Identification of a Bacillus thuringiensis Surface Layer Protein with Cytotoxic Activity against MDA-MB-231 Breast Cancer Cells

Abstract

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.

The Cytocidal Spectrum of Bacillus thuringiensis Toxins: From Insects to Human Cancer Cells

“…SLP proteins are other Bt toxins with both pesticide and anticancer activity. Recently studies have shown that these proteins also could be recognizing specific cell membrane receptors in cancer cells line [8], as Cry toxins do [153]. In addition to cytotoxic activity on insects and human cancer cell lines, SLP carry out structural and protection activities in several microorganisms.…”

“…Surface layer proteins (SLP) are widely represented, both in Gram-negative and Gram-positive bacteria, including Bacillus [17]. Similar to delta-endotoxins, SLP are assembled into parasporal positions with several shapes (oblique, square, or hexagonal) [8]. They have a molecular mass between 40 and 170 kDa [141,142], and are involved mainly in growth, survival, and maintenance of cell integrity [9].…”

“…A recent study reported an SLP from Bt with high selective cytotoxic activity in vitro against the MDA-MB-231 breast cancer cell line. Authors suggest that cadherin-11 receptor present in cancer cells seems to be involved in SLP recognition; however, the mechanism of action is still under study [8].…”

“…According to previous reports, S-layer proteins from Bt are associated with toxicity against Epilachna varivestis [9,18]. Furthermore, there is a report from an S-layer protein with selective cytotoxic activity against MDA-MB-231 breast cancer cells line [8].…”

“…Bacillus thuringiensis is a Gram-positive and sporulated bacterium that is widely distributed in soils, plants, and insects around the world [1,2]. Bt is well known because it produces a great variety of useful proteins for pest control in agriculture (Cry, Vip, Sip) [3,4], minimizes diseases transmitted by mosquitoes (Cyt) [5], inhibits pathogens development in animals [6], and because it induces cytotoxicity in human cancer cells (PS, SLP, and Cry) [7,8].…”