- PhD, University of North Carolina
- Associate Professor, Microbiology, Immunology, and Cancer Biology
Signal transduction in cancer cells
My primary research interest has focused on the mechanistic underpinnings of how signal transduction pathways cross-talk and contribute to cancer progression, with specific emphasis on identifying and understanding the nodes within the cell signaling network that cause cancer progression and resistance to therapy. My research to date has lead to the specific hypothesis that prostate cancer progression to castration-resistance is frequently driven by changes in CHK2 signaling that regulate AR activity, facilitate cell proliferation, and minimize hormone dependence. These studies will uncover new information on how kinases regulate the AR. We propose a CHK2-CDC25-CDK1-AR signaling pathway which links CHK2, AR, and prostate cancer proliferation. This has particular relevance since several CHK inhibitors and second-generation CDK1 inhibitors are now in patient trials. Moreover, the CHK2 signaling pathway is activated in response to DNA damage such as that generated by radiation therapy. Thus, delineating how CHK2 impinges upon AR activity will provide important insights into how to more effectively combine radiation therapy with androgen blockade. The research will reveal mechanistic information critical for the rational application of existing and novel therapies for CRPC.
The AR in prostate cancer
The Androgen Receptor (AR) is essential for the growth and survival of castration-resistant prostate cancer (CRPC). The recent FDA approval of the CYP17 inhibitor, abiraterone, and the novel anti-androgen, MDV3100, emphasize the clinical importance of targeting AR function in CRPC. Despite the justifiable excitement over these new therapies, the response to anti-androgens does not endure; the AR becomes reactivated with lethal consequences. It is essential to understand the mechanisms leading to AR reactivation, as they present targets for developing the combination therapies that will be required for effective deployment of next-gen anti-androgens. My research studies a mechanism of resistance to anti-androgens that represents a prime opportunity for therapeutic co-targeting: AR regulation by kinase signaling.
In spite of much research, understanding of the mechanisms by which AR functions as a driver of CRPC progression is poorly understood, and the tools available to therapeutically target this driver are one-dimensional. My work will expand the current view of AR biology from a static snap shot of AR as an androgen regulated transcription factor, to a dynamic one that integrates the complexity of cycling cells with regulation by signal transduction pathways. My research integrates preclinical in vivo xenograft models and patient samples with investigations into the molecular details of cell cycle signal transduction regulation of the AR.
Two separate lines of investigation in my laboratory have remarkably converged to generate the hypothesis above. First, we recently discovered through a kinome wide RNAi screen that CHK2 knockdown significantly increases prostate cancer cell proliferation. This observation is clinically relevant since CHK2 inactivating mutations arise in over 10% of prostate cancer patients and CHK2 expression decreases as prostate cancer progresses to a castration-resistant disease. These data strongly suggest that CHK2 functions as a negative regulator or tumor suppressor in prostate cancer. We have determined that CHK2 knockdown increases AR transcriptional activity, providing evidence that CHK2 effects prostate cancer cell proliferation, at least in part, through the AR. Second, we found that AR S308 phosphorylation is catalyzed by CDK1, a downstream effector of CHK2. This phosphorylation regulates AR localization and occurs in G2/M, where a unique subset of androgen-dependent genes is expressed. These findings have significant clinical implications since CDK1 activity is elevated in CRPC. My research is currently focused on determining the mechanism of CHK2 regulation of AR activity and CRPC cell proliferation.
My research will determine the role of CDC25 and CDK1 in CHK2 regulation of AR activity and prostate cancer cell proliferation. We are studying the functional interconnectedness of each of the steps in the CHK2-CDC25-CDK1-AR signaling pathway to determine the mechanism of CHK2 regulation of AR activity and prostate cancer cell growth as well as determine the point or points of greatest therapeutic susceptibility. We are using prostate tumor clinical specimens to establish links between clinicopathologic features and CHK2, CDC25, CDK1, and AR expression and activation using human tissue microarrays. Using knockdown of CHK2 we are determining if CHK2 drives castration resistance in androgen dependent LNCaP cells, if overexpression of CHK2 in castration resistant C4-2 cells restores androgen dependence, and if CHK2 biological effects are dependent on CDC25 or CDK1. Moreover, we will determine the individual and cooperative roles of CHK2, CDC25, and CDK1 in promoting in vivo prostate cancer tumorigenesis using xenografts in immunodeficient mice.
We are exploring the molecular mechanisms of how the CHK2 signaling effector CDK1 regulates AR function through phosphorylation of AR S308 and the functional impact of AR S308 phosphorylation in facilitating cell proliferation. Our data suggest that CDK1 phosphorylation of the AR on S308 regulates AR localization and correlates with changes in AR transcriptional activity during G2/M. Our studies are determining if the CHK2 effects on cell proliferation and in vivo xenograft growth are mediated by AR S308 phosphorylation by CDK1. We are evaluating the effect of AR S308 phosphorylation in regulating AR localization and AR levels in mitosis. Finally, we are determining the role of AR S308 phosphorylation in regulating the G2/M specific subset of androgen-regulated genes.
We are establishing the therapeutic potential of targeting CDK1 in combination with androgen blockade and radiation therapy using in vivo models. Our goal is to understand the regulatory pathway linking CHK2 to AR function, and identify the best approach for applying these insights to the clinical setting. Our preliminary findings on CHK2-CDC25-CDK1-AR signaling suggest that inhibiting CDK1 in conjunction with radiation and androgen deprivation provides an additive if not synergistic therapeutic response. In these studies we are evaluating how DNA damaging agents used to treat prostate cancer alter CHK2 regulation of AR activity and prostate cancer cell proliferation. Ultimately we will determine if androgen blockade cooperates with CHK2 inhibition and radiation therapy to inhibit in vivo prostate cancer xenograft growth.
We are performing an in-depth, quantitative, experimental and computational interrogation of CHK2-CDC25-CDK1-AR signaling to evaluate potential targets for novel and more effective therapies against this challenging and often fatal disease. The robust precedent for kinases as therapeutic targets has hastened the development of therapies targeting this pathway for prostate cancer; several CHK2 inhibitors and second-generation CDK1 inhibitors are now in clinical trials in other cancers. We believe that the thorough mechanistic evaluation of these potential kinase targets will pave the way for developing novel and more effective treatments for castration-resistant metastatic prostate cancer.
- Axelrod M, Gordon V, Mendez R, Leimgruber S, Conaway M, Sharlow E, Jameson M, Gioeli D, Weber M. p70S6 kinase is a critical node that integrates HER-family and PI3 kinase signaling networks. Cellular signalling. 2014. PMID: 24662264 | PMCID: PMC4091927
- Axelrod M, Gordon V, Conaway M, Tarcsafalvi A, Neitzke D, Gioeli D, Weber M. Combinatorial drug screening identifies compensatory pathway interactions and adaptive resistance mechanisms. Oncotarget. 2013;4(4): 622-35. PMID: 23599172 | PMCID: PMC3720609
- Roller D, Axelrod M, Capaldo B, Jensen K, Mackey A, Weber M, Gioeli D. Synthetic lethal screening with small molecule inhibitors provides a pathway to rational combination therapies for melanoma. Molecular cancer therapeutics. 2012. PMID: 22962324 | PMCID: NIHMS405900
- Whitworth H, Bhadel S, Ivey M, Conaway M, Spencer A, Hernan R, Holemon H, Gioeli D. Identification of kinases regulating prostate cancer cell growth using an RNAi phenotypic screen. PloS one. 2012;7(6): e38950. PMID: 22761715 | PMCID: PMC3384611
- Gioeli D, Wunderlich W, Sebolt-Leopold J, Bekiranov S, Wulfkuhle J, Petricoin E, Conaway M, Weber M. Compensatory pathways induced by MEK inhibition are effective drug targets for combination therapy against castration-resistant prostate cancer. Molecular cancer therapeutics. 2011;10(9): 1581-90. PMID: 21712477 | PMCID: PMC3315368
- Gordon V, Bhadel S, Wunderlich W, Zhang J, Ficarro S, Mollah S, Shabanowitz J, Hunt D, Xenarios I, Hahn W, Conaway M, Carey M, Gioeli D. CDK9 regulates AR promoter selectivity and cell growth through serine 81 phosphorylation. Molecular endocrinology (Baltimore, Md.). 2010;24(12): 2267-80. PMID: 20980437 | PMCID: PMC2999477
- Kelley J, Talley A, Spencer A, Gioeli D, Paschal B. Karyopherin alpha7 (KPNA7), a divergent member of the importin alpha family of nuclear import receptors. BMC cell biology. 2010;11 63. PMID: 20701745 | PMCID: PMC2929220
- Ni L, Yang C, Gioeli D, Frierson H, Toft D, Paschal B. FKBP51 promotes assembly of the Hsp90 chaperone complex and regulates androgen receptor signaling in prostate cancer cells. Molecular and cellular biology. 2010;30(5): 1243-53. PMID: 20048054 | PMCID: PMC2820886
- Tilghman R, Cowan C, Mih J, Koryakina Y, Gioeli D, Slack-Davis J, Blackman B, Tschumperlin D, Parsons J. Matrix rigidity regulates cancer cell growth and cellular phenotype. PloS one. 2010;5(9): e12905. PMID: 20886123 | PMCID: PMC2944843
- DaSilva J, Gioeli D, Weber M, Parsons S. The neuroendocrine-derived peptide parathyroid hormone-related protein promotes prostate cancer cell growth by stabilizing the androgen receptor. Cancer research. 2009;69(18): 7402-11. PMID: 19706771 | PMCID: PMC2803023
- Wu Z, Gioeli D, Conaway M, Weber M, Theodorescu D. Restoration of PTEN expression alters the sensitivity of prostate cancer cells to EGFR inhibitors. The Prostate. 2008;68(9): 935-44. PMID: 18386291 | PMCID: PMC2748221
- Bigler D, Gioeli D, Conaway M, Weber M, Theodorescu D. Rap2 regulates androgen sensitivity in human prostate cancer cells. The Prostate. 2007;67(14): 1590-9. PMID: 17918750
- Kesler C, Gioeli D, Conaway M, Weber M, Paschal B. Subcellular localization modulates activation function 1 domain phosphorylation in the androgen receptor. Molecular endocrinology (Baltimore, Md.). 2007;21(9): 2071-84. PMID: 17579212
- Wu Z, Conaway M, Gioeli D, Weber M, Theodorescu D. Conditional expression of PTEN alters the androgen responsiveness of prostate cancer cells. The Prostate. 2006;66(10): 1114-23. PMID: 16637073
- Gioeli D, Black B, Gordon V, Spencer A, Kesler C, Eblen S, Paschal B, Weber M. Stress kinase signaling regulates androgen receptor phosphorylation, transcription, and localization. Molecular endocrinology (Baltimore, Md.). 2005;20(3): 503-15. PMID: 16282370
- Bakin R, Gioeli D, Bissonette E, Weber M. Attenuation of Ras signaling restores androgen sensitivity to hormone-refractory C4-2 prostate cancer cells. Cancer research. 2003;63(8): 1975-80. PMID: 12702591
- Gioeli D, Ficarro S, Kwiek J, Aaronson D, Hancock M, Catling A, White F, Christian R, Settlage R, Shabanowitz J, Hunt D, Weber M. Androgen receptor phosphorylation. Regulation and identification of the phosphorylation sites. The Journal of biological chemistry. 2002;277(32): 29304-14. PMID: 12015328