APOPTOTIC EFFECTS IN RENAL CORTEX AFTER TREATMENT WITH 177LU-OCTREOTATE

Abstract: Purpose: The purpose of this project was to investigate gene regulation of a predetermined panel of apoptotic genes in murine renal cortex after treatment with 177Lu-octreotate after one day and seven days. Theory: The kidneys and bone marrow are the risk organs in 177Lu-octreotate treatment, but by fractioning the treatment the bone marrow recovers. This leads to the kidneys being the dose-limiting risk organ. Apoptosis is a known effect after irradiation of cells and can result in nephrotoxicity after treatment. Whether apoptosis is initiated or inhibited after irradiation depends on a balance of pro-apoptotic and anti-apoptotic signals in the cells and is controlled by many genes divided into gene families. By analysing the expression of apoptotic genes, information about the induction or inhibition of apoptosis can be obtained. The absorbed dose is calculated in order to relate the responses in the tissue to irradiation by 177Lu. The renal cortex receives a higher absorbed dose after treatment with 177Lu-octreotate and is therefore of high interest when studying apoptosis. Method: RNA from the kidney cortex of 12 different mice was used for the analysis. The mice were divided into two irradiated and two control groups and killed at one or seven days after administration of 150 MBq 177Lu-octreotate or physiological saline, respectively. A panel of both pro-apoptotic and anti-apoptotic genes was investigated with a quantitative real-time polymerase chain reaction (QPCR) array. Prior to this, the RNA-concentration was determined with the Qubit ® assay in order to use the same amount of RNA in the QPCR assay. The absorbed dose in the kidney cortex was calculated for each mouse in the irradiated groups and the transcriptional response was related to the absorbed dose and time of irradiation. Result: The group that received a lower absorbed dose and was killed after one day (group 1) showed a higher increase in transcriptional response to irradiation than the group killed after seven days (group 2). The regulation in group 1 indicated pro-apoptotic responses in the renal cortex, wheras in group 2, a shift to anti-apoptotic responses was observed.