Bcl-2 down-regulation is a novel mechanism of paclitaxel resistance

Site-specific delivery of cisplatin and paclitaxel mediated by liposomes: A promising approach in cancer chemotherapy

The site-specific delivery of drugs, especially anti-cancer drugs has been an interesting field for researchers and the reason is low accumulation of cytotoxic drugs in cancer cells. Although combination cancer therapy has been beneficial in providing cancer drug sensitivity, targeted delivery of drugs appears to be more efficient. One of the safe, biocompatible and efficient nano-scale delivery systems in anti-cancer drug delivery is liposomes. Their particle size is small and they have other properties such as adjustable physico-chemical properties, ease of functionalization and high entrapment efficiency. Cisplatin is a chemotherapy drug with clinical approval in patients, but its accumulation in cancer cells is low due to lack of targeted delivery and repeated administration results in resistance development. Gene and drug co-administration along with cisplatin/paclitaxel have resulted in increased sensitivity in tumor cells, but there is still space for more progress in cancer therapy. The delivery of cisplatin/paclitaxel by liposomes increases accumulation of drug in tumor cells and impairs activity of efflux pumps in promoting cytotoxicity. Moreover, phototherapy along with cisplatin/paclitaxel delivery can increase potential in tumor suppression. Smart nanoparticles including pH-sensitive nanoparticles provide site-specific delivery of cisplatin/paclitaxel. The functionalization of liposomes can be performed by ligands to increase targetability towards tumor cells in mediating site-specific delivery of cisplatin/paclitaxel. Finally, liposomes can mediate co-delivery of cisplatin/paclitaxel with drugs or genes in potentiating tumor suppression. Since drug resistance has caused therapy failure in cancer patients, and cisplatin/paclitaxel are among popular chemotherapy drugs, delivery of these drugs mediates targeted suppression of cancers and prevents development of drug resistance. Because of biocompatibility and safety of liposomes, they are currently used in clinical trials for treatment of cancer patients. In future, the optimal dose of using liposomes and optimal concentration of loading cisplatin/paclitaxel on liposomal nanocarriers in clinical trials should be determined.

Tephrosin Suppresses the Chemoresistance of Paclitaxel-Resistant Ovarian Cancer via Inhibition of FGFR1 Signaling Pathway

Ovarian cancer is the leading cause of death among gynecologic cancers. Paclitaxel is used as a standard first-line therapeutic agent for ovarian cancer. However, chemotherapeutic resistance and high recurrence rates are major obstacles to treating ovarian cancer. We have found that tephrosin, a natural rotenoid isoflavonoid, can resensitize paclitaxel-resistant ovarian cancer cells to paclitaxel. Cell viability, immunoblotting, and a flow cytometric analysis showed that a combination treatment made up of paclitaxel and tephrosin induced apoptotic death. Tephrosin inhibited the phosphorylation of AKT, STAT3, ERK, and p38 MAPK, all of which simultaneously play important roles in survival signaling pathways. Notably, tephrosin downregulated the phosphorylation of FGFR1 and its specific adapter protein FRS2, but it had no effect on the phosphorylation of the EGFR. Immunoblotting and a fluo-3 acetoxymethyl assay showed that tephrosin did not affect the expression or function of P-glycoprotein. Additionally, treatment with N-acetylcysteine did not restore cell cytotoxicity caused by a treatment combination made up of paclitaxel and tephrosin, showing that tephrosin did not affect the reactive oxygen species scavenging pathway. Interestingly, tephrosin reduced the expression of the anti-apoptotic factor XIAP. This study demonstrates that tephrosin is a potent antitumor agent that can be used in the treatment of paclitaxel-resistant ovarian cancer via the inhibition of the FGFR1 signaling pathway.

FBXL2 promotes E47 protein instability to inhibit breast cancer stemness and paclitaxel resistance

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with a high risk of metastasis and recurrence. Although chemotherapy has greatly improved the clinical outcome of TNBC patients, acquired drug resistance remains a huge challenge for TNBC treatment. Breast cancer stem cells (BCSCs) play a critical role in breast cancer development, metastasis, recurrence, and chemotherapy resistance. Thus, it is of great importance to decipher the underlying molecular mechanism of BCSCs regulation for TNBC drug resistance. In this study, we demonstrate that the F-box protein FBXL2 is a critical negative regulator of BCSCs stemness and that downregulation of FBXL2 plays a causal role in TNBC drug resistance. We show that expression levels of FBXL2 significantly influence CD44^high/CD24^low subpopulation and the mammosphere formation ability of TNBC cells. Ectopic expression of FBXL2 inhibits initiation of TNBC and overcomes paclitaxel resistance in vivo. In addition, activation of FBXL2 by nebivolol, a clinically used small-molecule inhibitor of the beta-1 receptor, markedly overcomes BCSCs-induced paclitaxel resistance. Mechanistically, we show that FBXL2 targets transcriptional factor E47 for polyubiquitin- and proteasome-mediated degradation, resulting in inhibition of BCSC stemness. Clinical analyses indicate that low expression of FBXL2 correlates with high expression of E47 as well as with high stemness features, and is associated with poor clinical outcomes of breast cancer patients. Taken together, these results highlight that the FBXL2-E47 axis plays a critical role in the regulation of BCSC stemness and paclitaxel resistance. Thus, targeting FBXL2 might be a potential therapeutic strategy for drug-resistant TNBC.

Chemopreventive effects of hesperidin against paclitaxel-induced hepatotoxicity and nephrotoxicity via amendment of Nrf2/HO-1 and caspase-3/Bax/Bcl-2 signaling pathways

Paclitaxel (PTX) is a widely used chemotherapeutic drug particularly effective against lung, breast, and ovarian cancer, though its usefulness is limited due to its multi-organ toxicity. The mechanisms underlying PTX toxicity are currently not yet known and there are no approved treatments for its control or prevention. This study aimed to investigate whether hesperidin (HSP) had a protective effect on paclitaxel-induced hepatotoxicity and nephrotoxicity from biochemical, and molecular perspectives. The rats were administered PTX 2 mg/kg, b.w. intraperitoneally for the first 5 consecutive days, then 100 or 200 mg/kg b.w. HSP orally for 10 consecutive days. Our results demonstrated that HSP decreased the PTX induced lipid peroxidation, improved the serum hepatic and renal functions (by decreasing the levels of AST, ALT, ALP, urea, and creatinine), and restored the liver and kidney antioxidant armory (SOD, CAT, GPx, and GSH). HSP also significantly reduced mRNA expression levels of NF-κB, TNF-α, IL-1β, IL-6, MAPK 14, Caspase-3, Bax, LC3A, LC3B, MMP2, and MMP9 whereas caused an increase in levels of Nrf2, HO-1, and Bcl-2 in the kidney and liver of PTX-induced rats. In addition, caspase-3, Bax, and Bcl-2 protein levels were examined by Western blot analysis, and it was determined that HSP decreased caspase-3 and Bax protein levels, but increased Bcl-2 protein levels. The findings of the study suggest that HSP has chemopreventive potential against PTX-induced hepatorenal toxicity plausibly through the attenuation of oxidative stress, inflammation, apoptosis, and autophagy.

Inhibition of Glutamine Uptake Resensitizes Paclitaxel Resistance in SKOV3-TR Ovarian Cancer Cell via mTORC1/S6K Signaling Pathway

Ovarian cancer is a carcinoma that affects women and that has a high mortality rate. Overcoming paclitaxel resistance is important for clinical application. However, the effect of amino acid metabolism regulation on paclitaxel-resistant ovarian cancer is still unknown. In this study, the effect of an amino acid-deprived condition on paclitaxel resistance in paclitaxel-resistant SKOV3-TR cells was analyzed. We analyzed the cell viability of SKOV3-TR in culture conditions in which each of the 20 amino acids were deprived. As a result, the cell viability of the SKOV3-TR was significantly reduced in cultures deprived of arginine, glutamine, and lysine. Furthermore, we showed that the glutamine-deprived condition inhibited mTORC1/S6K signaling. The decreased cell viability and mTORC1/S6K signaling under glutamine-deprived conditions could be restored by glutamine and α-KG supplementation. Treatment with PF-4708671, a selective S6K inhibitor, and the selective glutamine transporter ASCT2 inhibitor V-9302 downregulated mTOR/S6K signaling and resensitized SKOV3-TR to paclitaxel. Immunoblotting showed the upregulation of Bcl-2 phosphorylation and a decrease in Mcl-1 expression in SKOV3-TR via the cotreatment of paclitaxel with PF-4708671 and V-9302. Collectively, this study demonstrates that the inhibition of glutamine uptake can resensitize SKOV3-TR to paclitaxel and represents a promising therapeutic target for overcoming paclitaxel resistance in ovarian cancer.

MiR-181c sensitizes ovarian cancer cells to paclitaxel by targeting GRP78 through the PI3K/Akt pathway

Primary cytoreductive surgery with platinum-taxane-based chemotherapy is the standard treatment for ovarian cancer (OC) patients; however, resistance to chemotherapy is a contributing factor to OC mortality. Paclitaxel (PTX), the most widely used taxane, has become the first-line drug against OC. The molecular mechanism of PTX resistance is different from that of platinum-based agents and is still not completely elucidated. Our previous study showed that glucose-regulated protein 78 (GRP78) is involved in the resistance of OC cells to PTX. However, little is known regarding endogenous inhibitors of this gene. MicroRNAs (miRNAs) play critical roles in the regulation of gene expression; therefore, we sought to identify miRNA(s) with potential to target GRP78 under the hypothesis that miRNA(s) could serve as potential therapeutic targets. Here, we show that miR-181c, predicted to target GRP78, was downregulated in PTX-resistant OC cells and tissues. MiR-181c downregulated GRP78 expression and induced apoptosis by directly targeting its 3'-untranslated region (UTR). Overexpression of miR-181c sensitized resistant OC to PTX by inhibiting the PI3K/Akt pathway in vitro and in vivo. Taken together, our findings indicate that the delivery of miR-181c can efficiently suppress GRP78 expression and GRP78-mediated PTX resistance in OC and suggest that this strategy has therapeutic potential.

Fungal Endophytes: an Accessible Source of Bioactive Compounds with Potential Anticancer Activity

Endophytes either be bacteria, fungi, or actinomycetes colonize inside the tissue of host plants without showing any immediate negative effects on them. Among numerous natural alternative sources, fungal endophytes produce a wide range of structurally diverse bioactive metabolites including anticancer compounds. Considering the production of bioactive compounds in low quantity, genetic and physicochemical modification of the fungal endophytes is performed for the enhanced production of bioactive compounds. Presently, for the treatment of cancer, chemotherapy is majorly used, but the side effects of chemotherapy are of prime concern in clinical practices. Also, the drug-resistant properties of carcinoma cells, lack of cancer cells-specific medicine, and the side effects of drugs are the biggest obstacles in cancer treatment. The interminable requirement of potential drugs has encouraged researchers to seek alternatives to find novel bioactive compounds, and fungal endophytes seem to be a probable target for the discovery of anticancer drugs. The present review focuses a comprehensive literature on the major fungal endophyte-derived bioactive compounds which are presently been used for the management of cancer, biotic factors influencing the production of bioactive compounds and about the challenges in the field of fungal endophyte research.

Molecular mechanisms associated with chemoresistance in esophageal cancer

Esophageal cancer (EC) is one of the most incident and lethal tumors worldwide. Although surgical resection is an important approach in EC treatment, late diagnosis, metastasis and recurrence after surgery have led to the management of adjuvant and neoadjuvant therapies over the past few decades. In this scenario, 5-fluorouracil (5-FU) and cisplatin (CISP), and more recently paclitaxel (PTX) and carboplatin (CBP), have been traditionally used in EC treatment. However, chemoresistance to these agents along EC therapeutic management represents the main obstacle to successfully treat this malignancy. In this sense, despite the fact that most of chemotherapy drugs were discovered several decades ago, in many cases, including EC, they still represent the most affordable and widely employed treatment approach for these tumors. Therefore, this review summarizes the main mechanisms through which the response to the most widely chemotherapeutic agents used in EC treatment is impaired, such as drug metabolism, apoptosis resistance, cancer stem cells (CSCs), cell cycle, autophagy, energetic metabolism deregulation, tumor microenvironment and epigenetic modifications.

Chemotherapy in metastatic castration-resistant prostate cancer: Current scenario and future perspectives

Taxanes - docetaxel and cabazitaxel - are the most active chemotherapy drugs currently used for the treatment of metastatic castration-resistant prostate cancer (mCRPC). However, despite a good initial response and survival benefit, nearly all patients eventually develop resistance, which is an important barrier to long-term survival. Resistance to taxanes is also associated with cross-resistance to androgen receptor signaling inhibitors (ARSIs). Unfortunately, other than platinum-based treatments, which have demonstrated some benefit in a subset of patients with Aggressive Variant Prostate Cancer (AVPC), few therapeutic options are available to patients progressing to taxanes. Hence, more research is required to determine whether platinum-based chemotherapy will confer a survival benefit in mCRPC, and the identification of predictive biomarkers and the clinical evaluation of platinum compounds in molecularly selected patients is an urgent but unmet clinical need. The present review focuses on the current status of chemotherapy treatments in mCRPC, interactions with androgen deprivation therapy (ADT) and novel ARSIs, and the main mechanisms of resistance. We will examine the impact of platinum-based treatments in mCRPC and summarize the known predictive biomarkers of platinum response. Finally, future approaches and avenues will be discussed.

An in vivo genome-wide shRNA screen identifies BCL6 as a targetable biomarker of paclitaxel resistance in breast cancer

Paclitaxel is a common breast cancer drug; however, some tumors are resistant. The identification of biomarkers for paclitaxel resistance or sensitivity would enable the development of strategies to improve treatment efficacy. A genome-wide in vivo shRNA screen was performed on paclitaxel-treated mice with MDA-MB-231 tumors to identify genes associated with paclitaxel sensitivity or resistance. Gene expression of the top screen hits was associated with tumor response (resistance or sensitivity) among patients who received neoadjuvant chemotherapy containing paclitaxel. We focused our validation on screen hit B-cell lymphoma 6 (BCL6), which is a therapeutic target in cancer but for which no effects on drug response have been reported. Knockdown of BCL6 resulted in increased tumor regression in mice treated with paclitaxel. Similarly, inhibiting BCL6 using a small molecule inhibitor enhanced paclitaxel treatment efficacy both in vitro and in vivo in breast cancer models. Mechanism studies revealed that reduced BCL6 enhances the efficacy of paclitaxel by inducing sustained G1/S arrest, concurrent with increased apoptosis and expression of target gene cyclin-dependent kinase inhibitor 1A. In summary, the genome-wide shRNA knockdown screen has identified BCL6 as a potential targetable resistance biomarker of paclitaxel response in breast cancer.

Paclitaxel-Based Chemotherapy Targeting Cancer Stem Cells from Mono- to Combination Therapy

Paclitaxel (PTX) is a chemotherapeutical agent commonly used to treat several kinds of cancer. PTX is known as a microtubule-targeting agent with a primary molecular mechanism that disrupts the dynamics of microtubules and induces mitotic arrest and cell death. Simultaneously, other mechanisms have been evaluated in many studies. Since the anticancer activity of PTX was discovered, it has been used to treat many cancer patients and has become one of the most extensively used anticancer drugs. Regrettably, the resistance of cancer to PTX is considered an extensive obstacle in clinical applications and is one of the major causes of death correlated with treatment failure. Therefore, the combination of PTX with other drugs could lead to efficient therapeutic strategies. Here, we summarize the mechanisms of PTX, and the current studies focusing on PTX and review promising combinations.

Therapeutic strategies to overcome taxane resistance in cancer

One of the primary causes of attenuated or loss of efficacy of cancer chemotherapy is the emergence of multidrug resistance (MDR). Numerous studies have been published regarding potential approaches to reverse resistance to taxanes, including paclitaxel (PTX) and docetaxel, which represent one of the most important classes of anticancer drugs. Since 1984, following the FDA approval of paclitaxel for the treatment of advanced ovarian carcinoma, taxanes have been extensively used as drugs that target tumor microtubules. Taxanes, have been shown to affect an array of oncogenic signaling pathways and have potent cytotoxic efficacy. However, the clinical success of these drugs has been restricted by the emergence of cancer cell resistance, primarily caused by the overexpression of MDR efflux transporters or by microtubule alterations. In vitro and in vivo studies indicate that the mechanisms underlying the resistance to PTX and docetaxel are primarily due to alterations in α-tubulin and β-tubulin. Moreover, resistance to PTX and docetaxel results from: 1) alterations in microtubule-protein interactions, including microtubule-associated protein 4, stathmin, centriole, cilia, spindle-associated protein, and kinesins; 2) alterations in the expression and activity of multidrug efflux transporters of the ABC superfamily including P-glycoprotein (P-gp/ABCB1); 3) overexpression of anti-apoptotic proteins or inhibition of apoptotic proteins and tumor-suppressor proteins, as well as 4) modulation of signal transduction pathways associated with the activity of several cytokines, chemokines and transcription factors. In this review, we discuss the abovementioned molecular mechanisms and their role in mediating cancer chemoresistance to PTX and docetaxel. We provide a detailed analysis of both in vitro and in vivo experimental data and describe the application of these findings to therapeutic practice. The current review also discusses the efficacy of different pharmacological modulations to achieve reversal of PTX resistance. The therapeutic roles of several novel compounds, as well as herbal formulations, are also discussed. Among them, many structural derivatives had efficacy against the MDR phenotype by either suppressing MDR or increasing the cytotoxic efficacy compared to the parental drugs, or both. Natural products functioning as MDR chemosensitizers offer novel treatment strategies in patients with chemoresistant cancers by attenuating MDR and increasing chemotherapy efficacy. We broadly discuss the roles of inhibitors of P-gp and other efflux pumps, in the reversal of PTX and docetaxel resistance in cancer cells and the significance of using a nanomedicine delivery system in this context. Thus, a better understanding of the molecular mechanisms mediating the reversal of drug resistance, combined with drug efficacy and the application of target-based inhibition or specific drug delivery, could signal a new era in modern medicine that would limit the pathological consequences of MDR in cancer patients.

Towards a unified open access dataset of molecular interactions

The International Molecular Exchange (IMEx) Consortium provides scientists with a single body of experimentally verified protein interactions curated in rich contextual detail to an internationally agreed standard. In this update to the work of the IMEx Consortium, we discuss how this initiative has been working in practice, how it has ensured database sustainability, and how it is meeting emerging annotation challenges through the introduction of new interactor types and data formats. Additionally, we provide examples of how IMEx data are being used by biomedical researchers and integrated in other bioinformatic tools and resources.

Cabazitaxel exhibits more favorable molecular changes compared to other taxanes in androgen-independent prostate cancer cells

Taxane-based chemotherapy drugs (cabazitaxel, docetaxel, and paclitaxel) are microtubule inhibitors, which are effectively and frequently used to treat metastatic prostate cancer (PCa). Among these, cabazitaxel is offered as a new therapeutic option for patients with metastatic castration-resistant PC as that are resistant to other taxanes. Here, we investigated the cellular and molecular changes in response to cabazitaxel in comparison with docetaxel and paclitaxel in androgen-independent human PCas. The androgen-independent human PCa cell lines, PC3 and DU145, were treated with 1 to 5nM cabazitaxel, docetaxel, or paclitaxel, and assessed for cell viability (MTT assay), colony forming ability and migration (scratch assay). The induction of apoptosis was determined through measurement of mitochondrial membrane potential (JC-1 assay) and caspase-3 activity assay. The protein expression changes (caspase-3, caspase-8, Bax, Bcl-2, β-tubulin, nuclear factor-κB [NF-κB/p50, NF-κB/p65], vascular endothelial growth factor, WNT1-inducible signaling pathway protein-1 [WISP1], transforming growth factor β [TGF-β]) in response to drug treatment were screened via western blotting. Under our experimental conditions, all taxanes significantly reduced WISP1 and TGF-β expressions, suggesting an anti-metastatic/antiangiogenic effect for these drugs. On the other hand, cabazitaxel induced more cell death and inhibited colony formation compared to docetaxel or paclitaxel. The highest fold change in caspase-3 activity and Bax/Bcl-2 ratio was also detected in response to cabazitaxel. Furthermore, the induction of β-tubulin expression was lower in cabazitaxel-treated cells relative to the other taxanes. In summary, cabazitaxel shows molecular changes in favor of killing PCa cells compared to other taxanes, at least for the parameters analyzed herein. The differences with other taxanes may be important while designing other studies or in clinical settings.

The transcription factor ZEB1 promotes chemoresistance in prostate cancer cell lines

One of the factors promoting tumoral progress is the abnormal activation of the epithelial–mesenchymal transition (EMT) program which has been associated with chemoresistance in tumoral cells. The transcription factor zinc finger E-box-binding homeobox 1 (ZEB1), a key EMT activator, has recently been related to docetaxel resistance, the main chemotherapeutic used in advanced prostate cancer treatment. The mechanisms involved in this protective effect are still unclear. In a previous work, we demonstrated that ZEB1 expression induced an EMT-like phenotype in prostate cancer cell lines. In this work, we used prostate cancer cell lines 22Rv1 and DU145 to study the effect of ZEB1 modulation on docetaxel resistance and its possible mechanisms. The results showed that ZEB1 overexpression conferred to 22Rv1 cell resistance to docetaxel while its silencing made DU145 cells more sensitive to it. Analysis of resistance markers showed no presence of ATP-binding cassette subfamily B member 1 (MDR1) and no changes in breast cancer resistance protein (BCRP) or ATP-binding cassette subfamily C member 10 (MRP7). However, a correlation between ZEB1, multidrug resistance-associated protein 1 (MRP1), and ATP-binding cassette subfamily C member 4 (MRP4) expression was observed. MRP4 inhibition, using MK571, resensitized cells with ZEB1 overexpression to docetaxel treatment. In addition, modulation of ZEB1 and subsequent change in MRP4 expression correlated with a lower apoptotic response to docetaxel, characterized by lower B-cell lymphoma 2 (Bcl2), high BCL2-associated X protein (Bax), and high active caspase 3 expression. The response to docetaxel in our model seems to be mediated mainly by activation of the apoptotic death program. Our results showed that modulation of MRP4 could be a mediator of ZEB1-related resistance to docetaxel in prostate cancer, making it a possible marker for chemotherapy response in patients who do not express MDR1.

Role of Mitochondria in Cancer Stem Cell Resistance

Cancer stem cells (CSC) are associated with the mechanisms of chemoresistance to different cytotoxic drugs or radiotherapy, as well as with tumor relapse and a poor prognosis. Various studies have shown that mitochondria play a central role in these processes because of the ability of this organelle to modify cell metabolism, allowing survival and avoiding apoptosis clearance of cancer cells. Thus, the whole mitochondrial cycle, from its biogenesis to its death, either by mitophagy or by apoptosis, can be targeted by different drugs to reduce mitochondrial fitness, allowing for a restored or increased sensitivity to chemotherapeutic drugs. Once mitochondrial misbalance is induced by a specific drug in any of the processes of mitochondrial metabolism, two elements are commonly boosted: an increment in reactive nitrogen/oxygen species and, subsequently, activation of the intrinsic apoptotic pathway.

The microtubule targeting agents eribulin and paclitaxel activate similar signaling pathways and induce cell death predominantly in a caspase-independent manner

Microtubule-targeting agents (MTAs) are the most effective chemotherapeutics used in cancer therapy to date, but their clinical use is often hampered by the acquisition of resistance. Thereby, elucidation of the molecular signaling pathways activated by novel FDA-approved MTAs such as eribulin is important for future therapeutic applications. In contrast to several reports, we show here that regardless of the presence of caspase-3, clinically relevant concentrations of eribulin and the classical MTA paclitaxel predominantly induce caspase-independent cell death in MCF-7 breast carcinoma cells. On the molecular level, several key proteins involved in apoptosis such as p53, Plk1, caspase-2, and Bim as well as the two MAPKs ERK and JNK were activated by both compounds to a similar extent. However, none of them proved to be important for eribulin- and paclitaxel-induced cytotoxicity, as their siRNA-mediated knockdown or inactivation by small molecule inhibitors did not alter cell death rates. In contrast, knockdown of the anti-apoptotic Bcl-2 protein, which becomes heavily phosphorylated at Ser70 during MTA treatment, resulted surprisingly in a reduction of MTA-mediated cell death. This phenomenon can be most likely explained by our observation that the absence of Bcl-2 slowed down cell cycle progression resulting in fewer cells entering mitosis, thereby delaying the mitotic capability of these MTAs to induce cell death. Taken together, although eribulin and paclitaxel disturb the mitotic spindle differently, they exhibit no functional differences in downstream molecular cell death signaling in MCF-7 breast cancer cells.

CETSA-based target engagement of taxanes as biomarkers for efficacy and resistance

The use of taxanes has for decades been crucial for treatment of several cancers. A major limitation of these therapies is inherent or acquired drug resistance. A key to improved outcome of taxane-based therapies is to develop tools to predict and monitor drug efficacy and resistance in the clinical setting allowing for treatment and dose stratification for individual patients. To assess treatment efficacy up to the level of drug target engagement, we have established several formats of tubulin-specific Cellular Thermal Shift Assays (CETSAs). This technique was evaluated in breast and prostate cancer models and in a cohort of breast cancer patients. Here we show that taxanes induce significant CETSA shifts in cell lines as well as in animal models including patient-derived xenograft (PDX) models. Furthermore, isothermal dose response CETSA measurements allowed for drugs to be rapidly ranked according to their reported potency. Using multidrug resistant cancer cell lines and taxane-resistant PDX models we demonstrate that CETSA can identify taxane resistance up to the level of target engagement. An imaging-based CETSA format was also established, which in principle allows for taxane target engagement to be accessed in specific cell types in complex cell mixtures. Using a highly sensitive implementation of CETSA, we measured target engagement in fine needle aspirates from breast cancer patients, revealing a range of different sensitivities. Together, our data support that CETSA is a robust tool for assessing taxane target engagement in preclinical models and clinical material and therefore should be evaluated as a prognostic tool during taxane-based therapies.

The E-Cadherin and N-Cadherin Switch in Epithelial-to-Mesenchymal Transition: Signaling, Therapeutic Implications, and Challenges

Epithelial-to-Mesenchymal Transition (EMT) has been shown to be crucial in tumorigenesis where the EMT program enhances metastasis, chemoresistance and tumor stemness. Due to its emerging role as a pivotal driver of tumorigenesis, targeting EMT is of great therapeutic interest in counteracting metastasis and chemoresistance in cancer patients. The hallmark of EMT is the upregulation of N-cadherin followed by the downregulation of E-cadherin, and this process is regulated by a complex network of signaling pathways and transcription factors. In this review, we summarized the recent understanding of the roles of E- and N-cadherins in cancer invasion and metastasis as well as the crosstalk with other signaling pathways involved in EMT. We also highlighted a few natural compounds with potential anti-EMT property and outlined the future directions in the development of novel intervention in human cancer treatments. We have reviewed 287 published papers related to this topic and identified some of the challenges faced in translating the discovery work from bench to bedside.

In Preclinical Model of Ovarian Cancer, the SGK1 Inhibitor SI113 Counteracts the Development of Paclitaxel Resistance and Restores Drug Sensitivity

Ovarian cancer is the second most common gynecological malignancy worldwide. Paclitaxel is particularly important in the therapy of ovarian carcinomas, but the treatment efficacy is counteracted by the development of resistance to chemotherapy. The identification of target molecules that can prevent or control the development of chemoresistance might provide important tools for the management of patients affected by ovarian cancer. Serum- and glucocorticoid-regulated kinase 1 (SGK1) appears to be a key determinant of resistance to chemo- and radiotherapy. Specifically, SGK1 affects paclitaxel sensitivity in RKO colon carcinoma cells by modulating the specificity protein 1 (SP1)–dependent expression of Ran-specific GTPase-activating protein (RANBP1), a member of the GTP-binding nuclear protein Ran (RAN) network that is required for the organization and function of the mitotic spindle. SGK1 inhibition might thus be useful for counteracting the development of paclitaxel resistance. Here, we present in vitro data obtained using ovarian carcinoma cell lines that indicate that the SGK1 inhibitor SI113 inhibits cancer cell proliferation, potentiates the effects of paclitaxel-based chemotherapy, counteracts the development of paclitaxel resistance, and restores paclitaxel sensitivity in paclitaxel-resistant A2780 ovarian cancer cells. The results were corroborated by preclinical studies of xenografts generated in nude mice through the implantation of paclitaxel-resistant human ovarian cancer cells. The SGK1 inhibitor SI113 synergizes with paclitaxel in the treatment of xenografted ovarian cancer cells. Taken together, these data suggest that SGK1 inhibition should be investigated in clinical trials for the treatment of paclitaxel-resistant ovarian cancer.

Resistance to paclitaxel is associated with a variant of the gene BCL2 in multiple tumor types

Paclitaxel, the most commonly used form of chemotherapy, is utilized in curative protocols in different types of cancer. The response to treatment differs among patients. Biological interpretation of a mechanism to explain this personalized response is still unavailable. Since paclitaxel is known to target BCL2 and TUBB1, we used pan-cancer genomic data from hundreds of patients to show that a single-nucleotide variant in the BCL2 sequence can predict a patient’s response to paclitaxel. Here, we show a connection between this BCL2 genomic variant, its transcript structure, and protein abundance. We demonstrate these findings in silico, in vitro, in formalin-fixed paraffin-embedded (FFPE) tissue, and in patient lymphocytes. We show that tumors with the specific variant are more resistant to paclitaxel. We also show that tumor and normal cells with the variant express higher levels of BCL2 protein, a phenomenon that we validated in an independent cohort of patients. Our results indicate BCL2 sequence variations as determinants of chemotherapy resistance. The knowledge of individual BCL2 genomic sequences prior to the choice of chemotherapy may improve patient survival. The current work also demonstrates the benefit of community-wide, integrative omics data sources combined with in-lab experimentation and validation sets.

TP53 mutations in high grade serous ovarian cancer and impact on clinical outcomes: a comparison of next generation sequencing and bioinformatics analyses

Objective

Mutations in TP53 are found in the majority of high grade serous ovarian cancers, leading to gain of function or loss of function of its protein product, p53, involved in oncogenesis. There have been conflicting reports as to the impact of the type of these on prognosis. We aim to further elucidate this relationship in our cohort of patients.

Methods

229 patients with high grade serous ovarian cancer underwent tumor profiling through an institutional molecular screening program with targeted next generation sequencing. TP53 mutations were classified using methods previously described in the literature. Immunohistochemistry on formalin-fixed paraffin embedded tissue was used to assess for TP53 mutation. Using divisive hierarchal clustering, we generated patient clusters with similar clinicopathologic characteristics to investigate differences in outcomes.

Results

Six different classification schemes of TP53 mutations were studied. These did not show an association with first platinum-free interval or overall survival. Next generation sequencing reliably predicted mutation in 80% of cases, similar to the proportion detected by immunohistochemistry. Divisive hierarchical clustering generated four main clusters, with cluster 3 having a significantly worse prognosis (p<0.0001; log-rank test). This cluster had a higher concentration of gain of function mutations and these patients were less likely to have undergone optimal debulking surgery.

Conclusions

Different classifications of TP53 mutations did not show an impact on outcomes in this study. Immunohistochemistry was a good predictor for TP53 mutation. Cluster analysis showed that a subgroup of patients with gain of function mutations (cluster 3) had a worse prognosis.

CD24 Expression and differential resistance to chemotherapy in triple-negative breast cancer

Breast cancer (BC) is a leading cause of cancer-related death in women. Adjuvant systemic chemotherapies are effective in reducing risks of recurrence and have contributed to reduced BC mortality. Although targeted adjuvant treatments determined by biomarkers for endocrine and HER2-directed therapies are largely successful, predicting clinical benefit from chemotherapy is more challenging. Drug resistance is a major reason for treatment failures. Efforts are ongoing to find biomarkers to select patients most likely to benefit from chemotherapy. Importantly, cell surface biomarkers CD44+/CD24- are linked to drug resistance in some reports, yet underlying mechanisms are largely unknown. This study focused on the potential role of CD24 expression in resistance to either docetaxel or doxorubicin in part by the use of triple-negative BC (TNBC) tissue microarrays. In vitro assays were also done to assess changes in CD24 expression and differential drug susceptibility after chemotherapy. Further, mouse tumor xenograft studies were done to confirm in vitro findings. Overall, the results show that patients with CD24-positive TNBC had significantly worse overall survival and disease-free survival after taxane-based treatment. Also, in vitro cell studies show that CD44+/CD24+/high cells are more resistant to docetaxel, while CD44+/CD24-/low cells are resistant to doxorubicin. Both in vitro and in vivo studies show that cells with CD24-knockdown are more sensitive to docetaxel, while CD24-overexpressing cells are more sensitive to doxorubicin. Further, mechanistic studies indicate that Bcl-2 and TGF-βR1 signaling via ATM-NDRG2 pathways regulate CD24. Hence, CD24 may be a biomarker to select chemotherapeutics and a target to overcome TNBC drug resistance.

Association of the AA genotype of the BCL2 (–938C>A) promoter polymorphism with better survival in ovarian cancer

Background

Bcl-2 plays a key role in the regulation of apoptosis. Recently, a novel regulatory single nucleotide polymorphism (–938C>A) in the inhibitory P2 BCL2 promoter was described. In this study we investigated its potential association with survival in epithelial ovarian cancer.

Experimental design

Patients (n=110) with primary epithelial ovarian cancer were retrospectively genotyped by pyrosequencing.

Results

Genotype distribution was not significantly different between 110 ovarian cancer patients and 120 healthy controls, suggesting that genotypes of this polymorphism do not increase the susceptibility to ovarian cancer. Kaplan-Meier curves showed a significant association of the AA genotype with increased survival (p=0.002). Multivariate analysis revealed that the BCL2–938AC/CC genotype (hazard ratio 4.5; p=0.003) was an independent prognostic factor compared to other prognostic factors such as age, histological grade or tumor stage.

Conclusion

The results suggest a role for the BCL2-938C>A polymorphism as a marker for survival in patients with epithelial ovarian cancer.

Programmed death-1 pathway blockade produces a synergistic antitumor effect: combined application in ovarian cancer

Programmed death-1 (PD-1) and its ligand are part of the immune checkpoint pathway that down-regulates effector T cells in immune response, thereby causing immune suppression. The PD-1/programmed death-ligand 1 (PD-L1) pathway can be blocked by antibodies to reverse tumor-mediated immunosuppression. However, advanced cancers such as stage III-IV ovarian cancer (OC) and certain types such as ID8 OC (a clone of C57BL/6 mouse OC) may hijack the PD-1/PD-L1 pathway to escape immune attack. When combined with chemotherapy, radiotherapy, targeted therapy, immunotherapy, or other agents, these PD-1/PD-L1 pathway blockages can produce a synergistic antitumor response in OC. Combined immunotherapy significantly prolongs overall survival by changing the tumor microenvironment through processes such as increasing the number of CD4⁺ or CD8⁺ T cells or cytokines in mice with OC and decreasing the number of regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs). OC patients treated with combined immunotherapy received better prognoses than those treated with monotherapy. This review reflects the move toward novel therapy combinations for OC and discusses these promising immunotherapeutic approaches, which are more cost-effective and effective than other approaches.

Effect of SP600125 on the mitotic spindle in HeLa Cells, leading to mitotic arrest, endoreduplication and apoptosis

BACKGROUND

The JNK inhibitor SP600125 strongly inhibits cell proliferation in many human cancer cells by blocking mitosis progression and inducing cell death. Despite, all this study, the mechanism by which SP600125 inhibits mitosis-related effects in human cervical cells (HeLa cells) remains unclear. In this study, we investigated the effects of SP600125 on the cell viability, cell cycle, and on the spindle assembly during mitosis in HeLa cells.

METHODS

To explore this approach, we used a viability test, an immunofluorescence microscopy to detect Histone phosphorylation and mitotic spindle aberrations. Apoptosis was characterised using Western Blotting.

RESULTS

Treatment of HeLa cells with varying concentrations of SP600125 induces significant G2/M cell cycle arrest with elevated phosphorylation of histone H3 within 48 h, and endoreduplication after 48 h. SP600125 also induces significant abnormal mitotic spindle. High concentrations of SP600125 (20 μM) induce disturbing microtubule assembly in vitro. Additionally, SP600125- induced delayed apoptosis and cell death was accompanied by significant poly ADP-ribose polymerase (PARP) cleavage and caspase-3 activation in the late phase (at 72 h).

CONCLUSION

Our results confirmed that SP600125 induce mitosis arrest in G2/M, endoreduplication, mitotic spindle aberrations and apoptosis.

The role of docetaxel in the treatment of non-small cell lung cancer lung cancer: an update

INTRODUCTION

Non-small cell lung cancer lung cancer (NSCLC) is a devastating disease, with poor prognosis for patients with metastatic disease. The management of these patients has evolved during the past decade, challenging the role of cytotoxic chemotherapy as the only available treatment option. Nevertheless, chemotherapy still retains a dominant position for the majority of both treatment naïve and pretreated patients. Among the chemotherapeutic agents, docetaxel is one of the most commonly used in 1st and subsequent treatment lines, even in the current era of precision medicine. Areas covered: We searched Medline, Embase, Scopus and Cochrane Library for randomized phase III trials that evaluated docetaxel in various clinical settings of NSCLC and for meta-analyses of such trials and we present all relevant data regarding the pharmacology and clinical use of docetaxel in NSCLC. Expert commentary: Despite its diminishing role, docetaxel in combination with novel targeted agents remains an important option of the therapeutic armamentarium in advanced NSCLC.

An increase in glucosylceramide synthase induces Bcl-xL-mediated cell survival in vinorelbine-resistant lung adenocarcinoma cells

Reversing drug resistance with concurrent treatment confers anticancer benefits. In this study, we investigated the potential mechanism of glucosylceramide synthase (GCS)-mediated vinca alkaloid vinorelbine (VNR) resistance in human lung adenocarcinoma cells. Compared with PC14PE6/AS2 (AS2) and CL1-0 cells, apoptotic analysis showed that both A549 and CL1-5 cells were VNR-resistant, while these cells highly expressed GCS at the protein level. VNR treatment significantly converts ceramide to glucosylceramide in VNR-resistant cells; however, pharmacologically inhibiting GCS with (±)-threo-1-Phenyl-2-decanoylamino-3-morpholino-1-propanol hydrochloride (PDMP) induced ceramide accumulation, accompanied by a decrease in glucosylceramide. Under concurrent treatment with VNR and PDMP, an increase in cell apoptosis could be identified; furthermore, genetically silencing GCS confirmed these effects. In VNR-resistant cells, Bcl-xL expression was aberrantly increased, while pharmacologically inhibiting Bcl-xL with ABT-737 sensitized cells to VNR-induced apoptosis. Conversely, enforced expression of Bcl-xL strengthened the survival response of the VNR-susceptible cells AS2 and CL1-0. Without changes in mRNA expression, Bcl-xL was overexpressed independent of β-catenin-mediated transcriptional regulation in VNR-resistant cells. Simultaneous GCS inhibition and VNR treatment caused a decrease in Bcl-xL expression. According to these findings, an increase in GCS caused Bcl-xL augmentation, facilitating VNR resistance in lung adenocarcinoma cells.

β-III tubulin modulates the behavior of Snail overexpressed during the epithelial-to-mesenchymal transition in colon cancer cells

Class III β-tubulin (TUBB3) is a marker of drug resistance expressed in a variety of solid tumors. Originally, it was described as an important element of chemoresistance to taxanes. Recent studies have revealed that TUBB3 is also involved in an adaptive response to a microenvironmental stressor, e.g. low oxygen levels and poor nutrient supply in some solid tumors, independently of the microtubule targeting agent. Furthermore, it has been demonstrated that TUBB3 is a marker of biological aggressiveness associated with modulation of metastatic abilities in colon cancer. The epithelial-to-mesenchymal transition (EMT) is a basic cellular process by which epithelial cells lose their epithelial behavior and become invasive cells involved in cancer metastasis. Snail is a zinc-finger transcription factor which is able to induce EMT through the repression of E-cadherin expression. In the presented studies we focused on the analysis of the TUBB3 role in EMT-induced colon adenocarcinoma cell lines HT-29 and LS180. We observed a positive correlation between Snail presence and TUBB3 upregulation in tested adenocarcinoma cell lines. The cellular and behavioral analysis revealed for the first time that elevated TUBB3 level is functionally linked to increased cell migration and invasive capability of EMT induced cells. Additionally, the post-transcriptional modifications (phosphorylation, glycosylation) appear to regulate the cellular localization of TUBB3 and its phosphorylation, observed in cytoskeleton, is probably involved in cell motility modulation.

The significance and therapeutic potential of PD-1 and its ligands in ovarian cancer: A systematic review

Surgery, radiotherapy and chemotherapy are the mainstay of malignant cancer treatments. However, with the development of immunology, the emerging immunotherapy represents a rational and alternative approach for the treatment of human cancer, including ovarian cancer (OC). Based on a body of evidence and the clinical success of immunotherapy in many malignancies, it is confirmed that blocking the programmed death 1 (PD-1) and its ligands in OC is feasible and valid both in animal models and patients. Immunotherapy may play a significant role in the future clinical management and improve the prognosis of OC. This review will focus on the biological functions, treatment response, toxicity and viable target of PD-1 and its ligands in OC. Recognition of the multiple functions of PD-1 and its ligands in ovarian cancer will serve to deepen our understanding of the nature of OC, develop novel immunotherapy approaches and discover possible diagnostic and prognostic biomarkers in future clinical decisions.

Paclitaxel and the dietary flavonoid fisetin: a synergistic combination that induces mitotic catastrophe and autophagic cell death in A549 non-small cell lung cancer cells

Background

The use of the dietary polyphenols as chemosensitizing agents to enhance the efficacy of conventional cytostatic drugs has recently gained the attention of scientists and clinicians as a plausible approach for overcoming the limitations of chemotherapy (e.g. drug resistance and cytotoxicity). The aim of this study was to investigate whether a naturally occurring diet-based flavonoid, fisetin, at physiologically attainable concentrations, could act synergistically with clinically achievable doses of paclitaxel to produce growth inhibitory and/or pro-death effects on A549 non-small cell lung cancer cells, and if it does, what mechanisms might be involved.

Methods

The drug–drug interactions were analyzed based on the combination index method of Chou and Talalay and the data from MTT assays. To provide some insights into the mechanism underlying the synergistic action of fisetin and paclitaxel, selected morphological, biochemical and molecular parameters were examined, including the morphology of cell nuclei and mitotic spindles, the pattern of LC3-II immunostaining, the formation of autophagic vacuoles at the electron and fluorescence microscopic level, the disruption of cell membrane asymmetry/integrity, cell cycle progression and the expression level of LC3-II, Bax, Bcl-2 and caspase-3 mRNA.

Results

Here, we reported the first experimental evidence for the existence of synergism between fisetin and paclitaxel in the in vitro model of non-small cell lung cancer. This synergism was, at least partially, ascribed to the induction of mitotic catastrophe. The switch from the cytoprotective autophagy to the autophagic cell death was also implicated in the mechanism of the synergistic action of fisetin and paclitaxel in the A549 cells. In addition, we revealed that the synergism between fisetin and paclitaxel was cell line-specific as well as that fisetin synergizes with arsenic trioxide, but not with mitoxantrone and methotrexate in the A549 cells.

Conclusions

Our results provide rationale for further testing of fisetin in the combination with paclitaxel or arsenic trioxide to obtain detailed insights into the mechanism of their synergistic action as well as to evaluate their toxicity towards normal cells in an animal model in vivo. We conclude that this study is potentially interesting for the development of novel chemotherapeutic approach to non-small cell lung cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-016-0288-3) contains supplementary material, which is available to authorized users.

Mitochondrial dynamics regulating chemoresistance in gynecological cancers

Chemoresistance enables cancer cells to evade apoptotic stimuli and leads to poor clinical prognosis. It arises from dysregulation of signaling factors responsible for inducing cell proliferation and death and for modulating the microenvironment. In gynecologic cancers, p53 is a pivotal determinant of cisplatin sensitivity, while BCL-2 family members are associated with taxane sensitivity. Mitochondria fusion and fission dynamics are required for many mitochondrial functions and are also involved in mitochondria-mediated apoptosis, which is closely associated with chemosensitivity. Mitochondrial dynamics are controlled by a number of intracellular proteins, including fusion (Opa1 and mitofusion 1 and 2) and fission proteins (Drp1 and Fis1), which can be proapoptotic or antiapoptotic, depending on the cell types, status, and stimuli from the microenvironment. This paper describes the role of mitochondrial dynamics in the mechanism of chemoresistance and the evidence supporting a significant contribution of a hyperfusion state to chemoresistance in gynecological cancers. Moreover, we discuss our findings showing that enforced fission induces apoptosis of cancer cells and sensitizes them to chemotherapeutic agents. Understanding the regulation of mitochondrial dynamics in chemoresistance may provide insight into new biomarkers that better predict cancer chemosensitivity and may aid the development of effective therapeutic strategies for clinical management of gynecologic cancers.

Paclitaxel Through the Ages of Anticancer Therapy: Exploring Its Role in Chemoresistance and Radiation Therapy

Paclitaxel (Taxol^®) is a member of the taxane class of anticancer drugs and one of the most common chemotherapeutic agents used against many forms of cancer. Paclitaxel is a microtubule-stabilizer that selectively arrests cells in the G2/M phase of the cell cycle, and found to induce cytotoxicity in a time and concentration-dependent manner. Paclitaxel has been embedded in novel drug formulations, including albumin and polymeric micelle nanoparticles, and applied to many anticancer treatment regimens due to its mechanism of action and radiation sensitizing effects. Though paclitaxel is a major anticancer drug which has been used for many years in clinical treatments, its therapeutic efficacy can be limited by common encumbrances faced by anticancer drugs. These encumbrances include toxicities, de novo refraction, and acquired multidrug resistance (MDR). This article will give a current and comprehensive review of paclitaxel, beginning with its unique history and pharmacology, explore its mechanisms of drug resistance and influence in combination with radiation therapy, while highlighting current treatment regimens, formulations, and new discoveries.

MiRNA-149 modulates chemosensitivity of ovarian cancer A2780 cells to paclitaxel by targeting MyD88

Background

The low effectiveness of anticancer drugs remains a major unresolved obstacle to successful chemotherapy. Recently, much evidence on the roles of miRNAs in determining drug-sensitivity/resistance has been emerging. The relationship between miRNA-149 expression and paclitaxel chemoresistance in human ovarian cancer cells remains largely unknown.

Methods

This study investigated the relationship between miRNA-149 expression and the sensitivity of ovarian cancer A2780 cells to paclitaxel treatment. To achieve the down-regulation of miRNA-149 gene expression in A2780 cell line, the cells were infected with lentivirus carrying inhibitor of miRNA-149. Western blot and qRT-PCR were used to detect relevant protein levels and the expressions of mRNAs of interest. Cell proliferation was measured by CCK-8 assay. Flow cytometry was used to measure cell cycle and apoptosis. Transwell migration assay was used to observe the change of migration of transfected cells.

Results

Down-regulation of miRNA-149 decreased the sensitivity of ovarian cancer A2780 cells to paclitaxel. After paclitaxel treatment, decreased apoptosis and G2 phase ratio, increased cell migration, increased level of Bcl-2, and decreased level of Bax were found in miRNA-149-down-regulated A2780 cells. MiRNA-149 down-regulation resulted in increased expression of MyD88 in A2780 cells. Down-regulation of miRNA-149 in A2780 cells increased MyD88 expression and decreased their sensitivity to paclitaxel treatment.

Conclusion

Our findings suggest that miRNA-149 mediates the susceptibility of paclitaxel by regulating MyD88 expression in ovarian cancer cells.

Ursolic Acid and Oleanolic Acid from Eriobotrya fragrans Inhibited the Viability of A549 Cells

Loquat { Eriobotrya japonica (Lindl.)}, a kind of Chinese herb, has many efficacies such as anti-inflammatory, antimicrobial and curing chronic bronchitis. However, reports on the pharmacological action of wild loquat extract are limited. In this work, the A549 cell line was selected to study the inhibitory effect of ursolic acid and oleanolic acid (UA, OA) from the leaves of E. fragrans. Results showed that UA/OA inhibited A549 cell viability and induced apoptosis in a dose and time dependent manner. The cell fraction in the G0/G1 phase dramatically increased under treatment with UA/OA. Data showed that UA activated the expression of PARP. UA and OA down-regulated MMP-2 and Bcl-2; on the contrary, they up-regulated Bid. This work demonstrated that UA/OA extracted from wild loquat leaves can significantly inhibit the viability of A549 cells.

Differentially expressed proteins in human MCF-7 breast cancer cells sensitive and resistant to paclitaxel

Resistance of cancer cells to chemotherapeutic agents is one of the main causes of treatment failure. In order to detect proteins potentially involved in the mechanism of resistance to taxanes, we assessed differences in protein expression in MCF-7 breast cancer cells that are sensitive to paclitaxel and in the same cells with acquired resistance to paclitaxel (established in our lab). Proteins were separated using two-dimensional electrophoresis. Changes in their expression were determined and proteins with altered expression were identified using mass spectrometry. Changes in their expression were confirmed using western blot analysis. With these techniques, we found three proteins expressed differently in resistant MCF-7 cells, i.e., thyroid hormone-interacting protein 6 (TRIP6; upregulated to 650%), heat shock protein 27 (HSP27; downregulated to 50%) and cathepsin D (downregulated to 28%). Silencing of TRIP6 expression by specific siRNA leads to decreased number of grown resistant MCF-7 cells. In the present study we have pointed at some new directions in the studies of the mechanism of resistance to paclitaxel in breast cancer cells.

Hedyotis diffusa Willd extract inhibits the growth of human glioblastoma cells by inducing mitochondrial apoptosis via AKT/ERK pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Hedyotis diffusa Willd (Rubiaceae) (HDW) has been widely applied for the treatment of tumors, inflammation and toxication in traditional Chinese medicine. The antitumor effect of HDW on glioblastoma has been rarely reported. We aim to evaluate the activity of this extract and explore the underlying mechanism in U87 human glioblastoma cell line.

MATERIALS AND METHODS

Cytotoxicity of HDW extract on U87 cells was measured by MTT assay. Apoptosis, cell cycle arrest and mitochondrial membrane potential (MMP) collapse induced by HDW extract were determined by flow cytometry. Caspase activity was analyzed based on colorimetric assay with a microplate spectrophotometer. Protein expression was examined by Western blot.

RESULTS

HDW extract suppressed U87 cells growth in a dose- and time-dependent manner. Flow cytometry showed that HDW extract induced significant apoptosis, S/G2-M phase arrest and MMP collapse in U87 cells. Furthermore, dose-dependent activation of caspase-3, Bcl-2, Bax and ERK was observed with HDW extract treatment. Decreased Bcl-2/Bax ratio and Akt suppression were readily found as well.

CONCLUSIONS

Induction of mitochondria-mediated apoptosis played an essential role in antitumor activity of HDW extract in U87 cells, in which ERKs and Akt signaling proteins were also involved. These findings contributed to the feasibility of using HDW extract in glioblastoma treatment and the understanding of the molecular mechanism.

Microtubules and their role in cellular stress in cancer

Microtubules are highly dynamic structures, which consist of α- and β-tubulin heterodimers, and are involved in cell movement, intracellular trafficking, and mitosis. In the context of cancer, the tubulin family of proteins is recognized as the target of the tubulin-binding chemotherapeutics, which suppress the dynamics of the mitotic spindle to cause mitotic arrest and cell death. Importantly, changes in microtubule stability and the expression of different tubulin isotypes as well as altered post-translational modifications have been reported for a range of cancers. These changes have been correlated with poor prognosis and chemotherapy resistance in solid and hematological cancers. However, the mechanisms underlying these observations have remained poorly understood. Emerging evidence suggests that tubulins and microtubule-associated proteins may play a role in a range of cellular stress responses, thus conferring survival advantage to cancer cells. This review will focus on the importance of the microtubule-protein network in regulating critical cellular processes in response to stress. Understanding the role of microtubules in this context may offer novel therapeutic approaches for the treatment of cancer.

Bioenergetic analysis of ovarian cancer cell lines: profiling of histological subtypes and identification of a mitochondria-defective cell line

Epithelial ovarian cancer (EOC) is the most lethal of all gynecological cancers, and encompasses distinct histological subtypes that have specific genetic and tissues-of-origin differences. Ovarian clear cell carcinoma (OCCC) represents approximately 10% of cases and has been termed a stress responsive cancer. OCCC is characterized by increased expression of oxidative stress and glycolysis-related genes. In the present study, we hypothesized that bioenergetic profiling might uniquely distinguish OCCC from other EOC histological subtypes. Using an extracellular flux analyzer, OCCC lines (ES-2, TOV-21-G) were shown to be highly metabolically active, with high oxygen consumption rate (OCR) and high extracellular acidification rate (ECAR), indicative of enhanced mitochondrial oxidative phosphorylation and glycolytic rate, respectively. A high bioenergetics profile was associated with the cell lines' ability to form anchorage independent spheroids. Given their high glycolytic and mitochondrial activity, OCCC cells displayed strong sensitivity to 2-deoxy-D-glucose and Rotenone growth inhibition, although this chemosensitivity profile was not specific to only OCCC cells. Bioenergetic profiling also identified a non-OCCC cell line, OVCA420, to have severely compromised mitochondrial function, based on low OCR and a lack of stimulation of maximal respiration following application of the uncoupler FCCP. This was accompanied by mitochondrial morphology changes indicative of enhanced fission, increased expression of the mitochondrial fission protein Drp1, a loss of mitochondrial membrane potential and dependence on glycolysis. Importantly, this loss of mitochondrial function was accompanied by the inability of OVCA420 cells to cope with hypoxic stress, and a compromised ability to stabilize HIF-1α in response to 1% O₂ hypoxia. This knowledge may be imperative for researchers planning to utilize this cell line for further studies of metabolism and hypoxia, and suggests that altered mitochondrial fission dynamics represents a phenotype of a subpopulation of EOCs.

Canonical and new generation anticancer drugs also target energy metabolism

Significant efforts have been made for the development of new anticancer drugs (protein kinase or proteasome inhibitors, monoclonal humanized antibodies) with presumably low or negligible side effects and high specificity. However, an in-depth analysis of the side effects of several currently used canonical (platin-based drugs, taxanes, anthracyclines, etoposides, antimetabolites) and new generation anticancer drugs as the first line of clinical treatment reveals significant perturbation of glycolysis and oxidative phosphorylation. Canonical and new generation drug side effects include decreased (1) intracellular ATP levels, (2) glycolytic/mitochondrial enzyme/transporter activities and/or (3) mitochondrial electrical membrane potentials. Furthermore, the anti-proliferative effects of these drugs are markedly attenuated in tumor rho (0) cells, in which functional mitochondria are absent; in addition, several anticancer drugs directly interact with isolated mitochondria affecting their functions. Therefore, several anticancer drugs also target the energy metabolism, and hence, the documented inhibitory effect of anticancer drugs on cancer growth should also be linked to the blocking of ATP supply pathways. These often overlooked effects of canonical and new generation anticancer drugs emphasize the role of energy metabolism in maintaining cancer cells viable and its targeting as a complementary and successful strategy for cancer treatment.

Bcl-2-enhanced efficacy of microtubule-targeting chemotherapy through Bim overexpression: implications for cancer treatment

Bcl-2 is commonly overexpressed in tumors, where it is often associated with unfavorable outcome. However, it has also been linked to a favorable sensitivity to microtubule-targeting agents (MTAs). We show that Bcl-2-overexpressing lung and breast cancer cells were more sensitive to both paclitaxel and vinorelbine. Bcl-2 over-expression also significantly potentiated in vivo efficacy of paclitaxel, in terms of tumor volume decrease and survival benefits, in models of nude mice bearing lung cancer xenografts. To further investigate this favorable effect of Bcl-2, a genomic approach was taken. It revealed that Bcl-2 overexpression induced up-regulation of the proapoptotic protein Bim in lung cancer cells and that, conversely, Bcl-2 silencing decreased Bim expression level. A gene regulation study implicated the transcription factor Forkhead box-containing protein, class O3a in Bim up-regulation. Lastly, we show that Bim was responsible for MTA-triggered lung cancer cell death through a dynamin-related protein 1-mediated mitochondrial fragmentation. The Bcl-2-governed Bim induction evidence offers for the first time an explanation for the favorable higher sensitivity to treatment shown by Bcl-2-overexpressing cells. We suggest that Bim could be a powerful predictive factor for tumor response to MTA chemotherapy. Our data also give new insight into some failures in the efficacy of therapies targeted against Bcl-2.

Paclitaxel attenuates Bcl-2 resistance to apoptosis in breast cancer cells through an endoplasmic reticulum-mediated calcium release in a dosage dependent manner

To address the controversy regarding efficacy of paclitaxel in the presence of the anti-apoptotic protein Bcl-2, we investigated calcium stored in the endoplasmic reticulum as a potential factor. Our results showed that the ER calcium store is a common target for both paclitaxel and Bcl-2 protein. Paclitaxel directly associates with the endoplasmic reticulum to stimulate the release of calcium into the cytosol, contributing to the induction of apoptosis. However, Bcl-2 expression suppresses the cell's pro-apoptotic response of endoplasmic reticulum calcium release, thus inhibiting susceptibility of cancer cells to undergo apoptosis. Depending upon dosage, a paclitaxel-induced stimulatory effect can overcome the Bcl-2-mediated inhibitory effect on endoplasmic reticulum calcium release, thus attenuating the resistance of Bcl-2 to apoptosis. Our finding is the first to demonstrate that endoplasmic reticulum calcium plays a key role in the efficacy of paclitaxel in the presence of Bcl-2, thus providing insight into the complex but crucial paclitaxel-calcium-Bcl-2 relationship, which may impact breast cancer treatment.

Gli family transcription factors are drivers of patupilone resistance in ovarian cancer

Epothilones constitute a novel class of antitubulin agents that are active in patients who relapse after treatment with other chemotherapeutics. This study investigated the molecular mechanisms leading to the onset of epothilone-B (patupilone) resistance in ovarian cancer. Results demonstrated that the Gli family of transcription factors was overexpressed in resistant cells and that treatment with a specific Gli1 inhibitor (GANT58) made cells more susceptible to treatment, partially reversing drug resistance. We also demonstrated that Gli1 knockdown halted growth in resistant cells that were exposed to patupilone, confirming that Gli1 is capable of directly mediating epothilone-B resistance. Another observation from our research was that patupilone-resistant cells produced HGF and acquired characteristics of a mesenchymal phenotype. However, HGF silencing alone was not capable of converting the drug-resistant phenotype to a susceptible one, and in this case we demonstrated that Gli1 overexpression led to an increase in HGF, establishing a functional link between Gli1 and HGF. These results demonstrated that Gli1 played a key role in driving resistance to patupilone, suggesting that the combination of epothilones and Gli1-targeted agents could be exploited to improve outcomes in ovarian cancer patients resistant to standard treatments.

Vinflunine: a new vision that may translate into antiangiogenic and antimetastatic activity

Microtubules and tubulin are major dynamic and structural cellular components that play a key role in several cell functions, including division, signalling and intracellular trafficking. Normal epithelial cells have a highly structured, rigid cytoskeletal network that is compatible with cell motility. Thus, tubulin and microtubules are compelling cellular targets for chemotherapy. In fact, among anticancer agents, those that target microtubules constitute one of the most effective classes of chemotherapeutics in cancer. The list of compounds that target either tubulin or microtubules is extensive and consists of chemically unique compounds that bind to the tubulin dimers and destabilize microtubules (Vinca alkaloids) and those that bind to the microtubule polymer and stabilize microtubules (taxanes). Tumour-induced angiogenesis, the formation of new capillaries from existing blood vessels, and epithelial-mesenchymal transition are two steps that are critical for both tumour growth and metastatic spread. Three possible mechanisms of action are described with vinflunine, the new-generation Vinca alkaloid to arrive in clinical practice are as follows: it acts against tubulin and microtubules, disrupts newly formed blood vessels and seems to be able to reduce the metastatic process as shown in preclinical studies. These findings support the hypothesis that vinflunine, by blocking microtubule functions that contribute to cell shape, polarization, migration and other processes, might be responsible not only for tumour-cytostatic but also for specific antiangiogenic or antiepithelial-mesenchymal transition effects.

Tehranolide inhibits proliferation of MCF-7 human breast cancer cells by inducing G0/G1 arrest and apoptosis

Tehranolide, a novel natural sesquiterpene lactone with an endoperoxide group, bears a structural similarity to artemisinin and has been shown to inhibit cell growth. However, the underlying mechanisms of these activities remain obscure. The purpose of this study was to investigate the fundamental mechanisms by which tehranolide inhibits growth in MCF-7 cells. Cell growth was determined by using the MTT viability assay and counting cells. Apoptosis and cell-cycle progression were evaluated by means of Hoechst 33258 staining, flow cytometry with annexin-V/propidium iodide double staining, and ROS formation. The protein expression of Bax and Bcl-2 was demonstrated by Western blotting. Moreover, to determine the molecular mechanism whereby tehranolide mediates G0/G1 arrest, the expression of PI3K, p-PI3K, Akt, p-Akt, p27kip1, cyclin D1, and CDK4 was monitored. Cell proliferation was significantly inhibited by tehranolide in a dose- and time-dependent manner. This compound inhibited cell proliferation and induced G0/G1 arrest through the PI3K/Akt/cyclin D1 pathway. It also induced apoptosis and an increase in ROS. In addition, an increase in cytochrome c and Bax, as well as a decrease in Bcl-2, was observed. Moreover, blocking the CD95 receptor with an anti-CD95 antibody (ZB4) had no effect on tehranolide-mediated apoptosis. This study has yielded promising results, which show for the first time that tehranolide does inhibit the growth of cancer cells. The selective inhibition of cancer cell growth, the apoptosis induction via the mitochondrial pathway, and the G0/G1 arrest by modulating the PI3K/AKT signaling pathway and downregulating cyclin D1, which leads to the release of p27kip1 and the association of this inhibitor with the cyclin E/CDK2 complex, ultimately preventing cell-cycle progression from G1 to S phase, all serve to provide support for further studies of tehranolide as a possible anticancer drug in the clinical treatment of cancer.

Tyrosine-phosphorylated caveolin-1 (Tyr-14) increases sensitivity to paclitaxel by inhibiting BCL2 and BCLxL proteins via c-Jun N-terminal kinase (JNK)

Paclitaxel, an anti-microtubule agent, is an effective chemotherapeutic drug in breast cancer. Nonetheless, resistance to paclitaxel remains a major clinical challenge. The need to better understand the resistant phenotype and to find biomarkers that could predict tumor response to paclitaxel is evident. In estrogen receptor α-positive (ER(+)) breast cancer cells, phosphorylation of caveolin-1 (CAV1) on Tyr-14 facilitates mitochondrial apoptosis by increasing BCL2 phosphorylation in response to low dose paclitaxel (10 nM). However, two variants of CAV1 exist: the full-length form, CAV1α (wild-type CAV1 or wtCAV1), and a truncated form, CAV1β. Only wtCAV1 has the Tyr-14 region at the N terminus. The precise cellular functions of CAV1 variants are unknown. We now show that CAV1 variants play distinct roles in paclitaxel-mediated cell death/survival. CAV1β expression is increased in paclitaxel-resistant cells when compared with sensitive cells. Expression of CAV1β in sensitive cells significantly reduces their responsiveness to paclitaxel. These activities reflect an essential role for Tyr-14 phosphorylation because wtCAV1 expression, but not a phosphorylation-deficient mutant (Y14F), inactivates BCL2 and BCLxL through activation of c-Jun N-terminal kinase (JNK). MCF-7 cells that express Y14F are resistant to paclitaxel and are resensitized by co-treatment with ABT-737, a BH3-mimetic small molecule inhibitor. Using structural homology modeling, we propose that phosphorylation on Tyr-14 enables a favorable conformation for proteins to bind to the CAV1 scaffolding domain. Thus, we highlight novel roles for CAV1 variants in cell death; wtCAV1 promotes cell death, whereas CAV1β promotes cell survival by preventing inactivation of BCL2 and BCLxL via JNK in paclitaxel-mediated apoptosis.