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Detection of occult micrometastases in non-small cell lung carcinoma by reverse transcriptase-polymerase chain
C T Salerno1, S Frizelle, G A Niehans
1Department of Surgery, University of Minnesota, Minneapolis V.A. Medical Center, USA.
Background:
The 5-year survival rate following surgical resection of Stage I or Stage II non-small cell lung carcinoma (NSCLC) is 30% to 50%, probably because of undetected occult micrometastases (OMs) at the time of surgery. Other investigators have detected OMs in bone marrow and histologically negative lymph nodes from patients with NSCLC using immunohistochemical staining to cytokeratins and cell surface glycoproteins.
Study Objective:
To develop and evaluate an assay based on the reverse transcriptase-polymerase chain reaction (RT-PCR) for the detection of OMs in NSCLC.
Patients:
Twenty-eight patients with benign or malignant thoracic pathology. Samples of primary tumors and lymph nodes were collected at the time of surgical resection or mediastinoscopic lymph-node biopsy.
Results:
Using RT-PCR to detect messenger RNA (mRNA) transcripts for MUC1 (a cell surface glycoprotein present in lung tissue but absent from normal lymph nodes), OMs were identified in 33 of 88 lymph nodes determined to be free of tumor by hematoxylin and eosin staining. Eleven of 11 control mediastinal lymph nodes from patients without malignancy failed to express detectable MUC1 transcripts. Dilutional experiments demonstrate that the assay can detect one MUC1-positive NSCLC cell in 1x10(7) MUC1-negative cells. A comparison of our RT-PCR assay to immunohistochemistry specific for the MUC1 glycoprotein suggests that RT-PCR may be more sensitive than immunohistochemistry for the detection of NSCLC OMs.
Conclusions:
This study demonstrates that RT-PCR for MUC1 mRNA can detect the presence of MUC1 mRNA in histologically negative lymph nodes from patients with NSCLC. The prognostic significance of these findings is currently unknown.
Insights
A new reverse transcriptase-polymerase chain reaction (RT-PCR) assay detects occult micrometastases in non-small cell lung cancer (NSCLC) lymph nodes. This sensitive method identifies MUC1 mRNA in histologically negative nodes, potentially improving cancer detection.
Area of Science:
- Oncology
- Molecular Biology
- Diagnostic Assays
Background:
- The 5-year survival rate for Stage I/II non-small cell lung cancer (NSCLC) is suboptimal (30-50%), likely due to undetected occult micrometastases (OMs).
- Previous methods for OMs detection in NSCLC patients, such as immunohistochemistry, have limitations in sensitivity.
Purpose of the Study:
- To develop and validate a reverse transcriptase-polymerase chain reaction (RT-PCR) assay for detecting OMs in NSCLC.
- To assess the sensitivity of the RT-PCR assay compared to immunohistochemistry.
Main Methods:
- Utilized RT-PCR to detect MUC1 messenger RNA (mRNA) transcripts in lymph nodes from 28 patients with thoracic pathology.
- Collected primary tumor and lymph node samples during surgery or biopsy.
- Performed dilutional experiments to determine assay sensitivity.
Main Results:
- RT-PCR identified MUC1 mRNA in 33 of 88 histologically negative lymph nodes from NSCLC patients.
- Control lymph nodes from non-malignant cases showed no detectable MUC1 transcripts.
- The assay demonstrated high sensitivity, detecting one MUC1-positive cell among 10(7) negative cells, and may be more sensitive than immunohistochemistry.
Conclusions:
- RT-PCR for MUC1 mRNA effectively detects occult micrometastases in histologically negative lymph nodes of NSCLC patients.
- The clinical and prognostic significance of these MUC1 mRNA-positive findings requires further investigation.