Abstract
Recent studies have demonstrated that therapy with 212Pb-TCMC-trastuzumab resulted in (1) induction of apoptosis, (2) G2/M arrest, and (3) blockage of double-strand DNA damage repair in LS-174T i.p. (intraperitoneal) xenografts. To further understand the molecular basis of the cell killing efficacy of 212Pb-TCMC-trastuzumab, gene expression profiling was performed with LS-174T xenografts 24 h after exposure to 212Pb-TCMC-trastuzumab. DNA damage response genes (84) were screened using a quantitative real-time polymerase chain reaction array (qRT-PCR array). Differentially regulated genes were identified following exposure to 212Pb-TCMC-trastuzumab. These included genes involved in apoptosis (ABL, GADD45α, GADD45γ, PCBP4, and p73), cell cycle (ATM, DDIT3, GADD45α, GTSE1, MKK6, PCBP4, and SESN1), and damaged DNA binding (DDB) and repair (ATM and BTG2). The stressful growth arrest conditions provoked by 212Pb-TCMC-trastuzumab were found to induce genes involved in apoptosis and cell cycle arrest in the G2/M phase. The expression of genes involved in DDB and single-strand DNA breaks was also enhanced by 212Pb-TCMC-trastuzumab while no modulation of genes involved in double-strand break repair was apparent. Furthermore, the p73/GADD45 signaling pathway mediated by p38 kinase signaling may be involved in the cellular response, as evidenced by the enhanced expression of genes and proteins of this pathway. These results further support the previously described cell killing mechanism by 212Pb-TCMC-trastuzumab in the same LS-174T i.p. xenograft. Insight into these mechanisms could lead to improved strategies for rational application of radioimmunotherapy using α-particle emitters.The apoptotic response and associated gene modulations have not been clearly defined following exposure of cells to α-particle radioimmunotherapy (RIT). Gene expression profiling was performed with LS-174T i.p. (intraperitoneal) xenografts after exposure to 212Pb-TCMC-trastuzumab. Differentially regulated 22 genes were identified following the stressful growth arrest conditions provoked by 212Pb-TCMC-trastuzumab, providing an informative approach toward understanding the molecular basis of tumor biology in response to α-particle radiation and leading to improved strategies for RIT using α-particle emitters. This study provides data which is among the first to describe in detail, the cellular response to α-particle irradiation in vivo.
Highlights
Alpha particles provoke severe tissue damage and induce clusters of DNA strand breaks that lead to cell death by virtue of their high linear energy transfer (LET of ~100 KeV/lm) and short range in tissue
212Pb-TCMC-trastuzumab-induced cell killing is associated with upregulation of genes involved in apoptosis
212Pb-TCMC-human IgG (HuIgG), trastuzumab, and HuIgG resulted in the upregulation of only the GADD45c gene with a 3.5, 2.9, and 3.2-fold increase, respectively
Summary
Alpha particles provoke severe tissue damage and induce clusters of DNA strand breaks that lead to cell death by virtue of their high linear energy transfer (LET of ~100 KeV/lm) and short range in tissue. The unique cell killing capabilities of a-radiation make application of immunoconjugates labeled with a-emitter radionuclides a promising therapeutic option for the treatment of patients with carcinomas that are characterized by disseminated single tumor cells in the peritoneum such as ovarian or gastric cancer [2, 3]. Specific gene expression can be evaluated with greater accuracy and sensitivity by quantitative real-time polymerase chain reaction (qRT-PCR) [5,6,7]. Such gene expression profiling a 2013 The Authors.
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