Impact of α-Targeted Radiation Therapy on Gene Expression in a Pre-Clinical Model for Disseminated Peritoneal Disease when Combined with Paclitaxel

Abstract

To better understand the molecular basis of the enhanced cell killing effected by the combined modality of paclitaxel and 212Pb-trastuzumab (Pac/212Pb-trastuzumab), gene expression in LS-174T i.p. xenografts was investigated 24 h after treatment. Employing a real time quantitative PCR array (qRT-PCR array), 84 DNA damage response genes were quantified. Differentially expressed genes following therapy with Pac/212Pb-trastuzumab included those involved in apoptosis (BRCA1, CIDEA, GADD45α, GADD45γ, GML, IP6K3, PCBP4, PPP1R15A, RAD21, and p73), cell cycle (BRCA1, CHK1, CHK2, GADD45α, GML, GTSE1, NBN, PCBP4, PPP1R15A, RAD9A, and SESN1), and damaged DNA repair (ATRX, BTG2, EXO1, FEN1, IGHMBP2, OGG1, MSH2, MUTYH, NBN, PRKDC, RAD21, and p73). This report demonstrates that the increased stressful growth arrest conditions induced by the Pac/212Pb-trastuzumab treatment suppresses cell proliferation through the regulation of genes which are involved in apoptosis and damaged DNA repair including single and double strand DNA breaks. Furthermore, the study demonstrates that 212Pb-trastuzumab potentiation of cell killing efficacy results from the perturbation of genes related to the mitotic spindle checkpoint and BASC (BRCA1-associated genome surveillance complex), suggesting cross-talk between DNA damage repair and the spindle damage response.

Toxicological Studies of 212Pb Intravenously or Intraperitoneally Injected into Mice for a Phase 1 Trial

“…The radionuclide, 212 Pb, has been a focus of investigation for radioimmuno-therapy (RIT) [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ] as well as a supply of cytotoxic α-particles from the decay of its 212 Bi daughter, and the strategy of using the 212 Pb as an in vivo generator for 212 Bi circumvents the logistical difficulties of working directly with the short-lived 212 Bi (T ½ 60.6 min). The 10.6 h half-life of 212 Pb also extends the time to deliver and target tumors with 212 Bi.…”

Targeted α-Particle Radiation Therapy of HER1-Positive Disseminated Intraperitoneal Disease: An Investigation of the Human Anti-EGFR Monoclonal Antibody, Panitumumab

“…In a series of papers from this laboratory, initial investigations into the molecular mechanisms of cell killing by α-particle radiation using trastuzumab to target HER2 were methodically described. These studies also provided insight into the pathways invoked by GEM and paclitaxel to potentiate the sensitivity of tumor cells to 212 Pb-RIT with each chemotherapeutic affecting different pathways [57] , [58] , [59] , [60] , [61] , [62] , [63] . RIT with 212 Pb-trastuzumab was found to induce double-stranded DNA breaks, impaired DNA damage repair, arrested the cell cycle at the G2-M phase, and induced chromatin remodeling [57] .…”

Application of ²¹²Pb for Targeted α-particle Therapy (TAT): Pre-clinical and Mechanistic Understanding through to Clinical Translation

“…Irradiation results in major damage to DNA while Pac affects microtubules. Thus, modification in gene expression invoked by Pac/ 212 Pb-TCMC-trastuzumab may derive mainly from perturbation of the microtubule network and DNA damage signaling pathways [67]. The proposed cell killing mode by TAT using 212 Pb when combined with Pac is shown in Figure 4.…”

“…Many genes and proteins such as BRCA1, p73, and BubR1 are involved in these pathways. A fine cross talk between DNA damage and the spindle damage response is evident [67]. …”