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Cyclin D1 antisense RNA destabilizes pRb and retards lung cancer cell growth
1Deparment of Surgery, Childrens Hospital Los Angeles Research Institute, University of Southern California School of Medicine 90027, USA.
Abstract:
To investigate the role of cyclin D1 in the regulation of lung cancer cell growth, we created five stably transfected cell lines carrying a cyclin D1 antisense construct. The transfected cells exhibited a marked decrease in the rate of cell growth, in contrast to the original lines (A549 and NCI-H441). The expression of several cell cycle-regulating proteins, including cyclin A, the cyclin-dependent kinases (cdk) 2 and cdk4, in addition to cyclin D1 itself, was markedly decreased. The expression of one cdk inhibitor, p21WAF1/CIP1, increased in the A549-derived cell lines. A specific target of cyclin D1 activity, the growth-suppressing product of the retinoblastoma gene, pRb, exhibited decreased expression and a decreased level of phosphorylation in the transfected cells. Decreased expression of pRb due to a significant increase in its turnover rate suggested that the stability of the protein may depend on phosphorylation by cyclin D1-dependent cdk activity. In addition to the impact on pRb stability, decreased expression of cyclin D1 induced susceptibility to cell death after withdrawal of exogenous growth factors in the antisense transfected cell lines, a response that was not observed in the original cancer cell lines. We conclude that abrogation of cyclin D1 overexpression in lung cancer cells disrupts several key pathways that are required for uncontrolled cell growth and induces those that lead to cell death after growth factor deprivation. Therefore, we speculate that use of antisense cyclin D1 expression in appropriate gene vectors could be a useful method for retarding lung cancer cell growth in accessible tumors such as those of the lung epithelium.
Insights
Reducing cyclin D1 in lung cancer cells halts growth by decreasing cell cycle proteins and increasing cell death. Antisense cyclin D1 may offer a new lung cancer therapy.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Biology
Background:
- Cyclin D1 is a key regulator of the cell cycle.
- Overexpression of cyclin D1 is implicated in various cancers, including lung cancer.
- Understanding cyclin D1's precise role is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the function of cyclin D1 in regulating lung cancer cell proliferation.
- To assess the effects of inhibiting cyclin D1 expression on cell cycle proteins and cell death pathways.
- To explore the therapeutic potential of antisense cyclin D1 in lung cancer.
Main Methods:
- Creation of stably transfected lung cancer cell lines (A549, NCI-H441) with a cyclin D1 antisense construct.
- Analysis of cell growth rates in transfected versus original cell lines.
- Quantification of cell cycle-regulating proteins (cyclin A, cdk2, cdk4, p21WAF1/CIP1, pRb) and pRb phosphorylation levels.
- Assessment of cell death susceptibility following growth factor withdrawal.
Main Results:
- Antisense cyclin D1 transfection significantly decreased lung cancer cell growth rates.
- Expression of cyclin A, cdk2, cdk4, and cyclin D1 was markedly reduced in transfected cells.
- Increased expression of the cyclin-dependent kinase inhibitor p21WAF1/CIP1 was observed.
- Reduced expression and phosphorylation of the retinoblastoma protein (pRb) occurred, suggesting decreased stability.
- Transfected cells showed increased susceptibility to apoptosis upon growth factor deprivation.
Conclusions:
- Abrogating cyclin D1 overexpression disrupts critical pathways for uncontrolled lung cancer cell growth.
- Inhibition of cyclin D1 induces cell death pathways, particularly after growth factor withdrawal.
- Antisense cyclin D1 gene therapy holds potential for retarding lung cancer progression in accessible tumors.