a b s t r a c tMicroRNAs (miRNAs) represent a class of small non-coding RNAs that regulate gene expression at the post-transcriptional levels. Recent studies show that miRNAs may function as oncogenes or tumor suppressor genes. In this study, we demonstrated that miR-518b was down-regulated in esophageal squamous cell carcinoma (ESCC) tissues and correlated with metastasis and survival. miR-518b suppressed the proliferation by inducing apoptosis and repressed the invasion in ESCC cells, but had no effect on the cell cycle. Furthermore, Rap1b was revealed to be directly regulated by miR-518b. These findings indicate that miR-518b may function as a tumor suppressor by targeting Rap1b in the development of ESCC and has important clinical and prognostic value.

We report fluorescent carbon nanoparticle (FCN)-based small interfering RNA (siRNA) conjugates (C-siRNA) for gene regulation and cancer therapy. The C-siRNA has a core of chitosan-derived FCN and a shell of siRNA, and can down-regulate the expression of polo-like kinase-1 (Plk1), a master regulator of mitosis, via siRNA targeting Plk1 (siPlk1), for cancer therapy. The required amount of the FCNs is only ∼1/30 of that of the gold nanoparticles in delivering equal amount of siRNA. The C-siPlk1 led to ∼80% knockdown of cellular Plk1 mRNA in A375 cells, and induced apoptosis of the A375 cells (31.9%) and MCF-7 cells (20.33%), much higher than those by commercial nonviral gene delivery vectors, such as Lipofectamine 2000 in both cell lines (apoptosis rate < 10%). After the C-siPlk1 was administrated to A375 tumor-bearing mice intravenously, the tumor volume was less than 1/11 of the control groups. The C-siRNA can thus be powerful tools for gene delivery and gene therapy.

The camouflage with cell membrane bestows nanoparticles with cell‐like functions, such as specific recognition, long blood circulation, and immune escaping. For cancer therapy, the nanoparticles camouflaged with cancer cell membrane (CCM) from homologous cells show homotypic targeting delivery of small molecule compounds, photosensitizers, or enzymes to the tumors. However, effective gene therapy encounters difficulties by this approach due to the properties of nucleic acids. Herein, a cancer cell‐like gene delivery system is developed using an excellent polymer poly(β‐amino ester) (PBAE) to condense small interfering RNA (siRNA) (targeting to Plk1 gene) into nanoparticles (PBAE/siPlk1) as the core, which is further camouflaged with CCM. These novel biomimetic nanoparticles CCM/PBAE/siPlk1 (CCMPP) demonstrate highly specific targeting to homotypic cancer cells, effective downregulation of PLK1 level, and inducing apoptosis of cancer cells. Based on the homotypic binding adhesion molecules on the CCM, the cellular internalization and homotypic‐targeting accumulation to the tumors are clearly improved. CCMPP induces highly efficient apoptosis of cancer cells both in vitro and in vivo and results in significant tumor inhibition. The artificial cancer cells with homotypic properties can serve as a biomimetic delivery system for cancer‐targeted gene therapy.

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