Induction of ductal carcinomas by intraductal administration of 7,12-dimethylbenz(a)anthracene in Wistar rats

Contributions of nanotechnology to the intraductal drug delivery for local treatment and prevention of breast cancer

Breast cancer is a major public health problem, affecting millions of people. It is a very heterogeneous disease, with localized and invasive forms, and treatment generally consists of a combination of surgery and radiotherapy followed by administration of estrogen receptor modulators or aromatase inhibitors. Given its heterogeneity, management strategies that take into consideration the type of disease and biological markers and can provide more personalized and local treatment are required. More recently, the intraductal administration (i.e., into the breast ducts) of drugs has attracted significant attention due to its ability of providing drug distribution through the ductal tree in a minimally invasive manner. Although promising, intraductal administration is not trivial, and difficulties in duct identification and cannulation are important challenges to the further development of this route. New drug delivery strategies such as nanostructured systems can help to achieve the full benefits of the route due to the possibility of prolonging tissue retention, improving targeting and selectivity, increasing cytotoxicity and reducing the frequency of administration. This review aims at discussing the potential benefits and challenges of intraductal administration, focusing on the design and use of nanocarriers as innovative and feasible strategies for local breast cancer therapy and prevention.

Study of the cytotoxicity of asiaticoside on rats and tumour cells

Background

Cancer chemoprevention is considered one of the most promising areas in current cancer research, and asiaticoside, which is derived from the plant Centella asiatica, has a relative lack of systemic toxicity. The purpose of this study was to investigate whether asiaticoside is effective against 7,12-dimethylbenz(a)anthracene (DMBA)-induced carcinogenicity in vitro (MCF-7 and other cells) and in vivo (DMBA-induced rat cancer).

Methods

An MTT assay was performed involving the treatment of MCF-7 cells for 48 h with H₂O₂ alone and H₂O₂ + different asiaticoside concentrations. Flow cytometry was performed, and the level of caspase 3, tumour necrosis factor-alpha (TNF-α) and interleukin-1 (IL-1) were quantified. Adult female Sprague–Dawley (SD) rats were divided into five groups designated I (control), II (DMBA-induced cancer), III (pre- and post-treatment with asiaticoside (200 μg/animal) in DMBA-induced cancer), IV (post-treatment with asiaticoside in DMBA-induced cancer), and V (treated with asiaticoside alone, drug control). Twelve weeks post-DMBA, rats developed mammary tumours. Rats either were sacrificed or imaged with MIBI. Histological examination of tumour tissues was performed. Tumour MIBI uptake ratios were determined. The data are expressed as the means ± standard deviation. Appropriate t-test and ANOVA statistical methods were used to compare data.

Results

The IC50 of asiaticoside for MCF-7 cells was determined to be 40 μM. Asiaticoside has potential for hydrogen peroxide cytotoxicity, and the caspase-3 activity increased with increasing asiaticoside dose in MCF-7 cells treated for 48 h. The expression of the cytokines TNF-α and IL-1β was significantly decreased and correlated with MIBI uptake ratios in vitro and in vivo after asiaticoside administration.

Conclusion

This study demonstrates that asiaticoside is effective in vitro and in vivo in inducing apoptosis and enhancing anti-tumour activity.

Effects of dehydroepiandrosterone and other sex steroid hormones on mammary carcinogenesis by direct injection of 7,12-dimethylbenz(a) anthracene (DMBA) in hyperprolactinemic female rats

The present study was performed to investigate the effects of dehydroepiandrosterone (DHEA) compared with those of sex steroid hormones on the mammary tumor induced by local injection of 7,12-dimethylbenz(a) anthracene (DMBA) in hyperprolactinemic female rats. Under sustained hyperprolactinemia induced by pimozide (PMZ) from day 21, DMBA was injected locally into the mammary glandular tissues on day 73. Rats were divided into 5 groups as follows; steroid free (DP group), 17 beta-estradiol (DP + E2 group), testosterone (DP + T group), progesterone (DP + Prog group), or dehydroepiandrosterone (DP + DHA group). The growth pattern and histological classification of the tumor in these 5 groups and rats treated only with DMBA (D group) were examined. All of the tumors grew to a size of 10 mm in diameter and after retaining the size for a certain duration, increased the size rapidly again (onset of rapid tumor growth). The period from the day of DMBA administration to that of onset of the rapid tumor growth in DP group was shorter than in D group, and the period in DP + DHA was longer than DP group and longest in steroid-treated groups. The incidence of adenocarcinoma was 2 tumors/16 animals in D group, 9/11 in DP group, 5/11 in DP + Prog group, 2/7 in DP + E2 group, 2/8 in DP + T group, and 0/10 in DP + DHA group. The incidence of adenocarcinoma in each steroid group except in DP + Prog group was lower than in DP group. These results suggest that prolactin (PRL) increases the incidence of adenocarcinoma in the DMBA-induced mammary tumor model, and DHEA especially decreases the incidence of adenocarcinoma.