Signaling pathways and regulation of gene expression in hematopoietic cells

Cellular functions are regulated by signal transduction pathway networks consisting of protein-modifying enzymes that control the activity of many downstream proteins. Protein kinases and phosphatases regulate gene expression by reversible phosphorylation of transcriptional factors, which are their direct substrates. Casein kinase II (CK2) is a serine/threonine kinase that phosphorylates a large number of proteins that have critical roles in cellular proliferation, metabolism and survival. Altered function of CK2 has been associated with malignant transformation, immunological disorders and other types of diseases. Protein phosphatase 1 (PP1) is a serine/threonine phosphatase, which regulates the phosphorylation status of many proteins that are essential for cellular functions. IKAROS is a DNA-binding protein, which functions as a regulator of gene transcription in hematopoietic cells. CK2 directly phosphorylates IKAROS at multiple phosphosites which determines IKAROS activity as a regulator of gene expression. PP1 binds to IKAROS via the PP1-consensus recognition site and dephosphorylates serine/threonine residues that are phosphorylated by CK2. Thus, the interplay between CK2 and PP1 signaling pathways have opposing effects on the phosphorylation status of their mutual substrate - IKAROS. This review summarizes the effects of CK2 and PP1 on IKAROS role in regulation of gene expression and its function as a tumor suppressor in leukemia.

Abstract 2677: ROCK inhibitors synergize with the BCL2 inhibitor venetoclax for treatment of AML

Acute Myeloid Leukemia (AML) is a rare but catastrophic hematological cancer with a poor prognosis, high mortality, and relapse rates. Several new agents targeting specific genes or cell survival pathways have been recently approved by the FDA. AML treatment with single agents often results in resistance; therefore, combination therapies may provide more durable and effective responses. Rho kinases (ROCK1/2) are aberrantly expressed in AML patient cells, and ROCK1 has emerged lately as a potential therapeutic target for AML treatment. Previously, our group developed a new ROCK inhibitor DJ4 as an effective inducer of AML cell death. Our initial screening of DJ4 with AML standard therapy (cytarabine, daunorubicin, azacytidine, venetoclax) showed promising synergy between DJ4 and the BCL2 (B-cell lymphoma-2) inhibitor venetoclax (VEN). Enrichment of ROCK pathway in recent CRISPR drop-out screening after VEN treatment in MOLM-13 cells further validates the synergistic cooperation between ROCK and BCL2 pathways. Though VEN is widely used in hematological malignancies, its clinical efficacy is limited due to the development of resistance. Thus, we sought to investigate the novel strategy of combining VEN with ROCK inhibitors (ROCKi) for AML treatment. The combination of VEN with ROCKi (Fasudil, Y-27632, GSK269962A, DJ4) exhibited synergetic cytotoxicity in naïve (MOLM-13, MV4-11) and VEN-resistant (MV4-11/VENR, HL-60, OCI-AML3, U937) human AML cell lines. Flow cytometric analysis of Annexin V and cellular ROS levels in MV4-11 (naïve and VENR) cells upon co-treatment with sub-lethal doses of VEN and ROCKi demonstrated a significant (p<0.05) increase in the apoptosis and oxidative stress compared to single agents. Treatment of MV4-11 cells with VEN+ROCKi enhanced the activity of several caspases in the MultiCaspase assay. Furthermore, the colony-forming ability of AML cell lines and primary AML patient cells was significantly reduced with the combination treatment, while single agents exhibited minimal effects. MV4-11 (naïve and VENR) cells displayed alterations in the levels of critical apoptosis regulators (Bcl2, Bax, Mcl1, cleaved caspase-3) upon co-treatment in immunoblotting analysis. Additionally, MV4-11-Luc xenograft mice exhibited a significant reduction in the average leukemic burden after combination therapy relative to single agents (p<0.05). Altogether, our in vitro and in vivo findings established a synergetic interaction between VEN and ROCKi to effectively inhibit AML cell progression and overcome the VEN resistance (inherent or acquired). These results indicate that therapy co-targeting BCL2 and ROCK pathways exerted antileukemic activity by inducing apoptosis and may be particularly effective for AML treatment. Further studies are ongoing to explore the precise molecular mechanism of action of the VEN+ROCKi combination and its efficacy in pre-clinical animal models.

Citation Format: Upendarrao Golla, Satyam Patel, Diwakar B. Tukaramrao, Jeremy Hengst, Juliana Restrepo, Shantu Amin, Dhimant Desai, Sinisa Dovat, David Claxton, Arati Sharma. ROCK inhibitors synergize with the BCL2 inhibitor venetoclax for treatment of AML [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2677.

Abstract 3833: Leonurine derivatives as a potential novel therapeutic approach to acute lymphoblastic leukemias (ALL)

Background: Pre-B cell Acute lymphoblastic leukemia (B ALL) high risk (HR) subgroups continue to result in significant mortality and morbidity of pediatric oncology patients. T cell ALL is higher risk and therapy has made less improvement than B ALL with a higher rate of significant poor outcomes. Novel treatment strategies are required to overcome chemotherapy resistance and improve mortality/morbidity for HR B ALL. Leonurine is a bioactive alkaloid that is naturally occurring only in Herbra Leonuri which has been used in traditional herbal medicine. Traditionally, it has been used for menstrual disorders. Research has further described its ability to scavenge oxygen free radicals, anticoagulation properties, and other anti-inflammatory properties[1]. There are investigations in its role for myocardial infarction, stroke, chronic kidney disease, and other inflammatory disorders[2]. Our research data that suggests that leonurine and its derivatives have antileukemic effects.Methods/Results: We analyzed multiple derivatives of leonurine and selected a potent candidate based on cell viability assays use for further testing designated as investigational leonurine derivative (ILD). WST1 proliferation studies comparing ILD to vehicle were performed in cell lines Nalm6, 697, Molt4, CEM, and JM1 at multiple time points. The half maximal inhibitory concentration (IC50) values was variable depending on the treatment time and cell line although all values were consistently between 1.2-4.4 uM. Apoptosis activity was determined by flow cytometry Anexin/7AAD assays showed increased apoptosis in cell lines treated with ILD for Nalm6, Molt4, and 697 cell lines. Caspase 3/7 activity was increased in cells treated with ILD when compared to vehicle treatment. DNA damage assays were performed which revealed only an increased frequency in single strand breaks and not double strand breaks. Western blot was performed to determine levels of PI3K, p-AKT, BCL2/BCL-XL and caspases. The blots suggest that apoptosis may be a result of increased activation of PI3K/AKT signaling. We performed RNAseq on cells treated with ILD at the 24-hour time point and present gene ontology data for this analysis. Nalm6, 697, and Molt4 cell lines expressing GFP and Luciferase were injected into NRG mice as means for in vivo pharmacologic testing. NRG mice injected with these cell lines were treated with ILD five days a week for a total of 3 weeks. Nalm 6 leukemia cells showed minimal differences between treatment and control groups.Conclusion: In summary, leonurine derivatives have a promising impact on apoptosis and cell survival. Further investigation into mechanisms and pharmacokinetics/dynamics will be more revealing. Study of leonurine derivatives will result in further translational and therapeutic applications.

Citation Format: Joseph W. Schramm, Melanie Ehudin, Bing He, Chingakham Singh, Daniel Bogush, Jeremy Hengst, Diwakar Bastihalli Tukaramrao, Arati Sharma, Dhimant Desai, Sinisa Dovat. Leonurine derivatives as a potential novel therapeutic approach to acute lymphoblastic leukemias (ALL). [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3833.

Viral dominance patterns in chronic hepatitis delta determine early response to interferon alpha therapy

Chronic hepatitis D is caused by coinfection of hepatitis B and hepatitis D virus. While HDV is the dominant virus over HBV in the majority of cases, mechanisms and consequences of viral dominance are largely unknown. We aimed to investigate associations between viral dominance patterns and patients' characteristics and inflammatory features; 109 HDV-infected patients treated with PEG-IFNa-2α within the international multicentre, prospective HIDIT-2 trial were studied. Patients were classified as D- or B-dominant if the viral load of one virus exceeded that of the other virus by more than 1log₁₀ . Otherwise, no viral dominance (ND) was described. We used Luminex-based multiplex technology to study 50 soluble immune mediators (SIM) in pretreatment samples of 105 HDV RNA-positive patients. Dominance of HDV was evident in the majority (75%) of cases. While only 7% displayed B-dominance, 17% showed nondominance. D-dominance was associated with downregulation of 4 interleukins (IL-2ra, IL-13, IL-16 and IL-18) and 5 chemokines/cytokines (CTACK (CCL27), MCP-1 (CCL2), M-CSF, TRAIL and ICAM-1) while no analyte was increased. In addition, D-dominance could be linked to a delayed HDV RNA response to pegylated interferon as patients with B-dominance or nondominance showed higher early HDV RNA responses (61% at week 12) than D-dominant patients (11%; P < .001). In conclusion, this study revealed unexpected effects of viral dominance on clinical and immunological features in chronic hepatitis delta patients. Individualizing PEG-IFNa-2α treatment duration should consider viral dominance. Overall, our findings suggest an activated but exhausted IFN system in D-dominant patients.

Sphingosine kinase inhibitors decrease viability and induce cell death in natural killer-large granular lymphocyte leukemia

Sphingolipid metabolism has been identified as a potential therapeutic target in cancer. Sphingosine-1-phosphate (S1P) is a potent bioactive sphingolipid metabolite produced by sphingosine kinases-1 and -2 (SPHK1 and SPHK2). Elevated SPHK1 has been found in numerous cancer types and been shown to contribute to survival, chemotherapeutic resistance and malignancy. However, its role in large granular Natural Killer (NK) large granular lymphocyte (LGL) leukemia has not been investigated. Here, we examine SPHK1 as a therapeutic target in LGL leukemia. We found that SPHK1 is overexpressed in peripheral blood mononuclear cells (PBMCs) from LGL leukemia patients which results in elevated S1P in the sera. The use of SPHK1 inhibitors, SKI-II or SKI-178, decreased leukemic NK cell viability and induced caspase-dependent apoptosis. SKI-II and SKI-178 restored the sphingolipid balance by increasing ceramide and decreasing S1P in leukemic NKL cells. SKI-II and SKI-178 also induced apoptosis in primary NK-LGLs from leukemia patients. Mechanistic studies in NK-LGL cell lines demonstrated that SKI-178 and SKI-II induced cell cycle arrest at G2/M. We found that SKI-178 induced phosphorylation of Bcl-2 at Ser70, and that this was dependent on CDK1. We further show that SPHK1 inhibition with SKI-178 leads to decreased JAK-STAT signaling. Our data demonstrate that SPHK1 represents a novel therapeutic target for the treatment of NK-LGL leukemia.

Abstract 2933: The apoptotic mechanism of action of SKI-178, a novel Sphingosine kinase 1 selective inhibitor

We previously developed SKI-178 as a novel Sphingosine kinase 1 (SphK1) selective inhibitor that is cytotoxic toward a broad panel of cancer types. Herein, we sought to determine the mechanism-of-action of SKI-178-induced cell death. We present evidence that SKI-178 induces prolonged mitosis followed by apoptotic cell death through the intrinsic apoptotic cascade. Further examination of the mechanism-of-action (MOA) of SKI-178 implicated c-Jun NH2-terminal kinase (JNK) and cyclin-dependent protein kinase 1 (CDK1) as critical factors required for SKI-178-induced apoptosis. In cell cycle synchronized human AML cell lines, we demonstrate that entry into mitosis is required for apoptotic induction by SKI-178 and that CDK1, not JNK, is required for SKI-178-induced apoptosis. We further demonstrate that the sustained activation of CDK1 during prolonged mitosis, mediated by SKI-178, leads to the simultaneous phosphorylation of the pro-survival Bcl-2 family members, Bcl-2 and Bcl-xl, as well as the phosphorylation and subsequent degradation of Mcl-1. Moreover, multi-drug resistance mediated by MDR-1 and/or pro-survival Bcl-2 family member over-expression did not affect the sensitivity of AML cells to SKI-178. In addition to AML, we extend the MOA of SKI-178 to include various solid tumor cell lines, including pancreatic cancer and glioblastoma. Taken together, we provide evidence that SKI-178 induces apoptosis in a CDK1-dependent manner and is not a substrate for MDR1, making it a promising chemotherapeutic candidate for the treatment of various cancer types, including those known to be drug resistant.

Citation Format: Taryn E. Dick, Jeremy Hengst, Vijay Kale, Ashley Colledge, Jong K. Yun. The apoptotic mechanism of action of SKI-178, a novel Sphingosine kinase 1 selective inhibitor. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2933. doi:10.1158/1538-7445.AM2015-2933

Abstract 736: DJ4, a novel ROCK and MRCK inhibitor, potently inhibits migration and invasion of cancer cells

Rho-associated coiled-coil containing protein kinase (Rho kinase/ROCK) and myotonic dystrophy kinase-related Cdc42-binding kinase (MRCK) are involved in the aggressive migration of cancer cells. These are the key proteins involved in the formation of stress fibers that confer contractility to cancer cells during migration and invasion. ROCK and MRCK are primarily involved in amoeboid and mesenchymal type of migration of cancer cells respectively. Earlier studies reported that combined inhibition/silencing of ROCK and MRCK has more pronounced effect than inhibition of the individual kinases suggesting a more effective therapeutic strategy to combat metastatic cancers. With this hypothesis in mind, we developed a series of novel multikinase inhibitors and identified DJ4 as a potent ATP competitive inhibitor of ROCK1, ROCK2 and MRCKβ. DJ4 effectively inhibits the kinase activity of ROCK (ROCK1 and ROCK2) and MRCK in a cell-free system and multiple human non-small cell lung cancer cell lines. In cellular functional assays DJ4 inhibited migration of human melanoma, lung, pancreatic and breast cancer cells in a concentration-dependent manner. In live cell imaging over 20h by time-lapse microscopy, DJ4 (2.5µM ) reduced the migration rate of lung-and breast-cancer cells by 2.7 and 5.5 times compared to control cells respectively. DJ4 (5µM) also inhibited invasion of MDA-MB-231 breast cancer cells by ∼70%. Fluorescent microscopic observation also revealed that inhibition of activity of these kinases, by DJ4, causes reduction in stress fibers which leads to inhibition of cell contractility and migration.

In summary, our studies demonstrate that DJ4 is a potent ATP competitive inhibitor of ROCK and MRCK, and effectively inhibits migration and invasion of multiple cancers in vitro. Together these results indicate that DJ4 has a strong potential to be an anti-metastatic drug against multiple cancer types.

Citation Format: Vijaykumar P. Kale, Dhimant Desai, Taryn Dick, Katherine Choe, Ashley Colledge, Shantu Amin, Jeremy Hengst, Jong Yun. DJ4, a novel ROCK and MRCK inhibitor, potently inhibits migration and invasion of cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 736. doi:10.1158/1538-7445.AM2014-736

Targeting sphingosine kinase-1 to inhibit melanoma

Resistance to therapies develops rapidly for melanoma leading to more aggressive disease. Therefore, agents are needed that specifically inhibit proteins or pathways controlling the development of this disease, which can be combined, dependent on genes deregulated in a particular patient's tumors. This study shows that elevated sphingosine-1-phosphate (S-1-P) levels resulting from increased activity of sphingosine kinase-1 (SPHK1) occur in advanced melanomas. Targeting SPHK1 using siRNA decreased anchorage-dependent and -independent growth as well as sensitized melanoma cells to apoptosis-inducing agents. Pharmacological SPHK1 inhibitors SKI-I but not SKI-II decreased S-1-P content, elevated ceramide levels, caused a G2-M block and induced apoptotic cell death in melanomas. Targeting SPHK1 using siRNA or the pharmacological agent called SKI-I decreased the levels of pAKT. Furthermore, SKI-I inhibited the expression of CYCLIN D1 protein and increased the activity of caspase-3/7, which in turn led to the degradation of PARP. In animals, SKI-I but not SKI-II retarded melanoma growth by 25-40%. Thus, targeting SPHK1 using siRNAs or SKI-I has therapeutic potential for melanoma treatment either alone or in combination with other targeted agents.

Endemic infection with HTLV-IIB in Venezuelan Indians: molecular characterization

The peripheral blood of 41 Yaruro and Guahibo Indians from Venezuela was examined for HTLV antibodies and DNA. Twenty-five samples (61%) were found to be infected with HTLV-IIB. The sensitivities of the serologic and DNA polymerase chain reaction (PCR) analyses were 80% and 96%, respectively. Epidemiologic studies supported both sexual and perinatal transmission of the virus. Sequence analyses of the HTLV-IIB strains from these Indians indicate that they are unique relative to HTLV-II detected in other groups of humans. HTLV-IIB-G2 isolated from a Guahibo Indian is the most divergent HTLV-IIB strain relative to the prototype HTLV-II NRA.

Comparative performances of enzyme-linked immunosorbent, western blot, and polymerase chain reaction assays for human T-lymphotropic virus type II infection that is endemic among Indians of the Gran Chaco region of South America

BACKGROUND

Human T-cell lymphoma/leukemia viruses types I and II (HTLV-I and HTLV-II) are related exogenous human retroviruses. The former is definitely pathogenic while disease association with the latter is unclear. There are two subtypes of HTLV-II, A and B. Currently, enzyme-linked immunosorbent assays (ELISAs) based on HTLV-I antigens are used to screen for the presence of HTLV-I and -II antibodies. Confirmation and subtyping are accomplished by Western blot (WB) or ELISAs based on HTLV-I whole viral antigens and/or HTLV-I and HTLV-IIA peptides. The sensitivity and specificity of these serologic assays were compared to those of HTLV-I and-II-specific polymerase chain reaction (PCR) assays in tests on samples from Indians from South America in whom the HTLV-IIB subtype is endemic.

STUDY DESIGN AND METHODS

Sera from 246 Gran Chaco Indians were evaluated for HTLV antibodies with the use of four ELISAs (Retrotek HTLV-I; Cambridge Biotech rgp21 enhanced HTLV-I/II; Vironostika HTLV-I/II; and Select HTLV-I/II), and a WB assay. Peripheral blood leukocyte DNA from each Indian was analyzed for HTLV-I or HTLV-II pol DNA via PCR. Fifteen of the PCR-positive samples were further subtyped via cloning and sequencing and/or oligomer restriction.

RESULTS

Ninety-seven samples (39%) were positive for HTLV-II by serologic and/or PCR assays. All 15 positive DNA samples that were further analyzed were of the HTLV-IIB subtype and were clustered as a highly conserved phylogenetic group. Comparative analyses indicate that the sensitivity and specificity of the various assays were: PCR, 97 and 100 percent; Retrotek, 70 and 91 percent; Cambridge Biotech, 74 and 96 percent; Vironostika, 73 and 99 percent; Select 72 and 98 percent; and WB, 70 and 100 percent.

CONCLUSION

The sensitivities of the tested HTLV serologic assays were comparable. However, the specificity of the Retrotek ELISA was significantly lower than that of the others. When positive, the subtyping assays were very specific. However, PCR assays would seem preferable or to be a necessary adjunct for the sensitive detection of HTLV-IIB infection.

Endemic infection with human T cell leukemia/lymphoma virus type IIB in Argentinean and Paraguayan Indians: epidemiology and molecular characterization

Human T cell leukemia/lymphoma virus (HTLV-II) type II infection was detected by polymerase chain reaction or serologic analyses (or both) in 22% of 697 Indians of six different ethnic back-grounds inhabiting the Argentinean and Paraguayan Gran Chaco. None was infected with HTLV-I. The prevalence of HTLV-II increased with age (14% in those < 13 years and 23% in those > or = 13 years). HTLV-II infection was found in all 20 Gran Chaco communities studied, but marked differences (44%-4%) in the rate of infection were observed even in communities separated by only a few miles. These variations correlated closely with ethnicity. In the high-incidence communities, infection clustered within families, with evidence for both sexual and perinatal transmission, primarily via breast-feeding. By contrast, only 2% of 94 Mapuche Indians from southern Argentina were positive for HTLV-II. Analyses of pol and long terminal repeat sequences from 15 Gran Chaco HTLV-II strains indicated that they constitute a highly conserved branch of the HTLV-IIB substrain.

Characteristics of children with phonologic disorders of unknown origin

Descriptive data are presented from three studies of children referred for assessment of a developmental speech disorder of unknown origin. Group findings indicate that these children have involvements in mechanism, cognitive, and psychosocial areas that warrant attention in theoretical explication of and early intervention for their communication deficits. The reliability, learnability, and efficiency of a diagnostic classification system that attempts to provide characteristic speech profiles for diagnostic subtypes is also considered.