Diaminothiazoles evade multidrug resistance in cancer cells and xenograft tumour models and develop transient specific resistance: understanding the basis of broad-spectrum versus specific resistance

Tubulin Isotypes: Emerging Roles in Defining Cancer Stem Cell Niche

Although the role of microtubule dynamics in cancer progression is well-established, the roles of tubulin isotypes, their cargos and their specific function in the induction and sustenance of cancer stem cells (CSCs) were poorly explored. But emerging reports urge to focus on the transport function of tubulin isotypes in defining orchestrated expression of functionally critical molecules in establishing a stem cell niche, which is the key for CSC regulation. In this review, we summarize the role of specific tubulin isotypes in the transport of functional molecules that regulate metabolic reprogramming, which leads to the induction of CSCs and immune evasion. Recently, the surface expression of GLUT1 and GRP78 as well as voltage-dependent anion channel (VDAC) permeability, regulated by specific isotypes of β-tubulins have been shown to impart CSC properties to cancer cells, by implementing a metabolic reprogramming. Moreover, βIVb tubulin is shown to be critical in modulating EphrinB1signaling to sustain CSCs in oral carcinoma. These tubulin-interacting molecules, Ephrins, GLUT1 and GRP78, are also important regulators of immune evasion, by evoking PD-L1 mediated T-cell suppression. Thus, the recent advances in the field implicate that tubulins play a role in the controlled transport of molecules involved in CSC niche. The indication of tubulin isotypes in the regulation of CSCs offers a strategy to specifically target those tubulin isotypes to eliminate CSCs, rather than the general inhibition of microtubules, which usually leads to therapy resistance.

Inhibition of Polo-Like Kinase 1 by BI2536 Reverses the Multidrug Resistance of Human Hepatoma Cells In Vitro and In Vivo

BACKGROUND

Multi Drug Resistance (MDR) is the phenomenon that cancers develop resistance to majority of chemotherapy drugs and is a serious obstacle to the treatment for Hepatocellular Carcinoma (HCC). Polo-Like Kinase 1 (PLK1) is a serine/threonine kinase associated with tumor growth and clinical prognosis in HCC and BI2536 is its potent inhibitor with IC50 of 0.83nM.

AIMS

To test whether the down-regulation of PLK1 by its inhibitor BI2536 would have beneficial effects on the reversal of MDR in HCC cells.

METHODS

The CCK-8 assay was used to determine the viability of HepG2/ADM and SMMC7721/ADM cells and their parental cells treated with BI2536. Then animal model studies were performed. Cell invasion assay and wound healing assay were used to determine the invasion ability and motility. Flow cytometric was used to test the apoptosis induced by BI2536. Western blot and quantitative real-time PCR were performed to test the change of expression of MDR and apoptosis-related gene.

RESULTS

BI2536 down-regulated the expression of PLK1 protein and mRNA specifically. BI2536 can significantly reduce IC50 for ADM and other drugs in ADM-resistant HCC cells. Meanwhile, it inhibited cell viability, proliferation, and invasion, and induced cell cycle arrest and apoptosis in HCC cells with MDR.

CONCLUSION

Our results suggest that PLK1 inhibitor BI2536 can re-sensitize HCC cancer cell with MDR through induction of apoptosis. Thus, PLK1 inhibitor BI2536 may act as an effective chemotherapeutic drug in the clinical treatment of HCC patients with MDR.

A biosensor-based approach reveals links between efflux pump expression and cell cycle regulation in pleiotropic drug resistance of yeast

Multidrug resistance is highly conserved in mammalian, fungal, and bacterial cells, is characterized by resistance to several unrelated xenobiotics, and poses significant challenges to managing infections and many cancers. Eukaryotes use a highly conserved set of drug efflux transporters that confer pleiotropic drug resistance (PDR). To interrogate the regulation of this critical process, here we developed a small molecule-responsive biosensor that couples transcriptional induction of PDR genes to growth rate in the yeast Saccharomyces cerevisiae Using diverse PDR inducers and the homozygous diploid deletion collection, we applied this biosensor system to genome-wide screens for potential PDR regulators. In addition to recapitulating the activity of previously known factors, these screens identified a series of genes involved in a variety of cellular processes with significant but previously uncharacterized roles in the modulation of yeast PDR. Genes identified as down-regulators of the PDR included those encoding the MAD family of proteins involved in the mitotic spindle assembly checkpoint (SAC) complex. Of note, we demonstrated that genetic disruptions of the mitotic spindle assembly checkpoint elevate expression of PDR-mediating efflux pumps in response to exposure to a variety of compounds that themselves have no known influence on the cell cycle. These results not only establish our biosensor system as a viable tool for investigating PDR in a high-throughput fashion, but also uncover critical control mechanisms governing the PDR response and a previously uncharacterized link between PDR and cell cycle regulation in yeast.

Unlike Butylcycloheptylprodigiosin, Isolated Undecylprodigiosin from Streptomyces parvulus Is Not a MDR1 and BCRP Substrate in Multidrug-Resistant Cancers

The search for new chemotherapeutics unaffected by efflux pumps would significantly increase life expectancy in patients with malignant cancers. In this study, butylcycloheptylprodigiosin and undecylprodigiosin were HPLC-purified and verified, using nuclear magnetic resonance spectroscopy. Cell cytotoxicity and transportation kinetics on multiple-drug resistance (MDR) cells were evaluated. Daunorubicin and butylcycloheptylprodigiosin were less toxic in the MDR1 overexpressing line, but undecylprodigiosin revealed potent toxicity toward MDR1 and BCRP expressing malignant cells. There was no noticeable change in MDR1 and BCRP transcripts during 3 days of treatment with prodiginines. While daunorubicin and mitoxantrone uptake from the cell environment significantly decreased with increasing multidrug resistance up to 46% and 62%, respectively, the accumulation of undecylprodigiosin and to a lesser extent butylcycloheptylprodigiosin in the resistance cells occurred cell- and dose-dependently via a passive diffusion process and were almost equally sensitive to the parent lines. The efflux of xenobiotics commenced immediately with different kinetics in various cells. A greater amount of daunorubicin and mitoxantrone were rapidly thrown out of their corresponding MDR cells in the absence of the specific inhibitor (3.01 and 1.81 dF/min, respectively) and represented functional efflux pumps. MDR pumps did not apparently influence undecylprodigiosin efflux patterns; but butylcycloheptylprodigiosin was partially removed from EPG85.257RDB cells at the rate of 2.66 and 1.41 dF/min in the absence and presence of verapamil, respectively.

In Vitro and In Vivo Antitumor and Anti-Inflammatory Capabilities of the Novel GSK3 and CDK9 Inhibitor ABC1183

Glycogen synthase kinase-3s (GSK3α and GSK3β) are constitutively active protein kinases that target over 100 substrates, incorporate into numerous protein complexes, and regulate such vital cellular functions as proliferation, apoptosis, and inflammation. Cyclin-dependent kinase 9 (CDK9) regulates RNA production as a component of positive transcription elongation factor b and promotes expression of oncogenic and inflammatory genes. Simultaneous inhibition of these signaling nodes is a promising approach for drug discovery, although previous compounds exhibit limited selectivity and clinical efficacy. The novel diaminothiazole ABC1183 is a selective GSK3α/β and CDK9 inhibitor and is growth-inhibitory against a broad panel of cancer cell lines. ABC1183 treatment decreases cell survival through G2/M arrest and modulates oncogenic signaling through changes in GSK3, glycogen synthase, and β-catenin phosphorylation and MCL1 expression. Oral administration, which demonstrates no organ or hematologic toxicity, suppresses tumor growth and inflammation-driven gastrointestinal disease symptoms, owing in part to downregulation of tumor necrosis factor α and interleukin-6 proinflammatory cytokines. Therefore, ABC1183 is strategically poised to effectively mitigate multiple clinically relevant diseases.

ERK mediated upregulation of death receptor 5 overcomes the lack of p53 functionality in the diaminothiazole DAT1 induced apoptosis in colon cancer models: efficiency of DAT1 in Ras-Raf mutated cells

Background

p53 is a tumour suppressor protein that plays a key role in many steps of apoptosis, and malfunctioning of this transcription factor leads to tumorigenesis. Prognosis of many tumours also depends upon the p53 status. Most of the clinically used anticancer compounds activate p53 dependent pathway of apoptosis and hence require p53 for their mechanism of action. Further, Ras/Raf/MEK/ERK axis is an important signaling pathway activated in many cancers. Dependence of diaminothiazoles, compounds that have gained importance recently due to their anticancer and anti angiogenic activities, were tested in cancer models with varying p53 or Ras/Raf mutational status.

Methods

In this study we have used p53 mutated and knock out colon cancer cells and xenograft tumours to study the role of p53 in apoptosis mediated by diaminothiazoles. Colon cancer cell lines with varying mutational status for Ras or Raf were also used. We have also examined the toxicity and in vivo efficacy of a lead diaminothiazole 4-Amino-5-benzoyl-2-(4-methoxy phenylamino)thiazole (DAT1) in colon cancer xenografts.

Results

We have found that DAT1 is active in both in vitro and in vivo models with nonfunctional p53. Earlier studies have shown that extrinsic pathway plays major role in DAT1 mediated apoptosis. In this study, we have found that DAT1 is causing p53 independent upregulation of the death receptor 5 by activating the Ras/Raf/MEK/ERK signaling pathway both in wild type and p53 suppressed colon cancer cells. These findings are also confirmed by the in vivo results. Further, DAT1 is more efficient to induce apoptosis in colon cancer cells with mutated Ras or Raf.

Conclusions

Minimal toxicity in both acute and subacute studies along with the in vitro and in vivo efficacy of DAT1 in cancers with both wild type and nonfunctional p53 place it as a highly beneficial candidate for cancer chemotherapy. Besides, efficiency in cancer cells with mutations in the Ras oncoprotein or its downstream kinase Raf raise interest in diaminothiazole class of compounds for further follow-up.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-016-0505-7) contains supplementary material, which is available to authorized users.