Paclitaxel resistance in non-small-cell lung cancer associated with beta-tubulin gene mutations

YAP/TEAD involvement in resistance to paclitaxel chemotherapy in lung cancer

The Yes-associated protein (YAP) oncoprotein has been linked to both metastases and resistance to targeted therapy of lung cancer cells. We aimed to investigate the effect of YAP pharmacological inhibition, using YAP/TEA domain (TEAD) transcription factor interaction inhibitors in chemo-resistant lung cancer cells. YAP subcellular localization, as a readout for YAP activation, cell migration, and TEAD transcription factor functional transcriptional activity were investigated in cancer cell lines with up-regulated YAP, with and without YAP/TEAD interaction inhibitors. Parental (A549) and paclitaxel-resistant (A549R) cell transcriptomes were analyzed. The half-maximal inhibitory concentration (IC50) of paclitaxel or trametinib, which are Mitogen-Activated protein kinase and Erk Kinase (MEK) inhibitors, combined with a YAP/TEAD inhibitor (IV#6), was determined. A three-dimensional (3D) microfluidic culture device enabled us to study the effect of IV#6/paclitaxel combination on cancer cells isolated from fresh resected lung cancer samples. YAP activity was significantly higher in paclitaxel-resistant cell lines. The YAP/TEAD inhibitor induced a decreased YAP activity in A549, PC9, and H2052 cells, with reduced YAP nuclear staining. Wound healing assays upon YAP inhibition revealed impaired cell motility of lung cancer A549 and mesothelioma H2052 cells. Combining YAP pharmacological inhibition with trametinib in K-Ras mutated A549 cells recapitulated synthetic lethality, thereby sensitizing these cells to MEK inhibition. The YAP/TEAD inhibitor lowered the IC50 of paclitaxel in A549R cells. Differential transcriptomic analysis of parental and A549R cells revealed an increased YAP/TEAD transcriptomic signature in resistant cells, downregulated upon YAP inhibition. The YAP/TEAD inhibitor restored paclitaxel sensitivity of A549R cells cultured in a 3D microfluidic system, with lung cancer cells from a fresh tumor efficiently killed by YAP/TEAD inhibitor/paclitaxel doublet. Evidence of the YAP/TEAD transcriptional program's role in chemotherapy resistance paves the way for YAP therapeutic targeting.

[Mechanisms of cancer drug resistance]

Despite decades of research into the molecular mechanisms of cancer and the development of new treatments, drug resistance persists as a major problem. This is in part due to the heterogeneity of cancer, including the diversity of tumor cell lineage and cell plasticity, the spectrum of somatic mutations, the complexity of microenvironments, and immunosuppressive characteristic, then necessitating the use of many different therapeutic approaches. We summarize here the biological causes of resistance, thus offering new perspectives for tackle drug resistance.

LY103, a pomalidomide derivative, alleviates taxol resistance in NSCLC via energy metabolism crosstalk and tumor microenvironment intervention

In this study, we identified HIF 1α as a potential target for reversing taxol resistance in lung cancer by combining bioinformatics analysis with pharmacological analysis. Furthermore, pomalidomide derivative LY103 was also be synthesized by introducing an isatin analogue into the amino terminal ofpomalidomide, and it has a broad antitumor spectrum and showed excellent activity against A549/Taxol cells (IC50 = 6.33 ± 0.51 μM). The results of molecular docking showed that not only LY103 was inclined to bind to HIF 1α stably, it could also form multiple hydrogen bonds with VAL376, ASP256, ILE454, and GLU455 of HIF 1α even was reduced to LY103-NH2 by nitroreductase, which was further stabilized the complex formed by them, thereby inhibiting the activity of HIF 1α. LY103 was able to significantly induce DNA damage and inhibit angiogenesis. Concurrently, LY103 activated the immune response, reduced the expression of cytokines TNF-α, IL-6, and IL-1β, thus might be inhibit the proliferation and metastasis of tumor cells. Pharmacological analysis proved that LY103 led to cell apoptosis through the mitochondrial pathway, and its combination with taxol significantly promoted this process. In general, the consumption of glutathione, the crosstalk of energy metabolism, and the improvement of the tumor microenvironment caused by LY103 eventually led to the decrease of ABCC1 protein expression and the drug resistance was reversed. The rational design of LY103 provided a basis for the application of nitro compounds in the treatment of hypoxic tumors and the reversal of taxol resistance.

Study on the prognosis, immune and drug resistance of m6A-related genes in lung cancer

Background

Few studies have demonstrated that the relationship between m6A-related genes and the prognosis, tumor microenvironment and drug resistance of LC.

Methods

The main results were analyzed with bioinformatics methods.

Results

Hence, we found 10 m6A-related genes expressed less in tumor samples in comparison with normal ones. Using consensus clustering, all LC patients were grouped into 2 subgroups according to the overall expression of 10 differential expressed m6A-related genes. In two clusters, the OS and immune characteristics were different. We analyzed the predictive potential of 10 m6A-related genes in the prognosis of LC, and obtained a risk prognosis model on the strength of ZC3H13, CBLL1, ELAVL1 and YTHDF1 as the hub candidate genes through LASSO cox. The expression of 4 hub m6A-related genes was validated by IHC in the HPA database. The infiltration level of dendritic cell, CD4+ T cell and neutrophil that were affected by CNV level of m6A-related genes in LUAD and LUSC patients. Moreover, based on GSCALite database, we found that LUSC patients with hypermethylation tended to have a better overall survival. In terms of drug sensitivity, etoposide correlated negatively with ELAVL1, HNRNPC, RBM15B, YTHDF2 and CBLL1. ZC3H13 had positively association with afatinib, while HNRNPC was positively associated with dasatinib, erlotinib, lapatinib and TGX221. Crizotinib had a negative correlation with ELAVL1, CBLL1, HNRNPC and RBM15B.

Conclusion

In conclusion, m6A-related genes are important participants in LC and the expression levels of ZC3H13, CBLL1, ELAVL1 and YTHDF1 are significant for prediction and treatment of LC. Researches of drug resistance based on m6A-related genes need to pay more attention for producing new therapeutic strategies of LC and CBLL1 may contribute to target treatment for further research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-022-04984-5.

An EHMT2/NFYA-ALDH2 signaling axis modulates the RAF pathway to regulate paclitaxel resistance in lung cancer

Background

Lung cancer is a kind of malignancy with high morbidity and mortality worldwide. Paclitaxel (PTX) is the main treatment for non-small cell lung cancer (NSCLC), and resistance to PTX seriously affects the survival of patients. However, the underlying mechanism and potential reversing strategy need to be further explored.

Methods

We identified ALDH2 as a PTX resistance-related gene using gene microarray analysis. Subsequently, a series of functional analysis in cell lines, patient samples and xenograft models were performed to explore the functional role, clinical significance and the aberrant regulation mechanism of ALDH2 in PTX resistance of NSCLC. Furthermore, the pharmacological agents targeting ALDH2 and epigenetic enzyme were used to investigate the diverse reversing strategy against PTX resistance.

Results

Upregulation of ALDH2 expression is highly associated with resistance to PTX using in vitro and in vivo analyses of NSCLC cells along with clinicopathological analyses of NSCLC patients. ALDH2-overexpressing NSCLC cells exhibited significantly reduced PTX sensitivity and increased biological characteristics of malignancy in vitro and tumor growth and metastasis in vivo. EHMT2 (euchromatic histone lysine methyltransferase 2) inhibition and NFYA (nuclear transcription factor Y subunit alpha) overexpression had a cooperative effect on the regulation of ALDH2. Mechanistically, ALDH2 overexpression activated the RAS/RAF oncogenic pathway. NSCLC/PTX cells re-acquired sensitivity to PTX in vivo and in vitro when ALDH2 was inhibited by pharmacological agents, including the ALDH2 inhibitors Daidzin (DZN)/Disulfiram (DSF) and JIB04, which reverses the effect of EHMT2.

Conclusion

Our findings suggest that ALDH2 status can help predict patient response to PTX therapy and ALDH2 inhibition may be a promising strategy to overcome PTX resistance in the clinic.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01579-9.

Understanding Drug Sensitivity and Tackling Resistance in Cancer

Decades of research into the molecular mechanisms of cancer and the development of novel therapeutics have yielded a number of remarkable successes. However, our ability to broadly assign effective, rationally targeted therapies in a personalized manner remains elusive for many patients, and drug resistance persists as a major problem. This is in part due to the well-documented heterogeneity of cancer, including the diversity of tumor cell lineages and cell states, the spectrum of somatic mutations, the complexity of microenvironments, and immune-suppressive features and immune repertoires, which collectively require numerous different therapeutic approaches. Here, we describe a framework to understand the types and biological causes of resistance, providing translational opportunities to tackle drug resistance by rational therapeutic strategies.

Discovery of Proteins Responsible for Resistance to Three Chemotherapy Drugs in Breast Cancer Cells Using Proteomics and Bioinformatics Analysis

Chemoresistance is a daunting obstacle to the effective treatment of breast cancer patients receiving chemotherapy. Although the mechanism of chemotherapy drug resistance has been explored broadly, the precise mechanism at the proteome level remains unclear. Especially, comparative studies between widely used anticancer drugs in breast cancer are very limited. In this study, we employed proteomics and bioinformatics approaches on chemoresistant breast cancer cell lines to understand the underlying resistance mechanisms that resulted from doxorubicin (DR), paclitaxel (PR), and tamoxifen (TAR). In total, 10,385 proteins were identified and quantified from three TMT 6-plex and one TMT 10-plex experiments. Bioinformatics analysis showed that Notch signaling, immune response, and protein re-localization processes were uniquely associated with DR, PR, and TAR resistance, respectively. In addition, proteomic signatures related to drug resistance were identified as potential targets of many FDA-approved drugs. Furthermore, we identified potential prognostic proteins with significant effects on overall survival. Representatively, PLXNB2 expression was associated with a highly significant increase in risk, and downregulation of ACOX3 was correlated with a worse overall survival rate. Consequently, our study provides new insights into the proteomic aspects of the distinct mechanisms underlying chemoresistance in breast cancer.

The Current Treatment Paradigm for Pancreatic Ductal Adenocarcinoma and Barriers to Therapeutic Efficacy

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis, with a median survival time of 10-12 months. Clinically, these poor outcomes are attributed to several factors, including late stage at the time of diagnosis impeding resectability, as well as multi-drug resistance. Despite the high prevalence of drug-resistant phenotypes, nearly all patients are offered chemotherapy leading to modest improvements in postoperative survival. However, chemotherapy is all too often associated with toxicity, and many patients elect for palliative care. In cases of inoperable disease, cytotoxic therapies are less efficacious but still carry the same risk of serious adverse effects, and clinical outcomes remain particularly poor. Here we discuss the current state of pancreatic cancer therapy, both surgical and medical, and emerging factors limiting the efficacy of both. Combined, this review highlights an unmet clinical need to improve our understanding of the mechanisms underlying the poor therapeutic responses seen in patients with PDAC, in hopes of increasing drug efficacy, extending patient survival, and improving quality of life.

Cytoskeletal Dynamics in Epithelial-Mesenchymal Transition: Insights into Therapeutic Targets for Cancer Metastasis

In cancer cells, a vital cellular process during metastasis is the transformation of epithelial cells towards motile mesenchymal cells called the epithelial to mesenchymal transition (EMT). The cytoskeleton is an active network of three intracellular filaments: actin cytoskeleton, microtubules, and intermediate filaments. These filaments play a central role in the structural design and cell behavior and are necessary for EMT. During EMT, epithelial cells undergo a cellular transformation as manifested by cell elongation, migration, and invasion, coordinated by actin cytoskeleton reorganization. The actin cytoskeleton is an extremely dynamic structure, controlled by a balance of assembly and disassembly of actin filaments. Actin-binding proteins regulate the process of actin polymerization and depolymerization. Microtubule reorganization also plays an important role in cell migration and polarization. Intermediate filaments are rearranged, switching to a vimentin-rich network, and this protein is used as a marker for a mesenchymal cell. Hence, targeting EMT by regulating the activities of their key components may be a potential solution to metastasis. This review summarizes the research done on the physiological functions of the cytoskeleton, its role in the EMT process, and its effect on multidrug-resistant (MDR) cancer cells-highlight some future perspectives in cancer therapy by targeting cytoskeleton.

Tubulin acetylation enhances lung cancer resistance to paclitaxel-induced cell death through Mcl-1 stabilization

The posttranslational modifications (PTMs) of microtubules have been reported to play an important role in cancer aggressiveness, including apoptosis resistance. In this study, we aimed to investigate the biological role of microtubule PTMs in the regulation of paclitaxel responsiveness. The acetylated tubulin (Ace-tub) level was strongly associated with paclitaxel sensitivity, as observed in patient-derived primary lung cancer cells and xenografted immunodeficient mice. We showed that paclitaxel-resistant H460 lung cancer cells, generated by a stepwise increase in paclitaxel, exhibited markedly increased tubulin acetylation and consequently acquired paclitaxel resistance. Upregulation of tubulin acetylation by overexpression of α-tubulin acetyltransferase 1 wild-type (αTAT1^wt), an enzyme required for acetylation, or by treatment with trichostatin A (TSA), a histone deacetylase 6 (HDAC6) inhibitor, significantly attenuated paclitaxel-induced apoptosis. Investigation of the underlying mechanism revealed that the levels of antiapoptotic Mcl-1 appeared to increase in αTAT1^wt-overexpressing and TSA-treated cells compared to control cells, whereas the levels of other antiapoptotic regulatory proteins were unchanged. On the other hand, decreased tubulin acetylation by αTAT1 RNA interference downregulated Mcl-1 expression in patient-derived primary lung cancer and paclitaxel-resistant lung cancer cells. A microtubule sedimentation assay demonstrated that Mcl-1 binds to microtubules preferentially at Ace-type, which prolongs the Mcl-1 half-life (T_1/2). Furthermore, immunoprecipitation analysis revealed that polyubiquitination of Mcl-1 was extensively decreased in response to TSA treatment. These data indicate that tubulin acetylation enhances the resistance to paclitaxel-induced cell death by stabilizing Mcl-1 and protecting it from ubiquitin–proteasome-mediated degradation.

Molecular modeling approaches to address drug-metabolizing enzymes (DMEs) mediated chemoresistance: a review

Resistance against clinically approved anticancer drugs is the main roadblock in cancer treatment. Drug metabolizing enzymes (DMEs) that are capable of metabolizing a variety of xenobiotic get overexpressed in malignant cells, therefore, catalyzing drug inactivation. As evident from the literature reports, the levels of DMEs increase in cancer cells that ultimately lead to drug inactivation followed by drug resistance. To puzzle out this issue, several strategies inclusive of analog designing, prodrug designing, and inhibitor designing have been forged. On that front, the implementation of computational tools can be considered a fascinating approach to address the problem of chemoresistance. Various research groups have adopted different molecular modeling tools for the investigation of DMEs mediated toxicity problems. However, the utilization of these in-silico tools in maneuvering the DME mediated chemoresistance is least considered and yet to be explored. These tools can be employed in the designing of such chemotherapeutic agents that are devoid of the resistance problem. The current review canvasses various molecular modeling approaches that can be implemented to address this issue. Special focus was laid on the development of specific inhibitors of DMEs. Additionally, the strategies to bypass the DMEs mediated drug metabolism were also contemplated in this report that includes analogs and pro-drugs designing. Different strategies discussed in the review will be beneficial in designing novel chemotherapeutic agents that depreciate the resistance problem.

Novel Discoveries Targeting Pathogenic Gut Microbes and New Therapies in Pancreatic Cancer: Does Pathogenic E. coli Infection Cause Pancreatic Cancer Progression Modulated by TUBB/Rho/ROCK Signaling Pathway? A Bioinformatic Analysis

Pancreatic cancer (PC) is a pernicious cancer of the digestive system which remains a high degree of malignancy. Increasing studies demonstrated that regulating the gut microbiome may become a brand new strategy to improve the therapeutic outcomes of PC. This study is aimed at obtaining the pathway in the microbial tumorigenesis of PC. Microarray datasets GSE27890, GSE46234, and GSE17610 were downloaded from the GEO (Gene Expression Omnibus) database. Differential analysis was performed for every single gene chip using the R software package (“Limma” package), and functional enrichment analyses were carried out by DAVID (Database for Annotation, Visualization and Integrated Discovery). The PPI (protein-protein interaction) network was constructed with the Search Tool for the Retrieval of Interacting Genes (STRING). The survival analysis was performed by GEPIA and USCS. A total of 84 differentially expressed genes (DEGs) were identified, and 3 of them were extracted (TUBB, TUBA4A, and TLR5). Biological process analysis revealed that these 3 genes were mainly enriched in pathogenic Escherichia coli (E. coli) infection. Survival analysis and pathway analysis revealed that TUBB (tubulin, beta class I) may be associated with the pathogenic E. coli infection, which may be involved in the carcinogenesis and progression of PC by activating the TUBB/Rho/ROCK signaling pathway. Elevated evidence indicated that a specific gut microbe could affect the progression of PC by suppressing immune response. However, little attention has been paid to the relationship and crosstalk between TUBB/Rho/ROCK signaling, microbes, and PC. This article is aimed at deducing that gut and tumor microbes are related to the development of PC by stimulating TUBB/Rho/ROCK signaling, while ablation of microbes by antibiotics cotreated with inhibitors of TUBB/Rho/ROCK signaling were identified as a novel target for PC therapy.

The miR-195 Axis Regulates Chemoresistance through TUBB and Lung Cancer Progression through BIRC5

Chemoresistance and metastasis are the major reasons for non-small cell lung cancer (NSCLC) treatment failure and patient deaths. We and others have shown that miR-195 regulates the sensitivity of NSCLC to microtubule-targeting agents (MTAs) in vitro and in vivo and that miR-195 represses the migration and invasion of NSCLC cells in vitro. However, the relationship between miR-195 and microtubule structure and function and whether miR-195 represses NSCLC metastasis in vivo remain unknown. We assessed the correlation between tumor levels of TUBB and patient survival, the effect of TUBB on drug response, and the effect of miR-195 on migration, invasion, and metastasis in vitro and in vivo. We found that miR-195 directly targets TUBB; knockdown of TUBB sensitizes cells to MTAs, while overexpression confers resistance; high expression of TUBB is correlated with worse survival of lung adenocarcinoma; TUBB is also regulated by CHEK1, which has been shown to regulate chemoresistance; and miR-195 targets BIRC5 to repress migration and invasion in vitro and metastasis in vivo. Our findings highlight the relevance of the miR-195/TUBB axis in regulating the response of NSCLC to MTAs and the importance of the miR-195/BIRC5 axis in regulating NSCLC metastasis.

Revisiting microtubule targeting agents: α-Tubulin and the pironetin binding site as unexplored targets for cancer therapeutics

Molecules that bind to tubulin and disrupt tubulin dynamics are known as microtubule targeting agents. Treatment with a microtubule targeting agent leads to cell cycle arrest followed by apoptosis. Tubulin inhibitors have been highly effective in the clinical treatment of a variety of tumors and are being investigated for treatment of several other diseases. Currently, all FDA approved microtubule inhibitors bind to β-tubulin. Given the overall success of tubulin-binding agents in anticancer chemotherapy, α-tubulin is an attractive and unexplored target. Herein, we will discuss pironetin, the only compound known to bind α-tubulin, with particular focus on the known biological properties, the total syntheses, exploration of its structure-activity relationship, and future directions.

Analysis of SPARC and TUBB3 as predictors for prognosis in esophageal squamous cell carcinoma receiving nab-paclitaxel plus cisplatin neoadjuvant chemotherapy: a prospective study

PURPOSE

The purpose of the study is to evaluate the predictive efficacy of secreted protein, acidic and rich in cysteine (SPARC) and the class III β-tubulin (β-tubulin III, TUBB3) in predicting therapeutic effect in patients with locally advanced esophageal squamous cell carcinoma(ESCC) who received nab-paclitaxel plus cisplatin neoadjuvant chemotherapy(CT) followed by surgery.

METHODS

Patients with stage II to III esophageal squamous cell carcinoma of different stages are recruited. The tumor biopsy tissues prior treatment from enrolled patients were examined by SPARC and TUBB3 immunohistochemistry (IHC). Correlations between SPARC/TUBB3 expression and response to chemotherapy and long-term survival in patients received surgical resection was analyzed.

RESULTS

A total of 35 patients with stage II to III esophageal squamous cell carcinoma were enrolled. Of the 35 enrolled patients, 30 successfully completed neoadjuvant chemotherapy and underwent R0 resection, 3 refused surgery after chemotherapy, and 2 failed to undergo radical surgery after chemotherapy. Out of patients undergoing surgery, pathological complete response (pCR) was achieved in 6 patients (6/30, 20%). The 1, 2 and 5-year disease free survival (DFS) rates were 70.0%, 36.6% and 33.3%, respectively. The 1, 2 and 5-year overall survival (OS) rates were 83.3%, 63.3% and 36.6%, respectively. SPARC and TUBB3 IHC was performed on the tumor biopsy tissues which were obtained from patients before treatment. Correlation between SPARC/TUBB3 expression and long-term survival in patients was studied. Both the median DFS and OS between SPARC negative samples and SPARC positive staining samples have no statistical difference. However, the median DFS and OS in TUBB3 negative patients was better than those in TUBB3 positive patients (p = 0.002 for DFS, p = 0.001 for OS). In addition, patients with pCR had longer OS and DFS time than those without pCR.COX regression analysis showed that TUBB3 prior treatment and pCR were independent prognostic factors in ESCC patients undergoing sequential surgery after preoperative chemotherapy.

CONCLUSIONS

TUBB3 negative expression prior treatment and pCR may indicate a better prognosis for stage II and III ESCC patients after nab-paclitaxel plus cisplatin neoadjuvant chemotherapy following radical esophagectomy.

Polymorphisms in AURKA and AURKB are associated with the survival of triple-negative breast cancer patients treated with taxane-based adjuvant chemotherapy

Purpose

Triple-negative breast cancer (TNBC) is more than a single disease. Identifying biomarkers to further subdivide TNBC patients with distinct outcome is of great importance. It has been reported that single-nucleotide polymorphisms (SNPs) in Aurora kinase A (AURKA) or Aurora kinase B (AURKB) are associated with the risk and survival of several cancers. But till now, there is no research about these polymorphisms in TNBC patients.

Materials and methods

In this study, we investigated the association between polymorphisms in AURKA or AURKB gene and prognosis of TNBC patients treated with taxane-based adjuvant chemotherapy. A total of 273 TNBC patients were enrolled. Haploview 4.2 software was used to identify Tag SNPs. Genotyping was conducted using the MassARRAY MALDI-TOF system.

Results

We found that AURKA rs6099128 GG genotype carriers had significantly worse overall survival (OS) than TT+ TG genotype carriers (P = 0.003, HR = 12.499, 95% CI = 2.357–66.298). AURKB rs11651993 TT genotype carriers had better disease-free survival (DFS) than TC + CC genotype carriers (P = 0.018, HR = 1.876, 95% CI = 1.116–3.154). AURKB rs2289590 CC genotype carriers had worse DFS than CA + AA genotype carriers (P = 0.021, HR = 0.536, 95% CI = 0.315–0.912). After subgroup analysis, rs11651993 TC + CC genotype predicted worse DFS in subgroups of age ≤ 50, post-menopausal, grade unknown (UK), tumor size >2 cm, and lymph node negative. Rs2289590 CA + AA genotype could predict favorable DFS in pre-menopausal, grade 3 and lymph node-positive patients.

Conclusion

We first demonstrated that polymorphisms in AURKA or AURKB gene might predict the OS or DFS of TNBC patients treated with taxane-based adjuvant chemotherapy.

Eg5 inhibitor YL001 induces mitotic arrest and inhibits tumor proliferation

Eg5 is a kinesin spindle protein that controls chromosomal segregation in mitosis and is thus a critical drug target for cancer therapy. We report the discovery of a potent, selective inhibitor of Eg5 designated YL001. YL001 was obtained through shape similarity based virtual screening, and it bears a 1,5-disubstituted tetrazole scaffold. YL001 exhibits favorable bioactivity in a variety of cancer cell lines, including taxol-resistant ovarian cancer and 6TG-resistant breast cancer cell lines. This compound inhibits tumor growth by 60% and significantly prolongs median survival time by more than 50% in a xenograft mouse model. YL001 blocks the ATPase activity of Eg5 and causes mitotic failure, ultimately resulting in apoptosis of cancer cells through activation of the caspase-3 pathway. Our findings demonstrate that YL001 is a potent antitumor agent that may be developed for cancer therapeutics.

The synthetic diazonamide DZ-2384 has distinct effects on microtubule curvature and dynamics without neurotoxicity

Microtubule-targeting agents (MTAs) are widely used anticancer agents, but toxicities such as neuropathy limit their clinical use. MTAs bind to and alter the stability of microtubules, causing cell death in mitosis. We describe DZ-2384, a preclinical compound that exhibits potent antitumor activity in models of multiple cancer types. It has an unusually high safety margin and lacks neurotoxicity in rats at effective plasma concentrations. DZ-2384 binds the vinca domain of tubulin in a distinct way, imparting structurally and functionally different effects on microtubule dynamics compared to other vinca-binding compounds. X-ray crystallography and electron microscopy studies demonstrate that DZ-2384 causes straightening of curved protofilaments, an effect proposed to favor polymerization of tubulin. Both DZ-2384 and the vinca alkaloid vinorelbine inhibit microtubule growth rate; however, DZ-2384 increases the rescue frequency and preserves the microtubule network in nonmitotic cells and in primary neurons. This differential modulation of tubulin results in a potent MTA therapeutic with enhanced safety.

The Roles of β-Tubulin Mutations and Isotype Expression in Acquired Drug Resistance

The antitumor drug paclitaxel stabilizes microtubules and reduces their dynamicity, promoting mitotic arrest and eventually apoptosis. Upon assembly of the α/β-tubulin heterodimer, GTP becomes bound to both the α and β-tubulin monomers. During microtubule assembly, the GTP bound to β-tubulin is hydrolyzed to GDP, eventually reaching steady-state equilibrium between free tubulin dimers and those polymerized into microtubules. Tubulin-binding drugs such as paclitaxel interact with β-tubulin, resulting in the disruption of this equilibrium. In spite of several crystal structures of tubulin, there is little biochemical insight into the mechanism by which anti-tubulin drugs target microtubules and alter their normal behavior. The mechanism of drug action is further complicated, as the description of altered β-tubulin isotype expression and/or mutations in tubulin genes may lead to drug resistance as has been described in the literature. Because of the relationship between β-tubulin isotype expression and mutations within β-tubulin, both leading to resistance, we examined the properties of altered residues within the taxane, colchicine and Vinca binding sites. The amount of data now available, allows us to investigate common patterns that lead to microtubule disruption and may provide a guide to the rational design of novel compounds that can inhibit microtubule dynamics for specific tubulin isotypes or, indeed resistant cell lines. Because of the vast amount of data published to date, we will only provide a broad overview of the mutational results and how these correlate with differences between tubulin isotypes. We also note that clinical studies describe a number of predictive factors for the response to anti-tubulin drugs and attempt to develop an understanding of the features within tubulin that may help explain how they may affect both microtubule assembly and stability.

Mcl-1 stabilization confers resistance to taxol in human gastric cancer

Taxol has been extensively used as an antineoplastic drug to treat human gastric cancer. However, the acquired drug resistance invariably develops and greatly limits the therapeutic efficacy of Taxol. Identification of the underlying resistance mechanisms may inform the development of new therapies of gastric cancers to Taxol treatment. Here we report that upregulation of Mcl-1 (Myeloid cell leukemia-1) confers acquired resistance to Taxol in human gastric cancer. Mcl-1 is shown to be stabilized in Taxol -resistant gastric cancer cells because of the hyper-activation of the PI3K/Akt signaling pathway. The increased Mcl-1 prevents of the permeabilization of the outer mitochondrial membrane, thereby blocking the Taxol-induced apoptosis. Furthermore, inhibition of Mcl-1 or PI3K/Akt pathway significantly reversed the resistant phenotype of Taxol-resistant human gastric cancer cells. Taken together, our findings broaden the view of PI3K/Akt pathway as an important regulator in Taxol acquired resistance, and implicate Mcl-1 as a specific therapeutic target for the treatment of Taxol-resistant human gastric cancer.

Paclitaxel resistance development is associated with biphasic changes in reactive oxygen species, mitochondrial membrane potential and autophagy with elevated energy production capacity in lung cancer cells: A chronological study

Paclitaxel (Tx) is one of the first-line chemotherapeutic drugs used against lung cancer, but acquired resistance to this drug is a major challenge against successful chemotherapy. In this work, we have focused on the chronological changes of various cellular parameters and associated effect on Tx (10 nM) resistance development in A549 cell line. It was observed, at initial stage, the cell death percentage due to drug treatment had increased up to 20 days, and thereafter, it started declining and became completely resistant by 40 days. Expressions of βIII tubulin and drug efflux pumps also increased over the period of resistance development. Changes in cellular autophagy and reactive oxygen species generation showed a biphasic pattern and increased gradually over the course of upto 20 days, thereafter declined gradually; however, their levels remained higher than untreated cells when resistance was acquired. Increase in extracellular acidification rates and oxygen consumption rates was found to be directly correlated with acquisition of resistance. The depolarisation of mitochondrial membrane potential was also biphasic; first, it increased with increase of cell death up to 20 days, thereafter, it gradually decreased to normal level along with resistance development. Increase in activity of catalase, glutathione peroxidase and glutathione content over these periods may attribute in bringing down the reactive oxygen species levels and normalisation of mitochondrial membrane potential in spite of comparatively higher reactive oxygen species production by the Tx-resistant cells.

Aurora B expression modulates paclitaxel response in non-small cell lung cancer

Background:

Taxanes are mitotic poisons widely used in the treatment of non-small cell lung cancer (NSCLC), however, little is known about potential molecular modulators of response to these compounds. Aurora B (AURKB) is a critical regulator of the mitotic spindle assembly, previously shown overexpressed in NSCLC. Here we investigated the hypothesis that AURKB expression modulates the efficacy of taxanes in NSCLC cells.

Methods:

AURKB mRNA expression was determined by qPCR in 132 frozen NSCLC tissues and nine NSCLC cell lines. Aurora B expression was knocked down in cell lines using multiple shRNA constructs. Barasertib was used to specifically inhibit AURKB activity, determined by the level of H3S10 phosphorylation.

Results:

Frequent AURKB mRNA upregulation was observed in NSCLC tissues (P<0.0001), being more prominent in squamous carcinomas (P<0.0001). Aurora B expression in cell lines strongly correlated with sensitivity to both docetaxel (P=0.004) and paclitaxel (P=0.007). Aurora B knockdown derivatives consistently showed a dose-dependent association between low-AURKB expression and resistance to paclitaxel. Specific chemical inhibition of Aurora B activity also demonstrated a strong dose-dependent efficiency in triggering paclitaxel resistance.

Conclusions:

Aurora B activity is an important modulator of taxane response in NSCLC cells. This may lead to further insights into taxane sensitivity of NSCLC tumours.

PARP inhibitor combination therapy

In 2014, olaparib (Lynparza) became the first PARP (Poly(ADP-ribose) polymerase) inhibitor to be approved for the treatment of cancer. When used as single agents, PARP inhibitors can selectively target tumour cells with BRCA1 or BRCA2 tumour suppressor gene mutations through synthetic lethality. However, PARP inhibition also shows considerable promise when used together with other therapeutic agents. Here, we summarise both the pre-clinical and clinical evidence for the utility of such combinations and discuss the future prospects and challenges for PARP inhibitor combinatorial therapies.

Cathepsin L upregulation-induced EMT phenotype is associated with the acquisition of cisplatin or paclitaxel resistance in A549 cells

AIM

Cathepsin L (CTSL), a lysosomal acid cysteine protease, is known to play important roles in tumor metastasis and chemotherapy resistance. In this study we investigated the molecular mechanisms underlying the regulation of chemoresistance by CTSL in human lung cancer cells.

METHODS

Human lung cancer A549 cells, A549/PTX (paclitaxel-resistant) cells and A549/DDP (cisplatin-resistant) cells were tested. The resistance to cisplatin or paclitaxel was detected using MTT and the colony-formation assays. Actin remodeling was observed with FITC-Phalloidin fluorescent staining or immunofluorescence. A wound-healing assay or Transwell assay was used to assess the migration or invasion ability. The expression of CTSL and epithelial and mesenchymal markers was analyzed with Western blotting and immunofluorescence. The expression of EMT-associated transcription factors was measured with Western blotting or q-PCR. BALB/c nude mice were implanted subcutaneously with A549 cells overexpressing CTSL, and the mice were administered paclitaxel (10, 15 mg/kg, ip) every 3 d for 5 times.

RESULTS

Cisplatin or paclitaxel treatment (10-80 ng/mL) induced CTSL expression in A549 cells. CTSL levels were much higher in A549/PTX and A549/DDP cells than in A549 cells. Silencing of CTSL reversed the chemoresistance in A549/DDP and A549/TAX cells, whereas overexpression of CTSL attenuated the sensitivity of A549 cells to cisplatin or paclitaxel. Furthermore, A549/DDP and A549/TAX cells underwent morphological and cytoskeletal changes with increased cell invasion and migration abilities, accompanied by decreased expression of epithelial markers (E-cadherin and cytokeratin-18) and increased expression of mesenchymal markers (N-cadherin and vimentin), as well as upregulation of EMT-associated transcription factors Snail, Slug, ZEB1 and ZEB2. Silencing of CTSL reversed EMT in A549/DDP and A549/TAX cells; In contrast, overexpression of CTSL induced EMT in A549 cells. In xenograft nude mouse model, the mice implanted with A549 cells overexpressing CTSL exhibited significantly reduced sensitivity to paclitaxel treatment, and increased expression of EMT-associated proteins and transcription factors in tumor tissues.

CONCLUSION

Cisplatin and paclitaxel resistance is associated with CTSL upregulation-induced EMT in A549 cells. Thus, CTSL-mediated EMT may be exploited as a target to enhance the efficacy of cisplatin or paclitaxel against lung cancer and other types of malignancies.

Mucin 1-mediated chemo-resistance in lung cancer cells

Paclitaxel (PTX) is a commonly used drug to treat diverse cancer types. However, its treatment can generate resistance and the mechanisms of PTX-resistance in lung cancers are still unclear. We demonstrated that non-small cell lung cancers (NSCLCs) survive PTX treatment. Compared with the progenitor NSCLC A549 cells, the PTX-resistant A549 cells (A549/PTX) displayed enhanced sphere-formation ability. The proportion of the cancer stem cell marker, aldehyde dehydrogenase-positive cells, and epithelial-mesenchymal transition signaling protein levels were also elevated in A549/PTX. Importantly, the levels of oncoproteins phosphoinositide-3 kinase/Akt, mucin 1 cytoplasmic domain (MUC1-C) and β-catenin were also significantly elevated in A549/PTX. Furthermore, nuclear translocation of MUC1-C and β-catenin increased in A549/PTX. The c-SRC protein, an activator of MUC1-C, was also overexpressed in A549/PTX. These observations led to the hypothesis that enhanced expression of MUC1-C is associated with stemness and PTX resistance in NSCLCs. To test this, we knocked down or overexpressed MUC1-C in A549/PTX and found that inhibition of MUC1-C expression coupled with PTX treatment was sufficient to reduce the sphere-forming ability and survival of A549/PTX. In summary, our in vitro and in vivo studies have revealed a potential mechanism of MUC1-C-mediated PTX resistance and provided insights into a novel therapeutic measure for lung cancers.

Chemotherapy Resistance in Lung Cancer

Despite a growing interest in development of non-cytotoxic targeted agents, systemic chemotherapy is still the mainstay of treatment for both non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). However, chemotherapy resistance limits our ability to effectively treat advanced lung cancer. Some lung tumors are intrinsically resistant to chemotherapy, and in virtually all cases, even the initial responders rapidly develop acquired resistance. While targeting histology could result in enhanced tumor sensitivity to a particular chemotherapeutic agent, better understanding of molecular determinants of chemotherapy sensitivity/resistance would be critically important. Development of predictive biomarkers to personalize chemotherapeutic agents and combining novel agents targeting specific resistance pathways with standard chemotherapy could be some promising strategies to overcome chemotherapy resistance in lung cancer. In this chapter, we will discuss some key mechanisms of resistance for commonly used chemotherapeutic agents in lung cancer.

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.

Antimitotic drugs in the treatment of cancer

Cancer is a complex disease since it is adaptive in such a way that it can promote proliferation and invasion by means of an overactive cell cycle and in turn cellular division which is targeted by antimitotic drugs that are highly validated chemotherapy agents. However, antimitotic drug cytotoxicity to non-tumorigenic cells and multiple cancer resistance developed in response to drugs such as taxanes and vinca alkaloids are obstacles faced in both the clinical and basic research field to date. In this review, the classes of antimitotic compounds, their mechanisms of action and cancer cell resistance to chemotherapy and other limitations of current antimitotic compounds are highlighted, as well as the potential of novel 17-β estradiol analogs as cancer treatment.

Pharmacodynamics (PD) and pharmacokinetics (PK) of E7389 (eribulin, halichondrin B analog) during a phase I trial in patients with advanced solid tumors: a California Cancer Consortium trial

BACKGROUND

The California Cancer Consortium completed a phase I trial of E7389 (eribulin mesylate), an analog of the marine natural product halichondrin B. This trial was to determine the pharmacodynamics, pharmacokinetics, and MTD of E7389 administered by bolus injection weekly for 3 weeks out of four.

METHODS

This trial included a rapid titration design. Real-time pharmacokinetics were utilized to guide dose escalation. Initially, single-patient cohorts were enrolled with intra- and inter-patient dose doubling. The second phase was a standard 3 + 3 dose escalation schedule. At the MTD, a cohort of patients was enrolled for target validation studies (separate manuscript). The starting dose was 0.125 mg/m(2), and doses were doubled within and between patients in the first phase. Blood and urine sampling for E7389 pharmacokinetics was performed on doses 1 and 3 of cycle 1. Levels were determined using a LC/MS/MS assay.

RESULTS

Forty patients were entered. Thirty-eight were evaluable for toxicity and 35 for response. The rapid escalation ended with a grade 3 elevation of alkaline phosphatase at 0.5 mg/m(2)/week. The second phase ended at 2.0 mg/m(2)/week with dose-limiting toxicities of grades 3 and 4 febrile neutropenia. Other toxicities included hypoglycemia, hypophosphatemia, and fatigue. The MTD was 1.4 mg/m(2)/week. Responses included four partial responses (lung cancer [2], urothelial [1], and melanoma [1]).

CONCLUSIONS

E7389 was well tolerated in this trial with the major toxicity being myelosuppression. PD shows that E7389 induces significant morphologic changes (bundle formation) in the microtubules of peripheral blood mononuclear cells and tumor cells in vivo. The data suggest that lower intra-tumoral levels of β-tubulin III or higher intra-tumoral levels of MAP4 may correlate with response to E7389, while lower intra-tumoral levels of stathmin may be associated with progression. PK data reveal that E7389 exhibits a tri-exponential elimination from the plasma of patients receiving a rapid i.v. infusion. At sub-toxic doses, plasma concentrations of E7389 are maintained well above the levels required for activity in vitro for >72 h.

Nanoparticle-mediated drug delivery for treating melanoma

Melanoma originated from melanocytes is the most aggressive type of skin cancer with limited treatment options. New targeted therapeutic options with the discovery of BRAF and MEK inhibitors have shown significant survival benefits. Despite the recent progress, development of chemoresistance and systemic toxicity remains a challenge for treating metastatic melanoma. While the response from the first line of treatment against melanoma using dacarbazine remains only 5-10%, the prolonged use of targeted therapy against mutated oncogene BRAF develops chemoresistance. In this review, we will discuss the nanoparticle-based strategies for encapsulation and conjugation of drugs to the polymer for maximizing their tumor distribution through enhanced permeability and retention effect. We will also highlight photodynamic therapy and design of melanoma-targeted nanoparticles.

Are pharmacogenomic biomarkers an effective tool to predict taxane toxicity and outcome in breast cancer patients? Literature review

PURPOSE

Breast cancer is a heterogeneous disease, characterized by various molecular phenotypes that correlate with different prognosis and response to treatments. Taxanes are some of the most active chemotherapeutic agents for breast cancer; however, their utilization is limited, due to hematologic and cumulative neurotoxicity on treated patients. To understand why only some patients experience severe adverse effects and why patients respond and develop resistance with different rates to taxane therapy, the metabolic pathways of these drugs should be completely unraveled. The variant forms of several genes, related to taxane pharmacokinetics, can be indicative markers of clinical parameters, such as toxicity or outcome.

METHODS

The search of the data has been conducted through PubMed database, presenting clinical data, clinical trials and basic research restricted to English language until June 2015.

RESULTS

We studied the literature in order to find any possible association between the major pharmacogenomic variants and specific taxane-related toxicity and patient outcome. We found that the data of these studies are sometimes discordant, due to both the small number of enrolled patients and the heterogeneity of the examined population.

CONCLUSIONS

Among all analyzed genes, only CYP1B1 and ABCB1 resulted the strongest candidates to become biomarkers of clinical response to taxane therapy in breast cancer, although their utilization still remains an experimental procedure. In the future, greater studies on genetic polymorphisms should be performed in order to identify differentiating signatures for patients with higher toxicity and with resistant or responsive outcome, before the administration of taxanes.

Peloruside A is a microtubule-stabilizing agent with exceptional anti-migratory properties in human endothelial cells

Peloruside A is a novel antimitotic drug originally isolated from the marine sponge Mycale hentschieli. Previous studies showed that peloruside A stabilizes microtubules by binding to a site on tubulin distinct from paclitaxel, another microtubule stabilizing drug. Peloruside A blocks mitosis, but little is known about the effects on other cellular activities. Here we report that peloruside A is the most potent microtubule inhibitor yet tested for its ability to block endothelial cell migration. Quantitative analysis indicated that it inhibits microtubule dynamics and endothelial cell migration at 1/200(th) of the concentration needed to inhibit cell division (the cytotoxic concentration), indicating that it could potentially have a large margin of safety when used to specifically target angiogenesis. By comparison, paclitaxel, a well-known cancer therapeutic drug, suppresses cell migration at 1/13(th) of its cytotoxic concentration; and vinblastine suppresses cell migration at just slightly below its cytotoxic antimitotic concentration. Thus, different microtubule targeted drugs have varying relative potencies for inhibition of cell migration versus cell division. The results suggest that peloruside A may be an especially useful agent for anti-angiogenesis therapy and point to the likelihood that other antimitotic drugs might be found with an even larger potential margin of safety.

Use of TUBB3 for patient stratification and prognosis in lung cancer

SUMMARY 

Microtubules play a crucial role in the eukaryote replicative cell machinery and antimicrotubule drugs such as vinca alkaloids and taxanes are important drugs in the treatment of several solid tumors. TUBB3 has in retrospective studies shown to be of significance with regard to outcome in NSCLC patients treated with anti-microtubule drugs. However, it is still controversial whether or not TUBB3 has a prognostic or a predictive value. This review provides an overview of preclinical and clinical studies that have presented data on the role of TUBB3 in NSCLC.

Taxanes with high potency inducing tubulin assembly overcome tumoural cell resistances

We have found that four taxanes with chemical modifications at positions C10 and C13 were active against all types of taxane resistant cell lines, resistant by P-gp overexpression, by mutations in the β-tubulin binding site or by overexpression of the highly dynamic βIII-tubulin isotype. We have characterized the interaction of taxanes with high activity on chemotherapy resistant tumoural cells with microtubules, and also studied their cellular effects. The biochemical property enhanced in comparison with other taxanes is their potency at inducing tubulin assembly, despite the fact that their interactions with the microtubule binding sites (pore and luminal) are similar as studied by NMR and SAXS. A differential interaction with the S7-S9 loop (M-loop) is responsible for their enhanced assembly induction properties. The chemical changes in the structure also induce changes in the thermodynamic properties of the interaction, indicating a higher hydrophilicity and also explaining their properties on P-gp and βIII overexpressing cells and on mutant cells. The effect of the compounds on the microtubular network is different from those observed with the classical (docetaxel and paclitaxel) taxanes, inducing different bundling in cells with microtubules being very short, indicating a very fast nucleation effect and reflecting their high assembly induction power.

Targeting microtubules by natural agents for cancer therapy

Natural compounds that target microtubules and disrupt the normal function of the mitotic spindle have proven to be one of the best classes of cancer chemotherapeutic drugs available in clinics to date. There is increasing evidence showing that even minor alteration of microtubule dynamics can engage the spindle checkpoint, arresting cell-cycle progression at mitosis and subsequently leading to cell death. Our improved understanding of tumor biology and our continued appreciation for what the microtubule targeting agents (MTAs) can do have helped pave the way for a new era in the treatment of cancer. The effectiveness of these agents for cancer therapy has been impaired, however, by various side effects and drug resistance. Several new MTAs have shown potent activity against the proliferation of various cancer cells, including resistance to the existing MTAs. Sustained investigation of the mechanisms of action of MTAs, development and discovery of new drugs, and exploring new treatment strategies that reduce side effects and circumvent drug resistance could provide more effective therapeutic options for patients with cancer. This review focuses on the successful cancer chemotherapy from natural compounds in clinical settings and the challenges that may abort their usefulness.

Prognostic and predictive markers for personalized adjuvant therapy for non-small-cell lung cancer patients

Adjuvant chemotherapy following surgical resection in non-small-cell lung cancer patients with large tumors (>4 cm) or tumors with lymph node metastases has emerged as a standard of care. The benefits of adjuvant chemotherapy are modest, with a 5-year survival improvement of only 5–10%. In addition, survival rates of 25% or greater with surgery alone suggest that some patients do not need adjuvant therapy. Therefore, there is a need to develop prognostic and predictive markers to identify patients in need of adjuvant therapy and the patients likely to benefit from such therapy. Many factors have been evaluated for this purpose and some of these factors, such as visceral pleural invasion, can influence the decision to use adjuvant chemotherapy. However, most of the available data are retrospective, which limits the utility of these markers in current practice. Ongoing trials are evaluating many promising markers and may guide adjuvant therapy in the future.

Pharmacogenetics, enzyme probes and therapeutic drug monitoring as potential tools for individualizing taxane therapy

The taxanes are a class of chemotherapeutic agents that are widely used in the treatment of various solid tumors. Although taxanes are highly effective in cancer treatment, their use is associated with serious complications attributable to large interindividual variability in pharmacokinetics and a narrow therapeutic window. Unpredictable toxicity occurrence necessitates close patient monitoring while on therapy and adverse effects frequently require decreasing, delaying or even discontinuing taxane treatment. Currently, taxane dosing is based primarily on body surface area, ignoring other factors that are known to dictate variability in pharmacokinetics or outcome. This article discusses three potential strategies for individualizing taxane treatment based on patient information that can be collected before or during care. The clinical implementation of pharmacogenetics, enzyme probes or therapeutic drug monitoring could enable clinicians to personalize taxane treatment to enhance efficacy and/or limit toxicity.

[Muscle invasive bladder cancer after radical cystectomy. Prognostic factors of adjuvant chemotherapy]

BACKGROUND

The indications to administer adjuvant systemic chemotherapy to patients with urothelial carcinoma of the bladder who underwent radical cystectomy is discussed controversially and all international guidelines are very restrictive with regard to its recommendation for routine daily practice due to the low scientific evidence concerning its therapeutic benefit. Currently, adjuvant systemic chemotherapy should be preferably administered within clinical trials. In the daily routine adjuvant treatment might be given in patients with lymph node positive disease. Clinical, pathohistological and molecular biomarkers which might be associated with a positive or negative treatment response have been evaluated sparsely in the past.

RESULTS

The presence of hemangiosis/lymphangiosis carcinomatosa and/or extranodal expansion in patients with lymph node metastases appears to be associated with a poor outcome. The markers ERCC-1, XAF and anti-apoptotic proteins of the Bcl-2 family seem to represent the most promising biomarkers associated with response to adjuvant cisplatin-based chemotherapy.

Different regulatory pathways are involved in the proliferative inhibition of two types of leukemia cell lines induced by paclitaxel

Paclitaxel, one of the broadest-spectrum anticancer agents, is currently being used in the treatment of patients with solid tumors. In the present study, we compared the effect of paclitaxel on two types of leukemia cells. Our results showed that paclitaxel could inhibit the proliferation of MEL and K562 cells in a dose- and time-dependent manner. The mechanism of proliferative inhibition in K562 cells treated by paclitaxel was related to the cell cycle arrest in the G2/M phase, as well as the induction of apoptosis. By contrast, MEL cells treated by paclitaxel showed significant characteristics of necrosis, which indicated that the mode of cell death induced by paclitaxel in these two types of leukemia cells differed. Advances in research of the cell cycle, apoptosis and necrosis will extend our understanding of the mechanisms of paclitaxel-induced cell death, particularly in leukemia cells. Further elucidation of the mechanisms of necrosis in MEL cells may expedite the development of improved paclitaxel-based regimens for cancer therapy.

Synergistic suppression of noscapine and conventional chemotherapeutics on human glioblastoma cell growth

AIM

Noscapine (NOS) is a non-narcotic opium alkaloid with anti-tumor activity. The aim of this study was to investigate the effects of the combination of NOS with conventional chemotherapeutics temozolamide (TMZ), bis-chloroethylnitrosourea (BCNU), or cisplatin (CIS)on human glioblastoma cells.

METHODS

U87MG human glioblastoma cells were examined. Cell proliferation was quantified using MTT assay. Western blotting and flow cytometry were used to examine apoptosis and the expression of active caspase-3 and cleaved PARP. Mouse tumor xenograft model bearing U87MG cells was treated with TMZ (2 mg·kg(-1)·d(-1), ip) or CIS (2 mg/kg, ip 3 times a week) alone or in combination with NOS (200 mg·kg(-1)·d(-1), ig) for 3 weeks. Immunohistochemistry was used to investigate the expression of active caspase-3 and Ki67 following treatment in vivo. The safety of the combined treatments was evaluated based on the body weight and histological studies of the animal's organs.

RESULTS

NOS (10 or 20 mol/L) markedly increased the anti-proliferation effects of TMZ, BCNU, and CIS on U87MG cells in vitro. The calculated combination index (CI) values of NOS-CIS, NOS-TMZ, and NOS-BCNU (20 μmol/L) were 0.45, 0.51, and 0.57, respectively, demonstrating synergistic inhibition of the drug combinations. In tumor xenograft models, combined treatment with NOS robustly augmented the anti-cancer actions of TMZ and CIS, and showed no detectable toxicity. The combined treatments significantly enhanced the apoptosis, the activated caspase-3 and PARP levels in U87MG cells in vitro, and reduced Ki67 staining and increased the activated caspase-3 level in the shrinking xenografts in vivo.

CONCLUSION

NOS synergistically potentiated the efficacy of FDA-approved anti-cancer drugs against human glioblastoma cells, thereby allowing them to be used at lower doses and hence minimizing their toxic side effects.

An antimitotic and antivascular agent BPR0L075 overcomes multidrug resistance and induces mitotic catastrophe in paclitaxel-resistant ovarian cancer cells

Paclitaxel plays a major role in the treatment of ovarian cancer; however, resistance to paclitaxel is frequently observed. Thus, new therapy that can overcome paclitaxel resistance will be of significant clinical importance. We evaluated antiproliferative effects of an antimitotic and antivascular agent BPR0L075 in paclitaxel-resistant ovarian cancer cells. BPR0L075 displays potent and broad-spectrum cytotoxicity at low nanomolar concentrations (IC₅₀ = 2–7 nM) against both parental ovarian cancer cells (OVCAR-3, SKOV-3, and A2780-1A9) and paclitaxel-resistant sublines (OVCAR-3-TR, SKOV-3-TR, 1A9-PTX10), regardless of the expression levels of the multidrug resistance transporter P-gp and class III β-tubulin or mutation of β-tubulin. BPR0L075 blocks cell cycle at the G2/M phase in paclitaxel-resistant cells while equal concentration of paclitaxel treatment was ineffective. BPR0L075 induces cell death by a dual mechanism in parental and paclitaxel-resistant ovarian cancer cells. In the parental cells (OVCAR-3 and SKOV-3), BPR0L075 induced apoptosis, evidenced by poly(ADP-ribose) polymerase (PARP) cleavage and DNA ladder formation. BPR0L075 induced cell death in paclitaxel-resistant ovarian cancer cells (OVCAR-3-TR and SKOV-3-TR) is primarily due to mitotic catastrophe, evidenced by formation of giant, multinucleated cells and absence of PARP cleavage. Immunoblotting analysis shows that BPR0L075 treatment induced up-regulation of cyclin B1, BubR1, MPM-2, and survivin protein levels and Bcl-XL phosphorylation in parental cells; however, in resistant cells, the endogenous expressions of BubR1 and survivin were depleted, BPR0L075 treatment failed to induce MPM-2 expression and phosphorylation of Bcl-XL. BPR0L075 induced cell death in both parental and paclitaxel-resistant ovarian cancer cells proceed through caspase-3 independent mechanisms. In conclusion, BPR0L075 displays potent cytotoxic effects in ovarian cancer cells with a potential to overcome paclitaxel resistance by bypassing efflux transporters and inducing mitotic catastrophe. BPR0L075 represents a novel microtubule therapeutic to overcome multidrug resistance and trigger alternative cell death by mitotic catastrophe in ovarian cancer cells that are apoptosis-resistant.

Pharmacogenetics of conventional chemotherapy in non-small-cell lung cancer: a changing landscape?

Pharmacogenetics might be used to select patients who may benefit from specific chemotherapy that best matches the individual and tumor genetic profile, thus allowing maximum activity and minimal toxicity. Even if most studies in non-small-cell lung cancer yielded contradictory results, several potential biomarkers for sensitivity/resistance to platinum compounds, gemcitabine, taxanes and pemetrexed have been proposed. However, these markers need to be validated within larger prospective randomized trials of customized chemotherapy in homogeneous populations. Other critical points include the optimization/standardization of technical procedures, and further studies to unravel the extremely complex regulation of gene function. From this perspective, the evaluation of key factors influencing genotype-phenotype relationships, such as miRNAs, and functional studies to clarify pharmacokinetic/pharmacodynamic interactions, are fundamental for the pharmacogenetic optimization of cancer chemotherapy. Finally, limitation of the traditional pharmacogenetic approach relying only on candidate genes suspected of affecting drug response is now being overcome by the use of novel genome-wide studies.

Molecular aspects of cancer cell resistance to chemotherapy

Cancer cell resistance to chemotherapy is still a heavy burden that impairs treatment of cancer patients. Both intrinsic and acquired resistance results from the numerous genetic and epigenetic changes occurring in cancer cells. Most of the hallmarks of cancer cells provide general mechanisms to sustain stresses such as the ones induced by chemotherapeutic drugs. Moreover, specific changes in the target bring resistance to specific drugs like modification in nucleotide synthesis enzymes upon anti-metabolite exposure, in microtubule composition upon spindle poison treatment, in topoisomerase activity upon topoisomerase inhibitor incubation or in intracellular signaling pathways when targeting tyrosine kinase receptors. Finally, the stemness properties of a few cancer cells as well as components of the tumor stroma, like fibroblasts and tumor-associated macrophages but also hypoxia, also help tumor to resist to anticancer agents. These processes provide an additional level of complexity to the understanding of the tumor resistance phenomenon. This review aims to describe the different general mechanisms as well as some examples of specific on target modifications inducing cancer cell resistance to chemotherapy at the molecular level. Perspectives to develop more efficient treatment, using genomic signature or more specific biomarkers to characterize putative resistance mechanisms in patients before choosing the more appropriate treatment, will also be discussed.