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RASSF1A gene inactivation in non-small cell lung cancer and its clinical implication
Hideki Endoh1, Yasushi Yatabe, Shigeki Shimizu
1Department of Thoracic Surgery, Aichi Cancer Center Hospital, Nagoya, Japan.
Abstract:
Methylation-associated inactivation of RASSF1, a putative tumor suppressor identified at 3p21.3, is reported in several cancers. We examined RASSF1 in non-small lung cancer (NSCLC) to search for clinical implications. RT-PCR analysis showed no expression of RASSF1A in 12 of 20 lung cancer cell lines. Loss of expression correlated well with promoter methylation status of these lines. Sequence analysis revealed 2 polymorphisms (codons 21 and 133) in RASSF1A transcripts, but not in RASSF1C transcripts. No somatic mutations were found. Of 7 cell lines with K-ras mutations at codon 12 or 61, 2 lost expression of RASSF1A, whereas in 13 cell lines with wild-type K-ras gene, 10 lost RASSF1A gene expression (p = 0.0521). We investigated methylation status of this putative tumor suppressor gene in 100 primary NSCLCs to determine whether there is a clinical significance. Forty-two of primary NSCLCs demonstrated methylated allele. There is no correlation between promoter methylation of RASSF1A and clinicopathological findings, including histological type or grade, tumor staging, p53 and K-ras mutational status, or patients' survival. In the cases of Stage I and II disease, however, RASSF1A methylation was associated with earlier recurrence (p = 0.0247). Epigenetic silencing of RASSF1A is a frequent event in non-small lung cancer and will provide novel opportunities to develop diagnosis and therapy of NSCLC.
Insights
Epigenetic silencing of RASSF1A, a tumor suppressor, is frequent in non-small cell lung cancer (NSCLC). RASSF1A methylation correlates with earlier recurrence in early-stage NSCLC, offering potential diagnostic and therapeutic targets.
Area of Science:
- Oncology
- Molecular Biology
- Epigenetics
Background:
- RASSF1A is a tumor suppressor gene frequently inactivated by methylation in various cancers.
- Its role and clinical significance in non-small cell lung cancer (NSCLC) require further investigation.
Purpose of the Study:
- To investigate the frequency and clinical implications of RASSF1A promoter methylation in NSCLC.
- To explore the relationship between RASSF1A methylation and clinicopathological features, including patient survival and recurrence.
Main Methods:
- RT-PCR and methylation-specific PCR were used to analyze RASSF1A expression and promoter methylation in NSCLC cell lines and primary tumors.
- Sequence analysis was performed to identify RASSF1A polymorphisms and mutations.
- Statistical analysis was employed to correlate methylation status with clinical data.
Main Results:
- RASSF1A expression was lost in 12/20 NSCLC cell lines, correlating with promoter methylation.
- No somatic mutations in RASSF1A were detected.
- RASSF1A promoter methylation was found in 42/100 primary NSCLCs.
- RASSF1A methylation did not correlate with overall survival, p53, or K-ras mutational status.
- However, RASSF1A methylation was associated with earlier recurrence in Stage I and II NSCLC patients.
Conclusions:
- Epigenetic silencing of RASSF1A is a common event in NSCLC.
- RASSF1A methylation may serve as a predictive biomarker for earlier recurrence in early-stage NSCLC.
- Targeting RASSF1A epigenetic alterations could offer novel diagnostic and therapeutic strategies for NSCLC.