BMC Cancer Research article Over-representation of specific regions of chromosome 22 in cells from human glioma correlate with resistance to 1,3-bis(2-chloroethyl)-1-nitrosourea Nicole C Hank1, Joan Rankin Shapiro1 and Adrienne C Scheck*1,2 BioMed Central Open Access Address: 1Neuro-Oncology Research, Barrow Neurological Institute® of St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013 USA and 2Neurosurgery Research, Barrow Neurological Institute® of St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013 USA Email: Nicole C Hank - nicole.hank@chw.edu; Joan Rankin Shapiro - joan.shapiro@chw.edu; Adrienne C Scheck* - adrienne.scheck@chw.edu * Corresponding author Published: 04 January 2006 BMC Cancer 2006, 6:2 doi:10.1186/1471-2407-6-2 This article is available from: http://www.biomedcentral.com/1471-2407/6/2 Received: 07 September 2005 Accepted: 04 January 2006 © 2006 Hank et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: Glioblastoma multiforme is the most malignant form of brain tumor. Despite treatment including surgical resection, adjuvant chemotherapy, and radiation, these tumors typically recur. The recurrent tumor is often resistant to further therapy with the same agent, suggesting that the surviving cells that repopulate the tumor mass have an intrinsic genetic advantage. We previously demonstrated that cells selected for resistance to 1,3-bis(2-chloroethyl)- 1-nitrosourea (BCNU) are near-diploid, with over-representation of part or all of chromosomes 7 and 22. While cells from untreated gliomas often have over-representation of chromosome 7, chromosome 22 is typically under-represented. Methods: We have analyzed cells from primary and recurrent tumors from the same patient before and after in vitro selection for resistance to clinically relevant doses of BCNU. Karyotypic analyses were done to demonstrate the genetic makeup of these cells, and fluorescent in situ hybridization analyses have defined the region(s) of chromosome 22 retained in these BCNU- resistant cells. Results: Karyotypic analyses demonstrated that cells selected for BCNU resistance were near- diploid with over-representation of chromosomes 7 and 22. In cells where whole copies of chromosome 22 were not identified, numerous fragments of this chromosome were retained and inserted into several marker and derivative chromosomes. Fluorescent in situ hybridization analyses using whole chromosome paints confirmed this finding. Additional FISH analysis using bacterial artificial chromosome probes spanning the length of chromosome 22 have allowed us to map the over-represented region to 22q12.3–13.32. Conclusion: Cells selected for BCNU resistance either in vivo or in vitro retain sequences mapped to chromosome 22. The specific over-representation of sequences mapped to 22q12.3–13.32 suggest the presence of a DNA sequence important to BCNU survival and/or resistance located in this region of chromosome 22. Page 1 of 10 (page number not for citation purposes)