Antitumor effect and toxicity of free rhodium (II) citrate and rhodium (II) citrate-loaded maghemite nanoparticles in mice bearing breast cancer

Background: Magnetic fluids containing superparamagnetic iron oxide nanoparticles represent an attractive platform as nanocarriers in chemotherapy. Recently, we developed a formulation of maghemite nanoparticles coated with rhodium (II) citrate, which resulted in in vitro cytotoxicity enhanced up to 4.6 times when compared to free rhodium (II) citrate formulation on breast carcinoma cells. In this work, we evaluate the antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Methods: Mice were evaluated with regard to the treatments’ toxicity through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine; DNA fragmentation and cell cycle of bone marrow cells; and liver, kidney and lung histology. In addition, the antitumor activity of rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate was verified by tumor volume reduction, histology and immunohistochemistry. Results: Regarding the treatments’ toxicity, no experimental groups had alterations in levels of serum ALT or creatinine, and this suggestion was corroborated by the histopathologic examination of liver and kidney of mice. Moreover, DNA fragmentation frequency of bone marrow cells was lower than 15% in all experimental groups. On the other hand, the complexes rhodium (II) citrate-functionalized maghemite and free rhodium (II) citrate led to a marked growth inhibition of tumor and decrease in CD31 and Ki-67 staining. Conclusions: In summary, we demonstrated that both rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate formulations exhibited antitumor effects against 4T1 metastatic breast cancer cell line following intratumoral administration. This antitumor effect was followed by inhibition of both cell proliferation and microvascularization and by tumor tissue injury characterized as necrosis and fibrosis. Remarkably, this is the first published report demonstrating the therapeutic efficacy of maghemite nanoparticles coated with rhodium (II) citrate. This treatment prolonged the survival period of treated mice without inducing apparent systemic toxicity, which strengthens its use for future breast cancer therapeutic applications

Avaliação toxicológica e antitumoral do tratamento sistêmico com citrato de ródio (II) livre e associado a nanopartículas de maghemita em modelo experimental de câncer de mama

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Biologia Celular, 2012.O Câncer de mama é uma das principais causas de morte entre as mulheres em todo mundo, com estimativa do Instituto Nacional de Câncer de 52.680 novos casos no Brasil em 2012. Agentes antitumorais à base de metal, como a cisplatina, podem induzir respostas favoráveis em tumores sólidos humanos, embora seus efeitos colaterais limitem seu uso na clínica. Portanto, já foi descrito que citrato de ródio (II), um composto metálico análogo à cisplatina, apresentou atividade antitumoral em carcinoma ascítico de Ehrlich. Além disso, o desenvolvimento de técnicas que consigam entregar agentes antitumorais com maior seletividade representa uma das maiores áreas de interesse na pesquisa do câncer. Nanobiotecnologia é um novo campo de pesquisa envolvendo avanços na detecção, diagnóstico e tratamentos de câncer. Nanopartículas envolvem uma variedade de nanosistemas coloidais que podem ser usadas para entrega de drogas. Algumas delas possuem propriedades magnéticas e devido ao seu tamanho reduzido (4-12 nm) permitem maior permeabilidade e retenção no tumor. Assim, a associação de citrato de ródio (II) com nanopartículas magnéticas poderia melhorar o efeito antitumoral, em função da maior especificidade a células e a tecidos específicos. Deste modo, o objetivo deste estudo foi avaliar as respostas toxicológicas e os efeitos antitumorais do tratamento sistêmico com citrato de ródio (II) livre e associado com nanopartículas de maghemita em câncer de mama. Camundongos BALB/c fêmeas foram inoculados com 2 x 104 células de carcinoma mamário 4T1 para o estabelecimento do tumor. Após sete dias, os animais foram tratados com citrato de ródio (II) livre, citrato de ródio (II) associado com nanopartículas de maghemita e citrato associado com nanopartículas de maghemita, por via intravenosa. Os tratamentos foram realizados a cada três dias e os animais foram eutanasiados depois da terceira dose. Os tumores foram removidos cirurgicamente, medidos, pesados e processados para as análises histopatológicas com intuito de avaliar a atividade antitumoral. As imagens foram adquiridas em microscópio de luz Zeiss Axiophot e as áreas de necrose tumoral foram medidas com software Motic Images Plus 2.0. Para as avaliações toxicológicas, amostras de sangue foram analisadas por testes bioquímicos e hematológicos. Não foram observadas diferenças significativas de volume e peso tumoral, embora todos os tratamentos tenham resultado em redução não significativa comparados ao controle. Citrato de ródio (II) livre e associado com nanopartículas promoveram um aumento não significativo da área de necrose em relação ao grupo controle. Além disso, análises bioquímicas e hematológicas de camundongos BALB/c sem implante tumoral não apresentaram efeitos tóxicos relativos aos compostos utilizados. Assim, citrato de ródio (II) livre e associado com nanopartículas de maghemita apresentaram atividade antitumoral em carcinoma mamário 4T1, indicando que, com adequado ajuste da dose, essas composições podem apresentar potencial terapêutico para aplicação em câncer de mama. _________________________________________________________________________________ ABSTRACTBreast cancer is one of the main causes of death among women around the world, with an estimated of National Cancer Institute of 52,680 new cases in Brazil in 2012. Metal-based antitumor drugs like cisplatin can induce favorable response in human solid tumors, however its adverse side effects limit its clinical activity. Therefore, it was described that rhodium (II) citrate, an metal-based compound analog to cisplatin, showed antitumor activity in Ehrlich ascites breast carcinoma. Moreover, the development of techniques that can deliver anticancer agents selectively represents one of the major areas of interest in cancer research. Nanobiotecnology is a new field of research expected to advance in cancer detection, diagnosis, and treatments. Nanoparticles encompass a variety of colloidal nanosystems which can be used for drug delivery. Some metal nanoparticles has magnetic properties and extremely reduced size (4-12 nm), allowing tissue permeability and drug retention into the tumor. Then, the association of rhodium (II) citrate with magnetic nanoparticles could improve the antitumor effect by targeting specific cells or tissues. Hence, the aim of this study was to evaluate the toxicological responses and antitumor activity of systemic treatment with rhodium (II) citrate free and associated with maghemite nanoparticles in breast cancer. Females BALB/c mice were injected with 2 x 104 4T1 mammary carcinoma cells for tumor establishment. After seven days, animals were treated with free rhodium (II) citrate, rhodium (II) citrate loaded maghemite nanoparticles and citrate-loaded maghemite nanoparticles by intravenous administration. Treatments were carried out every three days and animals were euthanized after the third dose administration. Then, tumors were surgically removed, measured, weighted and prepared for histopathological analyses in order to evaluate the antitumor activity. Images were acquired in Zeiss Axiophot light microscopy and tumor necrosis areas were measured by Motic Images Plus 2.0 software. For toxicological investigation, blood samples were analyzed by biochemical and hematological tests. No significant differences were observed for tumor volume and weight, although all treatments resulted in a non-significant reduction compared to control. Free rhodium (II) citrate and rhodium (II) citrate associated with maghemite nanoparticles promoted a non-significant increased in necrosis area compared to control. Furthermore, biochemical and hematological analysis of BALB/c mice without tumor inoculation didn’t show toxic effects of the used compounds. Thus, free rhodium (II) citrate and rhodium (II) citrate loaded maghemite nanoparticles showed antitumor activity on 4T1 mammary carcinoma, indicating that, with adequate adjustment of the dose, this compound can have potential for application in breast cancer