prerequisite for these drugs to reach a biological effect, their presence does not guarantee the success of the therapy. Successful therapy also requires the proper functioning of the machinery of signal transduction and the finely tuned regulation of receptor desensitization, internalization and intracellular trafficking. The present Review provides an updated overview of the molecular factors underlying the pharmacological resistance of pituitary tumours. The Review discusses the experimental evidence that supports a role for receptors and intracellular proteins in the function of SSTs and DRD2 and their clinical importance.

CUL4high Lung Adenocarcinomas Are Dependent on the CUL4-p21 Ubiquitin Signaling for Proliferation and Survival

Cullin (CUL) 4A and 4B ubiquitin ligases are often highly accumulated in human malignant neoplasms and are believed to possess oncogenic properties. However, the underlying mechanisms by which CUL4A and CUL4B promote pulmonary tumorigenesis remain largely elusive. This study reports that CUL4A and CUL4B are highly expressed in patients with non-small cell lung cancer (NSCLC), and their high expression is associated with disease progression, chemotherapy resistance, and poor survival in adenocarcinomas. Depletion of CUL4A (CUL4Ak/d) or CUL4B (CUL4Bk/d) leads to cell cycle arrest at G1 and loss of proliferation and viability of NSCLC cells in culture and in a lung cancer xenograft model, suggesting that CUL4A and 4B are oncoproteins required for tumor maintenance of certain NSCLCs. Mechanistically, increased accumulation of the cell cycle-dependent kinase inhibitor p21/Cip1/WAF1 was observed in lung cancer cells on CUL4 silencing. Knockdown of p21 rescued the G1 arrest of CUL4Ak/d or CUL4Bk/d NSCLC cells, and allowed proliferation to resume. These findings reveal that p21 is the primary downstream effector of lung adenocarcinoma dependence on CUL4, highlight the notion that not all substrates respond equally to abrogation of the CUL4 ubiquitin ligase in NSCLCs, and imply that CUL4Ahigh/CUL4Bhigh may serve as a prognostic marker and therapeutic target for patients with NSCLC.

Battling Chemoresistance in Cancer: Root Causes and Strategies to Uproot Them

With nearly 10 million deaths, cancer is the leading cause of mortality worldwide. Along with major key parameters that control cancer treatment management, such as diagnosis, resistance to the classical and new chemotherapeutic reagents continues to be a significant problem. Intrinsic or acquired chemoresistance leads to cancer recurrence in many cases that eventually causes failure in the successful treatment and death of cancer patients. Various determinants, including tumor heterogeneity and tumor microenvironment, could cause chemoresistance through a diverse range of mechanisms. In this review, we summarize the key determinants and the underlying mechanisms by which chemoresistance appears. We then describe which strategies have been implemented and studied to combat such a lethal phenomenon in the management of cancer treatment, with emphasis on the need to improve the early diagnosis of cancer complemented by combination therapy.

Evolutionary predictability of genetic versus nongenetic resistance to anticancer drugs in melanoma

Therapy resistance arises from heterogeneous drug-tolerant persister cells or minimal residual disease (MRD) through genetic and nongenetic mechanisms. A key question is whether specific molecular features of the MRD ecosystem determine which of these two distinct trajectories will eventually prevail. We show that, in melanoma exposed to mitogen-activated protein kinase therapeutics, emergence of a transient neural crest stem cell (NCSC) population in MRD concurs with the development of nongenetic resistance. This increase relies on a glial cell line-derived neurotrophic factor-dependent signaling cascade, which activates the AKT survival pathway in a focal adhesion kinase (FAK)-dependent manner. Ablation of the NCSC population through FAK inhibition delays relapse in patient-derived tumor xenografts. Strikingly, all tumors that ultimately escape this treatment exhibit resistance-conferring genetic alterations and increased sensitivity to extracellular signal-regulated kinase inhibition. These findings identify an approach that abrogates the nongenetic resistance trajectory in melanoma and demonstrate that the cellular composition of MRD deterministically imposes distinct drug resistance evolutionary paths.

Molecular Mechanism Mediating Cytotoxic Activity of Cabazitaxel in Docetaxel-resistant Human Prostate Cancer Cells

BACKGROUND/AIM

Cabazitaxel is known to be effective in patients with castration-resistant prostate cancer (CRPC) showing resistance to docetaxel. The objective of this study was to investigate the molecular mechanism mediating cytotoxic activity of cabazitaxel in docetaxel-resistant human CRPC cells.

MATERIALS AND METHODS

Parental human CRPC cell line PC3 (PC3/P) was continuously exposed to increasing doses of docetaxel, and a cell line resistant to docetaxel, PC3/R, was developed. Phenotypic differences between these cell lines were investigated.

RESULTS

There were no significant differences in sensitivity to cabazitaxel between PC3/P and PC3/R. In PC3/P, both docetaxel and cabazitaxel markedly inhibited the phosphorylation of AKT serine/threonine kinase 1 (AKT) and p44/42 mitogen-activated protein kinase (MAPK). In PC3/R, however, phosphorylation of AKT and p44/42 MAPK were maintained following treatment with docetaxel, whereas treatment with cabazitaxel resulted in the marked down-regulation of phosphorylation of AKT but not that of p44/42 MAPK. Furthermore, additional treatment of PC3/R with a specific inhibitor of AKT significantly enhanced the cytotoxic activity of docetaxel but not that of cabazitaxel. Growth of PC3/R in nude mice after treatment with cabazitaxel was significantly inhibited compared with that after treatment with docetaxel.

CONCLUSION

Antitumor activity of cabazitaxel in docetaxel-resistant CRPC cells was explained, at least in part, by the inactivation of persistently phosphorylated AKT even after treatment with docetaxel.

Nuclear Her2 contributes to paclitaxel resistance in breast cancer cells

Translocation of full-length Her2 receptor into nucleus was reported by some studies. Here, we tested whether nuclear Her2 contributes to paclitaxel resistance in Her2-overexpressing breast cancer cells. Breast cancer cell was transfected with plasmids containing cDNA of wild-type Her2 or mutant-type Her2 lacking the nuclear localization signal (NLS) sequence which is required for Her2 nuclear transport. Cell resistance to paclitaxel was analyzed. Paclitaxel-resistant breast cancer cell was also developed and nuclear Her2 expression was tested. Then, correlation between nuclear Her2 and resistance to paclitaxel were analyzed. Expression of importin β1 was decreased to downregulate nuclear Her2 level and cell resistance to paclitaxel was tested. We found that Her2 overexpression increases Her2 nuclear expression and cells resistance to paclitaxel in MCF-7 cells. In the paclitaxel resistant cell (SK-BR-3/R), nuclear Her2 expression is upregulated compared with parental SK-BR-3 cells. Increased expression of nuclear Her2 after short-time (48 h) treatment of paclitaxel was also observed in SK-BR-3 cells. Further downregulation of Her2 nuclear expression through blocking expression of importin β1 sensitizes the cells to paclitaxel. The analysis showed that the Her2 nuclear expression increases the survivin expression which leads to resistance to paclitaxel. Her2 nuclear expression decreases paclitaxel-induced apoptosis. However, co-immunoprecipitation was applied, and the physical interaction of nuclear Her2 and survivin was not detected. We show for the first time that nuclear Her2 contributes to paclitaxel resistance in breast cancer cells which suggests that nuclear Her2 as a potential target to sensitize breast cancers to paclitaxel treatment.

Role of epidermal growth factor receptor signaling in a Pt(II)-resistant human breast cancer cell line

Platinum complexes are currently used for breast cancer therapy, but, as with other drug classes, a series of intrinsic and acquired resistance mechanisms hinder their efficacy. To better understand the mechanisms underlying platinum complexes resistance in breast cancer, we generated a [Pt(O,O'-acac)(γ-acac)(DMS)]-resistant MCF-7, denoted as [Pt(acac)₂]R. [Pt(O,O'-acac)(γ-acac)(DMS)] was chosen as previous works showed that it has distinct mechanisms of action from cisplatin, especially with regard to cellular targets. [Pt(acac)₂]R cells are characterized by increased proliferation rates and aggressiveness with higher PKC-δ, BCL-2, MMP-9 and EGFR protein expressions and also by increased expression of various genes covering cell cycle regulation, invasion, survival, and hormone receptors. These [Pt(acac)₂]R cells also displayed high levels of activated signaling kinases Src, AKT and ERK/2. [Pt(acac)₂]R cells incubated with [Pt(O,O'-acac)(γ-acac)(DMS)], showed a relevant EGFR activation due to PKC-δ and Src phosphorylation that provoked proliferation and survival through MERK1/2/ERK1/2 and PI3K/Akt pathways. In addition, EGFR shuttled from the plasma membrane to the nucleus maybe acting as co-transcriptional factor. The data suggest that growth and survival of resistant cells rely upon a remarkable increase in EGFR level which, in collaboration with an enhanced role of PKC-δ and Src kinases support [Pt(acac)₂]R cell. It could therefore be assumed that combination treatments targeting both EGFR and PKC-δ/Src can improve therapy for breast cancer patients.

Cisplatin induces autophagy-associated apoptosis in human oral squamous cell carcinoma (OSCC) mediated in part through reactive oxygen species

Oral Squamous Cell Carcinoma (OSCC) is the sixth most common cancer worldwide. Chemoresistance is a critical problem in OSCC leading to therapeutic failure and tumour recurrence. Recently, autophagy has acquired an emerging interest in cancer as it has been shown to be frequently activated in tumour cells treated with chemotherapeutics. Whether drug-induced autophagy represents a mechanism that allows cancer cells to survive or a pro-death mechanism associated with apoptosis remains controversial. This study evaluated the cellular response to cisplatin and the role of autophagy in mediating cisplatin resistance in OSCC cells. Our results demonstrated that cisplatin concurrently induced apoptosis and autophagy in OSCC cell lines partially through the ROS/JNK pathway. Moreover, inhibition of cisplatin-induced apoptosis abrogated autophagy, indicating a complex interplay between these pathways. Cisplatin-induced autophagy does not appear to elicit a pro-survival effect in OSCC as early-stage autophagy inhibition, using either a pharmacological inhibitor or knockdown of the key autophagy protein ATG5, did not sensitise cells to cisplatin. Additionally, autophagy did not play a role in acquired resistance to cisplatin in our novel cisplatin-resistant OSSC cell line (SCC-4cisR) obtained by pulsed stepwise exposure of SCC-4 cells to cisplatin (~14-fold change in sensitivity). There was no change in the basal levels of autophagy in the SCC-4cisR cells compared to the SCC-4 cells. Furthermore, a significant increase in cisplatin-induced autophagy was observed only in the SCC-4 cells, but not in the derived SCC-4cisR cells. Collectively, these data indicate that autophagy may not be implicated in acquired cisplatin resistance in OSCC.

RNF38 enhances 5-Fluorouracil resistance in colorectal cancer by activating the Wnt pathway

PURPOSE

Colorectal cancer (CRC) is a frequent fatal cancer worldwide. 5-Fluorouracil (5-FU) is extensively used in its chemotherapy. This drug resistance, however, should be well concerned. Ring finger proteins (RNF) are vital regulators involved in CRC development. In this article, HCT116R cells were first established. The roles of RNF38 and Wnt signaling in 5-FU-resistant CRC were further illustrated. Our study provides novel evidence for improving 5-FU chemotherapy outcome in CRC patients.

METHODS

The phenotype of established HCT116R cells was first examined. Next, the regulatory effect of RNF38 on 5-FU resistance in CRC was mainly explored. Nude mice bearing CRC were treated with 5-FU and in vivo overexpression of RNF38.

RESULTS

5-FU-resistant HCT-116 cells (HCT116R) were first established. 5-FU treatment markedly killed survival and induced apoptosis in HCT-116 cells. P53 was downregulated in HCT116R cells. Through microarray analysis, RNF38 was found to be upregulated in HCT116R cells compared to parental cells.

CONCLUSIONS

Overexpression of RNF38 enhanced 5-FU resistance in CRC. Furthermore, Wnt signaling was activated by RNF38 and involved in 5-FU resistance in CRC.

Identification of microRNAs that promote erlotinib resistance in non-small cell lung cancer

Lung cancer is the leading cause of cancer-related deaths, demanding improvement in current treatment modalities to reduce the mortality rates. Lung cancer is divided into two major classes with non-small cell lung cancer representing ~84% of lung cancer cases. One strategy widely used to treat non-small cell lung cancer patients includes targeting the epidermal growth factor receptor (EGFR) using EGFR-inhibitors, such as erlotinib, gefitinib, and afatinib. However, most patients develop resistance to EGFR-inhibitors within a year post-treatment. Although some mechanisms that drive resistance to EGFR-inhibitors have been identified, there are many cases in which the mechanisms are unknown. Thus, in this study, we examined the role of microRNAs in driving EGFR-inhibitor resistance. As mediators of critical pro-growth pathways, microRNAs are severely dysregulated in multiple diseases, including non-small cell lung cancer where microRNA dysregulation also contributes to drug resistance. In this work, through screening of 2019 mature microRNAs, multiple microRNAs were identified that drive EGFR-inhibitor resistance in non-small cell lung cancer cell lines, including miR-432-5p.

The Role of BCL-2 Proteins in the Development of Castration-resistant Prostate Cancer and Emerging Therapeutic Strategies

The development of androgen resistance in advanced prostate cancer remains a challenging clinical problem. Because androgen deprivation therapy constitutes the backbone of first-line treatments for metastatic prostate cancer, the phenotypic switch from an androgen-dependent to an androgen-independent growth state limits the treatment options for these patients. This critical change from an androgen-dependent to an androgen-independent growth state can be regulated by the B-cell lymphoma gene 2 (BCL-2) family of apoptotic proteins. While the roles of BCL-2 protein family members in the carcinogenesis of prostate cancer have been well-studied, emerging data also delineates their modulation of disease progression to castration-resistant prostate cancer (CRPC). Over the past 2 decades, investigators have sought to describe the mechanisms that underpin this development at the molecular level, yet no recent literature has consolidated these findings in a dedicated review. As new classes of BCL-2 family inhibitors are finding indications for other cancer types, it is time to evaluate how such agents might find stable footing for the treatment of CRPC. Several trials to date have investigated BCL-2 inhibitors as therapeutic agents for CRPC. These therapies include selective BCL-2 inhibitors, pan-BCL-2 inhibitors, and novel inhibitors of MCL-1 and BCL-XL. This review details the research regarding the role of BCL-2 family members in the pathogenesis of prostate cancer and contextualizes these findings within the contemporary landscape of prostate cancer treatment.

Suppression MGP inhibits tumor proliferation and reverses oxaliplatin resistance in colorectal cancer

Matrix Gla protein (MGP), an extracellular matrix protein, has been widely reported to participate in the tumorigenic process and is abnormally expressed in several tumors. However, the role of MGP in colorectal cancer (CRC) remains unknown. Chemotherapy resistance represents a significant limitation in the treatment of CRC. Here, a comprehensive bioinformatics analysis revealed that MGP, which is overexpressed in CRC, might act as one of the critical genes conferring resistance to oxaliplatin (OXA). Furthermore, we found that MGP overexpression in tumor tissue might be correlated with cancer stage and patient prognosis, consistent with the bioinformatics analysis. The upregulation of MGP may act as an independent risk factor for CRC. The knockdown of MGP or inhibition of MGP expression significantly increased the sensitivity of the CRC cell lines to OXA. Suppression of MGP may reverse OXA resistance by upregulating copper transporter 1 (CTR1) and downregulating ATP7A and ATP7B. When used in combination with OXA, the inhibition of MGP reduced cancer cell proliferation, invasion, and migration and increased cell apoptosis in vitro. Suppression of MGP or OXA treatment alone significantly inhibited tumor growth in the CRC mouse model. Additionally, we found that OXA might promote the antitumor immune response in vivo. In summary, our study is the first to provide evidence that MGP expression confers OXA chemotherapy resistance in CRC and provides novel strategies to overcome chemotherapy resistance in CRC.

MicroRNAs are involved in the development and progression of gastric cancer

MicroRNAs (miRNAs) are recognized as an essential component of the RNA family, exerting multiple and intricate biological functions, particularly in the process of tumorigenesis, proliferation, and metastatic progression. MiRNAs are altered in gastric cancer (GC), showing activity as both tumor suppressors and oncogenes, although their true roles have not been fully understood. This review will focus upon the recent advances of miRNA studies related to the regulatory mechanisms of gastric tumor cell proliferation, apoptosis, and cell cycle. We hope to provide an in-depth insight into the mechanistic role of miRNAs in GC development and progression. In particular, we summarize the latest studies relevant to miRNAs' impact upon the epithelial-mesenchymal transition, tumor microenvironment, and chemoresistance in GC cells. We expect to elucidate the molecular mechanisms involving miRNAs for better understanding the etiology of GC, and facilitating the development of new treatment regimens for the treatment of GC.

Phase II Multicenter Study of Enzalutamide in Metastatic Castration-Resistant Prostate Cancer to Identify Mechanisms Driving Resistance

PURPOSE

Enzalutamide is a second-generation androgen receptor (AR) inhibitor that has improved overall survival (OS) in metastatic castration-resistant prostate cancer (CRPC). However, nearly all patients develop resistance. We designed a phase II multicenter study of enzalutamide in metastatic CRPC incorporating tissue and blood biomarkers to dissect mechanisms driving resistance.

PATIENTS AND METHODS

Eligible patients with metastatic CRPC underwent a baseline metastasis biopsy and then initiated enzalutamide 160 mg daily. A repeat metastasis biopsy was obtained at radiographic progression from the same site when possible. Blood for circulating tumor cell (CTC) analysis was collected at baseline and progression. The primary objective was to analyze mechanisms of resistance in serial biopsies. Whole-exome sequencing was performed on tissue biopsies. CTC samples underwent RNA sequencing.

RESULTS

A total of 65 patients initiated treatment, of whom 22 (33.8%) had received prior abiraterone. Baseline biopsies were enriched for alterations in AR (mutations, amplifications) and tumor suppression genes (PTEN, RB1, and TP53), which were observed in 73.1% and 92.3% of baseline biopsies, respectively. Progression biopsies revealed increased AR amplifications (64.7% at progression vs. 53.9% at baseline) and BRCA2 alterations (64.7% at progression vs. 38.5% at baseline). Genomic analysis of baseline and progression CTC samples demonstrated increased AR splice variants, AR-regulated genes, and neuroendocrine markers at progression.

CONCLUSIONS

Our results demonstrate that a large proportion of enzalutamide-treated patients have baseline and progression alterations in the AR pathway and tumor suppressor genes. We demonstrate an increased number of BRCA2 alterations post-enzalutamide, highlighting the importance of serial tumor sampling in CRPC.

MicroRNA-29b-3p promotes 5-fluorouracil resistance <em>via</em> suppressing TRAF5-mediated necroptosis in human colorectal cancer

Drug resistance in colorectal cancer is a great challenge in clinic. Elucidating the deep mechanism underlying drug resistance will bring much benefit to diagnosis, therapy and prognosis in patients with colorectal cancer. In this study, miR-29b-3p was shown to be involved in resistance to 5-fluorouracil (5-FU)-induced necroptosis of colorectal cancer. Further, miR-29b-3p was shown to target a regulatory subunit of necroptosis TRAF5. Rescue of TRAF5 could reverse the effect of miR-29b-3p on 5-FU-induced necroptosis, which was consistent with the role ofnecrostatin-1 (a specific necroptosis inhibitor). Then it was demonstrated that miR-29b-3p was positively correlated with chemo-resistance in colorectal cancer while TRAF5 negatively. In conclusion, it is deduced that miR-29b-3p/TRAF5 signaling axis plays critical role in drug resistance in chemotherapy for colorectal cancer patients by regulating necroptosis. The findings in this study provide us a new target for interfere therapy in colorectal cancer.

MYC-Mediated Ribosomal Gene Expression Sensitizes Enzalutamide-resistant Prostate Cancer Cells to EP300/CREBBP Inhibitors

Patients with advanced prostate cancer are frequently treated with the antiandrogen enzalutamide. However, resistance eventually develops in virtually all patients, and various mechanisms have been associated with this process. The histone acetyltransferases EP300 and CREBBP are involved in regulation of cellular events in advanced prostate cancer. This study investigated the role of EP300/CREBBP inhibitors in enzalutamide-resistant prostate cancer. EP300/CREBBP inhibitors led to the same inhibition of androgen receptor activity in enzalutamide-resistant and -sensitive cells. However, enzalutamide-resistant cells were more sensitive to these inhibitors in viability assays. As indicated by the RNA-sequencing-based pathway analysis, genes related to the ribosome and MYC activity were significantly altered upon EP300/CREBBP inhibitor treatment. EP300/CREBBP inhibitors led to the down-regulation of ribosomal proteins RPL36 and RPL29. High-level ribosomal proteins amplifications and MYC amplifications were observed in castration-resistant prostate cancer samples of the publicly available Stand Up to Cancer data set. An inhibitor of RNA polymerase I-mediated transcription was used to evaluate the functional implications of these findings. The enzalutamide-resistant cell lines were more sensitive to this treatment. In addition, the migration rate of enzalutamide-resistant cells was strongly inhibited by this treatment. Taken together, the current data show that EP300/CREBBP inhibitors affect the MYC/ribosomal protein axis in enzalutamide-resistant cells and may have promising therapeutic implications.

How Neural Crest Transcription Factors Contribute to Melanoma Heterogeneity, Cellular Plasticity, and Treatment Resistance

Cutaneous melanoma represents one of the deadliest types of skin cancer. The prognosis strongly depends on the disease stage, thus early detection is crucial. New therapies, including BRAF and MEK inhibitors and immunotherapies, have significantly improved the survival of patients in the last decade. However, intrinsic and acquired resistance is still a challenge. In this review, we discuss two major aspects that contribute to the aggressiveness of melanoma, namely, the embryonic origin of melanocytes and melanoma cells and cellular plasticity. First, we summarize the physiological function of epidermal melanocytes and their development from precursor cells that originate from the neural crest (NC). Next, we discuss the concepts of intratumoral heterogeneity, cellular plasticity, and phenotype switching that enable melanoma to adapt to changes in the tumor microenvironment and promote disease progression and drug resistance. Finally, we further dissect the connection of these two aspects by focusing on the transcriptional regulators MSX1, MITF, SOX10, PAX3, and FOXD3. These factors play a key role in NC initiation, NC cell migration, and melanocyte formation, and we discuss how they contribute to cellular plasticity and drug resistance in melanoma.

Hyperactivation of HER2-SHCBP1-PLK1 axis promotes tumor cell mitosis and impairs trastuzumab sensitivity to gastric cancer

Trastuzumab is the backbone of HER2-directed gastric cancer therapy, but poor patient response due to insufficient cell sensitivity and drug resistance remains a clinical challenge. Here, we report that HER2 is involved in cell mitotic promotion for tumorigenesis by hyperactivating a crucial HER2-SHCBP1-PLK1 axis that drives trastuzumab sensitivity and is targeted therapeutically. SHCBP1 is an Shc1-binding protein but is detached from scaffold protein Shc1 following HER2 activation. Released SHCBP1 responds to HER2 cascade by translocating into the nucleus following Ser273 phosphorylation, and then contributing to cell mitosis regulation through binding with PLK1 to promote the phosphorylation of the mitotic interactor MISP. Meanwhile, Shc1 is recruited to HER2 for MAPK or PI3K pathways activation. Also, clinical evidence shows that increased SHCBP1 prognosticates a poor response of patients to trastuzumab therapy. Theaflavine-3, 3'-digallate (TFBG) is identified as an inhibitor of the SHCBP1-PLK1 interaction, which is a potential trastuzumab sensitizing agent and, in combination with trastuzumab, is highly efficacious in suppressing HER2-positive gastric cancer growth. These findings suggest an aberrant mitotic HER2-SHCBP1-PLK1 axis underlies trastuzumab sensitivity and offer a new strategy to combat gastric cancer.

Activation of unfolded protein response overcomes Ibrutinib resistance in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most widespread type of non-Hodgkin lymphoma (NHL). As the most aggressive form of the DLBCL, the activated B-cell-like (ABC) subtype is often resistant to standard chemotherapies. Bruton's tyrosine kinase (BTK) inhibitor ibrutinib provides a potential therapeutic approach for the DLBCL but fails to improve the outcome in the phase III trial. In the current study, we investigated the molecular mechanisms underlying ibrutinib resistance and explored new combination therapy with ibrutinib. We generated an ibrutinib-resistant ABC-DLBCL cell line (OCI-ly10-IR) through continuous exposure to ibrutinib. Transcriptome analysis of the parental and ibrutinib-resistant cell lines revealed that the ibrutinib-resistant cells had significantly lower expression of the unfolded protein response (UPR) marker genes. Overexpression of one UPR branch-XBP1s greatly potentiated ibrutinib-induced apoptosis in both sensitive and resistant cells. The UPR inhibitor tauroursodeoxycholic acid (TUDCA) partially reduced the apoptotic rate induced by the ibrutinib in sensitive cells. The UPR activator 2-deoxy-D-glucose (2-DG) in combination with the ibrutinib triggered even greater cell growth inhibition, apoptosis, and stronger calcium (Ca2+) flux inhibition than either of the agents alone. A combination treatment of ibrutinib (15 mg·kg-1·d-1, po.) and 2-DG (500 mg/kg, po, b.i.d.) synergistically retarded tumor growth in NOD/SCID mice bearing OCI-ly10-IR xenograft. In addition, ibrutinib induced the UPR in the sensitive cell lines but not in the resistant cell lines of the DLBCL. There was also a combined synergistic effect in the primary resistant DLBCL cell lines. Overall, our results suggest that targeting the UPR could be a potential combination strategy to overcome ibrutinib resistance in the DLBCL.

Biological functions of miR-183 on chemosensitivity of laryngeal cancer cells

PURPOSE

The purpose of this study was to investigate the effect of miR-183 on the sensitivity of laryngeal cancer cells to 5-fluorouracil (5-Fu) and its mechanism, so as to provide certain references for the clinical prevention of drug resistance in laryngeal cancer cells.

METHODS

Cell proliferation was determined via 5-ethynyl-2'-deoxyuridine (EdU) staining. Colony formation assay was applied to test the colony-formation ability in each group of cells. In addition, the expression levels of apoptosis-related proteins were measured through Western blotting. Wound-healing assay and Transwell assay were performed to examine the migratory and invasive abilities. Furthermore, the tumor-forming ability in vitro was detected by subcutaneous tumor formation assay.

RESULTS

MiR-183 declined remarkably in 5-Fu-RES group compared with that in Control group. After overexpressing miR-183, the DNA replication and colony forming abilities of the resistant human primary laryngeal cancer cells were weakened notably. MiR-183 overexpression could obviously up-regulate Bax and inhibit Bcl-2 in the resistant human primary laryngeal cancer cells. Moreover, the overexpression of miR-183 was able to repress the migratory and invasive abilities of the resistant human primary laryngeal cancer cells. Further, overexpression of miR-183 restrained the in vitro tumor-forming ability of the resistant human primary laryngeal cancer cells markedly. Finally, it was revealed that TBX3 in the resistant human primary laryngeal cancer cells was suppressed distinctly, while that of PTEN was up-regulated evidently after overexpressing miR-183.

CONCLUSIONS

The overexpression of miR-183 can inhibit the drug resistance of the human primary laryngeal cancer cells to 5-Fu, promote cancer cell apoptosis and inhibit their invasive and migratory abilities at the same time, whose mechanism may be associated with the targeted regulation of the TBX3/PTEN signaling pathway by miR-183.

Glutamine deficiency promotes stemness and chemoresistance in tumor cells through DRP1-induced mitochondrial fragmentation

Glutamine is essential for maintaining the TCA cycle in cancer cells yet they undergo glutamine starvation in the core of tumors. Cancer stem cells (CSCs), responsible for tumor recurrence are often found in the nutrient limiting cores. Our study uncovers the molecular basis and cellular links between glutamine deprivation and stemness in the cancer cells. We showed that glutamine is dispensable for the survival of ovarian and colon cancer cells while it is required for their proliferation. Glutamine starvation leads to the metabolic reprogramming in tumor cells with enhanced glycolysis and unaltered oxidative phosphorylation. Production of reactive oxygen species (ROS) in glutamine limiting condition induces MAPK-ERK1/2 signaling pathway to phosphorylate dynamin-related protein-1(DRP1) at Ser616. Moreover, p-DRP1 promotes mitochondrial fragmentation and enhances numbers of CD44 and CD117/CD45 positive CSCs. Besides the established features of cancer stem cells, glutamine deprivation induces perinuclear localization of fragmented mitochondria and reduction in proliferation rate which are usually observed in CSCs. Treatment with glutaminase inhibitor (L-DON) mimics the effects of glutamine starvation without altering cell survival in in vitro as well as in in vivo model. Interestingly, the combinatorial treatment of L-DON with DRP1 inhibitor (MDiVi-1) reduces the stem cell population in tumor tissue in mouse model. Collectively our data suggest that glutamine deficiency in the core of tumors can increase the cancer stem cell population and the combination therapy with MDiVi-1 and L-DON is a useful approach to reduce CSCs population in tumor.

Cultivation of Head and Neck Squamous Cell Carcinoma Cells with Wound Fluid Leads to Cisplatin Resistance via Epithelial-Mesenchymal Transition Induction

Locoregional recurrence is a major reason for therapy failure after surgical resection of head and neck squamous cell carcinoma (HNSCC). The physiological process of postoperative wound healing could potentially support the proliferation of remaining tumor cells. The aim of this study was to evaluate the influence of wound fluid (WF) on the cell cycle distribution and a potential induction of epithelial-mesenchymal transition (EMT). To verify this hypothesis, we incubated FaDu and HLaC78 cells with postoperative WF from patients after neck dissection. Cell viability in dependence of WF concentration and cisplatin was measured by flow cytometry. Cell cycle analysis was performed by flow cytometry and EMT-marker expression by rtPCR. WF showed high concentrations of interleukin (IL)-6, IL-8, IL-10, CCL2, MCP-1, EGF, angiogenin, and leptin. The cultivation of tumor cells with WF resulted in a significant increase in cell proliferation without affecting the cell cycle. In addition, there was a significant enhancement of the mesenchymal markers Snail 2 and vimentin, while the expression of the epithelial marker E-cadherin was significantly decreased. After cisplatin treatment, tumor cells incubated with WF showed a significantly higher resistance compared with the control group. The effect of cisplatin-resistance was dependent on the WF concentration. In summary, proinflammatory cytokines are predominantly found in WF. Furthermore, the results suggest that EMT can be induced by WF, which could be a possible mechanism for cisplatin resistance.

SPARC enhances 5-FU chemosensitivity in gastric cancer by modulating epithelial-mesenchymal transition and apoptosis

Previous studies have shown that secreted protein acidic and rich in cysteine (SPARC) proteins can inhibit the development of cancer cells in various ways, such as by inhibiting angiogenesis and inhibiting cell proliferation. In fact, SPARC proteins may have an effect on the chemoresistance of gastric cancer cells to 5-Fluorouracil (5-FU), which needs further research in the future. Therefore, the purpose of this study was to explore the relationship between SPARC proteins and the chemosensitivity of gastric cancer cells to 5-FU. In vitro, after SPARC protein levels were regulated by plasmid, siRNA and human recombinant SPARC protein transfection in MGC-803, SGC-7901 and BGC-823 cells, we detected epithelial-mesenchymal transition (EMT), apoptosis markers and cell viability after 5-FU treatment. In vivo, we implanted BGC-823 cells with stable SPARC overexpression into nude mice. Tumour size was measured to assess the effect of SPARC protein on tumour formation and 5-FU chemosensitivity. In SGC-7901 and BGC-823 cells, both endogenous and exogenous upregulation of SPARC protein levels decreased cell viability, destroyed cytoskeletal F-actin, inhibited cell migration, and downregulated a series of transcription factors to inhibit cell EMT; it also upregulated cell apoptosis-related proteins to promote cell apoptosis. However, we obtained opposite results in SPARC knockdown MGC-803 cells. In vivo, compared with the control group, the group engrafted with BGC-823 cells stably overexpressing SPARC had a significant smaller tumour size. After 5-FU treatment, the new tumour gradually decreased in size. Our results show that the SPARC protein could enhance 5-FU chemosensitivity in gastric cancer cell lines by inhibiting EMT and promoting cell apoptosis.

PI3Kγ inhibition suppresses microglia/TAM accumulation in glioblastoma microenvironment to promote exceptional temozolomide response

Precision medicine in oncology leverages clinical observations of exceptional response. Toward an understanding of the molecular features that define this response, we applied an integrated, multiplatform analysis of RNA profiles derived from clinically annotated glioblastoma samples. This analysis suggested that specimens from exceptional responders are characterized by decreased accumulation of microglia/macrophages in the glioblastoma microenvironment. Glioblastoma-associated microglia/macrophages secreted interleukin 11 (IL11) to activate STAT3-MYC signaling in glioblastoma cells. This signaling induced stem cell states that confer enhanced tumorigenicity and resistance to the standard-of-care chemotherapy, temozolomide (TMZ). Targeting a myeloid cell restricted an isoform of phosphoinositide-3-kinase, phosphoinositide-3-kinase gamma isoform (PI3Kγ), by pharmacologic inhibition or genetic inactivation disrupted this signaling axis by reducing microglia/macrophage-associated IL11 secretion in the tumor microenvironment. Mirroring the clinical outcomes of exceptional responders, PI3Kγ inhibition synergistically enhanced the anti-neoplastic effects of TMZ in orthotopic murine glioblastoma models. Moreover, inhibition or genetic inactivation of PI3Kγ in murine glioblastoma models recapitulated expression profiles observed in clinical specimens isolated from exceptional responders. Our results suggest key contributions from tumor-associated microglia/macrophages in exceptional responses and highlight the translational potential for PI3Kγ inhibition as a glioblastoma therapy.

ADAMTSL5 is an epigenetically activated gene underlying tumorigenesis and drug resistance in hepatocellular carcinoma

BACKGROUND & AIMS

The tumour microenvironment shapes tumour growth through cellular communications that include both direct interactions and secreted factors. The aim of this study was to characterize the impact of the secreted glycoprotein ADAMTSL5, whose role in cancer has not been previously investigated, on hepatocellular carcinoma (HCC).

METHODS

ADAMTSL5 methylation status was evaluated through bisulfite sequencing, and publicly available data analysis. ADAMTSL5 RNA and protein expression were assessed in mouse models and HCC patient samples and compared to data from published datasets. Functional studies, including association of ADAMTSL5 depletion with responsiveness to clinically relevant drugs, were performed in cellular and in vivo models. Molecular alterations associated with ADAMTSL5 targeting were determined using proteomics, biochemistry, and reverse-transcription quantitative PCR.

RESULTS

Methylome analysis revealed hypermethylated gene body CpG islands at the ADAMTSL5 locus in both mouse and human HCC, correlating with higher ADAMTSL5 expression. ADAMTSL5 targeting interfered with tumorigenic properties of HCC cells in vitro and in vivo, whereas ADAMTSL5 overexpression conferred tumorigenicity to pre-tumoural hepatocytes sensitized to transformation by a modest level of MET receptor expression. Mechanistically, ADAMTSL5 abrogation led to a reduction of several oncogenic inputs relevant to HCC, including reduced expression and/or phosphorylation levels of receptor tyrosine kinases MET, EGFR, PDGFRβ, IGF1Rβ, or FGFR4. This phenotype was associated with significantly increased sensitivity of HCC cells to clinically relevant drugs, namely sorafenib, lenvatinib, and regorafenib. Moreover, ADAMTSL5 depletion drastically increased expression of AXL, accompanied by a sensitization to bemcentinib.

CONCLUSIONS

Our results point to a role for ADAMTSL5 in maintaining the function of key oncogenic signalling pathways, suggesting that it may act as a master regulator of tumorigenicity and drug resistance in HCC.

LAY SUMMARY

The environment of cancer cells has profound effects on establishment, progression, and response of a tumour to treatment. Herein, we show that ADAMTSL5, a protein secreted by liver cancer cells and overlooked in cancer so far, is increased in this tumour type, is necessary for tumour formation and supports drug resistance. Adamtsl5 removal conferred sensitivity of liver cancer cells to drugs used in current treatment. This suggests ADAMTSL5 as a potential marker in liver cancer as well as a possible drug target.

ClC-3 promotes paclitaxel resistance via modulating tubulins polymerization in ovarian cancer cells

Epithelial ovarian cancers (EOC) present as malignant tumors with high mortality in the female reproductive system diseases. Acquired resistance to paclitaxel (PTX), one of the first-line treatment of EOC, remains a therapeutic challenge. ClC-3, a member of the voltage-gated Cl^- channels, plays an essential role in a variety of cellular activities, including chemotherapeutic resistance. Here, we demonstrated that the protein expression and channel function of ClC-3 was upregulated in PTX resistance A2780/PTX cells compared with its parental A2780 cells. The silence of ClC-3 expression by siRNA in A2780/PTX cells partly recovered the PTX sensitivity through restored the G2/M arrest and resumed the chloride channel blocked. ClC-3 siRNA both inhibited the expression of ClC-3 and β-tubulin, whereas the β-tubulin siRNA reduced the expression of itself only, without affecting the expression of ClC-3. Moreover, treatment of ClC-3 siRNA in A2780/PTX cells increased the polymerization ratio of β-tubulin, and the possibility of proteins interaction between ClC-3 and β-tubulin was existing. Take together, the over-expression of ClC-3 protein in PTX-resistance ovarian cancer cells promotes the combination of ClC-3 and β-tubulin, which in turn increase the ration of free form and decrease the quota of the polymeric form of β-tubulin, and finally reduce the sensitivity to PTX. Our findings elucidated a novel function of ClC-3 in regulating PTX resistance and ClC-3 could serve as a potential target to overcome the PTX resistance ovarian cancer.

Loss of FADD and Caspases Affects the Response of T-Cell Leukemia Jurkat Cells to Anti-Cancer Drugs

Programmed cell death (PCD) pathways play a crucial role in the response of cancer cells to treatment. Their dysregulation is one of the cancer hallmarks and one of the reasons of drug resistance. Here, we studied the significance of the individual members of PCD signaling pathways in response to treatment with common anti-cancer drugs using the T-cell leukemia Jurkat cells with single or double knockouts of necroptosis and/or apoptosis genes. We identified apoptosis as the primary cell death pathway upon anti-cancer drugs treatment. The cells with knocked out either Fas-associated protein with death domain (FADD) or all executioner caspases were resistant. This resistance could be partially overcome by induction of RIP1-dependent necroptosis through TNFR1 activation using combined treatment with TNF-α and smac mimetic (LCL161). RIP1 was essential for cellular response to TNF-α and smac mimetic, but dispensable for the response to anti-cancer drugs. Here, we demonstrated the significance of FADD and executioner caspases in carrying out programmed cell death upon anti-cancer drug treatments and the ability of combined treatment with TNF-α and smac mimetic to partially overcome drug resistance of FADD and/or CASP3/7/6-deficient cells via RIP1-dependent necroptosis. Thus, a combination of TNF-α and smac mimetic could be a suitable strategy for overcoming resistance to therapy in cells unable to trigger apoptosis.

IL-6 promotes nuclear translocation of HIF-1α to aggravate chemoresistance of ovarian cancer cells

The inflammatory milieu in tumor modulates the resistance to the conventional antitumoral therapies. Interleukin-6 (IL-6), a pleiotropic pro-inflammatory cytokine and a crucial mediator of tumor development, has been targeted as a therapeutic strategy to overcome chemoresistance in the treatment of tumors. The protein levels and nuclear translocation of HIFs (hypoxia-inducible factors), such as HIF-1α, are linked to the drug resistance of tumor cells. However, whether IL-6 promotes the nuclear translocation of HIF-1α and the related mechanism remain to be investigated. We applied two ovarian cancer (OvCa) cell lines, A2780 cells and SKOV3 cells for the in vivo and in vitro studies. We found that IL-6 up-regulates the HIF-1α expression via the signal transducer and activator of transcription 3 (STAT3) signaling under hypoxia in either endogenous or exogenous way, and then we proved that IL-6 enhances the transcriptional activity of HIF-1α via the STAT3 signaling. Further mechanism research revealed that IL-6 promotes the nuclear translocation of HIF-1α through the STAT3 signaling under hypoxia. Proliferation assay and apoptosis assay were applied and proved that IL-6 enhances the chemoresistance of OvCa cells against cisplatin through the upregulation of HIF-1α via the STAT3 signaling in vitro. The In vivo studies confirmed the effect of IL-6 in increasing the chemoresistance of OvCa cells against cisplatin through the IL-6/STAT3/HIF-1α loop in the animal models. Our data elucidates the explicit mechanism of IL-6/STAT3/HIF-1α loop in OvCa and also provides new insights into the development of different approaches for the inflammation-induced and hypoxia-induced resistance in tumor therapies.

PGC1α Promotes Cisplatin Resistance in Ovarian Cancer by Regulating the HSP70/HK2/VDAC1 Signaling Pathway

Mitochondrial apoptosis is one of the main mechanisms for cancer cells to overcome chemoresistance. Hexokinase 2 (HK2) can resist cancer cell apoptosis by expressing on mitochondria and binding to voltage-dependent anion channel 1 (VDAC1). We previously reported that peroxisome proliferator-activated receptor coactivator 1 α (PGC1α) is highly expressed in ovarian cancer cisplatin-resistant cells. However, the underlying mechanism remains unclear. Therefore, we evaluated the interaction between PGC1α and HK2 in ovarian cancer cisplatin-resistant cells. We found that the knockdown of PGC1α promotes the apoptosis of ovarian cancer cisplatin-resistant cells and increases their sensitivity to cisplatin. In addition, we found that the knockdown of PGC1α affects the mitochondrial membrane potential and the binding of HK2 and VDAC1. As the heat shock protein 70 (HSP70) family can help protein transport, we detected it and found that PGC1α can promote HSP70 gene transcription. Furthermore, HSP70 can promote an increase of HK2 expression on mitochondria and an increase of binding to VDAC1. Based on these results, PGC1α may reduce apoptosis through the HSP70/HK2/VDAC1 signaling pathway, thus promoting cisplatin resistance of ovarian cancer. These findings provide strong theoretical support for PGC1α as a potential therapeutic target of cisplatin resistance in ovarian cancer.

Increased S1P induces S1PR2 internalization to blunt the sensitivity of colorectal cancer to 5-fluorouracil via promoting intracellular uracil generation

Sphingosine-1-phosphate (S1P), the backbone of most sphingolipids, activating S1P receptors (S1PRs) and the downstream G protein signaling has been implicated in chemoresistance. In this study we investigated the role of S1PR2 internalization in 5-fluorouracil (5-FU) resistance in human colorectal cancer (CRC). Clinical data of randomly selected 60 CRC specimens showed the correlation between S1PR2 internalization and increased intracellular uracil (P < 0.001). Then we explored the regulatory mechanisms in CRC model of villin-S1PR2-/- mice and CRC cell lines. We showed that co-administration of S1P promoted S1PR2 internalization from plasma membrane (PM) to endoplasmic reticulum (ER), thus blunted 5-FU efficacy against colorectal tumors in WT mice, compared to that in S1PR2-/- mice. In HCT116 and HT-29 cells, application of S1P (10 μM) empowered S1PR2 to internalize from PM to ER, thus inducing 5-FU resistance, whereas the specific S1PR2 inhibitor JTE-013 (10 μM) effectively inhibited S1P-induced S1PR2 internalization. Using Mag-Fluo-AM-labeling [Ca2+]ER and LC-ESI-MS/MS, we revealed that internalized S1PR2 triggered elevating [Ca2+]ER levels to activate PERK-eLF2α-ATF4 signaling in HCT116 cells. The activated ATF4 upregulated RNASET2-mediated uracil generation, which impaired exogenous 5-FU uptake to blunt 5-FU therapy. Overall, this study reveals a previously unrecognized mechanism of 5-FU resistance resulted from S1PR2 internalization-upregulated uracil generation in colorectal cancer, and provides the novel insight into the significance of S1PR2 localization in predicting the benefit of CRC patients from 5-FU-based chemotherapy.