Effect of mid-late mouse fetus' microenvironment on the growth of tumor cells after intrauterine transplantation.

Successful intrauterine transplantation (IUT) of stem cells for treatment of fetal defects in some animal models of human diseases has prompted us to study the mechanisms of transplantation, immunological tolerance and embryonic environment. The objective of this study was to determine whether intrauterine transplantation of tumor cells would affect the survival and growth of the tumor cells themselves as well as fetus development. A total of 2 x 10(6) H(22) cells or S(180) cells were transplanted into the amniotic or abdominal cavity of NIH mice on D9-D12 or D13-D18 of gestation. The adult and newborn NIH mice which were inoculated with the same number of H(22) cells and S(180) cells by intraperitoneal injection were used as positive controls for the cancer bearing control group while undisrupted fetuses of the same gestation were used as negative controls (i.e. for the normal development) group. The development of fetuses transplanted with tumor cells in utero was monitored by several developmental indices, and the tumor growth of them were observed by some distinctive bearing cancer index. The H(22) transplanted group was further assessed for minimal cancer bearing by detection of alpha-fetoprotein (AFP) using radioimmunoassay (RIA) and reverse transcription-polymerase chain reaction (RT-PCR). In addition, tumor burden and the development of the F1 generation of the mice by IUT were also investigated. Protein kinase C (PKC) and proliferating cell nuclear antigen (PCNA) of GFP-expressing H(22) cells transplanted in the uterus were analyzed under laser confocal microscopy. There was no significant difference in the developmental indices between the experimental and control groups. HE staining of the major organs, including liver, kidney, and lung, showed that these organs properly developed. No tumor ascites were found in those delivered mice after intrauterine transplantation with H(22) cells and S(180) cells. Furthermore, as minimal bearing cancer index for H(22) cells, AFP expression analyzed by RIA and RT-PCR indicated that no tumor cells were detected in the experimental groups. The F1 progenies developed normally without any signs of tumor development. Fluorescence analysis revealed that expression of PKC and PCNA was markedly reduced in the H(22) cells after injection for 24, 48, and 72 h. Our study showed that the tumor cells did not grow in the mice by intrauterine transplantation, whereas transplantation of the same number of tumor cells resulted in obvious ascites tumor in the adult and newborn mice. Furthermore, the differentiation and proliferation of H(22) cells changed dramatically after injection. Our results suggest that, while the embryonic transplantation of tumor cells does not affect fetal development, the survival and growth of implanted tumor cells may be significantly inhibited in the embryonic microenvironment.