EGFR inhibitors exacerbate differentiation and cell cycle arrest induced by retinoic acid and vitamin D3 in acute myeloid leukemia cells

Demographics, Radiological Findings, and Clinical Outcomes of Klebsiella pneumonia vs. Non-Klebsiella pneumoniae Pyogenic Liver Abscess: A Systematic Review and Meta-Analysis with Trial Sequential Analysis

Pyogenic liver abscess (PLA) is a common cause of hepatobiliary sepsis. Klebsiella pneumoniae (KP) is the most common organism causing PLA. Evidence is scarce on the demographics, radiological findings, and outcomes of KPPLA versus non-KPPLA (N-KPPLA). PubMed, Embase, The Cochrane Library, and Scopus were systematically searched until 14 May 2022 for studies comparing KPPLA and N-KPPLA. Exclusion criteria were single-arm studies. Primary outcomes were mortality (30-day/in-hospital) and metastatic complications. There were 16 studies, including 5127 patients (KPPLA n = 3305, N-KPPLA n = 1822). Patients with KPPLA were younger (mean difference: −2.04 years, p = 0.02). History of hepatobiliary disease (Odds ratio (OR) 0.30, 95% CI: 0.20, 0.46) and malignancy (OR 0.26, 95% CI: 0.16, 0.42) were less common in KPPLA. KPPLA was associated with lower incidence of multiple abscesses (OR 0.52, 95% CI: 0.35, 0.76, p < 0.001) and bilobar abscesses (OR 0.60, 95% CI: 0.49, 0.74, p < 0.001). KPPLA has higher overall metastatic complications (KPPLA 9.7% vs. N-KPPLA 4.8%, OR 3.16, 95% CI: 2.00, 4.99, p < 0.001), but lower mortality (KPPLA 3.9% vs. N-KPPLA 7.6%, OR 0.51, 95% CI: 0.34, 0.78, p < 0.001). Trial sequential analysis showed conclusive evidence that KPPLA has lower mortality than N-KPPLA. In conclusion, KPPLA has lower mortality than N-KPPLA.

Design, synthesis and mechanistic studies of novel imidazo[1,2-a]pyridines as anticancer agents

Herein, the design, synthesis and mechanistic study of five series of imidazo[1,2-a]pyridines 8a-d, 9a-f, 11a-c, 12a-d and 14a-d as anticancer agents were discussed. The cytotoxicity of imidazo[1,2-a]pyridine derivatives was screened against NCI 60 cancer cell lines. The cytotoxicity of compounds 8b, 8c, 9e and 9f was then evaluated against leukemia K-562 cancer cell line and normal lung fibroblasts (WI38). The hydrazone derivatives 8b and 8c exhibited significant cytotoxic activities against the leukemia K-562 cancer cell line with good safety margins (IC₅₀ = 2.91 µM, SI = 8.32 and IC₅₀ = 1.09 µM, SI = 10.54, respectively). In addition, compounds 8b, 8c, 9e and 9f were tested for their EGFR and COX-2 inhibitory activities. The hydrazone derivatives 8b and 8c were the most active EGFR inhibitors with IC₅₀ values of 0.123 and 0.072 µM, respectively. Compound 8c selectively inhibited COX-2 (IC₅₀ = 1.09 µM, SI = 13.78). Moreover, the potential of compound 8c to induce apoptosis in leukemia K-562 cell line was determined. Compound 8c showed a pre-G1 apoptosis and a growth arrest of leukemia K-562 cell line at G1 phase of cell cycle. Also, compound 8c was able to induce caspase-3 overexpression (6.98 folds), if compared to control. Finally, molecular docking studies and physicochemical properties calculation of compounds 8b, 8c, 9e and 9f were carried out to explain the biological data and to predict bioavailability of the most active compounds.

Disruption of dNTP homeostasis by ribonucleotide reductase hyperactivation overcomes AML differentiation blockade

Differentiation blockade is a hallmark of acute myeloid leukemia (AML). A strategy to overcome such a blockade is a promising approach against the disease. The lack of understanding of the underlying mechanisms hampers development of such strategies. Dysregulated ribonucleotide reductase (RNR) is considered a druggable target in proliferative cancers susceptible to deoxynucleoside triphosphate (dNTP) depletion. Herein, we report an unanticipated discovery that hyperactivating RNR enables differentiation and decreases leukemia cell growth. We integrate pharmacogenomics and metabolomics analyses to identify that pharmacologically (eg, nelarabine) or genetically upregulating RNR subunit M2 (RRM2) creates a dNTP pool imbalance and overcomes differentiation arrest. Moreover, R-loop-mediated DNA replication stress signaling is responsible for RRM2 activation by nelarabine treatment. Further aggravating dNTP imbalance by depleting the dNTP hydrolase SAM domain and HD domain-containing protein 1 (SAMHD1) enhances ablation of leukemia stem cells by RRM2 hyperactivation. Mechanistically, excessive activation of extracellular signal-regulated kinase (ERK) signaling downstream of the imbalance contributes to cellular outcomes of RNR hyperactivation. A CRISPR screen identifies a synthetic lethal interaction between loss of DUSP6, an ERK-negative regulator, and nelarabine treatment. These data demonstrate that dNTP homeostasis governs leukemia maintenance, and a combination of DUSP inhibition and nelarabine represents a therapeutic strategy.

Targeting metabolism: A potential strategy for hematological cancer therapy

Most hematological cancer-related relapses and deaths are caused by metastasis; thus, the importance of this process as a target of therapy should be considered. Hematological cancer is a type of cancer in which metabolism plays an essential role in progression. Therefore, we are required to block fundamental metastatic processes and develop specific preclinical and clinical strategies against those biomarkers involved in the metabolic regulation of hematological cancer cells, which do not rely on primary tumor responses. To understand progress in this field, we provide a summary of recent developments in the understanding of metabolism in hematological cancer and a general understanding of biomarkers currently used and under investigation for clinical and preclinical applications involving drug development. The signaling pathways involved in cancer cell metabolism are highlighted and shed light on how we could identify novel biomarkers involved in cancer development and treatment. This review provides new insights into biomolecular carriers that could be targeted as anticancer biomarkers.

JAK-STAT core cancer pathway: An integrative cancer interactome analysis

Through a comprehensive review and in silico analysis of reported data on STAT-linked diseases, we analysed the communication pathways and interactome of the seven STATs in major cancer categories and proposed rational targeting approaches for therapeutic intervention to disrupt critical pathways and addictions to hyperactive JAK/STAT in neoplastic states. Although all STATs follow a similar molecular activation pathway, STAT1, STAT2, STAT4 and STAT6 exert specific biological profiles associated with a more restricted pattern of activation by cytokines. STAT3 and STAT5A as well as STAT5B have pleiotropic roles in the body and can act as critical oncogenes that promote many processes involved in cancer development. STAT1, STAT3 and STAT5 also possess tumour suppressive action in certain mutational and cancer type context. Here, we demonstrated member-specific STAT activity in major cancer types. Through systems biology approaches, we found surprising roles for EGFR family members, sex steroid hormone receptor ESR1 interplay with oncogenic STAT function and proposed new drug targeting approaches of oncogenic STAT pathway addiction.

Guanosine primes acute myeloid leukemia for differentiation via guanine nucleotide salvage synthesis

Differentiation arrest represents a distinct hallmark of acute myeloid leukemia (AML). Identification of differentiation-induction agents that are effective across various subtypes remains an unmet challenge. GTP biosynthesis is elevated in several types of cancers, considered to support uncontrolled tumor growth. Here we report that GTP overload by supplementation of guanosine, the nucleoside precursor of GTP, poises AML cells for differentiation and growth inhibition. Transcriptome profiling of guanosine-treated AML cells reveals a myeloid differentiation pattern. Importantly, the treatment compromises leukemia progression in AML xenograft models. Mechanistically, GTP overproduction requires sequential metabolic conversions executed by the purine salvage biosynthesis pathway including the involvement of purine nucleoside phosphorylase (PNP) and hypoxanthine phosphoribosyltransferase 1 (HPRT1). Taken together, our study offers novel metabolic insights tethering GTP homeostasis to myeloid differentiation and provides an experimental basis for further clinical investigations of guanosine or guanine nucleotides in the treatment of AML patients.

An online tool for predicting the prognosis of cancer patients with SARS-CoV-2 infection: a multi-center study

PURPOSE

During the 2019 coronavirus disease (COVID-19) pandemic, oncologists face new challenges, and they need to adjust their cancer management strategies as soon as possible to reduce the risk of SARS-CoV-2 infection and tumor recurrence. However, data on cancer patients with SARS-CoV-2 infection remains scarce.

METHODS

We conducted a retrospective study on 223 cancer patients with SARS-CoV-2 from 26 hospitals in Hubei, China. An individualized nomogram was constructed based on multivariate Cox analysis. Considering the convenience of the nomogram application, an online tool was also created. The predictive performance and clinical application of nomogram were verified by C-index, calibration curve and decision curve analysis (DCA).

RESULTS

Among cancer patients with SARS-CoV-2, there were significant differences in clinical characteristics between survivors and non-survivors, and compared with patients with solid tumors including lung cancer, patients with hematological malignancies had a worse prognosis. Male, dyspnea, elevated PCT, increased heart rate, elevated D-dimers, and decreased platelets were risk factors for these patients. Furthermore, a good prediction performance of the online tool (dynamic nomogram: https://covid-19-prediction-tool.shinyapps.io/DynNomapp/ ) was also fully demonstrated with the C-indexes of 0.841 (95% CI 0.782-0.900) in the development cohort and 0.780 (95% CI 0.678-0.882) in the validation cohort.

CONCLUSION

Overall, cancer patients with SARS-CoV-2 had unique clinical features, and the established online tool could guide clinicians to predict the prognosis of patients during the COVID-19 epidemic and to develop more rational treatment strategies for cancer patients.

Patients with Cancer Appear More Vulnerable to SARS-CoV-2: A Multicenter Study during the COVID-19 Outbreak

The novel COVID-19 outbreak has affected more than 200 countries and territories as of March 2020. Given that patients with cancer are generally more vulnerable to infections, systematic analysis of diverse cohorts of patients with cancer affected by COVID-19 is needed. We performed a multicenter study including 105 patients with cancer and 536 age-matched noncancer patients confirmed with COVID-19. Our results showed COVID-19 patients with cancer had higher risks in all severe outcomes. Patients with hematologic cancer, lung cancer, or with metastatic cancer (stage IV) had the highest frequency of severe events. Patients with nonmetastatic cancer experienced similar frequencies of severe conditions to those observed in patients without cancer. Patients who received surgery had higher risks of having severe events, whereas patients who underwent only radiotherapy did not demonstrate significant differences in severe events when compared with patients without cancer. These findings indicate that patients with cancer appear more vulnerable to SARS-CoV-2 outbreak. SIGNIFICANCE: Because this is the first large cohort study on this topic, our report will provide much-needed information that will benefit patients with cancer globally. As such, we believe it is extremely important that our study be disseminated widely to alert clinicians and patients.This article is highlighted in the In This Issue feature, p. 747.

Inhibition of epidermal growth factor receptor stimulates prolactin expression in primary culture of the mouse pituitary gland

The roles of epidermal growth factor (EGF) in the regulation of prolactin (PRL) gene expression in the normal pituitary gland remain poorly understood. In the present study, the effects of EGF and an inhibitor of the EGF receptor, erlotinib, on PRL gene expression were examined both in the pituitary tumour cell line GH3 and in a primary culture of the mouse pituitary gland under similar experimental conditions. The results showed that EGF stimulated PRL expression in GH3 cells, but not in normal cells. Erlotinib was found to counteract EGF in GH3 cells inhibiting the PRL expression enhanced by EGF. By contrast, erlotinib induced an elevation in the PRL mRNA levels in the primary culture of the adult pituitary gland and the initiation of PRL production in the culture of the foetal pituitary gland in which PRL production had not yet occurred. Western blot analyses showed that EGF induced and erlotinib inhibited the activation of extracellular regulated protein kinase equally in GH3 and normal cells. These results suggest that the consequences of EGF receptor activation in normal PRL cells contradict those in adenomatous PRL cells.

From epidemiology and neurometabolism to treatment: Vitamin D in pathogenesis of glioblastoma Multiforme (GBM) and a proposal for Vitamin D + all-trans retinoic acid + Temozolomide combination in treatment of GBM

Here we review tumoricidal efficacy of Vitamin D analogues in glioblastoma multiforme (GBM) and potential synergisms with retinoic acid and temozolomide based on epidemiological and cellular studies. Epidemiological data suggest that winter birth is associated with higher risk of GBM, and GBM debulking in the winter enhanced mortality, which may relate with lower exposure to sunlight essential to convert cholecalciferol to Vitamin D. Comparative studies on blood bank specimens revealed that higher prediagnosis levels of calcidiol are associated with lower risk of GBM in elderly men. Supplemental Vitamin D reduced mortality in GBM patients in comparison to nonusers. Expression of Vitamin D Receptor is associated with a good prognosis in GBM. Conversely, Vitamin D increases glial tumor synthesis of neutrophins NGF and NT-3, the low affinity neurotrophin receptor p75NTR, IL-6 and VEGF, which may enhance glioma growth. Antitumor synergisms between temozolomide and Vitamin D and Vitamin D with Vitamin A derivatives were observed. Hence, we hypothesize that Calcitriol + ATRA (All-Trans Retinoic Acid) + Temozolomide - CAT combination might be a safer approach to benefit from Vitamin D in the management of high-grade glial tumors. Adding acetazolomide to this protocol may reduce the risk of pseudotumor cerebri, as both Vitamin D and Vitamin A excess may cause intracranial hypertension; this approach may provide further benefit as acetazolomide also exhibits anticancer activity.

RACK1 deficiency synergizes with all-trans retinoic acid to induce apoptosis in human acute promyelocytic leukemia cells

As a classic differentiation agent, all-trans retinoic acid (ATRA) has been widely used in the treatment of acute promyelocytic leukemia (APL). However, the clinical application of ATRA has strict limitations, for its severe side effects due to the accumulation of peripheral blood leukocytes. The scaffold protein RACK1 (Receptor for activated C kinase 1), which regulates multiple signaling pathways, has been proposed to contribute to the survival of leukemic progenitors. But it remains unclear whether it is also involved in the oncogenic growth of APL. In the present study, we demonstrate that silencing of endogenous RACK1 expression synergized with ATRA to promote the death of NB4 and HL-60 APL cells without effect on cell differentiation induced by ATRA. Interestingly, RACK1 knockdown combined with ATRA treatment mainly induces apoptosis. It is distinct to the necrotic cell death induced by idarubicin in combination with ATRA, a regimen extensively used in the clinic to prevent neutrophil accumulation. Further exploration revealed that the lysosome-autophagy pathway is likely to be responsible for the anti-apoptotic role of RACK1. Taken together, our findings indicate that RACK1 is essential in maintaining the malignant features of APL, and targeting RACK1 may have promising therapeutic implications in the treatment of APL.

Vitamin D deficiency as a risk factor for thyroid cancer: A meta-analysis of case-control studies

OBJECTIVE

The association between vitamin D deficiency and thyroid cancer is controversial. Some studies have demonstrated that higher serum vitamin D levels might protect against thyroid cancer, whereas others have not, or have even indicated the opposite to be the case. The aim of this meta-analysis was to investigate the association between vitamin D deficicency and thyroid cancer and propose that vitamin D deficiency is a risk factor for thyroid cancer.

METHODS

This was a meta-analysis of 14 articles of the association between vitamin D deficiency and thyroid cancer. Databases including PubMed, Cochrane library, Sinomed, CNKI, Wanfang, and clinical trial register centers, were searched for case-control studies of vitamin D in thyroid cancer.

RESULTS

Fourteen studies were included in this meta-analysis. A fixed-effect model was used to merge the standardized mean difference value of serum 25-hydroxyvitamin D levels. The pooled effect showed that the levels of serum 25-hydroxyvitamin D were lower in patients with thyroid cancer preoperatively than in the controls (-0.22; 95% confidence interval [CI], -0.36 to -0.09; P = 0.001). There was no difference after thyroid cancer patients underwent thyroidectomy (-0.19; 95% CI, -0.47 to 0.10; P = 0.21). A fixed-effect model was used to pool the odds ratio of thyroid cancer and vitamin D deficiency. It showed that the pooled odds ratio from six studies was 1.30 (95% CI, 1.00-1.69; P = 0.05). Subgroup analysis of 25-hydroxyvitamin D levels between different pathologic characteristics in patients with thyroid cancer was summarized, but no statistical differences were determined.

CONCLUSIONS

Lower serum 25-hydroxyvitamin D levels were associated with increased risk for thyroid cancer. On the other hand, vitamin D deficiency may act as a risk factor for thyroid cancer.

Enhanced Response of Acute Monocytic Leukemia Cells to Low-dose Cytarabine by 1,25-dihydroxyvitamin D3

Low-dose cytarabine combined with differentiating or DNA hypomethylating agents, such as vitamin D compounds, is a potential regimen to treat acute myeloid leukemia (AML) patients who are unfit for high-intensity chemotherapy. The present study aimed to determine which subset of AML would be most responsive to low-dose cytarabine with the differentiating agent 1,25-dihydroxyvitamin D3 (1,25-D3). Here, firstly, cBioPortal database was used and we found out that vitamin D receptor (VDR) was highly expressed in acute monocytic leukemia (M5) and high VDR expression was associated with a poor survival of AML patients. Then, we confirmed that 1,25-D3 at clinical available concentration could induce more significant differentiation in acute monocytic leukemia cell lines (U937, MOLM-13, THP-1) and blasts from M5 patients than in non-monocytic cell lines (KGla and K562) and blasts from M2 patient. Finally, it was shown that the combination of 1,25-D3 and low-dose cytarabine further increased the differentiating rate, growth inhibition and G0/G1 arrest, while mild changes were found in the apoptosis in acute monocytic leukemia cell lines. Our study demonstrates that the enhanced response of acute monocytic leukemia cells to low-dose cytarabine by 1,25-D3 might indicate a novel therapeutic direction for patients with acute monocytic leukemia, especially for elderly and frail ones.

Design, synthesis, antiproliferative activity and docking studies of quinazoline derivatives bearing oxazole or imidazole as potential EGFR inhibitors

Six series of quinazoline derivatives bearing oxazole or imidazole (8a–f, 9a–f, 10a–d, 11a–f, 12a–d and 13a–i) were designed, synthesized and their IC₅₀ values evaluated against three cancer cell lines (A549, MCF-7 and PC-3).

EDIL3 knockdown inhibits retinal angiogenesis through the induction of cell cycle arrest in vitro

Pathological retinal angiogenesis is one of the most common causes of blindness, with limited treatment options being currently available. Epidermal growth factor (EGF)-like repeat and discoidin I-like domain-containing protein 3 (EDIL3) has been reported to serve an important role in embryonic vasculogenesis and tumor angiogenesis; however, its implication in retinal angiogenesis has yet to be elucidated. The present study aimed to investigate the putative roles of EDIL3 in retinal endothelial cells. RNA interference was used to disrupt the expression of EDIL3 in human retinal endothelial cells (HRECs) in vitro, and the resulting effects were examined. Cell proliferation was assessed using cell counting kit-8 reagent, Cell migration was investigated using a transwell chamber and a tube formation assay was used to study angiogenic capability in vitro. Flow cytometry was used to detect the cell cycle distribution and western blotting was used to study protein expression. The present results demonstrated that silencing EDIL3 expression significantly impaired the proliferative, migratory and tube forming capabilities of HRECs. Furthermore, EDIL3 knockdown was revealed to induce cell cycle arrest at the G₁ phase. Western blot analysis suggested that the possible mechanisms underlying the antiproliferative effects of EDIL3 silencing may involve the inhibition of EGF receptor-mediated pathways, and the suppression of cyclin D1 and cyclin E1 expression in HRECs. In conclusion, the findings of the present study suggested that EDIL3 may be implicated in retinal angiogenesis, and may have potential as a novel therapeutic target for the treatment of pathological angiogenesis.

Effects of 1,25(OH)₂D₃ on Cancer Cells and Potential Applications in Combination with Established and Putative Anti-Cancer Agents

The diverse effects of 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), the bio-active form of vitamin D, on cancer cell metabolism and proliferation has made it an interesting candidate as a supporting therapeutic option in cancer treatment. An important strategy in cancer therapy is the use of combination chemotherapy to overcome drug resistance associated with numerous anti-cancer agents and to provide better means of avoiding undesirable side effects. This complex strategy is widely adopted by oncologists and several established "cocktails" of chemotherapeutics are routinely administered to cancer patients. Among the principles followed in designing such treatment regimens is the use of drugs with different mechanisms of action to overcome the issue of tumor heterogeneity and to evade resistance. In light of the profound and diverse effects of 1,25(OH)₂D₃ reported by in vitro and in vivo studies, we discuss how these effects could support the use of this molecule in combination with "classical" cytotoxic drugs, such as platins and anti-metabolites, for the treatment of solid and hematological tumors. We also examine recent evidence supporting synergistic activities with other promising anti-cancer drug candidates, and postulate mechanisms through which 1,25(OH)₂D₃ may help evade chemoresistance.

Radotinib inhibits acute myeloid leukemia cell proliferation via induction of mitochondrial-dependent apoptosis and CDK inhibitors

Radotinib is a BCR-ABL1 tyrosine kinase inhibitor approved for the second-line treatment of chronic myeloid leukemia. However, effects of radotinib on acute myeloid leukemia (AML) are unclear. In the present study, we observed that radotinib exerted cytotoxic effects on AML cells. Of the various AML cell lines examined (NB4, HL60, HEL 92.1.7, and THP-1), Kasumi-1 was the most sensitive to radotinib. Results of microarray analysis showed that 417 and 595 genes associated with apoptosis and cell cycle regulation, respectively, were differently expressed (i.e., showed >2-fold difference in expression). Radotinib-induced apoptosis involved the mitochondrial pathway. Moreover, radotinib increased the apoptosis of and induced caspase-3 activity in both Kasumi-1 cells and bone marrow cells (BMCs) obtained from patients with AML. Radotinib also increased cleaved caspase-3, caspase-7, and caspase-9 levels and decreased the number of proliferating Kasumi-1 cells and BMCs from patients with AML. In addition, radotinib induced G0/G1 phase arrest by inducing CDKIs p21 and p27 and by inhibiting CDK2, CDK4, and CDK6. These results indicate that radotinib induces caspase-dependent apoptosis and G0/G1 phase arrest in AML cells by regulating CDKI-CDK-cyclin cascade. Moreover, these results indicate that radotinib inhibits AML cell proliferation by inducing mitochondria-dependent apoptosis and CDKIs p21 and p27. To our knowledge, this is the first study to show that radotinib can be potentially used for the anti-leukemic therapy of patients with AML.

Induction of adipose-derived stem cells into Schwann-like cells and observation of Schwann-like cell proliferation

The peripheral nervous system has the potential for full regeneration following injury and recovery, predominantly controlled by Schwann cells (SCs). Therefore, obtaining a sufficient number of SCs in a short duration is crucial. In the present study, rat adipose-derived stem cells (ADSCs) were isolated and cultured, following which characterization of the ADSCs was performed using flow cytometry. The results showed that the cells were positive for the CD29 and CD44 markers, and negative for the CD31, CD45, CD49 and CD106 markers. The multilineage differentiation potential of the ADSCs was assayed by determining the ability of the cells to differentiate into osteoblasts and adipocytes. Following this, the ADSCs were treated with a specific medium and differentiated into Schwann-like cells. Immunofluorescence, western blot and reverse transcription-quantitative polymerase chain reaction analyses showed that ~95% of the differentiated cells expressed glial fibrillary acidic protein, S100 and p75. In addition, the present study found that a substantial number of SCs can be produced in a short duration via the mitotic feature of Schwann-like cells. These data indicated that Schwann-like cells derived from ADSCs can undergo mitotic proliferation, which may be beneficial for the treatment of peripheral nerve injury in the future.

Vitamin D Control of Hematopoietic Cell Differentiation and Leukemia

It is now well known that in the mammalian body vitamin D is converted by successive hydroxylations to 1,25-dihydroxyvitamin D (1,25D), a steroid-like hormone with pleiotropic properties. These include important contributions to the control of cell proliferation, survival and differentiation, as well as the regulation of immune responses in disease. Here, we present recent advances in current understanding of the role of 1,25D in myelopoiesis and lymphopoiesis, and the potential of 1,25D and analogs (vitamin D derivatives; VDDs) for the control of hematopoietic malignancies. The reasons for the unimpressive results of most clinical studies of the therapeutic effects of VDDs in leukemia and related diseases may include the lack of a precise rationale for the conduct of these studies. Further, clinical trials to date have generally used extremely heterogeneous patient populations and, in many cases, small numbers of patients, generally without controls. Although low calcemic VDDs have been used and combined with agents that can increase the leukemia cell killing or differentiation effects in acute leukemias, the sequencing of agents used for combination therapy should to be more clearly delineated. Most importantly, it is recommended that in future clinical trials the rationale for the basis of the enhancing action of drug combinations should be clearly articulated and the effects on anticancer immunity should also be evaluated.

Applications and implications of the exponentially modified gamma distribution as a model for time variabilities related to cell proliferation and gene expression

A panel of published distributions of cell interdivision times (IDT) comprising 77 datasets related to 16 cell types, some studied under different conditions, was used to evaluate their conformance to the exponentially modified gamma distribution (EMGD) in comparison with distributions suggested for IDT data earlier. Lognormal, gamma, inverse Gaussian, and shifted Weibull and gamma distributions were found to be generally inferior to EMGD. Exponentially modified Gaussian (EMG) performed equally well. Although EMGD or EMG may be worse than some other distributions in specific cases, the reason that IDT distributions must be generated by a common mechanism of the cell cycle makes it unlikely that they differ essentially in different cell types. Therefore, exponentially modified peak functions, such as EMGD or EMG, are most appropriate if the use of a single distribution for IDT data is reasonable. EMGD is also shown to be the best descriptive tool for published data on the distribution of times between the bursts of mRNA synthesis at defined genes in single cells. EMG is inadequate to such data because its Gaussian component markedly extends to the negative time domain. The applicability of EMGD to comparable features of cells and genes behaviors are discussed to support the validity of the transition probability model and to relate the exponential component of EMGD to the times of cell dwelling in the restriction point of the cell cycle.

Valproic acid sensitizes human glioma cells to gefitinib-induced autophagy

Autophagy and apoptosis represent important cellular processes involved in cancer cell killing mechanisms. Epidermal growth factor receptor inhibitor gefitinib and valproic acid have been implicated in the treatment of malignancies including glioma involving autophagic and apoptotic mechanisms. Therefore, it is interesting to investigate whether a combination of gefitinib and valproic acid shows better cancer cell killing effect on human glioma cells. We found that a nontoxic concentration of valproic acid sensitized U87 and T98G glioma cells to gefitinib cytotoxicity by inhibiting cell growth and long-term clonogenic survival. The augmented consequences were accompanied by the formation of autophagic vacuoles, conversion of microtubule-associated protein-1 light chain 3-II (LC3-II), and degradation of p62. Autophagy inhibitor 3-methyladenosine and chloroquine and genetic silencing of LC3 but not broad-spectrum caspase inhibitor attenuated gefitinib/valproic acid-induced growth inhibition. Gefitinib/valproic acid-induced autophagy was accompanied by the activation of liver kinase-B1 (LKB1)/AMP-activated protein kinase (AMPK)/ULK1. Silencing of AMPK and ULK1 suppressed gefitinib/valproic acid-induced autophagy and growth inhibition. Mechanistic studies showed that gefitinib/valproic acid increased intracellular reactive oxygen species generation and N-acetyl cysteine attenuated gefitinib/valproic acid-caused autophagy and growth inhibition. In addition to demonstrating the autophagic mechanisms of gefitinib/valproic acid, the results of this study further suggest that intracellular oxidative stress and the LKB1/AMPK signaling might be a potential target for the development of therapeutic strategy against glioma.

In vitro baselining of new pyrrolopyrimidine EGFR-TK inhibitors with Erlotinib

Epidermal growth factor receptor tyrosine kinase inhibitors are useful in treatment of non-small cell lung cancer, and show promise in combination therapy settings. Two novel chiral pyrrolopyrimidines have been baselined towards Erlotinib, Lapatinib and Dasatinib using in vitro cellular studies and ADME profiling. One of these, (S)-2-((6-(4-(hydroxymethyl)-2-methoxyphenyl)-7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)-2-phenylethan-1-ol, was more active than Erlotinib in lung and breast cancer cell models. The compound also had promising activity towards ovarian cancer cell lines, while low activity was seen towards cells of haematological origin. ADME profiling revealed good solubility, higher metabolic stability than Erlotinib and no inhibitory effect towards the hERG voltage-gated ion channel. Investigation of inhibitory potency towards 6 CYP isoforms generally revealed low inhibitory potency, but in the case of CYP3A4, a substrate dependent inhibition was noted using testosterone as substrate (IC50: 12.5μM). No cellular or gene toxicity was noted for the compounds or products of phase I metabolism. However, permeability studies using Caco-2 cells revealed a high efflux ratio. Further experiments using ABC transporter inhibitors revealed that the pyrrolopyrimidines are actively transported by the breast cancer resistant protein and P-glycoprotein transporters, which might prevent their further development into drugs.

Radotinib Induces Apoptosis of CD11b+ Cells Differentiated from Acute Myeloid Leukemia Cells

Radotinib, developed as a BCR/ABL tyrosine kinase inhibitor (TKI), is approved for the second-line treatment of chronic myeloid leukemia (CML) in South Korea. However, therapeutic effects of radotinib in acute myeloid leukemia (AML) are unknown. In the present study, we demonstrate that radotinib significantly decreases the viability of AML cells in a dose-dependent manner. Kasumi-1 cells were more sensitive to radotinib than NB4, HL60, or THP-1 cell lines. Furthermore, radotinib induced CD11b expression in NB4, THP-1, and Kasumi-1 cells either in presence or absence of all trans-retinoic acid (ATRA). We found that radotinib promoted differentiation and induced CD11b expression in AML cells by downregulating LYN. However, CD11b expression induced by ATRA in HL60 cells was decreased by radotinib through upregulation of LYN. Furthermore, radotinib mainly induced apoptosis of CD11b⁺ cells in the total population of AML cells. Radotinib also increased apoptosis of CD11b⁺ HL60 cells when they were differentiated by ATRA/dasatinib treatment. We show that radotinib induced apoptosis via caspase-3 activation and the loss of mitochondrial membrane potential (ΔΨ_m) in CD11b⁺ cells differentiated from AML cells. Our results suggest that radotinib may be used as a candidate drug in AML or a chemosensitizer for treatment of AML by other therapeutics.

All-trans retinoic acid suppresses topoisomerase IIα through the proteasomal pathway

Topoisomerase IIα is a nuclear enzyme that alters DNA topology. It is a well-known anticancer target and related to cell differentiation status. All-trans retinoic acid (ATRA), an important active metabolite of vitamin A, is a promising anticancer agent in numerous malignancies. However, there are little data on the effect of retinoids on topoisomerase IIα regulation. In the present study, we investigated the relationship between ATRA and topoisomerase IIα, and the potential mechanisms of ATRA on topoisomerase IIα regulation. In several human carcinoma cell lines, ATRA was shown to suppress topoisomerase IIα protein, but not mRNA expression. ATRA induced the degradation of topoisomerase IIα through the proteasome pathway, but not the lysosome pathway. Ubiquitination was involved in this degradation. Western blot and immunocytochemistry proved that ATRA-induced topoisomerase IIα repression occurred only in the cell nuclei. ATRA not only influenced the cycle procession but also reduced the expression of cyclin D1. Cyclin D1, which is involved in cell differentiation, was regulated by topoisomerase IIα. Similar to cyclin D1, knockdown of topoisomerase IIα resulted in the increased differentiation of the cells, which was in contrast to the overexpression of topoisomerase IIα in the cells. Taken together, these data suggested that ATRA could target topoisomerase IIα and exert potential beneficial effects on cell differentiation.

The Potential of Vitamin D-Regulated Intracellular Signaling Pathways as Targets for Myeloid Leukemia Therapy

The current standard regimens for the treatment of acute myeloid leukemia (AML) are curative in less than half of patients; therefore, there is a great need for innovative new approaches to this problem. One approach is to target new treatments to the pathways that are instrumental to cell growth and survival with drugs that are less harmful to normal cells than to neoplastic cells. In this review, we focus on the MAPK family of signaling pathways and those that are known to, or potentially can, interact with MAPKs, such as PI3K/AKT/FOXO and JAK/STAT. We exemplify the recent studies in this field with specific relevance to vitamin D and its derivatives, since they have featured prominently in recent scientific literature as having anti-cancer properties. Since microRNAs also are known to be regulated by activated vitamin D, this is also briefly discussed here, as are the implications of the emerging acquisition of transcriptosome data and potentiation of the biological effects of vitamin D by other compounds. While there are ongoing clinical trials of various compounds that affect signaling pathways, more studies are needed to establish the clinical utility of vitamin D in the treatment of cancer.

Urokinase is a negative modulator of Egf-dependent proliferation and motility in the two breast cancer cell lines MCF-7 and MDA-MB-231

The epidermal growth factor receptor (EGFR) is involved in the regulation of various cellular processes and dysregulation of its signalling plays a critical role in the etiology of a variety of malignancies like breast cancer. At the same time, elevated levels of urokinase (uPA), its receptor uPAR, and other components of the plasminogen activation system are found to be correlated with a poor prognosis in breast cancer. Interestingly, EGFR appears to participate in transducing the signal generated upon binding of uPA to uPAR. However, whether uPA signalling would thereby interfere with ligand-driven EGFR signalling was not described before. Therefore, it was the aim of the present study to investigate the combined effects of uPA and EGF in the low invasive and high invasive breast adenocarcinoma cell lines MCF-7 and MDA-MB-231, respectively. Simultaneous exposure of cells to both signals negatively affected ERK1/2 and AKT activation whereas positive effects on p38 and Src kinase phosphorylation were noted in both cell lines. Furthermore, uPA attenuated the mitogenic effect of EGF on cellular proliferation, invasion and motility in both MCF-7 and MDA-MB-231 cells. Experiments with the uPA amino terminal fragment (ATF) revealed that the negative effects of uPA were independent from its protease activity. Together, these data suggest that enhanced levels of uPA in breast cancer modulate the mitogenic effects of EGF and thus, this knowledge may help to better understand breast cancer pathogenesis as well as to develop new therapeutic options.

Antagonism between granulocytic maturation and deacetylase inhibitor-induced apoptosis in acute promyelocytic leukaemia cells

Background:

Transcriptional repression is a key mechanism driving leukaemogenesis. In acute promyelocytic leukaemia (APL), the fusion protein promyelocytic leukaemia-retinoic acid receptor-α fusion (PML-RARα) recruits transcriptional repressors to myeloid differentiation genes. All-trans-retinoic acid (ATRA) induces the proteasomal degradation of PML-RARα and granulocytic differentiation. Histone deacetylases (HDACs) fall into four classes (I–IV) and contribute to the transcription block caused by PML-RARα.

Methods:

Immunoblot, flow cytometry, and May-Grünwald–Giemsa staining were used to analyze differentiation and induction of apoptosis.

Results:

A PML-RARα- and ATRA-dependent differentiation programme induces granulocytic maturation associated with an accumulation of the myeloid transcription factor CCAAT/enhancer binding protein (C/EBP)ɛ and of the surface protein CD11b. While this process protects APL cells from inhibitors of class I HDAC activity, inhibition of all Zinc-dependent HDACs (classes I, II, and IV) with the pan-HDACi (histone deacetylase inhibitor(s)) LBH589 induces apoptosis of immature and differentiated APL cells. LBH589 can eliminate C/EBPɛ and the mitochondrial apoptosis regulator B-cell lymphoma (BCL)-xL in immature and differentiated NB4 cells. Thus, BCL-xL and C/EBPɛ are newly identified molecular markers for the efficacy of HDACi against APL cells.

Conclusions:

Our results could explain the therapeutic limitations occurring with ATRA and class I HDACi combinations. Pro-apoptotic effects caused by pan-HDAC inhibition are not blunted by ATRA-induced differentiation and may provide a clinically interesting alternative.

Gefitinib resistance resulted from STAT3-mediated Akt activation in lung cancer cells

Hyperactivation of Epidermal Growth Factor Receptor (EGFR) tyrosine kinase is prevalent in human lung cancer and its inhibition by the tyrosine kinase inhibitors (TKIs), including gefitinib and erlotinib, initially controls tumor growth. However, most patients ultimately relapse due to the development of drug resistance. In this study, we have discovered a STAT3-dependent Akt activation that impairs the efficacy of gefitinib. Mechanistically, gefitinib increased association of EGFR with STAT3, which de-repressed STAT3 from SOCS3, an upstream suppressor of STAT3. Such a de-repression of STAT3 in turn fostered Akt activation. Genetic or pharmacological inhibition of STAT3 abrogated Akt activation and combined gefitinib with STAT3 inhibition synergistically reduced the growth of the tumor cells. Taken together, this study suggests that activation of STAT3 is an intrinsic mechanism of drug resistance in response to EGFR TKIs. Combinational targeting on both EGFR and STAT3 may enhance the efficacy of gefitinib or other EGFR TKIs in lung cancer.

A phase I/II trial of Erlotinib in higher risk myelodysplastic syndromes and acute myeloid leukemia after azacitidine failure

Survival after azacitidine (AZA) failure in higher-risk myelodysplastic syndromes (MDS) is poor and new treatment options are needed. Erlotinib, an oral inhibitor of the epidermal-growth-factor-receptor (EGFR), has shown in preclinical models some efficacy in higher risk MDS and acute myeloid leukemia (AML). In this phase I/II trial, 30 patients received 100mg/day (n=5) or 150mg/day (n=25) of Erlotinib orally after primary or secondary resistance to AZA treatment. Eighteen MDS and 12 AML patients were treated. This outpatient treatment was well tolerated with limited grade III-IV extra hematological toxicities (skin (n=1), and diarrhea (n=3). Response was observed in 6 patients (20%) including 1 complete remission (CR), 1 marrow CR and 4 hematological improvement (2 erythroid and 2 on platelets). Median duration of response was 5 months. Erlotinib appears to induce a significant number of responses in higher risk MDS/AML having failed AZA treatment. Given the good safety profile of Erlotinib, its combination with other drugs could be tested in the future in MDS and AML.

Post-transcriptional repression of FOXO1 by QKI results in low levels of FOXO1 expression in breast cancer cells

The RNA-binding protein Quaking (QKI) is known to be essential for embryonic development and postnatal myelination. Forkhead box O1 (FOXO1) is a critical tumor suppressor for cell proliferation control. Dysregulation of FOXO1 expression has been observed in a variety of cancers. In the present study, we demonstrated that QKI decreased FOXO1 mRNA expression at the post-transcriptional level. QKI was able to bind the 3'UTR of FOXO1 mRNA directly and decreased its mRNA stability. To determine whether QKI-mediated post-transcriptional repression of FOXO1 indeed plays a role in cancer cells, we first detected both QKI and FOXO1 expression in four breast cancer cell lines. FOXO1 expression was extremely low in these cell lines, whereas QKI expression was relative high. Knockdown of QKI significantly restored FOXO1 expression. ATRA, an inducer of apoptosis or differentiation, dramatically enhanced FOXO1 expression while it repressed QKI expression. Importantly, the ATRA-induced increase in FOXO1 expression was dependent on QKI-mediated post-transcriptional regulation. Consistently, 5-FU, a widely used chemotherapeutic agent, increased FOXO1 expression via inhibition of QKI. In summary, our study provides initial evidence demonstrating that QKI-mediated repression of FOXO1 may be one of the factors contributing to the oncogenesis and progression of breast carcinoma, which suggests that targeting QKI may serve as a novel strategy to sensitize breast cancers to chemotherapy.