About Dr. Lozano
Guillermina (Gigi) Lozano is a geneticist recognized for her studies of the p53 tumor suppressor pathway, from characterizing p53 as a transcriptional activator to characterizing the physiological importance of Mdm2 and Mdm4 proteins as inhibitors of p53, and the consequences of p53 mutations on tumor development. Lozano was born in East Chicago, Indiana before moving to Texas with her family where she completed undergraduate studies in Biology and Mathematics at Pan American University (now known as the University of Texas Rio Grande Valley). She completed graduate studies at Rutgers University and the University of Medicine and Dentistry of New Jersey, and a post doctoral fellowship at Princeton University. She was hired as an Instructor at The University of Texas MD Anderson Cancer Center in 1987 and rose through the ranks to her current position as chair of the department of Genetics. She was elected a Fellow of the American Association for the Advancement of Science. She received the Minorities in Cancer Research Jane Cooke Wright Lectureship, and Women in Cancer Research Charlotte Friend Lectureship awards both from the American Association for Cancer Research. Dr. Lozano is also the recipient of distinguished alumni awards from both her undergraduate and graduate alma maters. She is a member of the National Academy of Sciences and the National Academy of Medicine.
Professor and Chair, Department of Genetics, Division of Basic Science Research, The University of Texas MD Anderson Cancer Center, Houston, TX
Professor, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX
p53 pathway tumor suppressors mouse models
Mutation of the p53 gene is a critical event in the elaboration of many tumors of diverse origin. The p53 protein is activated in response to DNA damage, serving as a checkpoint in the elimination or repair of cells with damaged DNA. Alterations in components of the p53 pathway, such as amplification of the Mdm2 gene, which encodes a p53 inhibitor, also contribute to tumorigenesis. The overall goal of my laboratory is to understand the signals that regulate the p53 pathway and the consequences of expressing wild-type or mutant p53. Toward this goal, we are generating mouse models to address the importance of various p53 mutations in tumor development in vivo. The first mice generated were those expressing a common p53 mutation identified in human cancers. Mice expressing the p53R172H mutant develop osteosarcomas and carcinomas that metastasized at very high frequency. This study also indicates that mutant p53 is inherently unstable in vivo suggesting that other genetic alterations in tumor cells stabilize p53. We have generated mice with another interesting mutant that distinguishes the ability of p53 to induce apoptosis or cell cycle arrest. The p53R172P mutant cannot transactivate genes that induce apoptosis yet retains the ability to induce the p21 gene involved in cell cycle arrest. Importantly, this mutant shows delayed tumorigenesis suggesting that p53 activities other than apoptosis are also critical for tumor suppression. Tumors that arise in these mice are also genomically stable suggesting that the p53R172P mutant transactivates genes involved in maintaining a stable genome. Other mouse models generated probe the importance of components of the p53 pathway. For example, loss of Mdm2 or Mdm4 (genes that encode p53 inhibitors) results in embryonic lethality that is completely rescued by concomitant loss of p53. These studies indicate the importance of regulating p53 activity. We have made conditional loss-of-function allele of Mdm2 and Mdm4 to access the role of p53 in different cell types as a function of proliferation. Finally, we are studying individuals with Li-Fraumeni Syndrome, most of whom inherit a p53-missense mutation. Various factors including, modifiers of the p53 pathway alter the onset of tumorigenesis in these individuals.
|1986||Rutgers University and the University of Medicine and Dentistry of New Jersey, Piscataway, NJ, USA, PHD, Biochemistry|
|1979||Pan American University, Edinburg, TX, USA, BS, Biology/Mathematics|
|1985-1987||Postgraduate Training, Molecular Biology, Princeton University, Princeton, NJ|
|2017||Member, National Academy of Sciences|
|2014||Member, National Academy of Medicine (formerly Institute of Medicine)|
- Alexandrova EM, Yallowitz AR, Li D, Xu S, Schulz R, Proia DA, Lozano G, Dobbelstein M, Moll UM. Improving survival by exploiting tumour dependence on stabilized mutant p53 for treatment. Nature 523(7560):352-6, 2015. e-Pub 2015. PMID: 26009011.
- Jackson JG, Pant V, Li Q, Chang LL, Quintás-Cardama A, Garza D, Tavana O, Yang P, Manshouri T, Li Y, El-Naggar AK, Lozano G. p53 mediated senescence impairs the apoptotic response to chemotherapy and clinical outcome in breast cancer. Cancer Cell 21(6):793-806, 2012. PMID: 22698404.
- Pant V, Xiong S, Iwakuma T, Quintás-Cardama A, Lozano G. Heterodimerization of Mdm2 and Mdm4 is critical for regulating p53 activity during embryogenesis but dispensable for p53 and Mdm2 stability. Proc Natl Acad Sci USA 108(29):1995-2000, 2011. e-Pub 2011. PMID: 21730132.
- Wang Y, Suh YA, Fuller MY, Jackson JG, Xiong S, Terzian T, Quintas-Cardama A, Bankson JA, El-Naggar AK, Lozano G. Restoring expression of wild-type p53 suppresses tumor growth but does not cause tumor regression in mice with a p53 missense mutation. J Clin Invest 121(3):893-904, 2011.
- Post SM, Quintas-Cardama A, Pant V, Iwakuma T, Hamir A, Jackson JG, Maccio DR, Bond GL, Johnson DG, Levine AJ, Lozano G. A high-frequency regulatory polymorphism in the p53 pathway accelerates tumor development. Cancer Cell 18(3):220-230, 2010.
- Xiong S, Pant V, Suh YA, Van Pelt CS, Wang Y, Valentin-Vega YA, Post SM, Lozano G. Spontaneous tumorigenesis in mice overexpressing the p53-negative regulator Mdm4. Cancer Res 70(18):7148-7154, 2010. PMID: 20736370.
- Terzian T, Suh YA, Iwakuma T, Post SM, Neumann M, Lang GA, Van Pelt CS, Lozano G. The inherent instability of mutant p53 is alleviated by Mdm2 or p16INK4a loss. Genes Dev 22(10):1337-1344, 2008.
- Lang GA, Iwakuma T, Suh YA, Liu G, Rao VA, Parant JM, Valentin-Vega YA, Terzian T, Caldwell LC, Strong LC, El-Naggar AK, Lozano G. Gain-of-function of a p53 hot spot mutation in a mouse model of Li-Fraumeni syndrome. Cell 119(6):861-872, 2004.
- Liu G, Parant JM, Lang G, Chau P, Chavez-Reyes A, El-Naggar AK, Multani A, Chang S, Lozano G. Chromosome stability, in the absence of apoptosis, is critical for suppression of tumorigenesis in Trp53 mutant mice. Nat Genet 36(1):63-68, 2004. e-Pub 2003. PMID: 14702042.
- Montes de Oca Luna R, Wagner DS, Lozano G. Rescue of early embryonic lethality in mdm2-deficient mice by deletion of p53. Nature 378(6553):203-206, 1995. PMID: 7477326.