Malignant gliomas are typically treated with surgery, radiation and chemotherapy; however, recurrence is common and the median survival following diagnosis continues to be approximately one year. It is thought that recurrent tumors may arise, in part, from a subpopulation of cells present in the primary tumor that possess genetic and/or epigenetic attributes that confer resistance to radiation and chemotherapy. In addition, the treatments themselves cause DNA damage which can lead to genetic changes in the cells that survive. Many studies have investigated changes in DNA and RNA expression that lead to therapy resistance; however, few studies have been done to study the global protein changes that occur between the primary tumor and recurrence following therapy. An understanding of the changes that occur in the cell populations of primary tumors leading to the formation of recurrent tumor may point to additional targets for the design of novel therapies. We have used 2-dimensional polyacrylamide gel electrophoresis to analyze proteins isolated from cells from primary and recurrent tumor pairs with and without in vitro selection for drug resistance. The proteins were identified by MALDI-TOF analysis of a tryptic digest. To date we have analyzed total protein samples from 2 primary/recurrent tumor pairs prior to and following selection for resistance to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) or to temozolomide (TMZ). Thirty-one differentially expressed proteins were consistently seen. Sixteen of these have been identified to date. Six proteins are up-regulated in primary tumor cells relative to recurrent tumor cells. Thirteen proteins, including coiled-coil domain containing 2, RUN and FYVE domain-containing, tropomyosin 3, heat shock protein apg-1, and vimentin variant, are up-regulated in recurrent tumor cells relative to primary tumor cells. Six proteins, including suppressor of IKK epsilon, and CTCL tumor antigen se20-7, are up-regulated in mock-treated control cells relative to cells resistant to 10µg/mL BCNU. Two, including KIAA0251, are up-regulated in cells resistant to 10µg/mL BCNU relative to mock-treated control cells. Four proteins, including hexokinase-2, CTCL tumor antigen se20-7, and coiled-coil domain containing 2, are up-regulated in mock-treated control cells relative to cells resistant to 10µM TMZ. Four proteins are up-regulated in cells resistant to 10µM TMZ relative to mock-treated control cells. Global proteomic analysis of primary and recurrent malignant gliomas will provide critically needed additional data for the identification of new therapeutic targets for the treatment of recurrent tumor. This work was supported by The Brain Tumor Society and the Barrow Neurological Foundation.
98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA