Dr. M. Shahab Uddin - Academia.edu (original) (raw)

Papers by Dr. M. Shahab Uddin

Blood, 1997

Binding of interferon-alpha (IFN-alpha) to its receptor on hematopoietic cells activates the sign... more Binding of interferon-alpha (IFN-alpha) to its receptor on hematopoietic cells activates the signal transducers and activators of transcription (Stat)- and insulin receptor substrate (IRS)-pathways, and regulates expression of antiproliferative and antiviral activities. However, it remains unknown whether these two pathways cooperate in the generation of IFN-alpha responses or function independently, and whether IRS-proteins transduce distinct downstream signals in response to IFNs or insulin/insulin-like growth factor (IGF)-1-mediated activation. Our data show that in response to IFN-alpha treatment, IRS-1 functions selectively as a docking protein for the SH2 domains of the p85 subunit of the PI 3'-kinase, but not the SH2 domain of Grb-2 which is engaged during insulin/IGF-1 signaling. In studies with THP-1 human myelomonocytic cells and 32D mouse myeloid cells, which are IRS-defective, we found that the IFN-alpha-regulated activation of Stat-1, Stat-2, and Stat-3 does not req...

Blood, 1999

All-trans retinoic acid (ATRA) has previously been shown to inhibit the growth of OPM-2 human mye... more All-trans retinoic acid (ATRA) has previously been shown to inhibit the growth of OPM-2 human myeloma cells. The growth inhibition was postulated to result from a transcriptional downregulation of interleukin-6 receptor  (IL-6R) with IL-6Rβ (gp130) unaffected. To formally test this hypothesis, an expression vector designed for constitutive IL-6R expression was constructed and used for transfection of OPM-2 cells. Six stable transfectants were cloned. The expression of IL-6R was shown by immunofluorescence with anti–IL-6R antibody and 125I-IL-6 binding. In five of six transfectant clones, cellular IL-6R was 1.5- to 6-fold higher than the parental cells, with the ligand binding affinity unchanged. While ATRA reduced IL-6R expression in the parental OPM-2 cells, it enhanced its expression in these five transfectants. The clonogenic growth of these transfectants, however, remained strongly inhibited by ATRA. Further analysis, comparing the parental OPM-2 cells and a representativ...

AACR Annual Meeting-- Apr 18-22, 2009; Denver, CO The mechanisms that regulate mitogenic and anti... more AACR Annual Meeting-- Apr 18-22, 2009; Denver, CO The mechanisms that regulate mitogenic and anti-apoptotic signals in primary effusion lymphoma (PEL) are not well known. In efforts to identify novel approaches to block the proliferation of PEL cells, we found that, thymoquinone (TQ), an active component of black seed, inhibit cell viability and induce apoptosis in several PEL cell lines in a dose dependent manner. Such effects of TQ appear to result from release of reactive oxygen species (ROS) leading to suppression of the constitutively active kinase AKT, and its effectors FOXO transcription factor and p-Bad. Our data demonstrate that TQ treatment of PEL cell lines causes de-phosphorylation of Bad protein leading to down regulation of the anti-apoptotic protein, Bcl-2 and subsequent increase of Bax protein that leads to an increase in the Bax/Bcl2 ratio. TQ treatment of PEL cells also causes conformational changes of Bax protein and subsequently translocation from cytosole to mitochondria causing loss of mitochondrial membrane potential with subsequent release of cytochrome c from the mitochondria. Interestingly, Bax conformational changes following TQ treatment can be blocked by pre-treatment of PEL cells with N- acetylcysteine, an inhibitor of ROS. Released cytochrome c into the cytosole activates caspases-9 and -3, followed by polyadenosin-5\#8217;-diphosphate-ribose polymerase (PARP) cleavage. In addition, pretreatment of PEL cells with either zVAD-fmk, a universal inhibitor of caspases and NAC prevents caspase-3 activation and abrogates cell death induced by TQ treatment of PEL cells strongly suggesting that TQ-induced apoptosis is ROS as well as caspase dependent. Finally, treatment of PEL cells with TQ down-regulates the expression of inhibitor of apoptosis proteins (IAP). Altogether, these data suggest a novel function for TQ, acting as a suppressor of AKT/PKB pathway in PEL cells, and raise the possibility that this agent may have a future therapeutic role in PEL and possibly other malignancies with constitutive activation of the AKT/PKB pathway. Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 5506.

Biochemical Education, 1995

Proceedings of the National Academy of Sciences, 2003

p38α, p38β, p38γ, and p38δ are four isoforms of p38 mitogen-activated protein (MAP) kinase (MAPK)... more p38α, p38β, p38γ, and p38δ are four isoforms of p38 mitogen-activated protein (MAP) kinase (MAPK) involved in multiple cellular functions such as cell proliferation, differentiation, apoptosis, and inflammation response. In the present study, we examined the mRNA expression pattern of each of the four isoforms during erythroid differentiation of primary erythroid progenitors. We show that p38α and p38γ transcripts are expressed in early hematopoietic progenitors as well as in late differentiating erythroblasts, whereas p38δ mRNA is only expressed and active during the terminal phase of erythroid differentiation. On the other hand, p38β is minimally expressed in early CD34 + hematopoietic progenitors but not expressed in lineage-committed erythroid progenitors. We also determined the phosphorylation/activation of p38α, MAPK kinase 3/6, and MAPKAP-2 in response to erythropoietin and stem cell factor. We found that phosphorylation of p38α, MAPK kinase kinase 3/6 and MAPKAP-2 occurs onl...

Oncogene, 2005

The mechanisms that regulate induction of the antiapoptotic state and mitogenic signals in primar... more The mechanisms that regulate induction of the antiapoptotic state and mitogenic signals in primary effusion lymphoma (PEL) are not well known. In efforts to identify novel approaches to block the proliferation of PEL cells, we found that curcumin (diferuloylmethane), a natural compound isolated from the plant Curcuma Ionga, inhibits cell proliferation and induces apoptosis in a dose dependent manner in several PEL cell lines. Such effects of curcumin appear to result from suppression of the constitutively active STAT3 through inhibition of Janus kinase 1 (JAK1). Our data also demonstrate that curcumin induces loss of mitochondrial membrane potential with subsequent release of cytochrome c and activation of caspase-3, followed by polyadenosin-5 0-diphosphate-ribose polymerase (PARP) cleavage. Altogether, our findings suggest a novel function for curcumin, acting as a suppressor of JAK-1 and STAT3 activation in PEL cells, leading to inhibition of proliferation and induction of caspase-dependent apoptosis. Therefore, curcumin may have a future therapeutic role in PEL and possibly other malignancies with constitutive activation of STAT3.

Journal of Biological Chemistry, 2000

The p38 mitogen-activated protein (MAP) kinase is activated during engagement of the type I inter... more The p38 mitogen-activated protein (MAP) kinase is activated during engagement of the type I interferon (IFN) receptor and mediates signals essential for IFN␣dependent transcriptional activation via interferonstimulated response elements without affecting formation of the ISGF3 complex. In the present study, we provide evidence that the small GTPase Rac1 is activated in a type I IFN-dependent manner and that its function is required for downstream engagement of the p38 MAP kinase pathway. We also demonstrate that p38 is required for IFN␣-dependent gene transcription via GAS elements and regulates activation of the promoter of the PML gene that mediates growth inhibitory responses. In studies to determine whether the regulatory effects of p38 are mediated by serine phosphorylation of Stat1 or Stat3, we found that the p38 kinase inhibitors SB203580 or SB202190 or overexpression of a dominant negative p38 mutant do not inhibit phosphorylation of Stat1 or Stat3 on Ser-727 in several IFN␣-sensitive cell lines. Altogether these data demonstrate that the Rac1/ p38 MAP kinase signaling cascade plays a critical role in type I IFN signaling, functioning in cooperation with the Stat-pathway, to regulate transcriptional regulation of IFN␣-sensitive genes and generation of growth inhibitory responses.

Journal of Biological Chemistry, 1999

Journal of Biological Chemistry, 2002

Arsenic trioxide induces differentiation and apoptosis of malignant cells in vitro and in vivo, b... more Arsenic trioxide induces differentiation and apoptosis of malignant cells in vitro and in vivo, but the mechanisms by which such effects occur have not been elucidated. In the present study we provide evidence that arsenic trioxide induces activation of the small G-protein Rac1 and the ␣ and ␤ isoforms of the p38 mitogenactivated protein (MAP) kinase in several leukemia cell lines. Such activation of Rac1 and p38-isoforms results in downstream engagement of the MAP kinase-activated protein kinase-2 and is enhanced by pre-treatment of cells with ascorbic acid. Interestingly, pharmacological inhibition of p38 potentiates arsenic-dependent apoptosis and suppression of growth of leukemia cell lines, suggesting that this signaling cascade negatively regulates induction of antileukemic responses by arsenic trioxide. Consistent with this, overexpression of a dominant-negative p38 mutant (p38␤AGF) enhances the antiproliferative effects of arsenic trioxide on target cells. To further define the relevance of activation of the Rac1/p38 MAP kinase pathway in the induction of arsenic-dependent antileukemic effects, studies were performed using bone marrows from patients with chronic myelogenous leukemia. Arsenic trioxide suppressed the growth of leukemic myeloid (CFU-GM) progenitors from such patients, whereas concomitant pharmacological inhibition of the p38 pathway enhanced its growth-suppressive effects. Altogether, these data provide evidence for a novel function of the p38 MAP kinase pathway, acting as a negative regulator of arsenic trioxide-induced apoptosis and inhibition of malignant cell growth. Arsenic trioxide (As 2 O 3) suppresses the growth of malignant cells in vitro and in vivo (1-4). Several studies have shown that this agent exhibits potent growth inhibitory effects on several cell lines of diverse malignant phenotypes, including leukemia, multiple myeloma, prostate carcinoma, and neuroblastoma

Experimental Cell Research, 2004

The signals generated by the IFNg receptor to initiate mRNA translation and generation of protein... more The signals generated by the IFNg receptor to initiate mRNA translation and generation of protein products that mediate IFNg responses are largely unknown. In the present study, we provide evidence for the existence of an IFNg-dependent signaling cascade activated downstream of the phosphatidylinositol (PI) 3V-kinase, involving the mammalian target of rapamycin (mTOR) and the p70 S6 kinase. Our data demonstrate that p70 S6K is rapidly phosphorylated and activated during engagement of the IFNg receptor in sensitive cell lines. Such activation of p70 S6 kinase is blocked by pharmacological inhibitors of the PI 3V kinase and mTOR, and is abrogated in double-knockout mouse embryonic fibroblasts for the a and h isoforms of the p85 regulatory subunit of the PI 3V-kinase. The IFNg-activated p70 S6 kinase subsequently phosphorylates the 40S S6 ribosomal protein on serines 235/236, to regulate IFNg-dependent mRNA translation. In addition to phosphorylation of 40S ribosomal protein, IFNg also induces phosphorylation of the 4E-BP1 repressor of mRNA translation on threonines 37/ 46, threonine 70, and serine 65, sites whose phosphorylation is required for the inactivation of 4E-BP1 and its dissociation from the eukaryotic initiation factor-4E (eIF4E) complex. Thus, engagement of the PI 3V-kinase and mTOR by the IFNg receptor results in the generation of two distinct signals that play roles in the initiation of mRNA translation, suggesting an important role for this pathway in IFNg signaling.

Cytokine, 2013

Erythropoietin (EPO) and Stem Cell Factor (SCF) have partially distinct functions in erythroid ce... more Erythropoietin (EPO) and Stem Cell Factor (SCF) have partially distinct functions in erythroid cell development. The primary functions of EPO are to prevent apoptosis and promote differentiation, with a minor role as a mitogen. On the other hand SCF acts primarily as a mitogenic factor promoting erythroid cell proliferation with a minor role in inhibition of apoptosis. The concerted effects of these two growth factors are responsible for guiding initial commitment, expansion and differentiation of progenitors. The aim of the study was to identify signaling elements pertinent to translational control and elucidate whether both cytokines can contribute to protein translation providing some functional redundancy as seen with respect to apoptosis. The current study focused on non-apoptotic functions of SCF mediated through mTOR/p70S6 leading to protein translation and cell proliferation. We utilized a human primary erythroid progenitors and erythroblasts that are responsive to EPO and SCF to investigate the activation of mTOR/p70S6 kinases and their downstream effectors, the pathway primarily responsible for protein translation. We showed that mTOR, p70S6 kinases and their downstream signaling elements 4EBP1 and S6 ribosomal protein are all activated by SCF but not by EPO in primary erythroid progenitors. We also found that SCF is the sole contributor to activation of the protein translational machinery and activation of mTOR/p70S6 pathway is confined to the proliferative phase of erythroid differentiation program. Altogether these results demonstrate that unlike the survival function which is supported by both EPO and SCF protein translation essential for proliferation is governed by only SCF.

British Journal of Haematology, 1998

We investigated whether the src-family tyrosine kinase Lyn is involved in the generation of inter... more We investigated whether the src-family tyrosine kinase Lyn is involved in the generation of interferon α (IFNα) signals in haemopoietic cells. In vitro kinase assays using IFNα-sensitive cells of B-cell origin demonstrated the presence of IFNα-dependent kinase activity in anti-...

British Journal of Haematology, 2001

Interferon a (IFNa) has significant clinical activity in the treatment of patients with chronic m... more Interferon a (IFNa) has significant clinical activity in the treatment of patients with chronic myelogenous leukaemia (CML), but the mechanisms of its selective efficacy in the treatment of the disease are unknown. The CrkL adaptor protein interacts directly with the BCR±ABL fusion protein that causes the malignant transformation and is constitutively phosphorylated in BCR±ABL-expressing cells. In the present study, we provide evidence that CrkL was engaged in IFNa-signalling in the CML-derived KT-1 cell line, which expresses BCR±ABL and is sensitive to the growth inhibitory effects of IFNa. CrkL is constitutively associated with BCR±ABL in these cells and treatment with IFNa had no effect on the BCR±ABL/CrkL interaction. After IFNa stimulation, CrkL associated with Stat5, which also underwent phosphorylation in an IFNadependent manner. The interaction of CrkL with Stat5 was facilitated by the function of both the SH2 and the N-terminus SH3 domains of CrkL. The resulting CrkL±Stat5 complex translocated to the nucleus and could be detected in gel shift assays using elements derived from either the bcasein promoter or the promoter of the PML gene, an IFNainducible gene that mediates growth inhibitory responses. In addition to its interaction with Stat5, CrkL interacts with C3G in KT-1 cells and such an interaction regulates the downstream activation of the small GTPase Rap1, which also mediates inhibition of cell proliferation. Thus, despite its engagement by BCR±ABL in CML-derived cells, CrkL mediates activation of downstream signalling pathways in response to the activated type I IFN receptor and such signals may contribute to the generation of the anti-proliferative effects of IFNa in CML.

Biochemical and Biophysical Research Communications, 2000

Erythropoietin (Epo), stem cell factor (SCF), and insulin-like growth factor-1 (IGF-1) are key re... more Erythropoietin (Epo), stem cell factor (SCF), and insulin-like growth factor-1 (IGF-1) are key regulators of erythroid cell proliferation and differentiation. To understand the mechanisms of generation of signals by each of these growth factors, we determined the activation of the PI3-kinase/Akt pathway during proliferation and differentiation of primary human erythroid progenitors. Our results demonstrate that PKB/ Akt is activated by Epo and SCF, but not by IGF-1 in human primary erythroid progenitors. In addition, Epo treatment of erythroid progenitors induces phosphorylation of a member of the Forkhead family (FH) of transcription factors FKHRL1, downstream of activation of the Akt kinase. Such Epo-dependent activation of FKHRL1 apparently regulates the generation of Epo-dependent antiapoptotic signals as evidenced by the induction of apoptosis of erythroid progenitors during treatment of cells with the PI3-kinase (PI3K) inhibitor LY294002. Thus, the PI3K/Akt/FKHRL1 pathway is essential for inhibition of apoptosis in response to Epo and SCF, while the IGF-1 receptor utilizes a different pathway.