Individual and combined effects of polyhydroxysteroid glycosides from P. lincki and sulfated derivative of laminaran from A. angusta on the colony growth of 3D HCT 116 spheroids. The 3D HCT 116 spheroids were treated with (A) PL1, PL2, L1 (12.5, 25, 50 μM); (B) AaLs (100, 200, 400 μg/mL) or (C,D) PL1 (12.5 μM) in combination with AaLs (10, 20, 40 μg/mL); (E,F) PL2 (12.5 μM) in combination with AaLs (10, 20, 40 μg/mL); and (G,H) L1 (12.5 μM) in combination with AaLs (10, 20, 40 μg/mL) in soft agar. Photos of colonies were made using a Motic microscope (40× magnification, 500 μm scale). Results are expressed as mean ± standard deviation (SD). The Student’s t test was used to evaluate data with the following levels of significance: * p < 0.05, ** p < 0.01, *** p < 0.001. All analyses were performed in three independent experiments. (J) The Combination index (CI) calculated using the Compusyn software 1.0.1 (ComboSyn, Inc., Paramus, NJ, USA), is a quantitative measure of the interaction between L1 and AaLs in a 3D cell culture model. CI of less than 0.7 indicates a synergism of the effect of L1 and AaLs.