Embryonal carcinoma (EC) cells are the pluripotent stem cells of teratocarcinoma. The aggregates of P19, a mouse EC cell line, undergo differentiation and rapidly lose its colony-forming ability in culture with retinoic acid (RA) or DMSO. Loss of plating efficiency is used to assess the rate of drug-induced differentiation. When exposed respectively to DMSO or RA, the isolated EC cell mutants (D3 and RAC65) did not differentiate but the gap junctions could be formed. In RA-treated co-aggregates of RAC65 and O1A1, each cell line gave responses independent of the presence of the other cell line. However, in DMSO-treated co-aggregates of P19 and D3, D3 cells remained undifferentiated and P19 cell differentiation was much poorer than that in the absence of D3 cells. The results suggest that cell-cell interaction be present in the early stage of DMSO-induced differentiation and absent in the early stage of RA-induced differentiation.

In vivo experiment, in vitro assays (in vivo-in vitro system) is a kind of experimental technique which is different from both in vitro cell line and tumor line. The new model can be grown and studied either as an animal tumor or a cell culture. The specimen could be assayed for cell survival in vitro. This model can be used to study the response of malignant cells to the treatment in a precision and depth that is impossible in tumors grown in vivo. LA 795 Vv-Vt is the first in vivo-in vitro system developed in China. It was established with lung adenocarcinoma of T-739 mouse. The tumor cells could grow freely both in vivo and in vitro with a plating efficiency of 20%. Characteristics of LA 795 Vv-Vt tumor and cell in culture were described and compared. In order to estimate the radiation response of different doses, cell survival curves of tumors irradiated under oxic and hypoxic conditions were drawn and compared. The oxygen enhance ratio was 2.98. The experiments indicate that in vivo-in vitro system has a good dependent relation in dose and effect and is worth extensive application.

From Feb. to Dec. 1985, 15 patients were treated with fetal liver cell transfusion (FLT). They were 10 cases with malignant tumors treated by chemotherapy (tumor group) and 5 with blood diseases (blood group). Under strict aseptic technique, 3 1/2-6 month old fetus was selected for preparing suspension of the fetal liver cells on the superclean table. The speed of FLT should be increased gradually from slow to rapid. There are 1.8 X 10(8)-4 X 10(12) fetal liver cells in a fetus of more than 5 months old, in which most are CFU-C. In the tumor group, after FLT, white blood cell, platelet and hemoglobin increased by 700-3,900/mm3, 5,000-116,000/mm3 and 0.5-2.0 gm/mm3 respectively. But in the blood group, they increased by 800-1,300/mm3, 14,000-84,000/mm3 and 0.4-11.0 gm/mm3. In most of the cases, these hematological indexes reached up to the highest in 2 weeks after FLT. It suggests that FLT can improve the peripheral blood picture obviously and stimulate bone marrow. Experiment confirms that there are considerable hematopoietic stem cells in the fetal liver, by which the functions of hematopoiesis and immunity are able to recover. It is more marked in the tumor group than in the blood group. FLT provides a favourable condition for high dose chemotherapy.