This research addresses studying the lipid content of Hydroclathrus clathraus brown algae from the Red Sea, Egypt Region and their assess acute oral LD50 of sterol fraction in albino mice and anticancer activity against different cancer cell lines including; colon cancer cell line (Caco-2) and liver cancer cell line (Huh-7) using MMT, apoptosis analysis, EGFR and genes' expression. Total lipids, glycolipid, sulfolipid, and phospholipid of Hydroclathrus clathraus content were 1mg/g, 0.08 mg/g, 0.25±0.01 mg/g and 0.57±0.04 mg/g respectively. The LD50 of Hydroclathrus clathraus sterols was greater than 3g/kg in the mice. The major fatty acid is palmitic acid (67.04%). Polyunsaturated fatty acids content was arachidonic (8.05%), α-Linolenic acid (4.36%) and Linoleic acid (1.69%). The major sterols fractions were Hexacosane (18.54%), Octacosane (14.96%) and Nonadecane (13.31%). Cholesterol (8.32%), β-Sitosterol (2.08%) and Campesterol (1.36%) were presented as minor sterols. However, algal sterol showed the best potential antitumor activity with IC50 of 0.22 µg/ml and 3.09µg/ml against CaCo2 and HuH7. These sterols fraction reduced tumor genesis by three mechanisms that firstly, the cells' apoptosis which may reduce the regulatory suppressive activity of the epidermal growth factor receptor (EGFR) enzyme, secondly, gene expression of bcl2 was downregulated and thirdly, it induced cell cycle arrest at the G1/S. Thus, algal sterols can be used as medicine to treat disorders liver and colon cancers