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Objective: The development of nanomedicine, such as miRNA transfection to cancer cells,has widely gained interest in the past decade. Unfortunately, miRNA tends to decay easily by the cellular enzymatic process and requires a carrier. As a cationic biopolymer, chitosan is widely known as a non-viral vector. However, research about chitosan as a miRNA delivery system remains limited. This study aimed to investigate the effect and characters of synthetic miRNA loaded chitosan nanoparticles on breast cancer cell lines. Methods: To obtain the nanocomplex, chitosan-antimiR-106b-5p was formulated using natriumtripolyphosphate through ionic gelation methods. The nanochitosan formula was characterized by using gel electrophoresis; Nano Quant for encapsulation of entrapment quantification; morphology appearance as viewed by Scanning Electron Microscope (SEM), nanochitosan size analysis; in vitro analysis using MCF-7 and T47D breast cancer cell lines; in silico prediction of possible gene target; polymerase chain reaction analysis and gel electrophoresis for E2F1/GAPDH expression. Results: The efficiency entrapment value was 96.7%, particle size analysis was 458±11.79 nm, and polydispersity index (PDI) was 0.65±0.07, with spherical morphology as viewed in SEM. There was no significant difference between the nanochitosan supplemented group and the control group in MCF-7 cells (p=0.067). However, the ratio of E2F1 to GAPDH was significantly lower than the control group after nanochitosan antimiR-106b-5p was loaded at concentration 140 nmol (p=0.022) and 35 nmol (p=0.016). Conclusion: Our nanochitosan formula is non-toxic to use in MCF-7 cell lines. Most importantly, as the formula was conjugated to synthetic antimiR-106b-5p, the E2F1 expression decreased.

Doxorubicin (Dox) has been used widely in breast cancer therapy. One of the problems in chemotherapy is the development of resistance to chemotherapy that lead to metastasis and relapse aggressiveness of cancer. MicroRNAs (miRNAs) are small non-coding RNA that regulate protein expression and play role in carcinogenesis, as well as cancer chemotherapy resistance. miR-451 is classified as tumour suppressor miRNA, that binds to messenger RNA (mRNA) of MDR1, and leads disruption of P-glycoprotein (Pgp) expression. The study aimed to investigate the association between miR-451 and Pgp related with Dox resistance mechanism. In silico analysis was conducted to predict the binding affinity between miR-451 and mRNA of MDR1. The MCF-7 cell line was used as wild type model, while MCF-7/Dox was used as a model of resistance. qPCR was conducted to calculate miR-451 expression and immunocytochemistry was used to observe Pgp expression. miRNA was down-regulated in both on MCF-7 and MCF-7/Dox. On the other hand, Pgp expression was detectable in the cytoplasmic and cytoplasmic membrane in MCF-7/Dox. The Pgp expression was higher in the MCF-7/Dox compared to MCF-7. In conlusion, the over expression of Pgp is associated with the resistance to MCF-7/Dox. ABSTRAKDoxorubisin (Dox) adalah salah satu kemoterapi yang telah digunakan secara klinis dalam terapi kanker payudara. Salah satu masalah dalam kemoterapi adalah perkembangan resistensi terhadap kemoterapi yang akan mengarah pada metastasis dan kekambuhan agresivitas kanker. MicroRNAs (miRNAs) merupakan untai RNA kecil yang dapat mengatur ekspresi protein dan berperan dalam karsinogenesis, serta resistensi obat kemoterapi. miR-451 diklasifikasikan sebagai miRNA penekan tumor, yang berikatan dengan messenger RNA (mRNA) MDR1 yang, dan menyebabkan gangguan ekspresi P-glycoprotein (Pgp). Tujuan dari penelitian ini adalah untuk memahami hubungan antara miR-451 dan Pgp terkait dengan mekanisme resistensi Dox. Analisis in silico dilakukan untuk memprediksi afinitas pengikatan antara miR-451 dan mRNA MDR1. Sel line MCF-7 digunakan sebagai wild-type sedangkan MCF-7/Dox, digunakan sebagai model resistensi. Kuantifikasi ekspresi miR-451 diukur menggunakan qPCR dan imunositokimia digunakan untuk mengamati ekspresi Pgp. miRNA-451 ditemukan mengalami penurunan ekspresi baik pada sel MCF-7 dan MCF-7/Dox. Dalam penelitian ini, Pgp ditemukan terekspresi dalam membran sitoplasma dan sitoplasma sel MCF-7/Dox dan MCF-7. Ekspresi PgP ditemukan terekspresi lebih tinggi pada MCF-7/Dox dibandingkan dengan MCF-7 wild-type. Dapat disimpulkan, tingkat ekspresi Pgp ini berkaitan dengan resistensi MCF-7/Dox.

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