Sir Peter MacCallum Department of Oncology - Research Publications

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    MDM4 is a rational target for treating breast cancers with mutant p53
    Miranda, PJ ; Buckley, D ; Raghu, D ; Pang, J-MB ; Takano, EA ; Vijayakumaran, R ; Teunisse, AFAS ; Posner, A ; Procter, T ; Herold, MJ ; Gamell, C ; Marine, J-C ; Fox, SB ; Jochemsen, A ; Haupt, S ; Haupt, Y (WILEY, 2017-04)
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    An analysis of a multiple biomarker panel to better predict prostate cancer metastasis after radical prostatectomy
    Zhang, AY ; Chiam, K ; Haupt, Y ; Fox, S ; Birch, S ; Tilley, W ; Butler, LM ; Knudsen, K ; Comstock, C ; Rasiah, K ; Grogan, J ; Mahon, KL ; Bianco-Miotto, T ; Ricciardelli, C ; Bohm, M ; Henshall, S ; Delprado, W ; Stricker, P ; Horvath, LG ; Kench, JG (WILEY, 2019-03-01)
    A plethora of individual candidate biomarkers for predicting biochemical relapse in localized prostate cancer (PCa) have been proposed. Combined biomarkers may improve prognostication, and ensuring validation against more clinically relevant endpoints are required. The Australian PCa Research Centre NSW has contributed to numerous studies of molecular biomarkers associated with biochemical relapse. In the current study, these biomarkers were re-analyzed for biochemical relapse, metastatic relapse and PCa death with extended follow-up. Biomarkers of significance were then used to develop a combined prognostic model for clinical outcomes and validated in a large independent cohort. The discovery cohort (n = 324) was based on 12 biomarkers with a median follow-up of 16 years. Seven biomarkers were significantly associated with biochemical relapse. Three biomarkers were associated with metastases: AZGP1, Ki67 and PML. Only AZGP1 was associated with PCa death. In their individual and combinational forms, AZGP1 and Ki67 as a dual BM signature was the most robust predictor of metastatic relapse (AUC 0.762). The AZPG1 and Ki67 signature was validated in an independent cohort of 347 PCa patients. The dual BM signature of AZGP1 and Ki67 predicted metastasis in the univariable (HR 7.2, 95% CI, 1.6-32; p = 0.01) and multivariable analysis (HR 5.4, 95% CI, 1.2-25; p = 0.03). The dual biomarker signature marginally improved risk prediction compared to AZGP1 alone (AUC 0.758 versus 0.738, p < 0.001). Our findings indicate that biochemical relapse is not an adequate surrogate for metastasis or PCa death. The dual biomarker signature of AZGP1 and Ki67 offers a small benefit in predicting metastasis over AZGP1 alone.
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    Targeting Mdmx to treat breast cancers with wild-type p53
    Haupt, S ; Buckley, D ; Pang, J-MB ; Panimaya, J ; Paul, PJ ; Gamell, C ; Takano, EA ; Lee, YY ; Hiddingh, S ; Rogers, T-M ; Teunisse, AFAS ; Herold, MJ ; Marine, J-C ; Fox, SB ; Jochemsen, A ; Haupt, Y (NATURE PUBLISHING GROUP, 2015-07)
    The function of the tumor suppressor p53 is universally compromised in cancers. It is the most frequently mutated gene in human cancers (reviewed). In cases where p53 is not mutated, alternative regulatory pathways inactivate its tumor suppressive functions. This is primarily achieved through elevation in the expression of the key inhibitors of p53: Mdm2 or Mdmx (also called Mdm4) (reviewed). In breast cancer (BrCa), the frequency of p53 mutations varies markedly between the different subtypes, with basal-like BrCas bearing a high frequency of p53 mutations, whereas luminal BrCas generally express wild-type (wt) p53. Here we show that Mdmx is unexpectedly highly expressed in normal breast epithelial cells and its expression is further elevated in most luminal BrCas, whereas p53 expression is generally low, consistent with wt p53 status. Inducible knockdown (KD) of Mdmx in luminal BrCa MCF-7 cells impedes the growth of these cells in culture, in a p53-dependent manner. Importantly, KD of Mdmx in orthotopic xenograft transplants resulted in growth inhibition associated with prolonged survival, both in a preventative model and also in a treatment model. Growth impediment in response to Mdmx KD was associated with cellular senescence. The growth inhibitory capacity of Mdmx KD was recapitulated in an additional luminal BrCa cell line MPE600, which expresses wt p53. Further, the growth inhibitory capacity of Mdmx KD was also demonstrated in the wt p53 basal-like cell line SKBR7 line. These results identify Mdmx growth dependency in wt p53 expressing BrCas, across a range of subtypes. Based on our findings, we propose that Mdmx targeting is an attractive strategy for treating BrCas harboring wt p53.
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    E6AP promotes prostate cancer by reducing p27 expression
    Raghu, D ; Paul, PJ ; Gulati, T ; Deb, S ; Khoo, C ; Russo, A ; Gallo, E ; Blandino, G ; Chan, A-L ; Takano, E ; Sandhu, SK ; Fox, SB ; Williams, S ; Haupt, S ; Gamell, C ; Haupt, Y (IMPACT JOURNALS LLC, 2017-06-27)
    Prostate cancer (PC) is the most common cancer in men. Elevated levels of E3 ligase, E6-Associated Protein (E6AP) were previously linked to PC, consistent with increased protein expression in a subset of PC patients. In cancers, irregular E3 ligase activity drives proteasomal degradation of tumor suppressor proteins. Accordingly, E3 ligase inhibitors define a rational therapy to restore tumor suppression. The relevant tumor suppressors targeted by E6AP in PC are yet to be fully identified. In this study we show that p27, a key cell cycle regulator, is a target of E6AP in PC. Down regulation of E6AP increases p27 expression and enhances its nuclear accumulation in PC. We demonstrate that E6AP regulates p27 expression by inhibiting its transcription in an E2F1-dependent manner. Concomitant knockdown of E6AP and p27 partially restores PC cell growth, supporting the contribution of p27 to the overall effect of E6AP on prostate tumorigenesis. Overall, we unravelled the E6AP-p27 axis as a new promoter of PC, exposing an attractive target for therapy through the restoration of tumor suppression.
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    E6AP Promotes a Metastatic Phenotype in Prostate Cancer
    Gamell, C ; Bandilovska, I ; Gulati, T ; Kogan, A ; Lim, SC ; Kovacevic, Z ; Takano, EA ; Timpone, C ; Agupitan, AD ; Litchfield, C ; Blandino, G ; Horvath, LG ; Fox, SB ; Williams, SG ; Russo, A ; Gallo, E ; Paul, PJ ; Mitchell, C ; Sandhu, S ; Keam, SP ; Haupt, S ; Richardson, DR ; Haupt, Y (CELL PRESS, 2019-12-20)
    Although primary prostate cancer is largely curable, progression to metastatic disease is associated with very poor prognosis. E6AP is an E3 ubiquitin ligase and a transcriptional co-factor involved in normal prostate development. E6AP drives prostate cancer when overexpressed. Our study exposed a role for E6AP in the promotion of metastatic phenotype in prostate cells. We revealed that elevated levels of E6AP in primary prostate cancer correlate with regional metastasis and demonstrated that E6AP promotes acquisition of mesenchymal features, migration potential, and ability for anchorage-independent growth. We identified the metastasis suppressor NDRG1 as a target of E6AP and showed it is key in E6AP induction of mesenchymal phenotype. We showed that treatment of prostate cancer cells with pharmacological agents upregulated NDRG1 expression suppressed E6AP-induced cell migration. We propose that the E6AP-NDRG1 axis is an attractive therapeutic target for the treatment of E6AP-driven metastatic prostate cancer.
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    Restoration of tumor suppression in prostate cancer by targeting the E3 ligase E6AP
    Paul, PJ ; Raghu, D ; Chan, A-L ; Gulati, T ; Lambeth, L ; Takano, E ; Herold, MJ ; Hagekyriakou, J ; Vessella, RL ; Fedele, C ; Shackleton, M ; Williams, ED ; Fox, S ; Williams, S ; Haupt, S ; Gamell, C ; Haupt, Y (NATURE PUBLISHING GROUP, 2016-12-01)
    Restoration of tumor suppression is an attractive onco-therapeutic approach. It is particularly relevant when a tumor suppressor is excessively degraded by an overactive oncogenic E3 ligase. We previously discovered that the E6-associated protein (E6AP; as classified in the human papilloma virus context) is an E3 ligase that has an important role in the cellular stress response, and it directly targets the tumor-suppressor promyelocytic leukemia protein (PML) for proteasomal degradation. In this study, we have examined the role of the E6AP-PML axis in prostate cancer (PC). We show that knockdown (KD) of E6AP expression attenuates growth of PC cell lines in vitro. We validated this finding in vivo using cell line xenografts, patient-derived xenografts and mouse genetics. We found that KD of E6AP attenuates cancer cell growth by promoting cellular senescence in vivo, which correlates with restoration of tumor suppression by PML. In addition, we show that KD of E6AP sensitizes cells to radiation-induced death. Overall, our findings demonstrate a role for E6AP in the promotion of PC and support E6AP targeting as a novel approach for PC treatment, either alone or in combination with radiation.
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    Loss of PML cooperates with mutant p53 to drive more aggressive cancers in a gender-dependent manner
    Haupt, S ; Mitchell, C ; Corneille, V ; Shortt, J ; Fox, S ; Pandolfi, PP ; Castillo-Martin, M ; Bonal, DM ; Cordon-Cardo, C ; Lozano, G ; Haupt, Y (TAYLOR & FRANCIS INC, 2013-06-01)
    UNLABELLED: p53 mutations and downregulation of promyelocytic leukemia (PML) are common genetic alterations in human cancers. In healthy cells these two key tumor suppressors exist in a positive regulatory loop, promoting cell death and cellular senescence. However, the influence of their interplay on tumorigenesis has not been explored directly in vivo. The contribution of PML to mutant p53 driven cancer was evaluated in a mouse model harboring a p53 mutation (p53 (wild-type/R172H) ) that recapitulates a frequent p53 mutation (p53 (R175H) ) in human sporadic and Li-Fraumeni cancers. These mice with PML displayed perturbation of the hematopoietic compartment, manifested either as lymphoma or extramedullary hematopoiesis (EMH). EMH was associated with peripheral blood leucocytosis and macrocytic anemia, suggestive of myeloproliferative- myelodysplastic overlap. In contrast, a complete loss of PML from these mice resulted in a marked alteration in tumor profile. While the incidence of lymphomas was unaltered, EMH was not detected and the majority of mice succumbed to sarcomas. Further, males lacking PML exhibited a high incidence of soft tissue sarcomas and reduced survival, while females largely developed osteosarcomas, without impact on survival. Together, these findings demonstrate that PML is an important tumor suppressor dictating disease development in a pertinent mouse model of human cancer.   KEY POINTS: (1) A mutant p53 allele disrupts hematopoiesis in mice, by promoting lymphomas and myeloproliferative / myelodysplastic overlap. (2) Coincidental p53 allele mutation and PML loss shifts the tumor profile toward sarcoma formation, which is paralleled in human leiomyosarcomas (indicated by immunohistochemistry; IHC).
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    E6AP ubiquitin ligase regulates PML-induced senescence in Myc-driven lymphomagenesis
    Wolyniec, K ; Shortt, J ; de Stanchina, E ; Levav-Cohen, Y ; Alsheich-Bartok, O ; Louria-Hayon, I ; Corneille, V ; Kumar, B ; Woods, SJ ; Opat, S ; Johnstone, RW ; Scott, CL ; Segal, D ; Pandolfi, PP ; Fox, S ; Strasser, A ; Jiang, Y-H ; Lowe, SW ; Haupt, S ; Haupt, Y (AMER SOC HEMATOLOGY, 2012-07-26)
    Neoplastic transformation requires the elimination of key tumor suppressors, which may result from E3 ligase-mediated proteasomal degradation. We previously demonstrated a key role for the E3 ubiquitin ligase E6AP in the regulation of promyelocytic leukemia protein (PML) stability and formation of PML nuclear bodies. Here, we report the involvement of the E6AP-PML axis in B-cell lymphoma development. A partial loss of E6AP attenuated Myc-induced B-cell lymphomagenesis. This tumor suppressive action was achieved by the induction of cellular senescence. B-cell lymphomas deficient for E6AP expressed elevated levels of PML and PML-nuclear bodies with a concomitant increase in markers of cellular senescence, including p21, H3K9me3, and p16. Consistently, PML deficiency accelerated the rate of Myc-induced B-cell lymphomagenesis. Importantly, E6AP expression was elevated in ∼ 60% of human Burkitt lymphomas, and down-regulation of E6AP in B-lymphoma cells restored PML expression with a concurrent induction of cellular senescence in these cells. Our findings demonstrate that E6AP-mediated down-regulation of PML-induced senescence is essential for B-cell lymphoma progression. This provides a molecular explanation for the down-regulation of PML observed in non-Hodgkin lymphomas, thereby suggesting a novel therapeutic approach for restoration of tumor suppression in B-cell lymphoma.