Immunzellen in primären und metastasierten gastrointestinalen Stromatumoren (GISTs)

Abstract

AIM: This study investigated the immune cells within in the tumor stroma of primary and metastatic gastrointestinal stromal tumors (GISTs) by immunohistochemistry. GISTs appear usually as histological homogeneous tumors with a dense cell structure. However, GISTs have been shown to have a tumor stroma, in which different immune cells of the innate and acquired immune system are embedded. The frequency and function of these cells in GISTs remain widely unknown. In this work the various immune cells are described morphologically and their frequency in primary GISTs as well as peritoneal and liver metastases is being compared. Furthermore, the criteria proliferation activity, morphology, tumor size, organ localization and malignancy are examined and compared with the number of immune cells in the primary and metastatic GISTs. In a small number of metastases real time RT-PCR was performed to gain an overview of the functionality of immune cells using RT-PCR.MATERIAL & METHODS: A total of 188 untreated primary GISTs and 52 untreated GIST metastases were immunohistochemically processed to determine the percentage of tissue-associated fibrohistiocytic cells (Kim-1P) and cells of macrophage lineage (CD68). In addition, the number of several lymphocytes (T-Lymphocytes: CD3, B-Lymphocytes: CD20, NK-cells: CD56) was studied in these samples. For this purpose punches of the paraffin blocks of resected specimen or biopsies were lined up site by site in 22 tissue microarryas (TMAs) using a manual tissue arrayer. The photographs of 3-6 punches have been analysed computer-assisted with subsequent statistical evaluation of the results. This analysis resulted in very precise numbers of the percentage of immune cells in the respective tissue preparations. Furthermore, reverse transcription and real-time RT-PCR were used to detect the expression of the proinflammatory cytokines interleukin 1β, interleukin 6 and tumor necrosis factor α in a small sample size of snap-frozen tissue samples of metastases.RESULTS: GISTs have a tumor stroma, in which many immune cells are embedded. In the primary GISTs Kim-1P+ cells (28,8% ±7,1) dominated, but also lymphocytic cells (CD3+(2,2% ±1,8), CD20+(0,6% ±0,7), CD56+(1,1% ±0,9)) and macrophages (CD68+(3,6% ±2,1)) were present. Interestingly, the number of immune cells differ in the metastases of GISTs. On the one hand metastases show more lymphocytic cells than the primary GISTs (CD3+: 7,3% ±2,3 (p<0,01); CD20+: 1,8% ±0,3 (p<0,05)), on the other hand, the peritoneal metastases differ from the liver metastases. Peritoneal metastases have a significant higher number of Kim-1P+ cells (31,8% ±7,5) than liver metastases (18,2% ±3,8; p<0,01), while the latter in turn contain more CD3+ T-lymphocytes (11,7% ±1,8) than the peritoneal metastases (4,4% ±2,6; p<0,01). At the same time, the two sites differ in proliferation activity. Liver metastases have a lower proliferation activity (12,9% ±8,2) than peritoneal metastases of GISTs (18,3% ±7,3; p<0,05). In the RT-PCR of fresh-frozen tissue from metastases of a small cohort, one patient with a high percentage of Kim 1P+ cells (49,5% ±17) did not only show a comparatively high expression of Il-6 (CT value 26,8) and Il-1β (CT value 26,1) but also the lowest expression of TNF (CT 34,1) as well as a rapid clinical progress.CONCLUSION: The different numbers of the various immune cells in primary GISTs compared with metastatic GISTs as well as within the two metastatic sites, suggest a location specific microenvironment, which may play a part in the tumor growth of primary and secondary GISTs. Further studies will be needed to understand the type of communication between the immune cells of the GIST stroma and the tumor itself. In the future, the individuality of this tumor will come to the fore, elucidating that tumors with a different composition of their stromal cells, for example immune cells, might also need a different and individual treatment. Thus, not only the description of the immune cells is necessary, but also the understanding of GISTs as a family of tumors, which should not be seen as uniform, homogeneous tumors.