Mark A Nelson

The University of Arizona, Tucson, Arizona, United States

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Publications (62)257.51 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: MicroRNAs have emerged as important post-translational regulators of gene expression and are involved in several physiological and pathological states including the pathogenesis of human colon cancers. In regards to tumor development, microRNAs can act as oncogenes or tumor suppressors. Two hereditary predispositions (i.e., Lynch syndrome and familial adenomatous polyposis) contribute to the development of colon cancer. In addition, individuals who suffer from inflammatory bowel diseases such as Crohn's disease or ulcerative colitis have a higher risk of developing colon cancer. Here, we discuss the occurrence of the deregulated expression of microRNAs in colon cancer that arise as a result of hereditary predisposition and inflammatory bowel disease.
    Cancer Genetics 09/2013; 206(9-10). DOI:10.1016/j.cancergen.2013.06.005 · 2.42 Impact Factor
  • Cancer Research 08/2013; 73(8 Supplement):1806-1806. DOI:10.1158/1538-7445.AM2013-1806 · 9.28 Impact Factor
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    ABSTRACT: Accumulating evidence indicates that elevated S100P promotes the pathogenesis of cancers, including colon cancer. S100P exerts its effects by binding to and activating the Receptor for Advance Glycation End-products (RAGE). The effects of up-regulated S100P/RAGE signaling on cell functions are well documented. Despite these observations, little is known about the downstream targets of S100P/RAGE signaling. In the present study, we demonstrated for the first time that activation of RAGE by S100P regulates oncogenic microRNA-155 (miR-155) expression through Activator Protein-1 (AP-1) stimulation in colon cancer cells. Ectopic S100P up-regulated miR-155 levels in human colon cancer cells. Conversely, knockdown of S100P resulted in a decrease in miR-155 levels. Exogenous S100P induced miR-155 expression, but blockage of the RAGE with anti-RAGE antibody suppressed the induction of miR-155 by exogenous S100P. Attenuation of AP-1 activation through pharmacological inhibition of MEK activation or genetic inhibition of c-Jun activation using dominant negative c-Jun (TAM67) suppressed miR-155 induction by exogenous S100P. Also, S100P treatment stimulated the enrichment of c-Fos, an AP-1 family member, at the miR-155 host gene promoter site. Finally, a functional study demonstrated that miR-155 knockdown decreases colon cancer cell growth, motility, and invasion. Altogether, these data demonstrate that the expression of miR-155 is regulated by S100P and is dependent on RAGE activation and stimulation of AP-1.
    Experimental Cell Research 05/2013; 319(13). DOI:10.1016/j.yexcr.2013.05.009 · 3.37 Impact Factor
  • Cancer Research 06/2012; 72(8 Supplement):2398-2398. DOI:10.1158/1538-7445.AM2012-2398 · 9.28 Impact Factor
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    ABSTRACT: Expression of the PGE2 receptor, EP4, is up-regulated during colorectal carcinogenesis. However the mechanism leading to deregulation of the EP4 receptor is not known. The present study was conducted to investigate the regulation of EP4 receptor by miRNAs. We analyzed 26 colon cancers (i.e. 15 adenocarcinomas and 9 adenomas) and 16 normal colon specimens for EP4 receptor expression by immunohistochemistry. A bioinformatics approached identified putative microRNA binding sites with the 3'-UTR of the EP4 receptor. Both colon cancer cell lines and tumor specimens were analyzed for miR-101 and EP4 expression by qRT-PCR and Western analysis respectively and simultaneously in situ hybridizations was used to confirm our results. In vitro and in vivo assays were used to confirm our clinical findings. We observed an inverse correlation between the levels of miR-101 and EP4 receptor protein. Transfection of LS174T cells with miR-101 significantly suppressed a luciferase reporter containing the EP4 receptor-3'-UTR. In contrast, a mutant EP4 receptor-3'-UTR construct was unaffected. Ectopic expression of miR-101 markedly reduced cell proliferation and motility. Co-transfection of EP4 receptor could rescue colon cancer cells from the tumor suppressive effects of miR-101. Moreover, the pharmacologic inhibition of EP4 receptor signaling or silencing of EP4 receptor phenocopied the effect of miR-101. This is the first study to show that the EP4 receptor is negatively regulated by miR-101. These data provide new insights in the modulation of EP-4 receptor expression at the post-transcriptional level by miR-101 and suggests therapeutic strategies against miR-101 targets may be warranted.
    Cancer biology & therapy 02/2012; 13(3):175-83. DOI:10.4161/cbt.13.3.18874 · 3.63 Impact Factor
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    ABSTRACT: Mechanisms driving cancer-induced bone pain are poorly understood. A central factor implicated to be a key player in the process of tumorigenesis, osteoclastogenesis and nociception is p38 MAPK. We determined the role of p38 MAPK in a mouse model of breast cancer induced bone pain in which mixed osteolytic and osteoblastic remodeling occurs. In cancer-treated mice, acute as well as chronic inhibition of p38 MAPK with SB203580 blocked flinching and guarding behaviors in a dose-dependent manner whereas no effect on thresholds to tactile stimuli was observed. Radiographic analyses of bones demonstrated that chronic inhibition of p38 MAPK reduced bone loss and incidence of spontaneous fracture in cancer-treated mice. Histological analysis of bones collected from mice treated with the p38 MAPK inhibitor showed complete absence of osteoblastic growth in the intramedullary space as well as significantly reduced tumor burden. Blockade of non-evoked pain behaviors but not hypersensitivity suggests differences in the underlying mechanisms of specific components of the pain syndrome and a possibility to individualize aspects of pain management. While it is not known whether the role of p38 MAPK signaling can be expanded to other cancers, the data suggest a need for understanding molecular mechanisms and cellular events that initiate and maintain cancer-induced bone pain for effective management for both ongoing pain as well as breakthrough pain.
    Molecular Pain 10/2011; 7:81. DOI:10.1186/1744-8069-7-81 · 3.53 Impact Factor
  • Cancer Research 01/2011; 70(8 Supplement):2082-2082. DOI:10.1158/1538-7445.AM10-2082 · 9.28 Impact Factor
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    ABSTRACT: BACKGROUND: Prostaglandin E₂ (PGE₂) levels are frequently elevated in colorectal carcinomas. PGE₂ is perceived via four transmembrane G protein coupled receptors (EP1-4), among which the EP4 receptor is most relevant. PGE₂/EP4-receptor interaction activates CREB via the ERK/MEK pathway. However, the downstream target genes activated by this pathway remained to be investigated. METHODOLOGY/PRINICIPAL FINDINGS: Here, we have identified S100P (an EF-hand calcium binding protein) as a novel downstream target. We show by realtime RT-PCR that S100P mRNA levels are elevated in 14/17 (82%) colon tumor tissues as compared to paired adjacent normal colonic tissues. S100P expression is stimulated in the presence of PGE₂ in a time dependent manner at mRNA and protein levels in colon, breast and pancreatic cancer cells. Pharmacological and RNAi-mediated inhibition of the EP4 receptor attenuates PGE₂-dependent S100P mRNA induction. RNA(i)-mediated knockdown of CREB inhibits endogenous S100P expression. Furthermore, using luciferase reporter analysis and EMSA we show that mutation and/or deletion of the CRE sequence within the S100P promoter abolished PGE₂-mediated transcriptional induction. Finally, we demonstrate that RNA(i)-mediated knockdown of S100P compromised invadopodia formation, colony growth and motility of colon cancer cells. Interestingly, endogenous knock down of S100P decreases ERK expression levels, suggesting a role for ERK in regulating S100P mediated cell growth and motility. CONCLUSIONS/SIGNIFICANCE: Together, our findings show for the first time that S100P expression is regulated by PGE₂/EP4-receptor signaling and may participate in a feedback signaling that perpetuates tumor cell growth and migration. Therefore, our data suggest that dysregulated S100P expression resulting from aberrant PGE₂/EP4 receptor signaling may have important consequences relevant to colon cancer pathogenesis.
    Cancer biology & therapy 11/2010; 10(10):1056-66. DOI:10.4161/cbt.10.10.13373 · 3.63 Impact Factor
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    ABSTRACT: Estrogen receptor (ER)-negative breast cancer is an aggressive form that currently requires more drug treatment options. Thus, we have further modified cyclohexanone derivatives of curcumin and examined them for cytotoxicity towards ER-negative human breast cancer cells. Two of the analogs screened elicited increased cytotoxic potency compared to curcumin and other previously studied derivatives. Specifically, 2,6-bis(pyridin-3-ylmethylene)-cyclohexanone (RL90) and 2,6-bis(pyridin-4-ylmethylene)-cyclohexanone (RL91) elicited EC(50) values of 1.54 and 1.10 µM, respectively, in MDA-MB-231 cells and EC(50) values of 0.51 and 0.23 in SKBr3 cells. All other new compounds examined were less potent than curcumin, which elicited EC(50) values of 7.6 and 2.4 µM in MDA-MB-231 and SKBr3 cells, respectively. Mechanistic analyses demonstrated that RL90 and RL91 significantly induced G(2)/M-phase cell cycle arrest and apoptosis. RL90 and RL91 also modulated the expression of key cell signaling proteins, specifically, in SKBr3 cells, protein levels of Her-2, Akt, and NFκB were decreased in a time-dependent manner, while activity of stress kinases JNK1/2 and P38 MAPK were increased. Signaling events in MDA-MB-231 cells were differently implicated, as EGFR protein levels were decreased and activity of GSK-3β transiently decreased, while β-catenin protein level and activity of P38 MAPK, Akt, and JNK1/2 were transiently increased. In conclusion replacement of the phenyl group of cyclohexanone derived curcumin derivatives with heterocyclic rings forms a class of second-generation analogs that are more potent than both curcumin and other derivatives. These new derivatives provide a platform for the further development of drugs for the treatment of ER-negative breast cancer.
    Investigational New Drugs 10/2009; 29(1):87-97. DOI:10.1007/s10637-009-9339-0 · 2.93 Impact Factor
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    ABSTRACT: The heterogeneous nuclear ribonucleoprotein (hnRNP) K is an essential RNA and DNA binding protein involved in gene expression and signal transduction including DNA transcription, RNA splicing, RNA stability and translation. The role of hnRNP K in cancer is relatively understudied. However, several cellular functions strongly indicate that hnRNP K is involved in tumorigenesis. In this study, we investigated the altered protein expression and the subcellular distribution of the hnRNP K protein using tissue microarrays in pancreatic cancer. We showed an increased cytoplasmic hnRNP K in pancreatic cancer. This increase in hnRNP K protein occurs at the posttranscriptional level. We postulate that the cytoplasmic accumulation of hnRNP K will lead to silenced mRNA translation of tumor suppressor genes and thus contributes to pancreatic cancer development. We also demonstrated that knocking down of hnRNP K expression by siRNA inhibited pancreatic cancer cell growth and colony formation. hnRNP K was identified as a member of the p53/HDM2 pathway. Whether hnRNP K interacts with the mutant p53 is not known. Using two different pancreatic cancer cell lines, we can demonstrate that hnRNP K interacts with the mutant p53. The subcellular distribution and function of the mutant p53 and the interaction of hnRNP K/mutant p53 were affected by the Ras/MEK/ERK pathway, growth factors and the specific p53 mutations in pancreatic cancer cells. Since Kras is activated and p53 is mutated in most pancreatic cancers, these data unveiled an important new signaling pathway that linked by hnRNP K and mutant p53 in pancreatic cancer tumorigenesis.
    International Journal of Cancer 08/2009; 126(2):395-404. DOI:10.1002/ijc.24744 · 5.01 Impact Factor
  • Gastroenterology 05/2009; 136(5). DOI:10.1016/S0016-5085(09)60708-3 · 13.93 Impact Factor
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    ABSTRACT: Esophageal adenocarcinoma risk in Barrett's esophagus (BE) is increased 30- to 125-fold versus the general population. Among all BE patients, however, neoplastic progression occurs only once per 200 patient-years. Molecular biomarkers are therefore needed to risk-stratify patients for more efficient surveillance endoscopy and to improve the early detection of progression. We therefore performed a retrospective, multicenter, double-blinded validation study of eight BE progression prediction methylation biomarkers. Progression or nonprogression were determined at 2 years (tier 1) and 4 years (tier 2). Methylation was assayed in 145 nonprogressors and 50 progressors using real-time quantitative methylation-specific PCR. Progressors were significantly older than nonprogressors (70.6 versus 62.5 years; P < 0.001). We evaluated a linear combination of the eight markers, using coefficients from a multivariate logistic regression analysis. Areas under the ROC curve (AUC) were high in the 2-year, 4-year, and combined data models (0.843, 0.829, and 0.840; P < 0.001, <0.001, and <0.001, respectively). In addition, even after rigorous overfitting correction, the incremental AUCs contributed by panels based on the 8 markers plus age versus age alone were substantial (Delta-AUC = 0.152, 0.114, and 0.118, respectively) in all 3 models. A methylation biomarker-based panel to predict neoplastic progression in BE has potential clinical value in improving both the efficiency of surveillance endoscopy and the early detection of neoplasia.
    Cancer Research 05/2009; 69(10):4112-5. DOI:10.1158/0008-5472.CAN-09-0028 · 9.28 Impact Factor
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    Jiaqi Shi, John W B Hershey, Mark A Nelson
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    ABSTRACT: eIF3f is a subunit of eukaryotic initiation factor 3 (eIF3). We previously showed that eIF3f is phosphorylated by cyclin dependent kinase 11 (CDK11(p46)) which is an important effector in apoptosis. Here, we identified a second eIF3f phosphorylation site (Thr119) by CDK11(p46) during apoptosis. We demonstrated that eIF3f is directly phosphorylated by CDK11(p46) in vivo. Phosphorylation of eIF3f plays an important role in regulating its function in translation and apoptosis. Phosphorylation of eIF3f enhances the association of eIF3f with the core eIF3 subunits during apoptosis. Our data suggested that eIF3f may inhibit translation by increasing the binding to the eIF3 complex during apoptosis.
    FEBS letters 03/2009; 583(6):971-7. DOI:10.1016/j.febslet.2009.02.028 · 3.34 Impact Factor
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    ABSTRACT: Aberrant regulation of the translation initiation is known to contribute to tumorigenesis. eIF3 plays an important role in translation initiation. eIF3f is the p47 subunit of the eIF3 complex whose function in cancer is not clear. Initial studies from our group indicated that eIF3f expression is decreased in melanoma. Overexpression of eIF3f inhibits translation and induces apoptosis in melanoma cells. The eIF3f gene is located at chromosome region 11p15.4. Loss of 11p15.4 is a common event in many tumors including melanoma. In order to investigate the molecular mechanism of the decreased expression of eIF3f in melanoma, we performed loss of heterozygosity (LOH) analysis in 24 melanoma specimens using three microsatellite markers encompassing the eIF3f gene. We showed that the prevalence of LOH ranged from 75% to 92% in melanoma. We also performed eIF3f gene copy number analysis using quantitative real-time PCR to further confirm the specific allelic loss of the eIF3f gene in melanoma. We demonstrated a statistically significant decrease of the eIF3f gene copy number in melanoma compared with normal tissues with a tumor/normal ratio of 0.52. To further elucidate the somatic genetic alterations, we carried out mutation analysis covering the entire coding region and 5'UTR of the eIF3f gene in melanoma tissues and cell lines. Despite some polymorphisms, we did not find any mutations. Furthermore, immunohistochemistry analysis demonstrated that eIF3f protein expression is decreased in melanoma compared to benign nevi. These data provide new insight into the understanding of the molecular pathogenesis of eIF3f during melanoma tumorigenesis.
    Molecular Carcinogenesis 10/2008; 47(10):806-13. DOI:10.1002/mc.20436 · 4.77 Impact Factor
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    Durga P Cherukuri, Mark A Nelson
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    ABSTRACT: Dietary selenium (Se) supplementation has been shown to be effective against reducing the risk of incidence of different human cancers. Selenium exists in both organic and inorganic forms. Different chemical forms of selenium metabolize differently in vivo, activate distinct molecular mechanisms and exhibit varying degree of anti-carcinogenicity in different cancer types. The effectiveness of a Se compound could also vary depending on the genetic background of the tumor cells. Therefore, understanding the molecular mechanism(s) by which different Se compounds exert their anti-tumorigenic effects is necessary for their use in cancer chemoprevention.
    Cancer biology & therapy 05/2008; 7(5):697-8. DOI:10.4161/cbt.7.5.6088 · 3.63 Impact Factor
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    ABSTRACT: Aberrant regulation of the translation initiation is known to contribute to tumorigenesis. eIF3 plays an important role in translation initiation. eIF3f is the p47 subunit of the eIF3 complex whose function in cancer is not clear. Initial studies from our group indicated that eIF3f expression is decreased in pancreatic cancer. Overexpression of eIF3f induces apoptosis in pancreatic cancer cells. The eIF3f gene is located at chromosome band region 11p15.4. Loss of 11p15.4 is a common event in many tumors including pancreatic cancer. In order to investigate the molecular mechanism of the decreased expression of eIF3f in pancreatic cancer, we performed loss of heterozygosity (LOH) analysis in 32 pancreatic cancer specimens using three microsatellite markers encompassing the eIF3f gene. We showed that the prevalence of LOH ranged from 71% to 93%. We also performed eIF3f gene copy number analysis using quantitative real time PCR to further confirm the specific allelic loss of eIF3f gene in pancreatic cancer. We demonstrated a statistically significant decrease of eIF3f gene copy number in pancreatic tumors compared with normal tissues with a tumor/normal ratio of 0.24. Furthermore, RNA in situ hybridization and tissue microarray immunohistochemistry analysis demonstrated that eIF3f expression is significantly decreased in human pancreatic adenocarcinoma tissues compared to normal pancreatic tissues. These data provides new insight into the understanding of the molecular pathogenesis of eIF3f during pancreatic tumorigenesis.
    Molecular Carcinogenesis 03/2008; 47(3):235-44. DOI:10.1002/mc.20379 · 4.77 Impact Factor
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    ABSTRACT: Given the poor survival rate and efficacy of current therapy for esophageal adenocarcinoma (EAC), there is a need to identify and develop new therapeutic targets for treatment. Microarray analysis (Affymetrix U133A GeneChips, Robust Multi-Chip Analysis) was used to expression profile 11 normal squamous and 18 Barrett's esophagus biopsies, 7 surgically resected EACs and 3 EAC cell lines. Two hundred transcripts representing potential therapeutic targets were identified using the following criteria: significant overexpression in EAC by analysis of variance (p = 0.05, Benjamini Hochberg false discovery rate); 3-fold increase in EAC relative to normal and Barrett's esophagus and expression in at least 2 of the 3 EAC cell lines. From the list of potential targets we selected TNFRSF12A/Fn14/TWEAK receptor, a tumor necrosis factor super-family receptor, for further validation based on its reported role in tumor cell survival and potential as a target for therapy. Fn14 protein expression was confirmed in SEG-1 and BIC-1 cell lines, but Fn14 was not found to affect tumor cell survival after exposure to chemotherapeutics as expected. Instead, a novel role in EAC was discovered in transwell assays, in which modulating Fn14 expression affected tumor cell invasion. Fn14's potential as a therapeutic target was further supported by immunohistochemistry on a tissue microarray of patient samples that showed that Fn14 protein expression increased with disease progression in EAC.
    International Journal of Cancer 11/2007; 121(10):2132-9. DOI:10.1002/ijc.22898 · 5.01 Impact Factor
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    ABSTRACT: Accumulating evidence indicates that elevated levels of prostaglandin E(2) (PGE(2)) can increase intestinal epithelial cell proliferation, and thus play a role in colorectal tumorigenesis. PGE(2) exerts its effects through four G-protein-coupled PGE receptor (EP) subtypes, named the EP1, EP2, EP3, and EP4. Increased phosphorylation of extracellular regulated kinases (ERK1/2) is required for PGE(2) to stimulate cell proliferation of human colon cancer cells. However, the EP receptor(s) that are involved in this process remain unknown. We provide evidence that L-161,982, a selective EP4 receptor antagonist, completely blocks PGE(2)-induced ERK phosphorylation and cell proliferation of HCA-7 cells. In order to identify downstream target genes of ERK1/2 signaling, we found that PGE(2) induces expression of early growth response gene-1 (EGR-1) downstream of ERK1/2 and regulates its expression at the level of transcription. PGE(2) treatment induces phosphorylation of cyclic AMP response element binding protein (CREB) at Ser133 residue and CRE-mediated luciferase activity in HCA-7 cells. Studies with dominant-negative CREB mutant (ACREB) provide clear evidence for the involvement of CREB in PGE(2) driven egr-1 transcription in HCA-7 cells. In conclusion, this study reveals that egr-1 is a target gene of PGE(2) in HCA-7 cells and is regulated via the newly identified EP4/ERK/CREB pathway. Finally our results support the notion that antagonizing EP4 receptors may provide a novel therapeutic approach to the treatment of colon cancer.
    Experimental Cell Research 09/2007; 313(14):2969-79. DOI:10.1016/j.yexcr.2007.06.004 · 3.37 Impact Factor
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    ABSTRACT: The Cdc2L gene encodes for the cyclin-dependent kinase 11 (CDK11) protein. Loss of one allele of Cdc2L and reduced CDK11 expression has been observed in several cancers, implicating its association with carcinogenesis. To directly investigate the role of CDK11 in carcinogenesis, we first generated cdc2l haploinsufficient mice by gene trap technology and then studied the susceptibility of these gene-trapped (cdc2l(GT)) mice to chemical-mediated skin carcinogenesis in the 7,12-dimethylbenz[a]anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA)-induced two-stage skin carcinogenesis model. Wild-type and cdc2l(GT) mice were subjected to a single topical application of initiation by DMBA and promotion twice a week for 19 weeks with TPA. At 19 weeks, 70% of the cdc2l(GT) mice and 60% of the cdc2l+/+ mice developed benign papillomas. However, there was an overall 3-fold increase in the average number of tumors per mouse observed in cdc2l(GT) mice as compared with cdc2l+/+ mice. There was also an increased frequency of larger papillomas in cdc2l(GT) mice. By using the polymerase chain reaction-restriction fragment length polymorphism assay, we found A to T transversion mutations at the 61st codon of H-ras gene in the papilloma tissue of both cdc2l(GT) mice and cdc2l+/+ mice. Ki-67 staining revealed increased proliferation in the papillomas of cdc2l(GT) (77.75%) as compared with cdc2l+/+ (30.84%) tumors. These studies are the first to show that loss of one allele of cdc2l gene, encoding CDK11, facilitates DMBA/TPA-induced skin carcinogenesis in vivo.
    Carcinogenesis 09/2007; 28(9):2028-35. DOI:10.1093/carcin/bgm066 · 5.27 Impact Factor

Publication Stats

1k Citations
257.51 Total Impact Points


  • 1992–2013
    • The University of Arizona
      • • Department of Pathology
      • • Department of Pharmacology
      • • College of Medicine
      • • Department of Pharmacology and Toxicology
      • • Department of Radiation Oncology
      Tucson, Arizona, United States
  • 1999–2010
    • Arizona Research Center
      Phoenix, Arizona, United States
    • St. Jude Children's Research Hospital
      • Department of Tumor Cell Biology
      Memphis, Tennessee, United States
  • 2003
    • Penn State Hershey Medical Center and Penn State College of Medicine
      • Pharmacology
      Hershey, PA, United States
    • University of California, Davis
      • Area of Chemical Biology
      Davis, California, United States