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Differential expression of cell cycle regulators in CDK5-dependent medullary thyroid carcinoma tumorigenesis.

Pozo K, Hillmann A, Augustyn A, Plattner F, Hai T, Singh T, Ramezani S, Sun X, Pfragner R, Minna JD, Cote GJ, Chen H, Bibb JA, Nwariaku FE - Oncotarget (2015)

Bottom Line: Finally, the same set of cell cycle proteins was consistently overexpressed in human sporadic MTC but not in hereditary MTC.Together these findings suggest that aberrant CDK5 activity precedes cell cycle initiation and thus may function as a tumor-promoting factor facilitating cell cycle protein expression in MTC.Targeting aberrant CDK5 or its downstream effectors may be a strategy to halt MTC tumorigenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX, USA.

ABSTRACT
Medullary thyroid carcinoma (MTC) is a neuroendocrine cancer of thyroid C-cells, for which few treatment options are available. We have recently reported a role for cyclin-dependent kinase 5 (CDK5) in MTC pathogenesis. We have generated a mouse model, in which MTC proliferation is induced upon conditional overexpression of the CDK5 activator, p25, in C-cells, and arrested by interrupting p25 overexpression. Here, we identify genes and proteins that are differentially expressed in proliferating versus arrested benign mouse MTC. We find that downstream target genes of the tumor suppressor, retinoblastoma protein, including genes encoding cell cycle regulators such as CDKs, cyclins and CDK inhibitors, are significantly upregulated in malignant mouse tumors in a CDK5-dependent manner. Reducing CDK5 activity in human MTC cells down-regulated these cell cycle regulators suggesting that CDK5 activity is critical for cell cycle progression and MTC proliferation. Finally, the same set of cell cycle proteins was consistently overexpressed in human sporadic MTC but not in hereditary MTC. Together these findings suggest that aberrant CDK5 activity precedes cell cycle initiation and thus may function as a tumor-promoting factor facilitating cell cycle protein expression in MTC. Targeting aberrant CDK5 or its downstream effectors may be a strategy to halt MTC tumorigenesis.

No MeSH data available.


Related in: MedlinePlus

Gene expression analysis of cell cycle regulators in malignant and benign mouse MTC by RT-qPCRRelative mRNA expression of A) CDK genes, Cdk1, Cdk2, Cdk4, Cdk5 and Cdk6; B) cyclin genes, Ccna1, Ccnb1, Ccne1, Ccne2, Ccnd1, and Cdk5r1 and C) CKI genes, Cdkn2a, Cdkn2c, Cdkn2d, Cdkn1a, Cdkn1b and Cdkn2b in proliferating malignant (P) versus arrested benign NSE/p25-GFP mouse tumors. P-values are p < 0.0001 for Cdk1, Cdk2, Cdk4, Cdk6, p = 0.9838 for CDK5; p < 0.0001 for Ccna1, Ccnb1, Ccnd1, Ccne1 and Ccne2, p = 0.0057 for Cdk5r1; p = 0.1754 for Cdkn2b, p = 0.005 for Cdkn2a, p = 0.0052 for Cdkn2c, p = 0.0003 for Cdkn2d, p < 0.0001 for Cdkn1a and p = 0.0811 for Cdkn1b. Data are represented as mean +/− SEM, N = 6-7 for each condition.
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Figure 2: Gene expression analysis of cell cycle regulators in malignant and benign mouse MTC by RT-qPCRRelative mRNA expression of A) CDK genes, Cdk1, Cdk2, Cdk4, Cdk5 and Cdk6; B) cyclin genes, Ccna1, Ccnb1, Ccne1, Ccne2, Ccnd1, and Cdk5r1 and C) CKI genes, Cdkn2a, Cdkn2c, Cdkn2d, Cdkn1a, Cdkn1b and Cdkn2b in proliferating malignant (P) versus arrested benign NSE/p25-GFP mouse tumors. P-values are p < 0.0001 for Cdk1, Cdk2, Cdk4, Cdk6, p = 0.9838 for CDK5; p < 0.0001 for Ccna1, Ccnb1, Ccnd1, Ccne1 and Ccne2, p = 0.0057 for Cdk5r1; p = 0.1754 for Cdkn2b, p = 0.005 for Cdkn2a, p = 0.0052 for Cdkn2c, p = 0.0003 for Cdkn2d, p < 0.0001 for Cdkn1a and p = 0.0811 for Cdkn1b. Data are represented as mean +/− SEM, N = 6-7 for each condition.

Mentions: To validate the expression array data and investigate further the role of CDK5 in the cell cycle, we measured the relative expression of genes encoding CDK, cyclins and CKI by RT-qPCR analyses. Elevated Cdk1, Cdk2 and Cdk4 mRNA levels were detected in proliferating malignant tumors. Cdk5 mRNA levels remained unchanged despite p25 overexpression. Somewhat unexpectedly, Cdk6 mRNA expression was increased in arrested benign tumors (Figure 2A). Similarly, cyclin-D1 and p35 gene products, Ccnd1 and Cdk5r1, were up-regulated in benign tumors (Figure 2B). In contrast, the genes encoding cyclin-A1, -B1, -E1 and -E2, i.e. Ccna1, Ccnb1, Ccne1 and Ccne2, were up-regulated in malignant tumors. Finally, CKI gene expression analysis revealed elevated mRNA expression in malignant tumors for p16INK4a, p18INK4c, p19INK4d and p21CIP/WAF1 encoding genes, i.e. Cdkn2a, Cdkn2c, Cdkn2d and Cdkn1a, while p15INK4b and p27KIP1 encoding genes, i.e. Cdkn2b and Cdkn1b mRNA levels were unchanged between conditions (Figure 2C). Thus there is an overall elevation in the expression of several mRNAs encoding CDK, cyclins and CKI in proliferating malignant tumors compared to arrested benign MTC, thereby suggesting a role for CDK5 activity in the cell cycle.


Differential expression of cell cycle regulators in CDK5-dependent medullary thyroid carcinoma tumorigenesis.

Pozo K, Hillmann A, Augustyn A, Plattner F, Hai T, Singh T, Ramezani S, Sun X, Pfragner R, Minna JD, Cote GJ, Chen H, Bibb JA, Nwariaku FE - Oncotarget (2015)

Gene expression analysis of cell cycle regulators in malignant and benign mouse MTC by RT-qPCRRelative mRNA expression of A) CDK genes, Cdk1, Cdk2, Cdk4, Cdk5 and Cdk6; B) cyclin genes, Ccna1, Ccnb1, Ccne1, Ccne2, Ccnd1, and Cdk5r1 and C) CKI genes, Cdkn2a, Cdkn2c, Cdkn2d, Cdkn1a, Cdkn1b and Cdkn2b in proliferating malignant (P) versus arrested benign NSE/p25-GFP mouse tumors. P-values are p < 0.0001 for Cdk1, Cdk2, Cdk4, Cdk6, p = 0.9838 for CDK5; p < 0.0001 for Ccna1, Ccnb1, Ccnd1, Ccne1 and Ccne2, p = 0.0057 for Cdk5r1; p = 0.1754 for Cdkn2b, p = 0.005 for Cdkn2a, p = 0.0052 for Cdkn2c, p = 0.0003 for Cdkn2d, p < 0.0001 for Cdkn1a and p = 0.0811 for Cdkn1b. Data are represented as mean +/− SEM, N = 6-7 for each condition.
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Related In: Results  -  Collection

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Show All Figures
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Figure 2: Gene expression analysis of cell cycle regulators in malignant and benign mouse MTC by RT-qPCRRelative mRNA expression of A) CDK genes, Cdk1, Cdk2, Cdk4, Cdk5 and Cdk6; B) cyclin genes, Ccna1, Ccnb1, Ccne1, Ccne2, Ccnd1, and Cdk5r1 and C) CKI genes, Cdkn2a, Cdkn2c, Cdkn2d, Cdkn1a, Cdkn1b and Cdkn2b in proliferating malignant (P) versus arrested benign NSE/p25-GFP mouse tumors. P-values are p < 0.0001 for Cdk1, Cdk2, Cdk4, Cdk6, p = 0.9838 for CDK5; p < 0.0001 for Ccna1, Ccnb1, Ccnd1, Ccne1 and Ccne2, p = 0.0057 for Cdk5r1; p = 0.1754 for Cdkn2b, p = 0.005 for Cdkn2a, p = 0.0052 for Cdkn2c, p = 0.0003 for Cdkn2d, p < 0.0001 for Cdkn1a and p = 0.0811 for Cdkn1b. Data are represented as mean +/− SEM, N = 6-7 for each condition.
Mentions: To validate the expression array data and investigate further the role of CDK5 in the cell cycle, we measured the relative expression of genes encoding CDK, cyclins and CKI by RT-qPCR analyses. Elevated Cdk1, Cdk2 and Cdk4 mRNA levels were detected in proliferating malignant tumors. Cdk5 mRNA levels remained unchanged despite p25 overexpression. Somewhat unexpectedly, Cdk6 mRNA expression was increased in arrested benign tumors (Figure 2A). Similarly, cyclin-D1 and p35 gene products, Ccnd1 and Cdk5r1, were up-regulated in benign tumors (Figure 2B). In contrast, the genes encoding cyclin-A1, -B1, -E1 and -E2, i.e. Ccna1, Ccnb1, Ccne1 and Ccne2, were up-regulated in malignant tumors. Finally, CKI gene expression analysis revealed elevated mRNA expression in malignant tumors for p16INK4a, p18INK4c, p19INK4d and p21CIP/WAF1 encoding genes, i.e. Cdkn2a, Cdkn2c, Cdkn2d and Cdkn1a, while p15INK4b and p27KIP1 encoding genes, i.e. Cdkn2b and Cdkn1b mRNA levels were unchanged between conditions (Figure 2C). Thus there is an overall elevation in the expression of several mRNAs encoding CDK, cyclins and CKI in proliferating malignant tumors compared to arrested benign MTC, thereby suggesting a role for CDK5 activity in the cell cycle.

Bottom Line: Finally, the same set of cell cycle proteins was consistently overexpressed in human sporadic MTC but not in hereditary MTC.Together these findings suggest that aberrant CDK5 activity precedes cell cycle initiation and thus may function as a tumor-promoting factor facilitating cell cycle protein expression in MTC.Targeting aberrant CDK5 or its downstream effectors may be a strategy to halt MTC tumorigenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX, USA.

ABSTRACT
Medullary thyroid carcinoma (MTC) is a neuroendocrine cancer of thyroid C-cells, for which few treatment options are available. We have recently reported a role for cyclin-dependent kinase 5 (CDK5) in MTC pathogenesis. We have generated a mouse model, in which MTC proliferation is induced upon conditional overexpression of the CDK5 activator, p25, in C-cells, and arrested by interrupting p25 overexpression. Here, we identify genes and proteins that are differentially expressed in proliferating versus arrested benign mouse MTC. We find that downstream target genes of the tumor suppressor, retinoblastoma protein, including genes encoding cell cycle regulators such as CDKs, cyclins and CDK inhibitors, are significantly upregulated in malignant mouse tumors in a CDK5-dependent manner. Reducing CDK5 activity in human MTC cells down-regulated these cell cycle regulators suggesting that CDK5 activity is critical for cell cycle progression and MTC proliferation. Finally, the same set of cell cycle proteins was consistently overexpressed in human sporadic MTC but not in hereditary MTC. Together these findings suggest that aberrant CDK5 activity precedes cell cycle initiation and thus may function as a tumor-promoting factor facilitating cell cycle protein expression in MTC. Targeting aberrant CDK5 or its downstream effectors may be a strategy to halt MTC tumorigenesis.

No MeSH data available.


Related in: MedlinePlus