Bacillus thuringiensis (Bt) is a bacterium capable of producing Cry toxins, which are recognized for their bio-controlling actions against insects. However, a few Bt strains encode proteins lacking insecticidal activity but showing cytotoxic activity against different cancer cell lines and low or no cytotoxicity toward normal human cells. A subset of Cry anticancer proteins, termed parasporins (PSs), has recently arisen as a potential alternative for cancer treatment. However, the molecular receptors that allow the binding of PSs to cells and their cytotoxic mechanisms of action have not been well established. Nonetheless, their selective cytotoxic activity against different types of cancer cell lines places PSs as a promising alternative treatment modality. In this review, we provide an overview of the classification, structures, mechanisms of action, and insights obtained from genetic modification approaches for PS proteins.

Cry11 proteins are toxic to Aedes aegypti, the vector of dengue, chikungunya, and Zika viruses. Cry11Aa and Cry11Bb are protoxins, which when activated present their active-toxin form in two fragments between 30 and 35 kDa respectively. Previous studies conducted with Cry11Aa and Cry11Bb genes using DNA shuffling generated variant 8, which presented a deletion in the first 73 amino acids and one at position 572 and 9 substitutions including L553F and L556W. In this study, variant 8 mutants were constructed using site-directed mutagenesis, resulting in conversion of phenylalanine (F) and tryptophan (W) to leucine (L) at positions 553 and 556, respectively, producing the mutants 8F553L, 8W556L, and 8F553L/8W556L. Additionally, two mutants, A92D and C157R, derived from Cry11Bb were also generated. The proteins were expressed in the non-crystal strain BMB171 of Bacillus thuringiensis and subjected to median-lethal concentration (LC₅₀) tests on first-instar larvae of A. aegypti. LC₅₀ analysis showed that the 8F553L, 8W556L, 8F553L/8W556L, and C157R variants lost their toxic activity (>500 ng·mL⁻¹), whereas the A92D protein presented a loss of toxicity of 11.4 times that of Cry11Bb. Cytotoxicity assays performed using variant 8, 8W556L and the controls Cry11Aa, Cry11Bb, and Cry-negative BMB171 on the colorectal cancer cell line SW480 reported 30–50% of cellular viability except for BMB171. Molecular dynamic simulations performed to identify whether the mutations at positions 553 and 556 were related to the stability and rigidity of the functional tertiary structure (domain III) of the Cry11Aa protein and variant 8 showed the importance of these mutations in specific regions for the toxic activity of Cry11 against A. aegypti. This generates pertinent knowledge for the design of Cry11 proteins and their biotechnological applications in vector-borne disease control and cancer cell lines.

Background/Objectives: Parasporin PS2Aa1, recently designated as Mpp46Aa1, is recognized for its selective anticancer activity against various human cell lines. In this study, specific regions of the native protein were fragmented, and targeted amino acid substitutions were introduced to improve cytotoxic selectivity and potency. Methods: The modified fragments were evaluated individually and in combination with curcumin, a polyphenol with well-documented anticancer properties, and Sacha inchi-derived matrices, known for their antioxidant and antiproliferative activities. Results: Experimental results demonstrated that the substituted variant designated T104L-G108W exhibited superior anticancer activity compared to the native peptide P102-K11. Synergism assays revealed that curcumin-bioconjugated peptides were more effective against the tested cell lines, whereas combinations with Sacha inchi reduced cytotoxicity, suggesting possible interference in the mechanisms of action. Functional assays, including caspase 3/7 and 9 activation, Annexin V-Cy3 staining, and cell viability analysis with 6-CFDA, confirmed increased sensitivity in SiHa and HeLa cell lines, particularly for peptide T104L-G108W. Conclusions: Collectively, these findings support the effectiveness of a substitution-based strategy in improving parasporin fragments and underscore the therapeutic potential of peptide T104L-G108W as a novel anticancer candidate. Furthermore, this study provides preliminary evidence that natural biomolecules can be optimized through targeted modifications and rational combinations, establishing a framework for the development of sustainable and selective therapeutic approaches in cancer treatment.

Objetivo: Formular un medio de cultivo para la producción de proteínas parasporales de Bt.Método: Se evaluaron 5 medios de cultivo, contrastando su formulación con la producción de biomasa. Se extrajo la proteína total de cada uno de los cultivos y se cuantificó por espectrofotometría.Resultados: Se encontró que el caldo glucosado modificado con proporciones 2,4:1 de fuentes de nitrógeno orgánicas (extracto de levadura) e inorgánicas ((NH4)2SO4) mejoró hasta en 70 veces la producción de proteína con concentraciones entre 19,38 y 154,41 mg/mL.Conclusión: Este estudio contribuye a la afirmación de que la proporción entre Nitrógeno Orgánico e Inorgánico tiene efectos importantes sobre la fase III del crecimiento de Bt, contrastando con la producción de endosporas y en consecuencia proteínas totales en las cuales e incluyen el aumento de las δ-endotoxinas.