Human hepatoma cells rich in P-glycoprotein are sensitive to aclarubicin and resistant to three other anthracyclines

Aclarubicin: contemporary insights into its mechanism of action, toxicity, pharmacokinetics, and clinical standing

Aclarubicin (aclacinomycin A) is one of the anthracycline antineoplastic antibiotics with a multifaceted mechanism of antitumor activity. As a second-generation drug, it offers several advantages compared to standard anthracycline drugs such as doxorubicin or daunorubicin, which could position it as a potential blockbuster drug in antitumor therapy. Key mechanisms of action for aclarubicin include the inhibition of both types of topoisomerases, suppression of tumor invasion processes, generation of reactive oxygen species, inhibition of chymotrypsin-like activity, influence on cisplatin degradation, and inhibition of angiogenesis. Therefore, aclarubicin appears to be an ideal candidate for antitumor therapy. However, despite initial interest in its clinical applications, only a limited number of high-quality trials have been conducted thus far. Aclarubicin has primarily been evaluated as an induction therapy in acute myeloid and lymphoblastic leukemia. Studies have indicated that aclarubicin may hold significant promise for combination therapies with other anticancer drugs, although further research is needed to confirm its potential. This paper provides an in-depth exploration of aclarubicin's diverse mechanisms of action, its pharmacokinetics, potential toxicity, and the clinical trials in which it has been investigated.

New insights into the activities and toxicities of the old anticancer drug doxorubicin

The anthracycline drug doxorubicin is among the most used—and useful—chemotherapeutics. While doxorubicin is highly effective in the treatment of various hematopoietic malignancies and solid tumours, its application is limited by severe adverse effects, including irreversible cardiotoxicity, therapy‐related malignancies and gonadotoxicity. This continues to motivate investigation into the mechanisms of anthracycline activities and toxicities, with the aim to overcome the latter without sacrificing the former. It has long been appreciated that doxorubicin causes DNA double‐strand breaks due to poisoning topoisomerase II. More recently, it became clear that doxorubicin also leads to chromatin damage achieved through eviction of histones from select sites in the genome. Evaluation of these activities in various anthracycline analogues has revealed that chromatin damage makes a major contribution to the efficacy of anthracycline drugs. Furthermore, the DNA‐damaging effect conspires with chromatin damage to cause a number of adverse effects. Structure–activity relationships within the anthracycline family offer opportunities for chemical separation of these activities towards development of effective analogues with limited adverse effects. In this review, we elaborate on our current understanding of the different activities of doxorubicin and their contributions to drug efficacy and side effects. We then offer our perspective on how the activities of this old anticancer drug can be amended in new ways to benefit cancer patients, by providing effective treatment with improved quality of life.

Efficacy of high-dose cytarabine and aclarubicin in combination with G-CSF regimen compared to intermediate/high-dose cytarabine and standard-dose cytarabine induction regimen for non-remission acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) patients with non-remission (NR) after the first cycle of standard induction chemotherapy remain a challenge owing to poor response and tolerance to re-induction regimen. We retrospectively evaluated the efficacy and safety of three regimens in AML patients refractory to the first course of standard induction regimen.

MATERIALS AND METHODS

The three regimens consisted of (1) High-dose cytarabine, aclarubicin and granulocyte colony-stimulating factor (HD-CAG) regimen (n = 44); (2) intermediate/high-dose cytarabine (I/HDAC) regimen (n = 30); and (3) standard-dose cytarabine (SDAC) combination regimen that was identical to the first course of standard induction regimen (n = 27).

RESULTS

Results indicated that after the second course, the overall response (OR), i.e., complete remission [CR]+partial remission [PR]) rates in HD-CAG was higher than in the I/HDAC group (84.1% vs. 56.7%, P = 0.009), whereas the CR rates among 3 groups were not statistically different (P = 0.541). Meanwhile, the proportion of subjects reporting certain adverse effects in the HD-CAG group was lower than the I/HDAC or SDAC groups. There were no significant differences in overall survival (OS) and disease-free survival (DFS) rates among the 3 groups (P = 0.881 and P = 0.872, respectively).

CONCLUSION

Our preliminary results indicate that HD-CAG regimen may represent a better alternative option for AML patients with NR after the first course of standard induction chemotherapy.

Efficacy of common salvage chemotherapy regimens in patients with refractory or relapsed acute myeloid leukemia: A retrospective cohort study

To assess treatment response and overall survival (OS) in refractory or relapsed acute myeloid leukemia (R/R AML) patients treated by different common salvage chemotherapy regimens.Medical records data from 142 R/R AML patients were reviewed in this retrospective study. Patients were treated with regimens based on the following drugs: cytarabine, granulocyte colony-stimulating factor (G-CSF), and fludarabine (FLAG) (n = 46); cytarabine and G-CSF in addition to aclarubicin or daunorubicin (CAG/DAG) (n = 30); cytarabine, G-CSF, and cladribine (CLAG) (n = 27); cytarabine, etoposide, and mitoxantrone (MEA) (n = 17); cytarabine plus idarubicin, daunorubicin, or mitoxantrone (IA/DA/MA) (n = 12); and homoharringtonine, cytarabine, and aclarubicin or daunorubicin (HAA/HAD) (n = 10).A total of 43 (35.2%) patients achieved complete remission (CR), 60 (49.2%) patients achieved overall remission rate (ORR), and 18 (14.8%) patients received allogeneic hematopoietic stem cell transplantation (allo-HSCT) after CR. Median OS was 8.0 (95% CI 6.6-9.4) months with a 1-year OS rate of (29.9 ± 3.9)% and 3-year OS rate of (11.1 ± 3.6)%. No difference of CR (P = .621), ORR (P = .385), and allo-HSCT (P = .537) achievement was observed among different chemotherapy regimens. Interestingly, we observed that the CLAG-based regimen did not affect CR (P = .165), while it achieved a numerically higher ORR (P = .093) and was an independent factor for prolonged OS (P = .016). No other regimens were determined to be correlated with CR, ORR, or OS.FLAG-, CAG/DAG-, CLAG-, MEA-, IA/DA/MA- and HAA/HAD-based regimens were found to achieve similar CR rates, while the CLAG-based regimen achieved numerically higher ORR rates and significant favorable OS. Therefore, CLAG-based regimens should be a prioritized treatment option for R/R AML patients.

β-defensin 1 expression in HCV infected liver/liver cancer: an important role in protecting HCV progression and liver cancer development

β-defensin family plays a role in host defense against viral infection, however its role in HCV infection is still unknown. In this study, we demonstrated that β-defensin 1 was significantly reduced in HCV-infected liver specimens. Treatment with interferon and ribavirin upregulated β-defensin-1, but not other β-defensin tested, with the extent and duration of upregulation associated with treatment response. We investigated β-defensin family expression in liver cancer in publicly available datasets and found that among all the β-defensins tested, only β-defensin 1 was significantly downregulated, suggesting β-defensin 1 plays a crucial role in liver cancer development. Further analysis identified E-cadherin as the top positive correlated gene, while hepatocyte growth factor-regulated tyrosine kinase substrate as the top negative correlated gene. Expression of two proteoglycans were also positively correlated with that of β-defensin 1. We have also identified small molecules as potential therapeutic agents to reverse β-defensin 1-associated gene signature. Furthermore, the downregulation of β-defensin 1 and E-cadherin, and upregulation of hepatocyte growth factor-regulated tyrosine kinase substrate, were further confirmed in liver cancer and adjacent normal tissue collected from in-house Chinese liver cancer patients. Together, our results suggest β-defensin 1 plays an important role in protecting HCV progression and liver cancer development.

Increasing the dose of aclarubicin in low-dose cytarabine and aclarubicin in combination with granulocyte colony-stimulating factor (CAG regimen) can safely and effectively treat relapsed or refractory acute myeloid leukemia

It is difficult for relapsed and refractory acute myeloid leukemia (AML) patients to achieve complete remission (CR). The CAG regimen [low-dose cytarabine and aclarubicin in combination with granulocyte colony-stimulating factor (G-CSF)] has been used to treat relapsed and refractory AML patients, and showed good therapeutic efficacy. It is unknown, however, whether increasing the dose of aclarubicin in CAG regimen could treat relapsed or refractory AML safely and effectively. We evaluate the efficacy and tolerability of increasing the dose of aclarubicin in CAG regimen, in 37 relapsed or refractory AML patients. All patients were treated with CAG regimen including low-dose cytarabine (10 mg/m(2) every 12 h, days 1-14), aclarubicin (5-7 mg/m(2) every day, days 1-14), and G-CSF (200 μg/m(2) every day, days 1-14) priming. After a single course of therapy, the overall response [CR + partial remission (PR)] rate of all patients was 78.4 % (29/37), in which the CR rate was 62.2 % (23/37). There was no early death. The median overall survival was 6 months (range 2-36 months). Myelosuppression was ubiquitous, but tolerated. No severe non-hematologic toxicity was observed. Thus, increasing the dose of aclarubicin in CAG regimen can be used safely and effectively in the treatment of relapsed or refractory AML.

The connection between the toxicity of anthracyclines and their ability to modulate the P-glycoprotein-mediated transport in A549, HepG2, and MCF-7 cells

Multidrug resistance (MDR) is a major obstacle to the successful chemotherapy of solid tumors. We compared the resistance of the most popular solid tumors, breast adenocarcinoma (MCF-7 cell line) and nonsmall cell lung (A549 cell line) hepatocellular liver carcinoma (HepG2 cells), to aclarubicin (ACL) and doxorubicin (DOX). This research aimed at determining the relation between the toxicity of ACL and DOX, their cell accumulation, and then effect on P-glycoprotein functionality. ACL is more cytotoxic for tumor cells compared to DOX. The intracellular concentration of drugs in cancer cells was dependent on the dose of the drugs and the time of incubation. The P-gp inhibitor Verapamil (V) increased DOX accumulation in all tested cell lines. By contrast, the intracellular level of ACL was not affected by this modifying agent. The assessment of the uptake of 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolocarbocyanine iodide (JC-1) or Rhodamine 123 (R123) allows the evaluation of the different influence of drugs on P-gp activity which is in agreement with the estimation of expression measured by MDR-1 shift assay. These data suggest that ACL is less P-gp dependent than DOX and consequently may be used in a clinical setting to increase treatment efficacy in resistant human tumors.

A meta-analysis of CAG (cytarabine, aclarubicin, G-CSF) regimen for the treatment of 1029 patients with acute myeloid leukemia and myelodysplastic syndrome

The regimen of cytarabine, aclarubicin and G-CSF (CAG) has been widely used in China and Japan for treatment of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). We searched literature on CAG between 1995 and 2010 and performed a meta-analysis to determine its overall efficacy using a random-effects or fixed-effects model. Thirty five trials with a total of 1029 AML (n = 814) and MDS (n = 215) patients were included for analysis. The CR rate of AML (57.9%) was significantly higher than that of MDS (45.7%) (p < 0.01). No difference in CR was noted between the new (56.7%) and relapsed/refractory AML (60.1%) (p > 0.05). The CR rate was also significantly higher in patients with favorable (64.5%) and intermediate (69.6%) karyotypes than those with unfavorable one (29.5%) (p < 0.05). Remarkably, the CR rate of CAG was significantly higher than those of non-CAG regimens (odds ratio 2.43). CAG regimen was well tolerated, with cardiotoxicity in 2.3% and early death in 5.2% of the cases. In conclusion, CAG regimen was an effective and safe regimen for the treatment of AML, and may be more effective than non-CAG regimens. Randomized controlled trials are strongly recommended to evaluate its efficacy and safety in comparison with the current standard treatment.

Semantic similarity for automatic classification of chemical compounds

With the increasing amount of data made available in the chemical field, there is a strong need for systems capable of comparing and classifying chemical compounds in an efficient and effective way. The best approaches existing today are based on the structure-activity relationship premise, which states that biological activity of a molecule is strongly related to its structural or physicochemical properties. This work presents a novel approach to the automatic classification of chemical compounds by integrating semantic similarity with existing structural comparison methods. Our approach was assessed based on the Matthews Correlation Coefficient for the prediction, and achieved values of 0.810 when used as a prediction of blood-brain barrier permeability, 0.694 for P-glycoprotein substrate, and 0.673 for estrogen receptor binding activity. These results expose a significant improvement over the currently existing methods, whose best performances were 0.628, 0.591, and 0.647 respectively. It was demonstrated that the integration of semantic similarity is a feasible and effective way to improve existing chemical compound classification systems. Among other possible uses, this tool helps the study of the evolution of metabolic pathways, the study of the correlation of metabolic networks with properties of those networks, or the improvement of ontologies that represent chemical information.

Among the existing systems capable of computationally comparing chemical compounds, the majority use only structural and physicochemical properties. However, with the emergence of ChEBI and other chemical compound databases, it has become feasible to create a system that can use the relevance of compounds in a biological context as well. This setting enables the distinction of molecules with different roles in nature but similar structures, or similar roles and different structures. ChEBI is organized as an ontology that classifies chemical compounds, which we use to derive a semantic similarity measure that reflects the biological relevance of molecules. In an effort to use as much information as possible, we introduce Chym, a system that integrates structural and semantic information in a single hybrid metric, and we show the accuracy of the system in three distinct classification problems, which consist in deciding whether a compound crosses the blood brain barrier, is a P-glycoprotein substrate or an estrogen receptor ligand. Chym outperforms the previous attempts to solve these three problems, with a maximum accuracy of 90.0%.

Is resistance useless? Multidrug resistance and collateral sensitivity

When cancer cells develop resistance to chemotherapeutics, it is frequently conferred by the ATP-dependent efflux pump P-glycoprotein (MDR1, P-gp, ABCB1). P-gp can efflux a wide range of cancer drugs; its expression confers cross-resistance, termed "multidrug resistance" (MDR), to a wide range of drugs. Strategies to overcome this resistance have been actively sought for more than 30 years, yet clinical solutions do not exist. A less understood aspect of MDR is the hypersensitivity of resistant cancer cells to other drugs, a phenomenon known as "collateral sensitivity" (CS). This review highlights the extent of this effect for the first time, and discusses hypotheses (e.g. generation of reactive oxygen species) to account for the underlying generality of this phenomenon, and proposes exploitation of CS as a strategy to improve response to chemotherapy.

Overexpression of Ssl2p confers resistance to adriamycin and actinomycin D in Saccharomyces cerevisiae

Adriamycin is one of the most active anticancer drugs but the development of resistance to this drug hampers its efficacy. In an effort to identify novel genes that confer resistance to adriamycin, we introduced a yeast genomic library into Saccharomyces cerevisiae and selected transformants that grew in the presence of a normally toxic concentration of adriamycin. Detailed examination of a plasmid recovered from these transformants revealed that overexpression of the gene for Ssl2p rendered yeast cells resistant to adriamycin. Ssl2p is a protein that is involved in the initiation of transcription and in DNA repair. Overexpression of Ssl2p did not confer resistance to aclarubicin, an anthracycline anticancer drug, which, like adriamycin, is intercalated into DNA. Both adriamycin and aclarubicin inhibit topoisomerase II and, thus, topoisomerase II might not be a major factor in the acquired resistance to adriamycin that results from overexpression of Ssl2p. We tested several other compounds but the only one to which Ssl2p-overexpressing cells were cross-resistant was actinomycin D. Mammalian cells that overexpress P-glycoprotein, which is a transmembrane protein that is involved in the efflux of certain drugs, are resistant to both adriamycin and actinomycin D but not to aclarubicin. However, overexpression of Ssl2p had little or no effect on the intracellular accumulation of adriamycin. Our results suggest that a novel mechanism might be involved in the sensitivity of yeast to both adriamycin and actinomycin D.

Anthracycline drug targeting: cytoplasmic versus nuclear--a fork in the road

The anthracycline antibiotics doxorubicin (Adriamycin; DOX) and daunorubicin (DNR) continue to be essential components of first-line chemotherapy in the treatment of a variety of solid and hematopoietic tumors. The overall efficacies of DOX and DNR are, however, impeded by serious dose-limiting toxicities, including cardiotoxicity, and the selection of multiple mechanisms of cellular drug resistance. These limitations have necessitated the development of newer anthracyclines whose structural and functional modifications circumvent these impediments. In this review, we will present recent strategies in anthracycline design and assess their potential therapeutic merits. Current anthracycline design has diverged to target either cytoplasmic or nuclear sites. Nuclear targets have been broadened to include not only topoisomerase II (topo II) inhibition through ternary complex stabilization and catalytic inhibition, but also topoisomerase I (topo I) inhibition and transcriptional inhibition. In contrast, cytoplasmic targeting focuses on anthracycline binding to protein kinase C (PKC) regulatory domain with consequent modulation of activity.

Cytotoxic effect of the cyclosporin PSC 833 in multidrug-resistant leukaemia cells with increased expression of P-glycoprotein

Multidrug resistance (MDR) to anti-cancer agents is frequently associated with overexpression of the drug efflux transporter P-glycoprotein (Pgp) in cancer cells, ensuing drug expulsion and maintenance of tolerable intracellular levels of certain cytotoxic drugs. Pgp may also be present in normal tissue, providing protection against toxic substances, but the physiological role of Pgp is not fully understood. Recently, it was shown that Pgp also takes part in the transport of certain growth-regulating cytokines (Drach et al, 1996; Raghu et al, 1996). Therefore, we studied the effect of the highly potent Pgp inhibitor PSC 833 on proliferation of three pairs of MDR and parental human cell lines (HB8065 hepatoma cells, KG1a and K562 leukaemia cells). The MDR phenotypes were characterized by Pgp overexpression, which was demonstrated by flow cytometry using the anti-Pgp antibody MRK16. Electronic cell counting of 72-96 h cultures revealed a dose-dependent antiproliferative effect of PSC 833 in the resistant KG1a/200 and K562/150 cells. The half-maximal growth inhibitory concentrations (GI50) were 0.2 microM and 0.7 microM respectively. Exposure to PSC 833 induced cell death by apoptosis in both cell types, as revealed by flow cytometry and detection of 3'-hydroxy ends of DNA (the result of DNA fragmentation associated with apoptosis), by terminal transferase-mediated dUTP-biotin nick end-labelling (TUNEL). Similar effects were not found in the hepatoma cell lines or the parental leukaemia lines. These results demonstrated a discriminating cytotoxicity of PSC 833 in two human leukaemia MDR variants, representing a possible therapeutic indication which warrants consideration during the ongoing clinical evaluation of this drug.

Practical considerations in the treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents one of the most common neoplasms worldwide. To date, curative treatment options include liver transplantation or resection. Unfortunately, most patients are detected with nonresectable or -transplantable HCC due to disease extension or comorbid factors, and are therefore candidates only for palliative treatments. Palliative medical treatments, including systemic chemotherapy, immunotherapy or hormonal manipulation, have a borderline activity on HCC and cannot be recommended outside clinical trials. A high response rate has been reported with local therapies such as transcatheter arterial embolisation, intra-arterial chemotherapy or percutaneous alcohol (ethanol) injection, but as there is no clear evidence of a survival advantage for these treatment modalities, further investigations are required. Multidisciplinary treatment, including preoperative cytoreduction or postoperative adjuvant therapy, is currently under investigation, with encouraging survival results. HCC patients should be evaluated within clinical trials, possibly randomised and with homogeneous prognostic factors, in order that we may find the answer to all these important questions.