Genomic Profiles Associated with Early Micrometastasis in Lung Cancer: Relevance of 4q Deletion

Abstract

Purpose: Bone marrow is a common homing organ for early disseminated tumor cells (DTC) and their presence can predict the subsequent occurrence of overt metastasis and survival in lung cancer. It is still unclear whether the shedding of DTC from the primary tumor is a random process or a selective release driven by a specific genomic pattern. Experimental Design: DTCs were identified in bone marrow from lung cancer patients by an immunocytochemical cytokeratin assay. Genomic aberrations and expression profiles of the respective primary tumors were assessed by microarrays and fluorescence in situ hybridization analyses. The most significant results were validated on an independent set of primary lung tumors and brain metastases. Results: Combination of DNA copy number profiles (array comparative genomic hybridization) with gene expression profiles identified five chromosomal regions differentiating bone marrownegative from bone marrow-positive patients (4q12-q32, 10p12-p11, 10q21-q22, 17q21, and 20q11-q13). Copy number changes of 4q12-q32 were the most prominent finding, containing the highest number of differentially expressed genes irrespective of chromosomal size (P = 0.018). Fluorescence in situ hybridization analyses on further primary lung tumor samples confirmed the association between loss of 4q and bone marrow-positive status. In bone marrowpositive patients, 4q was frequently lost (37% versus 7%), whereas gains could be commonly found among bone marrow-negative patients (7% versus 17%). The same loss was also found to be common in brain metastases from both small and non-small cell lung cancer patients (39%). Conclusions:Thus, our data indicate, for the first time, that early hematogenous dissemination of tumor cells might be driven by a specific pattern of genomic changes.Lung cancer is one of the most frequently diagnosed cancers in developed countries and the main cause of cancer-related deaths, with an overall relative 5-year survival rate of 15% (1). Approximately 40% of patients with completely resected nonsmall cell lung cancer (NSCLC) without lymph node metastasis (N 0 ) or clinical signs of overt distant metastases (M 0 ) at time of the primary surgery relapse within 24 months.

Functional Studies on Viable Circulating Tumor Cells

“…Nevertheless, the development of cell lines or xenografts from hundreds of CTCs at the beginning is a major achievement, considering the enormous challenge to establish cell lines from even millions of primary tumor cells. This can be explained by the assumption that viable CTCs might already be selected for better survival and growth properties, which is consistent with published reports demonstrating that tumor cell dissemination and survival of disseminated tumor cells and CTCs is not a random process (34,35 ) and that CTC cell lines and xenografts express cancer stem cell properties (9,11 ). These studies nourish the hope that in-depth functional analysis of CTCs might lead to the identification of metastasisinitiator cells.…”

Suppression of Early Hematogenous Dissemination of Human Breast Cancer Cells to Bone Marrow by Retinoic Acid–Induced 2

“…An isotype-matched, murine monoclonal antibody (MOPC 21, IgG1; Sigma-Aldrich) served as a negative control. Screening for CK-positive cells was performed in an automated fashion (ACIS system) using color-based imaging technology and microscopy to automatically scan and analyze immunohistochemically stained slides ( 45 ).…”

Genetic and epigenetic changes in lung carcinoma and their clinical implications

“…Wrage et al 19 reported that the loss of 4q, especially 4q12-q23, in primary lung cancer was significantly associated with bone marrow metastasis. In addition, the same loss was also found to be common in brain metastases from lung cancer patients.…”