Molecular mechanisms for tumour resistance to chemotherapy

Small molecule BKM1972 inhibits human prostate cancer growth and overcomes docetaxel resistance in intraosseous models

Bone metastasis is a major cause of prostate cancer (PCa) mortality. Although docetaxel chemotherapy initially extends patients' survival, in most cases PCa becomes chemoresistant and eventually progresses without a cure. In this study, we developed a novel small-molecule compound BKM1972, which exhibited potent in vitro cytotoxicity in PCa and other cancer cells regardless of their differences in chemo-responsiveness. Mechanistic studies demonstrated that BKM1972 effectively inhibited the expression of anti-apoptotic protein survivin and membrane-bound efflux pump ATP binding cassette B 1 (ABCB1, p-glycoprotein), presumably via signal transducer and activator of transcription 3 (Stat3). BKM1972 was well tolerated in mice and as a monotherapy, significantly inhibited the intraosseous growth of chemosensitive and chemoresistant PCa cells. These results indicate that BKM1972 is a promising small-molecule lead to treat PCa bone metastasis and overcome docetaxel resistance.

Suppression of oncogenic protein translation via targeting eukaryotic translation initiation factor 4E overcomes chemo-resistance in nasopharyngeal carcinoma

Resistance to adjuvant chemotherapy remains therapeutic challenge in nasopharyngeal carcinoma (NPC). In this work, we demonstrate that targeting eukaryotic translation initiation factor 4E (eIF4E) is a potential sensitizing strategy to overcome chemoresistance in NPC. We observe the aberrant activation of eIF4E and translational upregulation of eIF4E-regulated oncogenes in NPC cell after pro-longed exposure of cisplatin. Functional analysis demonstrates that eIF4E depletion effectively inhibits proliferation and induces apoptosis in cisplatin-resistant NPC cells. Consistently, eIF4E knockdown significantly enhances cisplatin efficacy in cisplatin-sensitive cells. We identify eIF4E as a therapeutically actionable targets by showing that ribavirin, an anti-viral drug, phenocopies the effects of eIF4E knockdown in NPC. We further demonstrate that ribavirin acts on chemoresistant NPC cells through suppressing eIF4E activity and oncogenic protein translation. Using two independent NPC xenograft mouse models, we show that ribavirin not only is effective in inhibiting chemoresistant NPC growth but also significantly augments the inhibitory effects of cisplatin efficacy in vivo without causing significant toxicity in mice. Taken together, our work shows an activation of eIF4E-mediated growth and survival mechanisms in response to chemotherapy and suggests that inhibition of eIF4E activity represents an attractive sensitizing strategy for NPC treatment. Our findings also suggest that ribavirin is a useful addition to the treatment armamentarium for NPC.

Traditional Chinese medicine-combination therapies utilizing nanotechnology-based targeted delivery systems: a new strategy for antitumor treatment

Cancer is a major public health problem, and is now the world’s leading cause of death. Traditional Chinese medicine (TCM)-combination therapy is a new treatment approach and a vital therapeutic strategy for cancer, as it exhibits promising antitumor potential. Nano-targeted drug-delivery systems have remarkable advantages and allow the development of TCM-combination therapies by systematically controlling drug release and delivering drugs to solid tumors. In this review, the anticancer activity of TCM compounds is introduced. The combined use of TCM for antitumor treatment is analyzed and summarized. These combination therapies, using a single nanocarrier system, namely codelivery, are analyzed, issues that require attention are determined, and future perspectives are identified. We carried out a systematic review of >280 studies published in PubMed since 1985 (no patents involved), in order to provide a few basic considerations in terms of the design principles and management of targeted nanotechnology-based TCM-combination therapies.

Ion Channels: New Actors Playing in Chemotherapeutic Resistance

In the battle against cancer cells, therapeutic modalities are drastically limited by intrinsic or acquired drug resistance. Resistance to therapy is not only common, but expected: if systemic agents used for cancer treatment are usually active at the beginning of therapy (i.e., 90% of primary breast cancers and 50% of metastases), about 30% of patients with early-stage breast cancer will have recurrent disease. Altered expression of ion channels is now considered as one of the hallmarks of cancer, and several ion channels have been linked to cancer cell resistance. While ion channels have been associated with cell death, apoptosis and even chemoresistance since the late 80s, the molecular mechanisms linking ion channel expression and/or function with chemotherapy have mostly emerged in the last ten years. In this review, we will highlight the relationships between ion channels and resistance to chemotherapy, with a special emphasis on the underlying molecular mechanisms.

Obatoclax, a BH3 Mimetic, Enhances Cisplatin-Induced Apoptosis and Decreases the Clonogenicity of Muscle Invasive Bladder Cancer Cells via Mechanisms That Involve the Inhibition of Pro-Survival Molecules as Well as Cell Cycle Regulators

Several studies by our group and others have determined that expression levels of Bcl-2 and/or Bcl-xL, pro-survival molecules which are associated with chemoresistance, are elevated in patients with muscle invasive bladder cancer (MI-BC). The goal of this study was to determine whether combining Obatoclax, a BH3 mimetic which inhibits pro-survival Bcl-2 family members, can improve responses to cisplatin chemotherapy, the standard of care treatment for MI-BC. Three MI-BC cell lines (T24, TCCSuP, 5637) were treated with Obatoclax alone or in combination with cisplatin and/or pre-miR-34a, a molecule which we have previously shown to inhibit MI-BC cell proliferation via decreasing Cdk6 expression. Proliferation, clonogenic, and apoptosis assays confirmed that Obatoclax can decrease cell proliferation and promote apoptosis in a dose-dependent manner. Combination treatment experiments identified Obatoclax + cisplatin as the most effective treatment. Immunoprecipitation and Western analyses indicate that, in addition to being able to inhibit Bcl-2 and Bcl-xL, Obatoclax can also decrease cyclin D1 and Cdk4/6 expression levels. This has not previously been reported. The combined data demonstrate that Obatoclax can inhibit cell proliferation, promote apoptosis, and significantly enhance the effectiveness of cisplatin in MI-BC cells via mechanisms that likely involve the inhibition of both pro-survival molecules and cell cycle regulators.

Chemotherapy Resistance Explained through Endoplasmic Reticulum Stress-Dependent Signaling

Cancers cells have the ability to develop chemotherapy resistance, which is a persistent problem during cancer treatment. Chemotherapy resistance develops through different molecular mechanisms, which lead to modification of the cancer cells signals needed for cellular proliferation or for stimulating an immune response. The endoplasmic reticulum (ER) is an important organelle involved in protein quality control, by promoting the correct folding of protein and ER-mediated degradation of unfolded or misfolded protein, namely, ER-associated degradation. Disturbances of the normal ER functions causes an accumulation of unfolded or misfolded proteins in the ER lumen, resulting in a condition called “ER stress (ERS).” ERS triggers the unfolded protein response (UPR)—also called the ERS response (ERSR)—to restore homeostasis or activate cell death. Although the ERSR is one emerging potential target for chemotherapeutics to treat cancer, it is also critical for chemotherapeutics resistance, as well. However, the detailed molecular mechanism of the relationship between the ERSR and tumor survival or drug resistance remains to be fully understood. In this review, we aim to describe the most vital molecular mechanism of the relationship between the ERSR and chemotherapy resistance. Moreover, the review also discusses the molecular mechanism of ER stress-mediated apoptosis on cancer treatments.

Curcumin and tetrahydrocurcumin induce cell death in Ara-C-resistant acute myeloid leukemia

Most anticancer agents induce cancer cell death; however, multidrug-resistant cancers often lead to treatment failure. The effective use of curcumin as an anticancer agent has been demonstrated in clinical trials. Tetrahydrocurcumin, a major curcumin metabolite, exhibits pharmacological activities similar to those of curcumin. Curcumin induces cell death mainly through the apoptosis pathway, and tetrahydrocurcumin induces cell death mainly via an autophagy pathway in HL60 cells. Here, we investigated whether curcumin and tetrahydrocurcumin can induce apoptosis- and autophagy-mediated cell deaths in Ara-C-resistant cancer cells, respectively. The results demonstrated that curcumin and tetrahydrocurcumin induced cell death by apoptosis and autophagy, respectively, in Ara-C-resistant HL60 cells. Thus, curcumin and tetrahydrocurcumin have potential applications in the treatment of acute myeloid leukemia with Ara-C resistance.

Suppression of proliferation and activation of cell death by sodium selenite involves mitochondria and lysosomes in chemoresistant bladder cancer cells

The specific effects of sodium selenite (selenite) on a chemoresistant human bladder cancer cell line RT-112/D21 were investigated during 72 h. Selenite at low concentration of 2.5 μmol (otherwise tolerated in normal urothelial cells UROtsa) suppressed growth and proliferation of the tested cancer cells via induced oxidative stress. Selenite further altered mitochondrial functions (i.e. decreased mitochondrial membrane potential, increased production of superoxide and reduced ATP synthesis), disrupted lysosomal membranes and activated autophagy. These changes in selenite-exposed cells ultimately resulted in their demise via necrosis and other cell death modality displaying heterotypic apoptotic and autophagic features.

Ratiometric co-encapsulation and co-delivery of doxorubicin and paclitaxel by tumor-targeted lipodisks for combination therapy of breast cancer

Combination therapy is a promising treatment for certain advanced drug-resistant cancers. Although effective inhibition of various tumor cells was reported in vitro, combination treatment requires improvement in vivo due to uncontrolled ratiometric delivery. In this study, a tumor-targeting lipodisk nanoparticle formulation was developed for ratiometric loading and the transportation of two hydrophobic model drugs, doxorubicin (DOX) and paclitaxel (PTX), in one single platform. Furthermore, a slightly acidic pH-sensitive peptide (SAPSP) incorporated into lipodisks effectively enhanced the tumor-targeting and cell internalization. The obtained co-loaded lipodisks were approximately 30 nm with a pH-sensitive property. The ratiometric co-delivery of two drugs via lipodisks was confirmed in both the drug-resistant MCF-7/ADR cell line and its parental MCF-7 cell line in vitro, as well as in a tumor-bearing mouse model in vivo compared with a cocktail solution of free drugs. Co-loaded lipodisks exerted improved cytotoxicity to tumor cells in culture, particularly to drug-resistant tumor cells at synergistic drug ratios. In an in vivo xenograft mouse model, the anti-tumor ability of co-loaded lipodisks was evidenced by the remarkable inhibitory effect on tumor growth of either MCF-7 or MCF-7/ADR tumors, which may be attributed to the increased and ratiometric accumulation of both drugs in the tumor tissues. Therefore, tumor-specific lipodisks were crucial for the combination treatment of DOX and PTX to completely exert a synergistic anti-cancer effect. It is concluded that for co-loaded lipodisks, cytotoxicity data in vitro could be used to predict their inhibitory activity in vivo, potentially enhancing the clinical outcome of synergistic therapy.

Association of ABC gene profiles with time to progression and resistance in ovarian cancer revealed by bioinformatics analyses

Introduction

Ovarian cancer (OC) represents a serious disease with high mortality and lack of efficient predictive and prognostic biomarkers. ATP‐binding cassette (ABC) proteins constitute a large family dedicated to active transmembrane transport including transport of xenobiotics.

Materials and methods

mRNA level was measured by quantitative RT‐PCR in tumor tissues from OC patients. Bioinformatics analyses were applied to two gene expression datasets (60 primary tumors and 29 peritoneal metastases). Two different approaches of expression data normalization were applied in parallel, and their results were compared. Data from publically available cancer datasets were checked to further validate our conclusions.

Results

The results showed significant connections between ABC gene expression profiles and time to progression (TTP), chemotherapy resistance, and metastatic progression in OC. Two consensus ABC gene profiles with clinical meaning were documented. (a) Downregulation of ABCC4, ABCC10, ABCD3, ABCE1, ABCF1, ABCF2, and ABCF3 was connected with the best sensitivity to chemotherapy and TTP. (b) Oppositely, downregulation of ABCB11 and upregulation of ABCB1 and ABCG2 were connected with the worst sensitivity to chemotherapy and TTP. Results from publicly available online databases supported our conclusions.

Conclusion

This study stressed the connection between two well‐documented ABC genes and clinicopathological features—ABCB1 and ABCG2. Moreover, we showed a comparable connection also for several other ABC genes—ABCB11, ABCC4, ABCC10, ABCD3,ABCE1, ABCF1, ABCF2, and ABCF3. Our results add new clinically relevant information to this oncology field and can stimulate further exploration.

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.

Biomolecular Targets of Oxyprenylated Phenylpropanoids and Polyketides

Oxyprenylated secondary metabolites (e.g. phenylpropanoids and polyketides) represent a rare class of natural compounds. Over the past two decades, this group of phytochemicals has become a topic of intense research activity by several teams worldwide due to their in vitro and in vivo pharmacological activities, and to their great therapeutic and nutraceutical potential for the chemoprevention of acute and chronic diseases affecting humans. Such investigations have provided evidence that oxyprenylated secondary metabolites are able to interact with several biological targets at different levels accounting for their observed anticarcinogenic, anti-inflammatory, neuroprotective, immunomodulatory, antihypertensive, and metabolic effects. The aim of the present contribution is to provide a detailed survey of the so far reported data on the capacities of selected oxyprenylated phenylpropanoids and polyketides to trigger receptors, enzymes, and other types of cellular factors for which they exhibit a high degree of affinity and therefore evoke specific responses. With respect to the rather small amounts of these compounds available from natural sources, their chemical synthesis is also highlighted.

Nuclear factor I/B promotes colorectal cancer cell proliferation, epithelial-mesenchymal transition and 5-fluorouracil resistance

Nuclear factor I/B (NFIB) is a widely studied transcription factor that participates in tumor progression; nevertheless, studies on NFIB in colorectal cancer (CRC) are limited. In our study, Western blot and RT‐PCR analyses showed that NFIB was overexpressed in CRC tissues and cell lines, which was consistent with our bioinformatic analysis results. Furthermore, NFIB expression was closely related to the TNM stage of CRC. NFIB promoted cell proliferation and migration and inhibited cell apoptosis in vitro. Meanwhile, we discovered that NFIB accelerated xenograft tumor growth in vivo. In addition, NFIB weakened the sensitivity of CRC cells to 5‐fluorouracil (5‐FU). NFIB induced epithelial‐mesenchymal transition (EMT) by upregulating snail expression, which was accompanied by decreased E‐cadherin and Zo‐1 expression and increasedd Vimentin expression. Because the Akt pathway plays an important role in CRC progression, we examined whether there was a correlation between NFIB and the Akt pathway in cell proliferation and migration. Our results showed that NFIB promoted cell proliferation and increased 5‐FU resistance by activating the Akt pathway. In summary, our findings suggested that NFIB induced EMT of CRC cells via upregulating snail expression and promoted cell proliferation and 5‐FU resistance by activating the Akt pathway.

CD56 and CD11b Positivity with Low Smac/DIABLO Expression as Predictors of Chemoresistance in Acute Myeloid Leukaemia: Flow Cytometric Analysis

Background: Resistance to chemotherapy is a major obstacle to curing acute myeloid leukaemia (AML), and several antigens are claimed to play primary roles in this resistance. Purpose: The aim of this study was to evaluate the roles of CD56, CD11b and Smac/DIABLO gene expression levels as prognostic markers of the clinical outcome, response to chemotherapy and survival of AML patients. Materials and Methods: A cross-sectional observational study was conducted on 60 naïve-AML patients who received induction therapy with mitoxantrone and cytarabine combined with a high dose of cytarabine. The CD56,CD11b and Smac/DIABLO expression levels were assessed using flow cytometry at diagnosis and were analysed for correlation with the possible associated risk factors, response to chemotherapy, and median duration of disease-free survival (DFS) and overall survival (OS). Results: The overall results revealed that AML patients who exhibited positive expression for CD56 and CD11b had short median durations of DFS and OS.(P = 0.019, 0.006, 0.029 and 0.024, respectively). Additionally, low Smac/DIABLO expression had a negative impact on treatment outcome in terms of CR rate (p=0.012) and reduced DFS (p=0.000) and OS(p=0.000) values. Conclusions: CD56 and CD11b positivity and low Smac/DIABLO expression are important predictive factors for the occurrence of chemoresistance, in addition to other risk factors, among AML patients.

Olmutinib (BI1482694/HM61713), a Novel Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor, Reverses ABCG2-Mediated Multidrug Resistance in Cancer Cells

The main characteristic of tumor cell resistance is multidrug resistance (MDR). MDR is the principle cause of the decline in clinical efficacy of chemotherapeutic drugs. There are several mechanisms that could cause MDR. Among these, one of the most important mechanisms underlying MDR is the overexpression of adenosine triphosphate (ATP)-binding cassette (ABC) super-family of transporters, which effectively pump out cytotoxic agents and targeted anticancer drugs across the cell membrane. In recent years, studies found that ABC transporters and tyrosine kinase inhibitors (TKIs) interact with each other. TKIs may behave as substrates or inhibitors depending on the expression of specific pumps, drug concentration, their affinity for the transporters and types of co-administered agents. Therefore, we performed in vitro experiments to observe whether olmutinib could reverse MDR in cancer cells overexpressing ABCB1, ABCG2, or ABCC1 transporters. The results showed that olmutinib at 3 μM significantly reversed drug resistance mediated by ABCG2, but not by ABCB1 and ABCC1, by antagonizing the drug efflux function in ABCG2-overexpressing cells. In addition, olmutinib at reversal concentration affected neither the protein expression level nor the localization of ABCG2. The results observed from the accumulation/efflux study of olmutinib showed that olmutinib reversed ABCG2-mediated MDR with an increasing intracellular drug accumulation due to inhibited drug efflux. We also had consistent results with the ATPase assay that olmutinib stimulated ATPase activity of ABCG2 up to 3.5-fold. Additionally, the molecular interaction between olmutinib and ABCG2 was identified by docking simulation. Olmutinib not only interacts directly with ABCG2 but also works as a competitive inhibitor of the transport protein. In conclusion, olmutinib could reverse ABCG2-mediated MDR. The reversal effect of olmutinib on ABCG2-mediated MDR cells is not due to ABCG2 expression or intracellular localization, but rather related to its interaction with ABCG2 protein resulting in drug efflux inhibition and ATPase stimulation.

MicroRNAs and DNA-Damaging Drugs in Breast Cancer: Strength in Numbers

MicroRNAs are a class of small non-coding regulatory RNAs playing key roles in cancer. Breast cancer is the most common female malignancy worldwide and is categorized into four molecular subtypes: luminal A and B, HER2+ and triple-negative breast cancer (TNBC). Despite the development of multiple targeted therapies for luminal and HER2+ breast tumors, TNBC lacks specific therapeutic approaches, thus they are treated mainly with radio- and chemotherapy. The effectiveness of these therapeutic regimens is based on their ability to induce DNA damage, which is differentially resolved and repaired by normal vs. cancer cells. Recently, drugs directly targeting DNA repair mechanisms, such as PARP inhibitors, have emerged as attractive candidates for the future molecular targeted-therapy in breast cancer. These compounds prevent cancer cells to appropriate repair DNA double strand breaks and induce a phenomenon called synthetic lethality, that results from the concurrent inhibition of PARP and the absence of functional BRCA genes which prompt cell death. MicroRNAs are relevant players in most of the biological processes including DNA damage repair mechanisms. Consistently, the downregulation of DNA repair genes by miRNAs have been probe to improve the therapeutic effect of genotoxic drugs. In this review, we discuss how microRNAs can sensitize cancer cells to DNA-damaging drugs, through the regulation of DNA repair genes, and examine the most recent findings on their possible use as a therapeutic tools of treatment response in breast cancer.

MicroRNAs in cancer drug resistance: Basic evidence and clinical applications

Development of drug resistance has considerably limited the efficacy of cancer treatments, including chemotherapy and targeted therapies. Hence, understanding the molecular mechanisms underpinning the innate or the acquired resistance to these therapies is critical to improve drug efficiency and clinical outcomes. Several studies have implicated microRNAs (miRNA) in this process. MiRNAs repress gene expression by specific binding to complementary sequences in the 3' region of target messenger RNAs (mRNAs), followed by target mRNA degradation or blocked translation. By targeting molecules specific to a particular pathway within tumor cells, the new generation of cancer treatment strategies has shown significant advantages over conventional chemotherapy. However, the long-term efficacy of targeted therapies often remains poor, because tumor cells develop resistance to such therapeutics. Targeted therapies often involve monoclonal antibodies (mAbs), such as those blocking the ErB/HER tyrosine kinases, epidermal growth factor receptor (cetuximab) and HER2 (trastuzumab), and those inhibiting vascular endothelial growth factor receptor signaling (e.g., bevacizumab). Even though these are among the most used agents in tumor medicine, clinical response to these drugs is reduced due to the emergence of drug resistance as a result of toxic effects in the tumor microenvironment. Research on different types of human cancers has revealed that aberrant expression of miRNAs promotes resistance to the aforementioned drugs. In this study, we review the mechanisms of tumor cell resistance to mAb therapies and the role of miRNAs therein. Emerging treatment strategies combine therapies using innovative miRNA mimics or antagonizers with conventional approaches to maximize outcomes of patients with cancer.

Ambra1 modulates the sensitivity of breast cancer cells to epirubicin by regulating autophagy via ATG12

The sensitivity of breast cancer cells to epirubicin (EPI) is closely related to the efficacy of the drug and the prognosis of patients. A growing body of research has suggested that autophagy is involved in the treatment of a variety of cancers, including breast cancer, and modifies the sensitivity of anticancer drugs. However, the mechanism by which autophagy participates in cancer therapy and modulates drug sensitivity has not been fully elucidated. In this study, we showed that the expression of Autophagy/Beclin 1 regulator 1 (Ambra1), a key protein of autophagy, was negatively correlated with EPI sensitivity in breast cancer cells. In addition, it altered the sensitivity of breast cancer cells to EPI by regulating EPI-induced autophagy. As a potential mechanism, we demonstrated that autophagy-related protein 12 (ATG12) was a downstream protein that Ambra1-regulated EPI-induced autophagy. Therefore, Ambra1 plays an important role in regulating the sensitivity of breast cancer cells to EPI. And the regulatory effect of Ambra1 on EPI sensitivity is achieved through the regulation of autophagy by targeting ATG12. Overall, we propose a novel mechanism by which autophagy modulates the sensitivity of breast cancer cells to EPI. ATG12 is a novel targeting protein of Ambra1 in regulating EPI-induced autophagy. In addition, the important role of Ambra1 in modulating the sensitivity of breast cancer cells to EPI is confirmed in vivo. This finding indicates that Ambra1 might be a target for developing breast cancer treatments.

Dimetallic Ru(II) arene complexes appended on bis-salicylaldimine induce cancer cell death and suppress invasion via p53-dependent signaling

A series of bis-salicylaldimine ligands bearing two ON-donor functions were reacted with dichloro(p-cymene)ruthenium(II) dimer in the presence of base (NaOAc) and a series of four dimetallic Ru(II) arene complexes (Ru(p-cymene))₂(bis-salicylaldimine)Cl₂ (C1C4) were prepared. These complexes were obtained in excellent isolated yields and characterized in detail by using different spectroscopic techniques. The structure of C1 was also determined in solid state by single crystal X-ray analysis. These complexes were studied for their cytotoxic effect against three different types of human cancer cells including hepatocellular carcinoma (HepG2), non-small-cell lung cancer (A549) and breast cancer (MCF-7) cells by MTT assay. These complexes showed considerable cytotoxic effect in all the above-mentioned cell lines that was comparable to the effect of cisplatin. C1 and C2 showed moderate anticancer effect while C3 and C4 showed reasonable cytotoxicity. We found the cytotoxicity was increased in series from C1 to C4 representing the effect of ligand modification from small to bulky group at the amine functionality of the salicylaldimine. We selected C3 and C4 for mechanistic anticancer study in MCF-7 cells. The acridine orange/ethidium bromide and DAPI staining assays of MCF-7 cells treated with Ru(II) complexes showed apoptosis in cancer cells. Similarly, these complexes induced p53 protein expression in MCF-7 cells. Further, increased mRNA levels of p63, p73, PUMA, BAX and NOXA genes were observed in response to the treatment with C3 and C4, while cyclinD1, MMP3 and ID1 gene expression was significantly reduced. We found reduced invasion ability in breast cancer cells treated with C3 and C4. Taken together, we demonstrated that bis-salicylaldimine based dimetallic Ru-(p-cymene) complexes exerts anticancer effects by p53 pathway, suggesting the promising chemotherapeutic potentials of these Ru(II) complexes for the treatment of cancer. This study may further pave for their in depth in vitro or in vivo anticancer investigations.

Platinum-induced muscle wasting in cancer chemotherapy: Mechanisms and potential targets for therapeutic intervention

Platinum-based drugs are among the most effective anticancer therapies, integrating the standard of care for numerous human malignancies. However, platinum-based chemotherapy induces severe side-effects in cancer patients, such as cachexia. Weight loss, as well as fatigue and systemic inflammation are characteristics of this syndrome that adversely affects the survival and the quality of life of cancer patients. The signalling pathways involved in chemotherapy-induced cachexia are still to be fully understood, but the activity of several mediators associated with muscle wasting, such as myostatin and pro-inflammatory cytokines are increased by platinum-based drugs like cisplatin. Indeed, the molecular mechanisms behind chemotherapy-induced muscle wasting seem to be similar to the ones promoted by cancer in treatment-naive patients. Although some therapeutic agents are under investigation for treating muscle wasting in cancer patients, no effective treatment is yet available. Herein, we review the molecular mechanisms proposed to be involved in chemotherapy-related muscle wasting with a focus on the typical platinum-based drug cisplatin. Therapeutic strategies presently under investigation are also reviewed, providing an overview of the current efforts to preserve muscle mass and quality of life among cancer patients.

PPARs are mediators of anti-cancer properties of superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with conjugated linoleic acid

Breast cancer chemotherapy can cause side effects due to nonspecific drug delivery, low solubility and fast metabolism of drugs used in conventional therapy. Moreover, the therapeutic effect of the drugs is often reduced by the strengthening of chemoresistance, which occurs via a variety of mechanisms. Different strategies have been developed to reduce multidrug resistance (MDR)-associated gene expressions including the use of surfactants and polymers. In this study superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with conjugated linoleic acid (CLA) reduced the number and viability of cells in comparison with both untreated cells or cells treated with SPIONs alone. This cytostatic effect correlated with the increase of peroxisome proliferator-activated receptors γ (PPARγ). The necrotic cell death induced, as a consequence, an inflammatory process, as evidenced by the decrease of the anti-inflammatory PPARα and increase of pro-inflammatory TNFα and IL-1β. PPARs were examined because CLA is one of their natural ligands. The antitumor effect observed was accompanied by a down-regulation of p-glycoprotein (P-gp), which was the first important discovered efflux transporter belonging to MDR, and of ALDH3A1, an enzyme able to metabolize some drugs, reducing their effects. The down-regulation of P-gp correlated with the increase of cytokines. The ALDH3A1 decrease correlated with the increase of PPARγ. Based on these results, PPARs are molecular mediators of anti-cancer effect of SPIONs functionalized with CLA, being changes in these nuclear receptors correlated with induction of cytotoxicity and inflammation, and decreased ability of cancer cells in blocking anti-cancer drug effect.

Inhibition of eukaryotic translation initiation factor 4E is effective against chemo-resistance in colon and cervical cancer

Although cancer patients initially respond well to chemotherapy, they eventually develop resistance and relapse. In this work, we demonstrate that eIF4E-targeting therapy is a potential sensitizing strategy for overcoming chemoresistance and progression in cancer. We show that ribavirin, an anti-viral drug and pharmacological eIF4E inhibitor, effectively inhibits proliferation and decreases viability of paclitaxel-resistant cervical cancer and 5-FU-resistant colon cancer cells while is less toxic to human fibroblast cells. Importantly, oral administration of ribavirin significantly inhibits paclitaxel-resistant colon and 5-FU-resistant cervical cancer growth in xenograft mouse cancer model without causing significant toxicity in mice. Consistently, combination of ribavirin with paclitaxel or 5-FU sensitizes colon and cervical cancer cells to chemotherapeutic agents treatment in vitro and in vivo. We further confirm that the mechanism of the action of ribavirin in chemoresistant cancer cells is through suppressing eIF4E function. In addition, specific eIF4E knockdown via two independent siRNA mimics the effects of ribavirin in chemoresistant colon and cervical cancer cells. Cell cycle analysis indicate that ribavirin enhances the anti-proliferative effect of 5-FU by additionally arresting cells at G2/M phase via increasing cyclin B1, p-histone H3(Ser10) and Mad2 levels. Our work demonstrates that eIF4E inhibition using inhibitor or siRNA, either as single agent or in combination, could sensitize chemoresistant cancer cells to paclitaxel or 5-FU treatment and thereby improving the efficacy of chemodrug. Our findings demonstrate the therapeutic value of inhibiting eIF4E, particularly in chemoresistant cancers. Our findings also suggest ribavirin as a promising sensitizing drug for cancer treatment.

Pharmacological Targeting of Cell Cycle, Apoptotic and Cell Adhesion Signaling Pathways Implicated in Chemoresistance of Cancer Cells

Chemotherapeutic drugs target a physiological differentiating feature of cancer cells as they tend to actively proliferate more than normal cells. They have well-known side-effects resulting from the death of highly proliferative normal cells in the gut and immune system. Cancer treatment has changed dramatically over the years owing to rapid advances in oncology research. Developments in cancer therapies, namely surgery, radiotherapy, cytotoxic chemotherapy and selective treatment methods due to better understanding of tumor characteristics, have significantly increased cancer survival. However, many chemotherapeutic regimes still fail, with 90% of the drug failures in metastatic cancer treatment due to chemoresistance, as cancer cells eventually develop resistance to chemotherapeutic drugs. Chemoresistance is caused through genetic mutations in various proteins involved in cellular mechanisms such as cell cycle, apoptosis and cell adhesion, and targeting those mechanisms could improve outcomes of cancer therapy. Recent developments in cancer treatment are focused on combination therapy, whereby cells are sensitized to chemotherapeutic agents using inhibitors of target pathways inducing chemoresistance thus, hopefully, overcoming the problems of drug resistance. In this review, we discuss the role of cell cycle, apoptosis and cell adhesion in cancer chemoresistance mechanisms, possible drugs to target these pathways and, thus, novel therapeutic approaches for cancer treatment.

Betulinic acid chemosensitizes breast cancer by triggering ER stress-mediated apoptosis by directly targeting GRP78

Stress-induced cellular defense machinery has a critical role in mediating cancer drug resistance, and targeting stress-related signaling has become a novel strategy to improve chemosensitivity. Betulinic acid (BA) is a naturally occurring pentacyclic triterpenoid with potent anticancer bioactivities in multiple malignancies, whereas its underlying mechanisms remain unclear. Here in, we found that BA has synergistic effects with taxol to induce breast cancer cells G2/M checkpoint arrest and apoptosis induction, but had little cytotoxicity effects on normal mammary epithelial cells. Drug affinity responsive target stability (DARTS) strategy further identified glucose-regulated protein 78 (GRP78) as the direct interacting target of BA. BA administration significantly elevated GRP78-mediated endoplasmic reticulum (ER) stress and resulted in the activation of protein kinase R-like ER kinase (PERK)/eukaryotic initiation factor 2a/CCAAT/enhancer-binding protein homologous protein apoptotic pathway. GRP78 silencing or ER stress inhibitor salubrinal administration was revealed to abolish the anticancer effects of BA, indicating the critical role of GRP78 in mediating the bioactivity of BA. Molecular docking and coimmunoprecipitation assay further demonstrated that BA might competitively bind with ATPase domain of GRP78 to interrupt its interaction with ER stress sensor PERK, thereby initiating the downstream apoptosis cascade. In vivo breast cancer xenografts finally validated the chemosensitizing effects of BA and its biofunction in activating GRP78 to trigger ER stress-mediated apoptosis. Taken together, our study not only uncovers GRP78 as a novel target underlying the chemosensitizing effects of BA, but also highlights GRP78-based targeting strategy as a promising approach to improve breast cancer prognosis.

Co-Delivery of Doxorubicin and Anti-BCL-2 siRNA by pH-Responsive Polymeric Vector to Overcome Drug Resistance in In Vitro and In Vivo HepG2 Hepatoma Model

Drug resistance, developed through multiple mechanisms, is a major hindrance to successful chemotherapy of tumor. Combination therapy of chemotherapeutic drugs and siRNA represents an emerging strategy which may improve anticancer effect by synergistic actions. In this study, triblock copolymer of poly(ethylene glycol)- block-poly(l-lysine)- block-poly aspartyl ( N-( N', N'-diisopropylaminoethyl)) (PEG-PLL-PAsp(DIP)) was synthesized for the first time to enable the codelivery of BCL-2 siRNA and DOX. The system is supposed to not only bypass drug efflux but also down-regulate the antiapoptotic gene and consequently confronting against chemoresistance as well. Moreover, the pH responsive ability of the codelivery system can prevent drug leakage during circulation and guarantee swift drug release at tumors. The codelivered siRNA serves to suppress the expression of antiapoptotic BCL-2 and hence sensitize the cancer cells to anticancer drugs and produce improved therapeutic effect. Consequently, the codelivery of BCL-2 siRNA and anticancer drug DOX serves as a promising strategy against drug resistance in chemotherapy.

Nanotechnology for Cancer Therapy Based on Chemotherapy

Chemotherapy has been widely applied in clinics. However, the therapeutic potential of chemotherapy against cancer is seriously dissatisfactory due to the nonspecific drug distribution, multidrug resistance (MDR) and the heterogeneity of cancer. Therefore, combinational therapy based on chemotherapy mediated by nanotechnology, has been the trend in clinical research at present, which can result in a remarkably increased therapeutic efficiency with few side effects to normal tissues. Moreover, to achieve the accurate pre-diagnosis and real-time monitoring for tumor, the research of nano-theranostics, which integrates diagnosis with treatment process, is a promising field in cancer treatment. In this review, the recent studies on combinational therapy based on chemotherapy will be systematically discussed. Furthermore, as a current trend in cancer treatment, advance in theranostic nanoparticles based on chemotherapy will be exemplified briefly. Finally, the present challenges and improvement tips will be presented in combination therapy and nano-theranostics.

Protein arginine methylation: an emerging regulator of the cell cycle

Protein arginine methylation is a common post-translational modification where a methyl group is added onto arginine residues of a protein to alter detection by its binding partners or regulate its activity. It is known to be involved in many biological processes, such as regulation of signal transduction, transcription, facilitation of protein–protein interactions, RNA splicing and transport. The enzymes responsible for arginine methylation, protein arginine methyltransferases (PRMTs), have been shown to methylate or associate with important regulatory proteins of the cell cycle and DNA damage repair pathways, such as cyclin D1, p53, p21 and the retinoblastoma protein. Overexpression of PRMTs resulting in aberrant methylation patterns in cancers often correlates with poor recovery prognosis. This indicates that protein arginine methylation is also an important regulator of the cell cycle, and consequently a target for cancer regulation. The effect of protein arginine methylation on the cell cycle and how this emerging key player of cell cycle regulation may be used in therapeutic strategies for cancer are the focus of this review.

Euphorbia lunulata extract acts on multidrug resistant gastric cancer cells to inhibit cell proliferation, migration and invasion, arrest cell cycle progression, and induce apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

The milky sap or the aboveground part of the plant Euphorbia lunulata has long been used by Chinese people to treat noncancerous growths and cancerous ailments but the specific mode of action and the action mechanism remain to be elucidated.

AIM OF THE STUDY

To investigate the effects of Euphorbia lunulata extract on cell proliferation, migration, invasion, cell cycle progression, and apoptosis of multidrug resistant human gastric cancer cells; To study the mechanism of apoptosis induction by Euphorbia lunulata extract in multidrug resistant human gastric cancer cells.

MATERIALS AND METHODS

The aboveground part of fresh Euphorbia lunulata plant was extracted first with ethanol and then with n-hexane. The aseptic extract at varying concentrations was used to treat the multidrug resistant human gastric cancer SGC7901/ADR cells. After treatment, the inhibition of cell proliferation was examined by MTT assay. The inhibitions of cell migration and invasion were detected by Transwell method. The alteration of cell cycle progression was studied by flow cytometry. The morphological changes of cell nuclei were observed with fluorescence microscopy following Hoechst 33258 staining and the apoptotic indexes were calculated. The activation of caspase enzymes was analyzed by spectrophotometry. The sub-cellular distribution of cytochrome complex and the expression of Bax and Bcl-2 proteins were determined by Western blot.

RESULTS

The proliferation, migration, and invasion of SGC7901/ADR cells were significantly inhibited by Euphorbia lunulata extract, which showed time- and dose-dependent manners. Cell cycle was arrested in G2/M phase. Significant apoptotic morphological changes were observed in the nuclei of the treated cells, and apoptotic indexes were increased significantly; these changes were diminished when Z-VAD-FMK, a caspase inhibitor, was also presented. The activities of caspase-3, caspase-8, and caspase-9 were increased. The sub-cellular distribution of cytochrome complex was altered----reduced in the mitochondria and increased in the cytoplasm. The expression of Bax was upregulated, while that of Bcl-2 was downregulated.

CONCLUSION

Euphorbia lunulata extract inhibited the proliferation, migration, and invasion of SGC7901/ADR cells, arrested cell cycle progression, and induced cell apoptosis; the mechanism of apoptosis induction involved both the extrinsic and the intrinsic pathways.

Single-cell Transcriptome Analyses Reveal Molecular Signals to Intrinsic and Acquired Paclitaxel Resistance in Esophageal Squamous Cancer Cells

Paclitaxel is widely used in the combination chemotherapy for many cancers including esophageal squamous cell carcinoma (ESCC). However, the paclitaxel resistance occurs frequently in treating ESCC and the mechanism is not fully understood yet. The heterogeneity of gene expression within the drug-resistant cancer cells may be one of the major factors contributing to its resistance. In the present study, we successfully induced paclitaxel resistance in ESCC cell line KYSE-30 through low dose and long-term treatment of paclitaxel. Gene expression profiles were measured utilizing population RNA-seq and single-cell RNA-seq (scRNA-seq). 37 single cells from KYSE-30 cells and 73 single cells from paclitaxel resistant KYSE-30 cells (Taxol-R) were subjected to scRNA-seq. Weighted gene co-expression network analysis (WGCNA) of scRNA-seq data revealed two major subpopulations in both KYSE-30 and Taxol-R cancer cells. Two subpopulations based on the KRT19 expression levels in KYSE-30 cells exhibited different paclitaxel sensitivity, suggesting the existence of an intrinsic paclitaxel resistance in KYSE-30 cells. In addition, the Taxol-R cells that acquired the resistance to paclitaxel through induction were characterized with higher expressions of proteasomes but a lower expression of HIF-1 signaling genes. Furthermore, we showed that carfilzomib (CFZ), a proteasome inhibitor, could attenuate the paclitaxel resistance in Taxol-R cancer cells through activating the HIF-1 signaling. Our new finding may pave a way leading to an improvement in the treatment on cancers including ESCC by combining CFZ with paclitaxel as a novel approach for cancer therapy.

Dacomitinib antagonizes multidrug resistance (MDR) in cancer cells by inhibiting the efflux activity of ABCB1 and ABCG2 transporters

The development of multidrug resistance (MDR) to chemotherapy remains a major challenge in the treatment of cancer. Numerous mechanisms have been recognized that cause MDR, but one of the most important mechanisms is overexpression of adenosine triphosphate (ATP)-binding cassette (ABC) transporters, through which the efflux of various anticancer drugs against their concentration gradients is powered by ATP. In recent years, small molecular tyrosine kinase inhibitors (TKIs) have been developed for treatment in various human cancers overexpressing epidermal growth factor receptor (EGFR). At the same time, some TKIs have been shown to be capable of inhibiting ABC transporter-mediated MDR. Dacomitinib (PF-00299804) is a second generation, irreversible TKI, which has shown positive anticancer activities in some preclinical and clinical trials. As many TKIs are substrates or inhibitors of ABC transporters, this study investigates whether dacomitinib could interact with ABC subfamily members that mediate MDR, including ABCB1 (P-gp), ABCG2 (BCRP) and ABCC1 (MRP1). The results showed that dacomitinib at 1.0 μM significantly reversed drug resistance mediated by ABCB1 and ABCG2, but not ABCC1, doing so by antagonizing the drug efflux function in ABCB1- and ABCG2-overexpressing cell lines. The reversal effect on ABCB1-overexpressing cells is more potent than that on ABCG2-overexpressing cells. In addition, dacomitinib at reversal concentration affected neither the protein expression level nor the localization of ABCB1 and ABCG2. Therefore, the mechanisms of this modulating effect are likely to be the following: first, as an inhibitor of ABCB1 or ABCG2 transporters, dacomitinib binds to drug-substrate site in transmembrane domains (TMD) stably in a noncompetitive manner; or second, dacomitinib inhibits ATPase activity and maintains the stability of TMD conformation in a concentration-dependent manner thereby inhibiting the drug efflux function of ABCB1 or ABCG2 transporter. This study provides a useful combinational therapeutic strategy with dacomitinib and substrates of ABCB1 and/or ABCG2 transporters in ABCB1- or ABCG2-overexpressing cancers.

First enantioselective total synthesis of altersolanol A

The first enantioselective total synthesis of altersolanol A was accomplished by Diels–Alder cycloaddition promoted by (R)-3,3′-BINOL/boron Lewis acid.

A chloroquine-loaded Prussian blue platform with controllable autophagy inhibition for enhanced photothermal therapy

A controllable CQ delivery platform consisting of hollow mesoporous Prussian blue nanoparticles and phase changing material was developed here to realize tumor specific autophagy inhibition for enhanced PTT.

Nutritional shortage augments cisplatin-effects on murine melanoma cells

Melanoma incidence increases every year worldwide and is responsible for 80% of skin cancer deaths. Due to its metastatic potential and resistance to almost any treatments such as chemo, radio, immune and targeted-therapy, the patients still have a poor prognosis, especially at metastatic stage. Considering that, it is crucial to find new therapeutic approaches to overcome melanoma resistance. Here we investigated the effect of cisplatin (CDDP), one of the chemotherapeutic agents used for melanoma treatment, in association with nutritional deprivation in murine melanoma cell lines. Cell death and autophagy were evaluated after the treatment with cisplatin, nutritional deprivation and its association using an in vitro model of murine melanocytes malignant transformation to metastatic melanoma. Our results showed that nutritional deprivation augmented cell death induced by cisplatin in melanoma cells, especially at the metastatic subtype, with slight effects on melanocytes. Mechanistic studies revealed that although autophagy was present at high levels in basal conditions in melanoma cells, was not essential for cell death process that involved mitochondrial damage, reactive oxygen species production and possible glycolysis inhibition. In conclusion, nutritional shortage in combination with chemotherapeutic drugs as cisplatin can be a valuable new therapeutic strategy to overcome melanoma resistance.

Selective inhibition of cancer cells by enzyme-induced gain of function of phosphorylated melittin analogues

The selective killing of cancer cells and the avoidance of drug resistance are still difficult challenges in cancer therapy. Here, we report a new strategy that uses enzyme-induced gain of function (EIGF) to regulate the structure and function of phosphorylated melittin analogues (MelAs). Original MelAs have the capacity to disrupt plasma membranes and induce cell death without selectivity. However, phosphorylation of Thr23 on one of the MelAs (MelA2-P) efficiently ameliorated the membrane lysis potency as well as the cytotoxicity for normal mammalian cells. After treatment with alkaline phosphatase (ALP), which is more active in cancer cells than normal cells, MelA2-P restored the pore-forming function around the cancer cells and induced cancer cell death selectively. This mechanism was independent of the receptor proteins and the cell uptake process, which may partially bypass the development of drug resistance in cancer cells.

Hedyotis diffusa Willd inhibits proliferation and induces apoptosis of 5‑FU resistant colorectal cancer cells by regulating the PI3K/AKT signaling pathway

Hedyotis diffusa Willd (HDW) is a major component frequently used in Traditional Chinese Medicine for the clinical treatment of colorectal cancer (CRC) and its associated drug resistance. However, the underlying mechanism of HDW circumventing drug resistance of cancer cells remains to be elucidated. Cancer cell resistance to apoptosis and activation of the phosphatidylinositol‑3‑kinase (PI3K)/protein kinase B (AKT) signaling pathway have been implicated as major factors in the acquired resistance to chemotherapeutic anti‑cancer drugs. The present study investigated the effect and mechanisms of action of ethanol extract of Hedyotis diffusa Willd (EEHDW) on the proliferation and apoptosis of CRC 5‑fluorouracil (5‑FU) resistant (HCT‑8/5‑FU) cells. CRC HCT‑8/5‑FU cell viability following treatment with EEHDW was determined using MTT and colony formation assay. In addition, Annexin V/propidium iodide staining with flow cytometry analysis and 4',6‑diamidino‑2‑phenylindole staining were used to determine the apoptosis of drug‑resistant cancer cells following treatment with EEHDW. The mRNA and protein expression levels of B cell leukemia/lymphoma (Bcl‑2), Bcl‑2 associated X (Bax), cyclin dependent kinase 4 (CDK4), cyclin D1 and p21 were evaluated using reverse transcription‑polymerase chain reaction and western blot analysis, respectively. Furthermore, activation of the PI3K/AKT signaling pathway and expression of phosphatase and tensin homolog (PTEN), PI3K, AKT and phosphorylated (p)‑AKT were determined. EEHDW significantly reduced cell viability, inhibited cell colony formation and promoted apoptosis of HCT‑8/5‑FU cells. Furthermore, EEHDW significantly downregulated the expression of Bcl‑2, cyclin D1 and CDK4 and upregulated the expression of Bax and p21. In addition, EEHDW inhibited the activation of the PI3K/AKT pathway by increasing expression of PTEN and suppressing the expression of PI3K and p‑AKT. The present study provided the first direct evidence that EEHDW may overcome drug‑resistance in human CRC cells by inhibiting PI3K/AKT signaling pathway and provides a basis for the improved therapeutic use of HDW in the clinical treatment of cancer.

Transcription factor EB is involved in autophagy-mediated chemoresistance to doxorubicin in human cancer cells

Transcription factor EB (TFEB) is a master regulator of autophagy activity and lysosomal biogenesis, but its role in autophagy-mediated cell survival and chemotherapy resistance is not completely understood. In this study, we explored whether TFEB played an important role in autophagy-mediated chemotherapy resistance in human cancer LoVo and HeLa cells in vitro. Treatment of human colon cancer LoVo cells with doxorubicin (0.5 μmol/L) induced autophagy activation and nuclear translocation of TFEB, which resulted from inactivation of the mTOR pathway. In both LoVo and HeLa cells, overexpression of TFEB enhanced doxorubicin-induced autophagy activation and significantly decreased doxorubicin-induced cell death, whereas knockdown of TFEB with small interfering RNA blocked doxorubicin-induced autophagy and significantly enhanced the cytotoxicity of doxorubicin. In LoVo cells, autophagy inhibition by 3-methyladenine (3-MA) or knockdown of autophagy-related gene Atg5 increased cell death in response to doxorubicin, and abolished TFEB overexpression-induced chemotherapy resistance, suggesting that the inhibition of autophagy made cancer cells more sensitive to doxorubicin. The results demonstrate that TFEB-mediated autophagy activation decreases the sensitivity of cancer cells to doxorubicin.

Targeting P-glycoprotein: Investigation of piperine analogs for overcoming drug resistance in cancer

P-glycoprotein (P-gp) is a drug transporter that effluxes chemotherapeutic drugs and is implicated in the development of resistance of cancer cells to chemotherapeutic drugs. To date, no drug has been approved to inhibit P-gp and restore chemotherapy efficacy. Moreover, majority of the reported inhibitors have high molecular weight and complex structures, making it difficult to understand the basic structural requirement for P-gp inhibition. In this study, two structurally simple, low molecular weight piperine analogs Pip1 and Pip2 were designed and found to better interact with P-gp than piperine in silico. A one step, acid-amine coupling reaction between piperic acid and 6,7-dimethoxytetrahydroisoquinoline or 2-(3,4-dimethoxyphenyl)ethylamine afforded Pip1 and Pip2, respectively. In vitro testing in drug resistant P-gp overexpressing KB (cervical) and SW480 (colon) cancer cells showed that both analogs, when co-administered with vincristine, colchicine or paclitaxel were able to reverse the resistance. Moreover, accumulation of P-gp substrate (rhodamine 123) in the resistant cells, a result of alteration of the P-gp efflux, was also observed. These investigations suggest that the natural product analog - Pip1 ((2E,4E)-5-(benzo[d][1,3]dioxol-5-yl)-1-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1 H)-yl)penta-2,4-dien-1-one) - is superior to piperine and could inhibit P-gp function. Further studies are required to explore the full potential of Pip1 in treating drug resistant cancer.

Nanotechnology-based combination therapy for overcoming multidrug-resistant cancer

Multidrug resistance (MDR) is a major obstacle to successful cancer treatment and is crucial to cancer metastasis and relapse. Combination therapy is an effective strategy for overcoming MDR. However, the different pharmacokinetic (PK) profiles of combined drugs often undermine the combination effect in vivo, especially when greatly different physicochemical properties (e.g., those of macromolecules and small drugs) combine. To address this issue, nanotechnology-based codelivery techniques have been actively explored. They possess great advantages for tumor targeting, controlled drug release, and identical drug PK profiles. Thus, a powerful tool for combination therapy is provided, and the translation from in vitro to in vivo is facilitated. In this review, we present a summary of various combination strategies for overcoming MDR and the nanotechnology-based combination therapy.

Dual inhibition of P-glycoprotein and midkine may increase therapeutic effects of anticancer drugs

Multidrug resistance (MDR) to chemotherapy may significantly affect the outcome of cancer treatment. ATP-dependent drug efflux pumps, including P-glycoprotein (P-gp), contribute to the resistance of various chemotherapeutic agents. Overexpression of P-gp in tumor cells induces chemoresistance via pumping the anticancer drugs out of the cells. In addition to taking part in many biological processes such as development, reproduction and repair, midkine (MK) also plays important roles in the pathogenesis of malignant diseases as well as in the regulation of MDR. Although, the mechanisms of action of P-gp and MK are different, overexpression of both proteins prevents the accumulation of many chemotherapeutics in tumor cells, leading to decreased therapeutic effects of anticancer drugs. Therefore, identification of the result of dual inhibition of P-gp and MK in overcoming chemoresistance may enhance the likelihood for a more efficient chemotherapy.

Phospholipase C δ1 negatively regulates autophagy in colorectal cancer cells

Colorectal cancer (CRC) is one of the leading causes of cancer-related death worldwide. Kirsten rat sarcoma viral oncogene homolog (KRAS) is frequently mutated in CRC, and KRAS mutations promote cell motility, growth, and survival. We previously revealed that the expression of phospholipase C (PLC) δ1, one of the most basal PLCs, is down-regulated in colon adenocarcinoma, and that the KRAS signaling pathway suppresses PLCδ1 expression. Although recent studies revealed that KRAS mutations activate autophagy in cancer cells, a relation between PLCδ1 and autophagy remains unclear. Here, we found that PLCδ1 overexpression suppresses the formation of autophagosomes, which are key structures of autophagy, whereas endogenous PLCδ1 knockdown increases autophagosome formation in CRC cells. We also showed that PLCδ1 overexpression promotes cell death under nutrient deprivation. Furthermore, PLCδ1 overexpression suppresses the autophagy induced by the anti-cancer drug oxaliplatin and promotes cell death under oxaliplatin treatment. These data suggest that PLCδ1 negatively regulates autophagy, and PLCδ1 suppression contributes to the tolerance of CRC cells harboring KRAS mutations to nutrient deprivation and anti-cancer drug treatment.

Antiproliferative effects of ruthenium-based nucleolipidic nanoaggregates in human models of breast cancer in vitro: insights into their mode of action

Looking for new metal-based anticancer treatments, in recent years many ruthenium complexes have been proposed as effective and safe potential drugs. In this context we have recently developed a novel approach for the in vivo delivery of Ru(III) complexes, preparing stable ruthenium-based nucleolipidic nanoaggregates endowed with significant antiproliferative activity. Herein we describe the cellular response to our ruthenium-containing formulations in selected models of human breast cancer. By in vitro bioscreens in the context of preclinical studies, we have focused on their ability to inhibit breast cancer cell proliferation by the activation of the intrinsic apoptotic pathway, possibly via mitochondrial perturbations involving Bcl-2 family members and predisposing to programmed cell death. In addition, the most efficient ruthenium-containing cationic nanoaggregates we have hitherto developed are able to elicit both extrinsic and intrinsic apoptosis, as well as autophagy. To limit chemoresistance and counteract uncontrolled proliferation, multiple cell death pathways activation by metal-based chemotherapeutics is a challenging, yet very promising strategy for targeted therapy development in aggressive cancer diseases, such as triple-negative breast cancer with limited treatment options. These outcomes provide valuable, original knowledge on ruthenium-based candidate drugs and new insights for future optimized cancer treatment protocols.

Growth Hormone Receptor Knockdown Sensitizes Human Melanoma Cells to Chemotherapy by Attenuating Expression of ABC Drug Efflux Pumps

Melanoma remains one of the most therapy-resistant forms of human cancer despite recent introductions of highly efficacious targeted therapies. The intrinsic therapy resistance of human melanoma is largely due to abundant expression of a repertoire of xenobiotic efflux pumps of the ATP-binding cassette (ABC) transporter family. Here, we report that GH action is a key mediator of chemotherapeutic resistance in human melanoma cells. We investigated multiple ABC efflux pumps (ABCB1, ABCB5, ABCB8, ABCC1, ABCC2, ABCG1, and ABCG2) reportedly associated with melanoma drug resistance in different human melanoma cells and tested the efficacy of five different anti-cancer compounds (cisplatin, doxorubicin, oridonin, paclitaxel, vemurafenib) with decreased GH action. We found that GH treatment of human melanoma cells upregulates expression of multiple ABC transporters and increases the EC50 of melanoma drug vemurafenib. Also, vemurafenib-resistant melanoma cells had upregulated levels of GH receptor (GHR) expression as well as ABC efflux pumps. GHR knockdown (KD) using siRNA in human melanoma cells treated with sub-EC50 doses of anti-tumor compounds resulted in significantly increased drug retention, decreased cell proliferation and increased drug efficacy, compared to mock-transfected controls. Our set of findings identify an unknown mechanism of GH regulation in mediating melanoma drug resistance and validates GHR as a unique therapeutic target for sensitizing highly therapy-resistant human melanoma cells to lower doses of anti-cancer drugs.