Michael Cox - Academia.edu (original) (raw)

Papers by Michael Cox

bioRxiv (Cold Spring Harbor Laboratory), Sep 14, 2023

Journal of Biological Chemistry, 1994

A classical biochemical approach was taken to identify mitogen-activated protein kinase kinase (M... more A classical biochemical approach was taken to identify mitogen-activated protein kinase kinase (MEK) activators in bovine brain. Fractionation revealed the presence of one major MEK-stimulating activity that was distinct from c-Raf-1 and MEK kinase. Similar results were obtained using bovine adrenal chromaffin cells, and in both cases, immunoblotting and immunoprecipitation experiments demonstrated co-purification of MEK activator with B-Raf. Partially purified MEK activator stimulated phosphorylation of MEKl on residues tentatively identified as serine 218 and serine 222. Little or no MEK activator was associated with c-Raf-1 in bovine brain or chromaffin cells, although this protein was expressed, suggesting that B-Raf might be the major MEK activator in cells of neural origin. The MAP' kinase pathway is activated by diverse agonists that stimulate cell division, differentiation, and secretion (reviewed in Ref. 1). MAP kinase activation requires phosphorylation on both tyrosine and threonine residues (2, 31, reactions that are catalyzed by a novel family of dual-specificity kinases named ME& (M A p or Erk kinases) (4-10). MEK activity is in turn regulated by reversible serinekhreonine phosphorylation (11-14), implying the existence of MEK kinases that function as MEK activators. A number of candidate MEK-activating kinases have been reported, most notably c-Raf-1. A variety of biochemical (15-20), genetic (9, 15-17, 21-26), and regulatory (27,28) evidence points to the importance of c-Raf-1 as a MEK activator. For example, partially purified preparations of c-Raf-1 can activate MEK in vitro (15-17, 20, 29); a rafhomologue in C. elegans has been shown to function "upstream" of MAP kinase and "downstream" of tyrosine kinases (24), and overexpression of mutant inactive forms of c-Raf-1 have been shown to block MAP kinase activation, presumably by a dominant-negative mechanism (26). In addition, c-Mos (30) and MEK kinase (31) have been shown to be potential MEK activators. The latter is a mammalian homologue of the yeast Stell and Byr2 proteins (31), which function as activators of the yeast ME&, Ste7 and Byrl, respectively. GM47332 (to M. J. W.) and DK44199 (to S. J. P.). The costs of publica-* This work was supported by National Institutes of Health Grants tion of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. $ Supported by a postdoctoral fellowship from Deutsche Forschungsgemeinschaft.

Biomicrofluidics, 2019

Efforts to further improve the clinical management of prostate cancer (PCa) are hindered by delay... more Efforts to further improve the clinical management of prostate cancer (PCa) are hindered by delays in diagnosis of tumours and treatment deficiencies, as well as inaccurate prognoses that lead to unnecessary or inefficient treatments. The quantitative and qualitative analysis of circulating tumour cells (CTCs) may address these issues and could facilitate the selection of effective treatment courses and the discovery of new therapeutic targets. Therefore, there is much interest in isolation of elusive CTCs from blood. We introduce a microfluidic platform composed of a multiorifice flow fractionation (MOFF) filter cascaded to an integrated microfluidic magnetic (IMM) chip. The MOFF filter is primarily employed to enrich immunomagnetically labeled blood samples by size-based hydrodynamic removal of free magnetic beads that must originally be added to samples at disproportionately high concentrations to ensure the efficient immunomagnetic labeling of target cancer cells. The IMM chip is then utilized to capture prostate-specific membrane antigen-immunomagnetically labeled cancer cells from enriched samples. Our preclinical studies showed that the proposed method can selectively capture up to 75% of blood-borne PCa cells at clinically-relevant low concentrations (as low as 5 cells/ml), with the IMM chip showing up to 100% magnetic capture capability.

Rationally designed therapeutics that target the phosphatidy- linositol 3V -kinase (PI3K) cell su... more Rationally designed therapeutics that target the phosphatidy- linositol 3V -kinase (PI3K) cell survival pathway are currently in preclinical and clinical development for cancer therapy. Drugs targeting the PI3K pathway aim to inhibit proliferation, promote apoptosis, and enhance chemosensitivity and radio- sensitivity of cancer cells. The phosphatase and tensin homo- logue (PTEN) phosphatidylinositol 3V -phosphatase is a key negative regulator of

Journal of Biological Chemistry, 2000

Neuroendocrine (NE) differentiation within prostate tumors is proposed to be a contributing facto... more Neuroendocrine (NE) differentiation within prostate tumors is proposed to be a contributing factor in disease progression. However, the cellular origin and molecular mechanism controlling differentiation of prostatic NE cells are unresolved. The prostate tumor cell line, LN-CaP, can reversibly acquire many NE characteristics in response to treatment with ␤-adrenergic receptor agonists and activators of adenylate cyclase. In this study, we demonstrate that these treatments induce protein kinase A (PKA) activation in LNCaP cells and that ectopic expression of a constitutively activated form of the PKA catalytic subunit, CI␣, results in acquisition of NE characteristics, including the extension of neuritic processes, cessation of mitotic activity, and production of neuron-specific enolase. Forskolin-, epinephrine-, and isoproterenol-dependent NE differentiation of LNCaP cells was significantly inhibited by expressing a dominant negative mutant of the PKA regulatory subunit, RI␣. These results demonstrate that prostatic NE differentiation in response to these agents depends on PKA activation, and this signaling pathway may provide a therapeutic target for treating advanced forms of prostate cancer.

Journal of Biological Chemistry, 2003

Src family kinases (SFKs) are abundant in chromaffin cells that reside in the adrenal medulla and... more Src family kinases (SFKs) are abundant in chromaffin cells that reside in the adrenal medulla and respond to cholinergic stimulation by secreting catecholamines. Our previous work indicated that SFKs regulate acetylcholine-or nicotine-induced secretion, but the site of modulatory action was unclear. Using whole cell recordings, we found that inhibition of SFK tyrosine kinase activity by PP2 (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo(3,4-d)pyrimidine) treatment or expression of a kinase-defective c-Src reduced the peak amplitude of nicotine-induced currents in chromaffin cells or in human embryonic kidney cells ectopically expressing functional neuronal ␣3␤4␣5 acetylcholine receptors (AChRs). Conversely, the phosphotyrosine phosphatase inhibitor, sodium vanadate, or expression of mutationally activated c-Src resulted in enhanced current amplitudes. These results suggest that SFKs and putative phosphotyrosine phosphatases regulate the activity of AChRs by opposing actions. This proposed model was supported further by the findings that SFKs physically associate with the receptor and that the AChR is tyrosine-phosphorylated.

Endocrinology, 1998

The present study examined the effect of alterations in GnRH signal pattern (pulsatile vs. contin... more The present study examined the effect of alterations in GnRH signal pattern (pulsatile vs. continuous; pulse frequency) on mitogenactivated protein kinase (MAPK) activity and whether MAPK plays a role in regulating gonadotrope gene expression. Pituitary MAPK activity was measured by immunoblot, using a phospho-specific MAPK antibody, corrected to the amount of total MAPK per sample. In vivo studies were conducted in adult castrate testosterone-replaced male rats (to suppress endogenous GnRH). Animals received pulsatile or continuous GnRH (or BSA-saline for controls) via jugular cannulas. Initial studies revealed that pulsatile GnRH stimulated a dose-dependent rise in MAPK activity (30 ng, 2-fold increase; 100 ng, 4-fold; 300 ng, 8-fold) 4 min after the pulse. The effect of pulsatile vs. continuous GnRH was examined by administering 50-ng pulses (60-min interval) or a continuous infusion (25 ng/min) for 1, 2, 4, or 8 h. Pulsatile GnRH stimulated a 2-to 4-fold rise in MAPK activity (P Ͻ 0.05 vs. controls) that was maintained over the 8-h duration. In contrast, continuous GnRH only increased MAPK activity (2-to 3-fold; P Ͻ 0.05 vs. controls) for 2 h, with MAPK activity returning to baseline at later time points. The effect of GnRH pulse frequency on MAPK activation was determined by giving GnRH pulses (50 ng) at 30-, 60-, or 120-min intervals for 8 h. Maximal increases (3-fold vs. controls; P Ͻ 0.05) were seen after 120-min pulses, with faster (30-to 60-min interval) pulses stimulating 2-fold increases in MAPK activity (P Ͻ 0.05 vs. controls and 120-min GnRH pulse group). The role of MAPK activation on gonadotrope (␣, LH␤, FSH␤, and GnRH receptor) gene expression was determined in vitro. Preliminary studies demonstrated that the MAPK inhibitor, PD-098059 (50 M), completely blocked GnRH-induced increases in MAPK activity in adult male pituitary cells. Further studies revealed that PD-098059 blocked gonadotrope messenger RNA (mRNA) responses to pulsatile GnRH (100 pg/ml, 60-min interval, 24-h duration) in a selective manner, with ␣, FSH␤, and GnRH receptor (but not LH␤) mRNA responses being suppressed. These results show that a pulsatile GnRH signal is required to maintain MAPK activation for durations of longer than 2 h, and that slower frequency pulses are more effective. Further, MAPK plays a crucial role in ␣, FSH␤, and GnRH receptor mRNA responses to pulsatile GnRH. Thus, divergent MAPK responses to alterations in GnRH signal pattern may be one mechanism involved in differential regulation of gonadotrope gene expression.

Scientific reports, Jan 13, 2017

Prostate cancer (PCa) is among the most commonly-occurring cancers worldwide and a leader in canc... more Prostate cancer (PCa) is among the most commonly-occurring cancers worldwide and a leader in cancer-related deaths. Local non-invasive PCa is highly treatable but limited treatment options exist for those with locally-advanced and metastatic forms of the disease underscoring the need to identify mechanisms mediating PCa progression. The semaphorins are a large grouping of membrane-associated or secreted signalling proteins whose normal roles reside in embryogenesis and neuronal development. In this context, semaphorins help establish chemotactic gradients and direct cell movement. Various semaphorin family members have been found to be up- and down-regulated in a number of cancers. One family member, Semaphorin 3 C (SEMA3C), has been implicated in prostate, breast, ovarian, gastric, lung, and pancreatic cancer as well as glioblastoma. Given SEMA3C's roles in development and its augmented expression in PCa, we hypothesized that SEMA3C promotes epithelial-to-mesenchymal transition...

Frontiers in pharmacology, 2017

Psoriasis, a chronic inflammatory skin disease marked by hyper proliferation and aberrant differe... more Psoriasis, a chronic inflammatory skin disease marked by hyper proliferation and aberrant differentiation of keratinocytes, affects 2-3% of the world's population. Research into the pathogenesis of psoriasis has been hampered by the lack of models that accurately reflect the biology of the psoriatic phenotype. We have previously reported that East Indian Sandalwood oil (EISO) has significant anti-inflammatory properties in skin models and hypothesized that EISO might provide therapeutic benefit to psoriasis patients due to its anti-inflammatory and anti-proliferative properties. Here we present interim results from an on-going proof-of-concept Phase 2 clinical trial in which topically applied EISO is demonstrating to be well tolerated and helpful in alleviating mild to moderate psoriasis symptoms. This led us to evaluate the ability of EISO to affect the psoriatic phenotype using MatTek Corporation reconstituted organotypic psoriatic and normal human skin models. EISO had no imp...

Journal of Biochemical and Molecular Toxicology, 2015

The effects of six organophosphate flame retardants (OPFRs) tris(2-butoxyethyl) phosphate, tris(2... more The effects of six organophosphate flame retardants (OPFRs) tris(2-butoxyethyl) phosphate, tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate, tris(methylphenyl) phosphate, tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), and triethyl phosphate on the activities of androgen receptor (AR), estrogen receptor (ER), and aryl hydrocarbon receptor (AhR) were assessed in human prostate and endometrial cancer cells. OPFRs had no effect on ER or AhR target gene activation in ECC-1 cells. The effect of TDCIPP on mRNA and protein accumulation of AR target genes was examined further. AR-inducible gene and protein expression were significantly altered by TDCIPP exposure and repressed PSA levels in conditioned media of prostate cancer cells. We demonstrated that TDCIPP has no affinity for the AR ligand binding domain (AR-LBD) and exerts its antiandrogenic effects in a noncompetitive fashion. Thus, the clinical relevance of TDCIPP exposure on prostate cancer detection and progression to a therapeutically refractile state ought to be investigated further.

Cell cycle (Georgetown, Tex.), Jan 15, 2015

Anti-integrin-linked kinase (ILK) therapies result in aberrant mitosis including altered mitotic ... more Anti-integrin-linked kinase (ILK) therapies result in aberrant mitosis including altered mitotic spindle organization, centrosome declustering and mitotic arrest. In contrast to cells that expressed the retinoblastoma tumour suppressor protein Rb, we have shown that in retinoblastoma cell lines that do not express Rb, anti-ILK therapies induced aberrant mitosis that led to the accumulation of temporarily viable multinucleated cells. The present work was undertaken to: 1) determine the ultimate fate of cells that had survived anti-ILK therapies and 2) determine whether or not Rb expression altered the outcome of these cells. Our data indicate that ILK, a chemotherapy drug target is expressed in both well-differentiated, Rb-positive, and relatively undifferentiated, Rb-negative retinoblastoma tissue. We show that small molecule targeting of ILK in Rb-positive and Rb-deficient cancer cells results in increased centrosomal declustering, aberrant mitotic spindle formation and multinuclea...

Cancer research, 1999

Neuroendocrine (NE) cells occur as scattered foci within prostatic adenocarcinoma, similar to the... more Neuroendocrine (NE) cells occur as scattered foci within prostatic adenocarcinoma, similar to their distribution within ductal epithelial cells of the normal prostate. However, the density of NE cells is often greater in prostate carcinomas than in normal tissue, and the frequency of NE cells correlates with tumor grade, loss of androgen sensitivity, autocrine/paracrine activity, and poor prognosis. Although NE cells are nonmitotic, proliferating cells are found in direct proximity to them, suggesting that NE cells provide paracrine stimuli for surrounding carcinoma cells. In vitro, differentiation of the LNCaP and PC3M prostatic tumor cell lines to a NE phenotype can be induced by dibutyryl cyclic AMP (cAMP), suggesting that physiological agents that increase intracellular concentrations of cAMP might regulate NE differentiation in vivo. Indeed, we demonstrate in this report that LNCaP cells acquire NE characteristics in response to treatment with physiological and pharmacological ...

Cancer research, 2003

Activation of alternative growth factor pathways after androgen withdrawal is one mechanism media... more Activation of alternative growth factor pathways after androgen withdrawal is one mechanism mediating androgen-independent (AI) progression in advanced prostate cancer. Insulin-like growth factor (IGF) I activation is modulated by a family of IGF binding proteins (IGFBPs). Although IGFBP-2 is one of the most commonly overexpressed genes in hormone refractory prostate cancer, the functional significance of changes in IGF-I signaling during AI progression remains poorly defined. In this article, we characterize changes in IGFBP-2 in the LNCaP tumor model after androgen withdrawal and evaluate its functional significance in AI progression using gain-of-function and loss-of-function analyses. IGFBP-2 mRNA and protein levels increase 2-3-fold after androgen withdrawal in LNCaP cells in vitro in LNCaP tumors during AI progression in vivo. Increased IGFBP-2 levels after castration were also identified using a human prostate tissue microarray of untreated and posthormone therapy-treated pro...

The Prostate, 2009

BACKGROUND. Although recent laboratory and population studies suggest that prostate cancer may be... more BACKGROUND. Although recent laboratory and population studies suggest that prostate cancer may be responsive to insulin, there is a gap in knowledge concerning the expression of insulin receptors on benign or malignant prostate tissue. METHODS. We immunostained 644 cores on tissue microarrays prepared from 29 prostate tissue samples without malignancies, 78 Gleason grade 3 cancers, 21 Gleason grade 4 cancers and 33 Gleason grade 5 cancers with antibodies against the insulin-like growth factor I receptor and the insulin receptor. RESULTS. We observed immunoreactivity with both antibodies, which implies the presence of hybrid receptors as well as IGF-I receptors and insulin receptors. Insulin receptor staining intensity was significantly (P < 0.001) higher on malignant than benign prostate epithelial cells. Analysis of information from public gene expression databases confirmed that co-expression of insulin receptor mRNA and IGF-I receptor mRNA is common in prostate cancer specimens. RT-PCR methods provided evidence for the presence of mRNA for both IR-A and IR-B insulin receptor isoforms. CONCLUSION. These observations document the presence of insulin receptors on primary human prostate cancers. The findings are relevant not only to ongoing clinical trials of drug candidates that target IGF-I and/or insulin receptors, but also to the hypothesis that obesityassociated hyperinsulinemia mediates the adverse effect of obesity on prostate cancer prognosis.

Oncogene, 2003

Recent reports suggest that the b-catenin-T-cell factor (Tcf) (BCT) signaling pathway is importan... more Recent reports suggest that the b-catenin-T-cell factor (Tcf) (BCT) signaling pathway is important in the progression of prostate cancer. Evidence suggests that the androgen receptor (AR) can repress BCT-mediated transcription both in prostate cancer and colon cancer cells (Chesire and Isaacs, 2002). In this study, we validate such findings and show that repression of BCT signaling is facilitated by competition between the AR and Tcf. Measurements of the Tcf transcriptional reporter (TOP-FLASH) indicated that AR þ DHT-mediated repression can inhibit BCT transcription in the presence of WT and exogenous activating b-catenin (D1-130 bp). Transient transfections in SW480 cells (APC mut/mut) showed that this mode of repression is functionally independent of APCmediated b-catenin ubiquitination. Using a recently developed red flourescent protein (HcRed), we demonstrate novel observations about the nuclear distribution of Tcf. Furthermore, with the use of red (HcRed-AR and HcRed-Tcf) and green fusion proteins (b-catenin-EGFP), we provide morphological evidence of a reciprocal balance of nuclear b-catenin-EGFP (BC-EGFP). By cotransfecting in LNCaP prostate tumor cells and using quantitative imaging software, we demonstrated a 62.0% colocalization of HcRed-AR and BC-EGFP in the presence of DHT and 63.3% colocalization of HcRed-Tcf/BC-EGFP in the absence of DHT. Costaining for activated RNA Pol II (phosphoserine 2) and HcRed-Tcf suggested that Tcf foci contain transcriptional 'hotspots' validating that these sites have the capacity for transcriptional activity. Given this apparent androgen-dependent competition for nuclear BC-EGFP, we chose to assess our hypothesis by in vivo and in vitro binding assays. SW480 cells transiently transfected with an AR expression construct, treated with DHT and immunoprecipitated for Tcf showed less associated b-catenin when compared to Tcf precipitates from untreated cells. Furthermore, by treating cells with DHT þ Casodex, we were able to abrogate the androgensensitive AR/b-catenin interaction, in addition to relieving transcriptional repression of the TOPFLASH reporter. In vitro binding assays, with increasing amounts of AR S35 , resulted in decreased Tcf S35 association with immunoprecipitated recombinant b-catenin-HIS. These data suggest that in steady-state conditions, AR has the ability to compete out Tcf binding for b-catenin. Finally, using SW480 cells, we show that AR-mediated repression of the BCT pathway has implications for cell cycle progression and in vitro growth. Using FACs analysis, we observed a 26.1% increase in accumulation of cells in the G1 phase of the cell cycle, while in vitro growth assays showed a 35% reduction in viable cells transfected with AR þ DHT treatment. Together, our data strongly suggest that a reciprocal balance of nuclear b-catenin facilitates ARmediated repression of BCT-driven transcription and cell growth.

Journal of Biological Chemistry, 1999

Accumulating evidence indicates that interactions between the epidermal growth factor receptor (E... more Accumulating evidence indicates that interactions between the epidermal growth factor receptor (EGFR) and the nonreceptor tyrosine kinase c-Src may contribute to an aggressive phenotype in multiple human tumors. Previous work from our laboratory demonstrated that murine fibroblasts which overexpress both these tyrosine kinases display synergistic increases in DNA synthesis, soft agar growth, and tumor formation in nude mice, and increased phosphorylation of the receptor substrates Shc and phospholipase ␥ as compared with single overexpressors. These parameters correlated with the ability of c-Src and EGFR to form an EGF-dependent heterocomplex in vivo. Here we provide evidence that association between c-Src and EGFR can occur directly, as shown by receptor overlay experiments, and that it results in the appearance of two novel tyrosine phosphorylations on the receptor that are seen both in vitro and in vivo following EGF stimulation. Edman degradation analyses and co-migration of synthetic peptides with EGFR-derived tryptic phosphopeptides identify these sites as Tyr 845 and Tyr 1101. Tyr 1101 lies within the carboxyl-terminal region of the EGFR among sites of receptor autophosphorylation, while Tyr 845 resides in the catalytic domain, in a position analogous to Tyr 416 of c-Src. Phosphorylation of Tyr 416 and homologous residues in other tyrosine kinase receptors has been shown to be required for or to increase catalytic activity, suggesting that c-Src can influence EGFR activity by mediating phosphorylation of Tyr 845. Indeed, EGF-induced phosphorylation of Tyr 845 was increased in MDA468 human breast cancer cells engineered to overexpress c-Src as compared with parental MDA 468 cells. Furthermore, transient expression of a Y845F variant EGFR in murine fibroblasts resulted in an ablation of EGF-induced DNA synthesis to nonstimulated levels. Together, these data support the hypothesis that c-Srcmediated phosphorylation of EGFR Tyr 845 is involved in regulation of receptor function, as well as in tumor progression.

Cancer Research, 2007

The neuroendocrine status of prostatic adenocarcinomas is considered a prognostic indicator for d... more The neuroendocrine status of prostatic adenocarcinomas is considered a prognostic indicator for development of aggressive, androgen-independent disease. Neuroendocrine-like cells are thought to function by providing growth and survival signals to surrounding tumor cells, particularly following androgen ablation therapy. To test this hypothesis directly, LNCaP cells were engineered to inducibly express a constitutively activated form of the cyclic AMP–dependent protein kinase A catalytic subunit (caPKA), which was previously found upon transient transfection to be sufficient for acquisition of neuroendocrine-like characteristics and loss of mitotic activity. Clonal cells that inducibly expressed caPKA enhanced the growth of prostate tumor cells in anchorage-dependent and anchorage-independent in vitro assays as well as the growth of prostate tumor xenografts in vivo, with the greatest effects seen under conditions of androgen deprivation. These results suggest that neuroendocrine-lik...

Cancer Research, 2006

Progression to androgen independence is the lethal end stage of prostate cancer. We used expressi... more Progression to androgen independence is the lethal end stage of prostate cancer. We used expression of androgen receptor (AR)-targeted short hairpin RNAs (shRNA) to directly test the requirement for AR in ligand-independent activation of androgen-regulated genes and hormone-independent tumor progression. Transient transfection of LNCaP human prostate cancer cells showed that AR shRNA decreased R1881 induction of the prostate-specific antigen (PSA)-luciferase reporter by 96%, whereas activation by forskolin, interleukin-6, or epidermal growth factor was inhibited 48% to 75%. Whereas the antiandrogen bicalutamide provided no further suppression, treatment with the mitogen-activated protein kinase (MAPK) inhibitor U0126 completely abrogated the residual activity, indicating a MAPK-dependent, AR-independent pathway for regulating the PSA promoter. Expression of doxycycline-inducible AR shRNA expression in LNCaP cells resulted in decreased levels of AR and PSA as well as reduced prolifer...

Cancer Research, 2012

Introduction: It is proposed that advanced Prostate Cancer (PCa) tumors develop mechanisms, which... more Introduction: It is proposed that advanced Prostate Cancer (PCa) tumors develop mechanisms, which re-activate the androgen receptor (AR) axis via oncogenic pathways, in which tyrosine kinases play a crucial role. Genetic manipulation of several tyrosine kinases in vivo revealed that only a knockout of Lyn tyrosine Kinase, compromised prostate gland development suggesting that Lyn plays a critical role in the regulation of AR in normal prostate development. Our results demonstrated that Lyn kinase enhances AR transcriptional activity and promotes prostate cancer cell survival. Thus, we hypothesized that Lyn kinase overexpression accelerates castrate-resistant LNCaP tumor growth and serum PSA relapse to pre-castration levels. Method: LNCaP cells stably overexpressing Lyn kinase (LNCaP Lyn ) or Empty vector (LNCap Empty ) were generated using clonal selection. 1 × 10 6 LNCaP Lyn and LNCaP Empty were injected into the male nude mice. Serum PSA level and tumor volumes were followed weekly and mice were castrated when serum PSA values reached 50ng/ml. Results: Interestingly, a higher rate of tumor growth and PSA relapse was observed after casteration in mice bearing the LNCaP Lyn compare to the LNCap Empty -bearing mice. Total protein was extracted from the xenograft tumors and levels of AR, PSA, FKBP52, AKT, pAKT were analyzed. Results of Protein analysis further confirmed the role of Lyn kinase in prostate cancer cell survival and progression to castrate resistant stage. Conclusion: Together, these results suggest that Lyn plays a key role in CRPC development and that inhibiting Lyn expression could be considered as a potential therapeutic target for CRPC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1241. doi:1538-7445.AM2012-1241

Cancer Research, 2004

Apoptosis and inhibition of mitosis are primary mechanisms mediating androgen ablation therapy-in... more Apoptosis and inhibition of mitosis are primary mechanisms mediating androgen ablation therapy-induced regression of prostate cancer (PCa). However, PCa readily becomes androgen independent, leading to fatal disease. Up-regulated growth and survival signaling is implicated in development of resistance to androgen ablation therapy. We are testing the hypothesis that insulin-like growth factor (IGF) responsiveness is required for androgen-independent (AI) progression. Using the LNCaP human PCa progression model, we have determined that IGF-I–mediated protection from apoptotic stress and enhanced mitotic activity is androgen dependent in LNCaP cells but is androgen independent in lineage-derived C4-2 cells. Both cell lines exhibit androgen-responsive patterns of IGF-I receptor (IGF-IR) expression, activation, and signaling to insulin receptor substrate-2 and AKT. However, C4-2 cells express higher levels of IGF-IR mRNA and protein and exhibit enhanced IGF-I–mediated phosphorylation and...