Study the impact of purified staphyloxanthin extracted from Staphylococcus aureus on CAL‑51 cancer cell line

Background. Breast cancer is a disease characterized by the abnormal growth of breast cells, which can grow uncontrollably and form tumors. If left untreated, these tumors can spread throughout the body and become life-threatening.
The CAL51 cell line was first isolated from a malignant pleural effusion of a woman with metastatic breast cancer. These cells grow in continuous culture and exhibit the morphological and ultrastructural features of epithelial cells of mammary origin. They are tumorigenic in nude mice and form colonies in soft agar. Estrogen receptors are not detected in these cells.
This study aimed to investigate the cytotoxicity of purified staphyloxanthin on a specific breast cancer model, the CAL51 cell line, and to demonstrate the pigment's effect as a potential treatment for this type of cancer. The study also sought to determine the ideal concentration of staphyloxanthin required to inhibit tumor cell growth. In addition, it evaluated the effect of the pigment on a normal, non-malignant cell line (REF cells).
Materials and methods. A total of 106 specimens were collected from hospitals in Baghdad. Patients of different age groups, both male and female, were included in the study, which spanned from October to April 2023. All bacterial isolates were examined for their microscopic, biochemical, and cultural characteristics. The results were further confirmed using the Vitek2 system.
Staphyloxanthin was extracted using ethyl acetate and acetone as solvents and purified through column chromatography. Four concentrations of the staphyloxanthin pigment, incubated for 24 hours, were used in the trial treatment of the CAL-51 tumor cell line and the normal REF cell line in vitro.
Results. A total of 53 bacterial isolates were collected, with 50% identified as Staphylococcus aureus. The results indicated that the primary source of S. aureus infection was the nasal cavity (from patients and medical staff), followed by wound ulcers and burns, which accounted for 38.7% of the infections. These sites were identified as the most common sources of bacterial infection.
In addition, the results showed that bacterial infections in urine and blood samples accounted for 22% and 26%, respectively, while 21% of the isolates were obtained from eye samples. Other sources of bacterial isolates were found at lower levels.
The ability of the bacteria to produce the pigment was tested, with the TID12 strain showing the highest production value of 1.87.
The extracted pigment concentration was 170.997 U/cell. In the CAL-51 tumor cell line, the maximum inhibition rate was 83% at a concentration of 1000 µg/ml, followed by 76% at 500 µg/ml, 73% at 250 µg/ml, and 70% at 125 µg/ml.
In contrast, for the normal REF cell line, tested at the maximum time point of 72 hours, the inhibition rate was significantly lower: 28% at 1000 µg/ml, 25% at 500 µg/ml, 22% at 250 µg/ml, and 20% at 125 µg/ml.
Conclusion. The purified staphyloxanthin pigment demonstrated a cytotoxic effect on the CAL-51 cell line at varying concentrations. However, it exhibited little to no effect on the normal REF cell line.