Influence of cecropin on the progression of breast cancer in the animal model

Mahnoosh Fatemi,1 Fereshte ghandehari,2,* Malahat rezaee,3 Somaye davoodi,4

1. 1. Department of Biology, Falavarjan Branch, Islamic Azad University, Isfahan, Iran
2. 2. Department of Microbiology, Falavarjan Branch, Islamic Azad University, Isfahan, Iran
3. 3. Department of Biochemistry, Falavarjan Branch, Islamic Azad University, Isfahan, Iran
4. 2. Department of Microbiology, Falavarjan Branch, Islamic Azad University, Isfahan, Iran

Abstract


Introduction

Antimicrobial peptide (amps) are short cationic peptides with an amphipathic structure that are essential component of the host innate immunity. amps generally recognize their target via electrostatic interactions with negatively charged lipids on cell membranes. while amp investigations have been largely focused on antimicrobial properties, there is increasing evidence that antimicrobial peptides display antitumor functions. the overexpression of anionic membrane components, including glycoproteins, glycolipids, proteoglycans, phospholipids and the increase in surface area with increasing number of microvilli on the surface of cancer cells compared with non-cancerous cells enhance amp binding to cancer cells, which may either disrupt the membrane or penetrate the cell and attack the mitochondria leading to apoptosis. in spite of the efficient properties of amp, there are few in-vivo studies on cancer therapy of these peptides. therefore, the aim of this study was to evaluate the effect of cecropin b, as an antimicrobial peptide on the progression of breast cancer induced in rats.

Methods

: 24 female rats (150±20g) were randomly divided into three groups. control group: rats were fed with water and food throughout the experimental period and 0.5 ml of sesame oil was injected in their right nipple at the beginning of the test. cancerous group: dmba (60 mg/kg dissolved in 0.5 ml of sesame oil) was injected into their right nipple. cecropin b-treated group: the breast cancer was induced in these rats in the same way as the cancerous group. when tumors reached an average diameter of 10 mm, cecropin b (25 µg/ml) was intratumorally injected on a daily basis for 3 weeks. the tumor size was measured at the beginning and the end of the treatment period. the blood samples were collected directly from the heart. then blood cells and their indexes were analyzed using an automated hematology analyzer xe-5000. for histopathological studies, the tissue sections of the tumors were stained with hematoxylin and eosin. the separated and homogenized tumor tissues was then centrifuged. bax and bcl-2 concentration in the prepared samples was measured by elisa method. data were expressed as mean±sd and analyzed by paired-samples t-test to determine the size of tumors. one-way analysis of variance (anova) was used to analysis the other data. the analyses were performed using spss 20 software. the significance level was set at p≤0.05.

Results

The result showed that tumor volume had a significant increase in cancerous group (p≤0.01) and cecropin-treated group (p≤0.05) at the end of the treatment than the beginning. platelet number increased in cancerous group and cecropin-treated group (p≤0.001 and p≤0.01, respectively). however, there was a decrease in mean platelet volume (mpv) and platelet distribution width (pdw) (p-≤0.01 and p≤0.05, respectively). in cancerous group, a significant increase was observed in red blood cell (rbc) (p≤0.01), mean cell volume (mcv) (p≤0.001) and mean capsular hemoglobin (mch) (p≤0.001) while red cell distribution width (rdw) was significantly decreased (p≤0.01). in cecropin-treated group, rbc and mch were decreased (p≤0.05). hemoglobin content and hematocrit in cancerous group was decreased (p≤0.001 and p≤0.01, respectively). these factors was also decreased in cecropin-treated group (p≤0.05). in addition, there was an increase in wbc and lymphocytes in cancerous group (p≤0.001 and p≤0.01, respectively) and in cecropin-treated group (p≤0.05) in comparison to the control. since avoidance of apoptosis is one of the characteristics in cancer cells, bax and bcl-2 concentration were calculated as apoptotic markers. the results demonstrated that an increase in bax (p≤0.01) and a decrease in bcl-2 (p≤0.05) was observed in cecropin-treated group compared to cancerous group. histopathological study also showed stromal and muscular invasion of mitotic cells in breast tissue, while in cecropin-treated group focal destruction of tissue and cell death was observed.

Conclusion

In present study, decrease in tumor size and cell death in tumor could indicate an inhibitory effect of the cecropin b on tumor growth in the cecropin-treated group. in addition, an increase in bax and a decrease in bcl-2 in this group compared to cancerous group could represent the induction of cell death through the pathway of apoptosis. further investigation is necessary to introduce cecropin b as an efficient candidate for treatment of cancer.

Keywords

Breast cancer, cecropin, animal model