e15610 Background: Cancer stem cells (CSCs) are promising targets in modern oncology. A lot of CSCs enrichment and cultivation techniques are being currently developed. Most of the approaches deploy high doses of growth factors in culture media, - EGF and FGF2 above all, - without prior testing. Since prolonged exposition to growth factors may cause paradoxical growth inhibition it is worth developing test systems to evaluate culturing conditions before establishing the main experiment. Encapsulation in alginate may serve as a promising approach to develop such test-systems due to alginate reduced ability to adsorb proteins and maintain proper attachment to the ECM of non-stem cell even in the presence of serum. It is important to notice that serum addition may be crucial during initial stages of primary CSCs culture establishment. The aim of the study was to test EGF and FGF2 effects on anoikis resistant cells growth in permanent colorectal cancer cell lines. Methods: The cells of Caco-2, HT-29, and HCT 116 cultures were encapsulated in 1% alginate beads at a concentration of 100 000 cells/ml. Subsequently encapsulated cells were kept in 2 variants of culture media: DMEM/F12 + 10%FBS with and without addition of growth factors (EGF 20 ng/ml, FGF2 10 ng/ml). The cultivation was carried out for 10 days, after that the colonies area (A) was measured. Data are given as: Mean ± 95% confidence interval. Results: The average area of Caco-2 culture colonies increased significantly with the addition of growth factors (FBS only A = 1755.16±195.87 μm2, with additional growth factors Af = 3270.57±274.91 μm2), the difference was significant (t = 8.83, n = 300, p < 0,05). The area of HCT116 colonies after growth factors addition increased only slightly (A = 2844.89±461.57 μm2, Af = 3530.31±503.85 μm2), the difference nevertheless did not reach significant values (t = 1.94, n = 300, p > 0.05). At the same time, the area of HT-29 colonies significantly decreased in the culture medium containing additional growth factors (A = 4605.10±324.02 μm2, Af = 3167.85±249.07 μm2), the difference was significant (t = 6.92, n = 300, p < 0.05). Conclusions: Combining alginate encapsulation and colonies size measurement enabled us to evaluate culturing conditions of anoikis resistant cells in permanent CRC cultures and proved growth factors addition to be an ambiguous practice in CSCs research. This tactics can be applied in a broad spectrum of tasks concerning more effective CSCs medium formulations development.