Functions of tumor-associated macrophages and macrophages residing in remote anatomical niches in Ehrlich carcinoma bearing mice

BACKGROUND

The impact of growing tumor on polarization and functions of tumor-associated macrophages is well known while its influence on residential macrophages occupying different anatomical niches reminds to be elucidated.

AIM

To study changes in polarization and functions of macrophages isolated from discrete anatomical niches in tumor-bearing mice at different stages of tumor growth.

MATERIALS AND METHODS

Ehrlich carcinoma was transplanted intramuscularly to Balb/c male mice. On days 7, 14, 21 and 28 after tumor transplantation, macrophages from tumor tissue, peritoneal cavity and spleen were isolated and analyzed. Nitric oxide production was measured by standard Griess reaction, arginase activity was determined by the measurement of urea, reactive oxygen species production was checked using NBT dye reduction assay and electron paramagnetic resonance spectroscopy, cytotoxic activity was estimated in MTT-assay.

RESULTS

Independently of their localization in different anatomic niches, macrophages in mice with transplanted Ehrlich carcinoma gradually lose their tumoricidal activities while arginase activity is upregulated. This indicates the shift of polarization from M1-like towards M2-like phenotype.

CONCLUSION

Our findings demonstrated that growing tumor could be able to subvert functioning of macrophages at the systemic level.

Macrophage polarization in dynamics of Lewis lung carcinoma growth and metastasis

AIM

To assess the functional state of macrophages based on various manifestations of their activity at the different stages of metastatic tumor growth in C57Bl mice.

MATERIALS AND METHODS

On days 7, 14, 21 and 28 after Lewis lung carcinoma transplantation to C57Bl mice, macrophages from various anatomic sites were isolated and tested on their cytotoxicity, metabolic activity, NO production and arginase activity.

RESULTS

In the populations of peritoneal and splenic macrophages, on days 7 and 21 of tumor growth antitumor (M1) cells prevailed while on days 14 and 28 tumor-promoting (M2) macrophages predominated. In the population of lung macrophages, cells with M1 phenotype were in the majority in the early stages of tumor growth. On days 21 and 28, M1 cells were gradually substituted by cells exhibiting M2 phenotype. This shift correlated with metastasis to lungs.

CONCLUSION

Lewis lung carcinoma growth is accompanied by the gradual change in macrophage polarization from antitumor (M1) towards tumor-promoting (M2) type. These changes were more evident in population of lung macrophages and correlated with the parameters of metastasis.

The effects of early postoperative immunization with xenogeneic embryo proteins on Lewis lung carcinoma model

AIM

To investigate the effect of chicken embryo proteins (CEP) as a prototype of xenogeneic vaccine on immune reactions in mice immunized after Lewis lung carcinoma (LLC) surgical removal.

MATERIALS AND METHODS

C57Bl male mice were immunized on days 1, 8, and 15 after surgical removal of LLC. The immune response was assessed on days 7, 14, 21 and 28 after tumor resection. Cytotoxic activity of natural killer cells (NK) and cytotoxic T-lymphocytes as well as antibody dependent cellular cytotoxicity was estimated in MTT-assay; specific antibodies were detected in ELISA; lymphocyte proliferation was tested in reaction of in vitro blast transformation.

RESULTS

None of the immunized mice developed LLC metastases. Immunization with CEP seems to prevent the potential decrease in NK cell cytotoxic activity and spontaneous blast transformation activity of lymphocytes following the surgically induced stress. Further research on improving immunization schedule and elucidating the mechanisms of NK modulation with CEP is needed.

Anticancer effectiveness of vaccination based on xenogeneic embryo proteins applied in different schedules

THE AIM

To evaluate anticancer activity of vaccination with chicken embryo proteins (CEP) applied in different schedules.

MATERIALS AND METHODS

C57Bl mice were vaccinated with CEP before (prophylactic schedule) or after (different therapeutic schedules with or without preliminary tumor removal) the Lewis lung carcinoma cells transplantation. The latent period of tumor development, tumor volume and metastasis rate were evaluated.

RESULTS

Potent antimetastatic effect of CEP-based vaccination was seen in case of therapeutic regimen after primary tumor removal. The metastasis inhibition index (MII) reached 96.9 and 97.8% on 18(th) and 34(th) day after tumor removal, respectively. When CEP vaccination was performed in the settings of therapeutic regimen without primary tumor removal the anticancer effect was evident only if vaccinations started as early as 24 h after the cancer cells injections. The highest MII achieved in such condition was 77.6%, tumor volume in the group of vaccinated animals was by 53.1-42.1% lower than in the control tumor-bearing mice. CEP vaccination before tumor challenge (prophylactic immunization) led to a statistically significant prolongation of the latent period of tumor development, a reduction of tumor volume (35.8-48.8% compared to control unvaccinated mice) and a marked inhibition of metastasis (MII was 71.1%).

CONCLUSION

Vaccination based on CEP exhibited both prophylactic and therapeutic anticancer effects. The last one is more pronounced when the vaccination starts shortly after the primary tumor resection.