1
|
Gary JM, Simmons JK, Xu J, Zhang S, Peat TJ, Watson N, Gamache BJ, Zhang K, Kovalchuk AL, Michalowski AM, Chen JQ, Thaiwong T, Kiupel M, Gaikwad S, Etienne M, Simpson RM, Dubois W, Testa JR, Mock BA. Hypomorphic mTOR Downregulates CDK6 and Delays Thymic Pre-T LBL Tumorigenesis. Mol Cancer Ther 2020; 19:2221-2232. [PMID: 32747423 DOI: 10.1158/1535-7163.mct-19-0671] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 01/14/2020] [Accepted: 07/13/2020] [Indexed: 11/16/2022]
Abstract
PI3K/AKT/mTOR pathway hyperactivation is frequent in T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/LBL). To model inhibition of mTOR, pre-T-cell lymphoblastic leukemia/lymphoma (pre-T LBL) tumor development was monitored in mice with T lymphocyte-specific, constitutively active AKT (Lck-MyrAkt2) that were either crossed to mTOR knockdown (KD) mice or treated with the mTOR inhibitor everolimus. Lck-MyrAkt2;mTOR KD mice lived significantly longer than Lck-MyrAkt2;mTOR wild-type (WT) mice, although both groups ultimately developed thymic pre-T LBL. An increase in survival was also observed when Lck-MyrAkt2;mTOR WT mice were treated for 8 weeks with everolimus. The transcriptional profiles of WT and KD thymic lymphomas were compared, and Ingenuity Pathway Upstream Regulator Analysis of differentially expressed genes in tumors from mTOR WT versus KD mice identified let-7 and miR-21 as potential regulatory genes. mTOR KD mice had higher levels of let-7a and miR-21 than mTOR WT mice, and rapamycin induced their expression in mTOR WT cells. CDK6 was one of the most downregulated targets of both let-7 and miR21 in mTOR KD tumors. CDK6 overexpression and decreased expression of let-7 in mTOR KD cells rescued a G1 arrest phenotype. Combined mTOR (rapamycin) and CDK4/6 (palbociclib) inhibition decreased tumor size and proliferation in tumor flank transplants, increased survival in an intravenous transplant model of disseminated leukemia compared with single agent treatment, and cooperatively decreased cell viability in human T-ALL/LBL cell lines. Thus, mTOR KD mice provide a model to explore drug combinations synergizing with mTOR inhibitors and can be used to identify downstream targets of inhibition.
Collapse
Affiliation(s)
- Joy M Gary
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland.,Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan
| | - John K Simmons
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland
| | - Jinfei Xu
- Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania
| | - Shuling Zhang
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland
| | - Tyler J Peat
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland
| | - Nicholas Watson
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland
| | - Benjamin J Gamache
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland.,American University, Washington, DC
| | - Ke Zhang
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland
| | | | | | - Jin-Qiu Chen
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland
| | - Tuddow Thaiwong
- Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan
| | - Matti Kiupel
- Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan
| | - Snehal Gaikwad
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland
| | - Maudeline Etienne
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland
| | - R Mark Simpson
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland
| | - Wendy Dubois
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland
| | - Joseph R Testa
- Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
| | - Beverly A Mock
- Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland.
| |
Collapse
|
2
|
Grant SG. Qualitatively and quantitatively similar effects of active and passive maternal tobacco smoke exposure on in utero mutagenesis at the HPRT locus. BMC Pediatr 2005; 5:20. [PMID: 15987524 PMCID: PMC1185547 DOI: 10.1186/1471-2431-5-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Accepted: 06/29/2005] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Induced mutagenesis in utero is likely to have life-long repercussions for the exposed fetus, affecting survival, birth weight and susceptibility to both childhood and adult-onset diseases, such as cancer. In the general population, such exposures are likely to be a consequence of the lifestyle choices of the parents, with exposure to tobacco smoke one of the most pervasive and easily documented. Previous studies attempting to establish a direct link between active smoking and levels of somatic mutation have largely discounted the effects of passive or secondary exposure, and have produced contradictory results. METHODS Data from three studies of possible smoking effects on in utero mutagenesis at the HPRT locus were compiled and reanalyzed, alone and in combination. Where possible, passive exposure to environmental tobacco smoke was considered as a separate category of exposure, rather than being included in the non-smoking controls. Molecular spectra from these studies were reanalyzed after adjustment for reported mutation frequencies from the individual studies and the entire data set. RESULTS A series of related studies on mutation at the X-linked HPRT locus in human newborn cord blood samples has led to the novel conclusion that only passive maternal exposure to tobacco mutagens has a significant effect on the developing baby. We performed a pooled analysis of the complete data from these studies, at the levels of both induced mutation frequency and the resulting mutational spectrum. CONCLUSION Our analysis reveals a more commonsensical, yet no less cautionary result: both active maternal smoking and secondary maternal exposure produce quantitatively and qualitatively indistinguishable increases in fetal HPRT mutation. Further, it appears that this effect is not perceptibly ameliorated if the mother adjusts her behavior (i.e. stops smoking) when pregnancy is confirmed, although this conclusion may also be affected by continued passive exposure.
Collapse
Affiliation(s)
- Stephen G Grant
- Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
| |
Collapse
|