Replication-defective recombinant Semliki Forest virus encoding GM-CSF as a vector system for rapid and facile generation of autologous human tumor cell vaccines.

This paper describes the production of recombinant Semliki Forest virus encoding murine or human granulocyte-macrophage colony-stimulating factor (GM-CSF) and the capacity of these vectors to transduce murine and human tumor cells ex vivo. High-titer stocks (up to 3 x 10(9) particles/ml) of conditionally infective, replication-defective, recombinant SFV particles were generated using the SFV Helper-2 system. It is shown that the recombinant SFV/GM-CSF virus, as well as recombinant SFV carrying the beta-galactosidase reporter gene, efficiently transduce both murine tumor cell lines as well as primary human renal carcinoma cells. Using ELISA's specific for GM-CSF, levels of GM-CSF production by the cells were determined. Levels of murine GM-CSF (mGM-CSF) produced by SFV/mGM-CSF transduced renal cell cancer cultures were equal to or higher than corresponding levels reported in the literature after transduction of similar renal carcinoma cell cultures using a retroviral vector system. The biological activity of GM-CSF was demonstrated by using cells which are dependent on GM-CSF for growth and by using primary bone marrow cells. All the transduced cell cultures (including the human renal cell carcinoma samples) produced GM-CSF for up to at least 4 days after transduction. The results imply that the recombinant SFV system can be used for rapid and facile preparation of autologous cancer cell vaccines.

Serum obtained from rats after partial hepatectomy enhances growth of cultured colon carcinoma cells.

Tumour-bearing rats were randomized to a 70% partial hepatectomy or a sham operation. At days 1, 3 or 14, portal and systemic serum was obtained and colon carcinoma cells were cultured in the presence of 5, 10, 20 or 50% serum. Proliferation and epidermal growth factor receptor (EGFr) expression was measured in tumour cells. Proliferation was 25-40% higher in tumour cells cultured with portal serum after hepatectomy than after sham operation when using serum obtained at day 3, but not days 1 and 14 after operation. In cultures with serum obtained at day 14 after operation CC 531 cells showed a 30% higher proliferation rate with systemic hepatectomy serum than CC 531 cells with sham systemic serum. These effects were not mediated by a change in EGFr mRNA and protein levels as the used colon carcinoma cells did not reveal EGFr activity by any of the three detection methods used.

The effect of partial hepatectomy on tumor growth in rats: in vivo and in vitro studies.

Residual tumor in the remnant liver after partial hepatectomy (PH) for colorectal liver metastases is a serious clinical problem. This fact is reflected by the high number of recurrences after potentially curative liver resections. Liver regeneration, it appears, might influence the growth of remaining micrometastases in the liver. Using rats, we demonstrated enhancement of growth of a syngeneic colon carcinoma (CC 531) in the remnant liver after 70% PH. Fourteen days after PH, tumor weights in the liver were twice as high as those of sham-operated rats. This difference in tumor weight was not found in extrahepatic tumors. In vitro experiments did not show stimulation of cultured CC 531 cells by portal or systemic serum withdrawn 24 hours or 14 days after hepatectomy as compared with sera obtained after sham operation. Co-cultures of CC 531 cells and hepatocytes (in ratios of 1:10 or 1:1) demonstrated a higher 3H-thymidine incorporation than was the case in separately cultured cells. In co-cultures, bromodeoxyuridine (BrdU) incorporation in DNA was found primarily in CC 531 cells and rarely in hepatocytes. Cell density appeared to be of influence on 3H-thymidine incorporation in co-cultures. Hepatocytes were found to have a stimulating effect on CC 531 cells in low-density cultures, whereas high-density cultures exhibited an inhibiting effect after a culture time of 120 hours. These results show that, depending on cell density in co-cultures, a paracrine stimulating influence of hepatocytes on this type of colon carcinoma cells (CC 531) might be responsible for the increased tumor growth in vivo.