P-glycoprotein and breast cancer resistance protein in acute myeloid leukaemia cells treated with the aurora-B kinase inhibitor barasertib-hQPA

Bruton’s Tyrosine Kinase Inhibitor Zanubrutinib Effectively Modulates Cancer Resistance by Inhibiting Anthracycline Metabolism and Efflux

Zanubrutinib (ZAN) is a Bruton’s tyrosine kinase inhibitor recently approved for the treatment of some non-Hodgkin lymphomas. In clinical trials, ZAN is often combined with standard anthracycline (ANT) chemotherapy. Although ANTs are generally effective, drug resistance is a crucial obstacle that leads to treatment discontinuation. This study showed that ZAN counteracts ANT resistance by targeting aldo-keto reductase 1C3 (AKR1C3) and ATP-binding cassette (ABC) transporters. AKR1C3 catalyses the transformation of ANTs to less potent hydroxy-metabolites, whereas transporters decrease the ANT-effective concentrations by pumping them out of the cancer cells. In our experiments, ZAN inhibited the AKR1C3-mediated inactivation of daunorubicin (DAUN) at both the recombinant and cellular levels. In the drug combination experiments, ZAN synergistically sensitised AKR1C3-expressing HCT116 and A549 cells to DAUN treatment. Gene induction studies further confirmed that ZAN did not increase the intracellular level of AKR1C3 mRNA; thus, the drug combination effect is not abolished by enzyme induction. Finally, in accumulation assays, ZAN was found to interfere with the DAUN efflux mediated by the ABCB1, ABCG2, and ABCC1 transporters, which might further contribute to the reversal of ANT resistance. In summary, our data provide the rationale for ZAN inclusion in ANT-based therapy and suggest its potential for the treatment of tumours expressing AKR1C3 and/or the above-mentioned ABC transporters.

Dual Targeting of Aurora Kinases with AMG 900 Exhibits Potent Preclinical Activity Against Acute Myeloid Leukemia with Distinct Post-Mitotic Outcomes

Aurora kinase A and B have essential and non-overlapping roles in mitosis, with elevated expression in a subset of human cancers, including acute myeloid leukemia (AML). In this study, pan-aurora kinase inhibitor (AKI) AMG 900 distinguishes itself as an anti-leukemic agent that is more uniformly potent against a panel of AML cell lines than are isoform-selective AKIs and classic AML drugs. AMG 900 inhibited AML cell growth by inducing polyploidization and/or apoptosis. AMG 900 and aurora-B-selective inhibitor AZD1152-hQPA showed comparable cellular effects on AML lines that do not harbor a FLT3-ITD mutation. AMG 900 was active against P-glycoprotein-expressing AML cells resistant to AZD1152-hQPA and was effective at inducing expression of megakaryocyte-lineage markers (CD41, CD42) on human CHRF-288-11 cells and mouse Jak2 V617F cells. In MOLM-13 cells, inhibition of p-histone H3 by AMG 900 was associated with polyploidy, extra centrosomes, accumulation of p53 protein, apoptosis, and cleavage of Bcl-2 protein. Co-administration of cytarabine (Ara-C) with AMG 900 potentiated cell killing in a subset of AML lines, with evidence of attenuated polyploidization. AMG 900 inhibited the proliferation of primary human bone marrow cells in culture, with a better proliferation recovery profile relative to classic antimitotic drug docetaxel. In vivo, AMG 900 significantly reduced tumor burden in a systemic MOLM-13 xenograft model where we demonstrate the utility of 3'-deoxy-3'-18F-fluorothymidine [18F]FLT positron emission tomographic (PET)-CT imaging to measure the antiproliferative effects of AMG 900 in skeletal tissues in mice.

Early changes in rpS6 phosphorylation and BH3 profiling predict response to chemotherapy in AML cells

Blasts from different patients with acute myeloid leukemia (AML) vary in the agent(s) to which they are most responsive. With a myriad of novel agents to evaluate, there is a lack of predictive biomarkers to precisely assign targeted therapies to individual patients. Primary AML cells often survive poorly in vitro, thus confounding conventional cytotoxicity assays. The purpose of this work was to assess the potential of two same-day functional predictive assays in AML cell lines to predict long-term response to chemotherapy. (i) Ribosomal protein S6 (rpS6) is a downstream substrate of PI3K/akt/mTOR/ kinase and MAPK kinase pathways and its dephosphorylation is also triggered by DNA double strand breaks. Phospho-rpS6 is reliably measurable by flow cytometry and thus has the potential to function as a biomarker of responsiveness to several therapeutic agents. (ii) A cell's propensity for apoptosis can be interrogated via a functional assay termed "Dynamic BH3 Profiling" in which mitochondrial outer membrane permeabilization in drug-treated cells can be driven by pro-apoptotic BH3 domain peptides such as PUMA-BH3. The extent to which a particular cell is primed for apoptosis by the drug can be determined by measuring the amount of cytochrome C released on addition of BH3 peptide. We demonstrate that phospho-rpS6 expression and PUMA-BH3 peptide-induced cytochrome C release after 4 hours both predict long term chemoresponsiveness to tyrosine kinase inhibitors and DNA double strand break inducers in AML cell lines. We also describe changes in expression levels of the prosurvival BCL-2 family member Mcl-1 and the pro-apoptotic protein BIM after short term drug culture.

Novel Mechanisms of Resistance to Investigational Molecularly Targeted Drugs

Drug resistance is a critical problem inhibiting the effective use of targeted molecular cancer therapies. Investigators have revealed a variety of resistance mechanisms, including alterations in drug targets, activation of pro-survival pathways, and the ineffective induction of cell death. The key alterations driving this resistance are likely condition-dependent, and a detailed analysis would be required to characterize these diverse alterations under a variety of conditions in order to facilitate practical precision medicine for treating individual cancer patients. We have been investigating the molecular mechanisms of anti-cancer drug resistance, and analyzed our original resistant cells against anti-mitotic kinase inhibitors. This study suggests that novel mechanisms reduce cytokinetic dysregulation caused by those inhibitors, and anti-apoptotic activities are associated with resistant phenotypes. These observations suggest that the activation of various bypass mechanisms may allow cancer cells to avoid the selective antiproliferative effect of molecularly targeted drugs, and such bypass activation mechanism would thus be a critical target for designing combination chemotherapy to overcome non-genetic drug resistance.

Anti-mitotic agents: Are they emerging molecules for cancer treatment?

Mutations in cancer cells frequently result in cell cycle alterations that lead to unrestricted growth compared to normal cells. Considering this phenomenon, many drugs have been developed to inhibit different cell-cycle phases. Mitotic phase targeting disturbs mitosis in tumor cells, triggers the spindle assembly checkpoint and frequently results in cell death. The first anti-mitotics to enter clinical trials aimed to target tubulin. Although these drugs improved the treatment of certain cancers, and many anti-microtubule compounds are already approved for clinical use, severe adverse events such as neuropathies were observed. Since then, efforts have been focused on the development of drugs that also target kinases, motor proteins and multi-protein complexes involved in mitosis. In this review, we summarize the major proteins involved in the mitotic phase that can also be targeted for cancer treatment. Finally, we address the activity of anti-mitotic drugs tested in clinical trials in recent years.

Functional Effects of AKT3 on Aurora Kinase Inhibitor-induced Aneuploidy

The suppression of mitotic Aurora kinases (AURKs) by AURK inhibitors frequently causes cytokinetic failure, leading to polyploidy or aneuploidy, indicating the critical role of AURK-mediated phosphorylation during cytokinesis. We demonstrate the deregulated expression of AKT3 in Aurora kinase inhibitor (AURKi)-resistant cells, which we established from human colorectal cancer HCT 116 cells. The AKT family, which includes AKT1, -2, and -3, plays multiple roles in antiapoptotic functions and drug resistance and is involved in cell growth and survival pathways. We found that an AKT inhibitor, AZD5363, showed synergistic effect with an AURKi, VX-680, on two AKT3-expressing AURKi-resistant cell lines, and AKT3 knockdown sensitized cells to VX-680. Consistent with these activities, AKT3 expression suppressed AURKi-induced apoptosis and conferred resistance to AURKi. Thus, AKT3 expression affects cell sensitivity to AURKi. Moreover, we found that AKT3 expression suppressed AURKi-induced aneuploidy, and inversely AKT3 knockdown enhanced it. In addition, partial co-localization of AKT3 with AURKB was observed during anaphase. Overall, this study suggests that AKT3 could repress the antiproliferative effects of AURKi, with a novel activity particularly suppressing the aneuploidy induction.

Improvement of DC vaccine with ALA-PDT induced immunogenic apoptotic cells for skin squamous cell carcinoma

Dendritic cell (DC) based vaccines have emerged as a promising immunotherapy for cancers. However, most DC vaccines so far have achieved only limited success in cancer treatment. Photodynamic therapy (PDT), an established cancer treatment strategy, can cause immunogenic apoptosis to induce an effective antitumor immune response. In this study, we developed a DC-based cancer vaccine using immunogenic apoptotic tumor cells induced by 5-aminolevulinic acid (ALA) mediated PDT. The maturation of DCs induced by PDT-treated apoptotic cells was evaluated using electron microscopy, FACS, and ELISA. The anti-tumor immunity of ALA-PDT-DC vaccine was tested with a mouse model. We observed the maturations of DCs potentiated by ALA-PDT treated tumor cells, including morphology maturation (enlargement of dendrites and increase of lysosomes), phenotypic maturation (upregulation of surface expression of MHC-II, DC80, and CD86), and functional maturation (enhanced capability to secrete IFN-γ and IL-12, and to induce T cell proliferation). Most interestingly, PDT-induced apoptotic tumor cells are more capable of potentiating maturation of DCs than PDT-treated or freeze/thaw treated necrotic tumor cells. ALA-PDT-DC vaccine mediated by apoptotic cells provided protection against tumors in mice, far stronger than that of DC vaccine obtained from freeze/thaw treated tumor cells. Our results indicate that immunogenic apoptotic tumor cells can be more effective in enhancing a DC-based cancer vaccine, which could improve the clinical application of PDT-DC vaccines.

Coexpression of Multiple ABC-Transporters is Strongly Associated with Treatment Response in Childhood Acute Myeloid Leukemia

BACKGROUND

To analyze whether expression of ABC-transporters is associated with remission rate and long-term outcome in a prospective clinical trial of childhood acute myeloid leukemia (AML).

PROCEDURE

The expression of four ABC-transporter genes (ABCA3 encoding drug transporter ABCA3, ABCB1 encoding multidrug resistance protein 1, ABCC3 encoding multidrug resistance-associated protein 3, and ABCG2 encoding breast cancer resistance protein) was measured by TaqMan real time polymerase chain reaction in pretreatment samples from 112 children with AML. Patients were treated according to multicenter study AML-Berlin, Frankfurt, Munich (BFM) 2004.

RESULTS

ABCC3 (P = 0.009) and ABCG2 (P = 0.03) were associated with a lower chance to achieve remission after the first course of chemotherapy. ABCC3 was associated with lower relapse free survival (RFS) (P = 0.02). ABCG2 was expressed at higher levels in subtypes of AML with favorable outcome but within standard- and high-risk patients, it was associated with poor outcome (P = 0.02). A strong association was observed between the number of overexpressed ABC-transporters and the chance to achieve remission (P = 0.01) or the chance of RFS (P < 0.001).

CONCLUSIONS

The intensive treatment regimen of AML-BFM 2004 did not readily overcome drug resistance caused by ABC-transporters. Inhibition of ABC-transporters might be particularly useful in patients who express multiple of these genes.

P-glycoprotein (MDR1/ABCB1) and breast cancer resistance protein (BCRP/ABCG2) restrict brain accumulation of the JAK1/2 inhibitor, CYT387

CYT387 is an orally bioavailable, small molecule inhibitor of Janus family of tyrosine kinases (JAK) 1 and 2. It is currently undergoing Phase I/II clinical trials for the treatment of myelofibrosis and myeloproliferative neoplasms. We aimed to establish whether the multidrug efflux transporters P-glycoprotein (P-gp; MDR1; ABCB1) and breast cancer resistance protein (BCRP;ABCG2) restrict oral availability and brain penetration of CYT387. In vitro, CYT387 was efficiently transported by both human MDR1 and BCRP, and very efficiently by mouse Bcrp1 and its transport could be inhibited by specific MDR1 inhibitor, zosuquidar and/or specific BCRP inhibitor, Ko143. CYT387 (10 mg/kg) was orally administered to wild-type (WT), Bcrp1(-/-), Mdr1a/1b(-/-) and Bcrp1;Mdr1a/1b(-/-) mice and plasma and brain concentrations were analyzed. Over 8h, systemic exposure of CYT387 was similar between all the strains, indicating that these transporters do not substantially limit oral availability of CYT387. Despite the similar systemic exposure, brain accumulation of CYT387 was increased 10.5- and 56-fold in the Bcrp1;Mdr1a/1b(-/-) mice compared to the WT strain at 2 and 8h after CYT387 administration, respectively. In single Bcrp1(-/-) mice, brain accumulation of CYT387 was more substantially increased than in Mdr1a/1b(-/-) mice, suggesting that CYT387 is a slightly better substrate of Bcrp1 than of Mdr1a at the blood-brain barrier. These results indicate a marked and additive role of Bcrp1 and Mdr1a/1b in restricting brain penetration of CYT387, potentially limiting efficacy of this compound against brain (micro) metastases positioned behind a functional blood-brain barrier.

Inhibiting aurora kinases reduces tumor growth and suppresses tumor recurrence after chemotherapy in patient-derived triple-negative breast cancer xenografts

Triple-negative breast cancers (TNBC) have an aggressive phenotype with a relatively high rate of recurrence and poor overall survival. To date, there is no approved targeted therapy for TNBCs. Aurora kinases act as regulators of mammalian cell division. They are important for cell-cycle progression and are frequently overexpressed or mutated in human tumors, including breast cancer. In this study, we investigated the therapeutic potential of targeting Aurora kinases in preclinical models of human breast cancers using a pan-inhibitor of Aurora kinases, AS703569. In vitro, AS703569 was tested in 15 human breast cancer cell lines. TNBC cell lines were more sensitive to AS703569 than were other types of breast cancer cells. Inhibition of proliferation was associated with cell-cycle arrest, aneuploidy, and apoptosis. In vivo, AS703569 administered alone significantly inhibited tumor growth in seven of 11 patient-derived breast cancer xenografts. Treatment with AS703569 was associated with a decrease of phospho-histone H3 expression. Finally, AS703569 combined to doxorubicin-cyclophosphamide significantly inhibited in vivo tumor recurrence, suggesting that Aurora kinase inhibitors could be used both in monotherapy and in combination settings. In conclusion, these data indicate that targeting Aurora kinases could represent a new effective approach for TNBC treatment.

Quinazoline derivatives as potential anticancer agents: a patent review (2007 - 2010)

INTRODUCTION

Due to the increase in knowledge about cancer pathways, there is a growing interest in finding novel potential drugs. Quinazoline is one of the most widespread scaffolds amongst bioactive compounds. A number of patents and papers appear in the literature regarding the discovery and development of novel promising quinazoline compounds for cancer chemotherapy. Although there is a progressive decrease in the number of patents filed, there is an increasing number of biochemical targets for quinazoline compounds.

AREAS COVERED

This paper provides a comprehensive review of the quinazolines patented in 2007 - 2010 as potential anticancer agents. Information from articles published in international peer-reviewed journals was also included, to give a more exhaustive overview.

EXPERT OPINION

From about 1995 to 2006, the anticancer quinazolines panorama has been dominated by the 4-anilinoquinazolines as tyrosine kinase inhibitors. The extensive researches conducted in this period could have caused the progressive reduction in the ability to file novel patents as shown in the 2007 - 2010 period. However, the growing knowledge of cancer-related pathways has recently highlighted some novel potential targets for therapy, with quinazolines receiving increasing attention. This is well demonstrated by the number of different targets of the patents considered in this review. The structural heterogeneity in the patented compounds makes it difficult to derive general pharmacophores and make comparisons among claimed compounds. On the other hand, the identification of multi-target compounds seems a reliable goal. Thus, it is reasonable that quinazoline compounds will be studied and developed for multi-target therapies.