In this work, we isolated a surface layer protein (SLP) from a (Bt) strain to evaluate it cytotoxic effects against MDA-MB-231 human breast cancer cells. AP11 was selected from a group of Bt strains using SLP oligonucleotides developed from conserved regions. The AP11 strain was grown in Luria Bertani medium until the late exponential phase; an 86 kDa protein was extracted using 5 M LiCl and identified by liquid chromatography- tandem mass spectrometry. It corresponded to a multispecies SLP highly similar to previously described SLPs in Bt. The MDA-MB-231 breast cancer cells LC was obtained using 0.25 μg/ml of the isolated SLP. HaCat non-cancerous cells presented 90% survival using the same protein concentration. Our data suggest that SLP cytotoxicity against MDA-MB-231 could be induced by an interaction with the CDH11 cell membrane receptor.

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Dunaliella salina is genus most important species for β-carotene production. Several investigations have demonstrated that D. salina produces more than 10% of its dry mass. β-carotene is an important pro-vitamin A source and can also act as a lipid radical scavenger and as a singlet oxygen quencher. Vitamin A Deficiency (VAD) has been related with cancer, for this reason synthetic and natural β-carotene has been used for prevention and treatment of the disease. Synthetic β-carotene is cheaper than natural molecule but only contains all-trans-β-carotene (ATβC), while 9-cis-β-carotene (9CβC) and ATβC are both produce by D. salina. Meta-analysis of controlled trials using high levels of synthetic β-carotene supplementation in smoker's individuals, mention that instead to prevent and control lung cancer, treatment increases risk and percentage of positive cases. Results obtained in cancer cell lines and animal models using β-carotene from Dunaliella, prevented and controlled diseases proliferation. In this work, effects of synthetic and natural β-carotene from D. salina were evaluated on MDA-MB-231 breast cancer cells, and even when apoptosis induction results were obtained with both sources, natural β-carotene generates considerable higher cell rates mortality.