Development, Characterization, and Evaluation of SLN-Loaded Thermoresponsive Hydrogel System of Topotecan as Biological Macromolecule for Colorectal Delivery.

BACKGROUND: Chemotherapeutic drugs cause severe toxicities if administered unprotected, without proper targeting, and controlled release. In this study, we developed topotecan- (TPT-) loaded solid lipid nanoparticles (SLNs) for their chemotherapeutic effect against colorectal cancer. The TPT-SLNs were further incorporated into a thermoresponsive hydrogel system (TRHS) (TPT-SLNs-TRHS) to ensure control release and reduce toxicity of the drug. Microemulsion technique and cold method were, respectively, used to develop TPT-SLNs and TPT-SLNs-TRHS. Particle size, polydispersive index (PDI), and incorporation efficiency (IE) of the TPT-SLNs were determined. Similarly, gelation time, gel strength, and bioadhesive force studies of the TPT-SLNs-TRHS were performed. Additionally, in vitro release and pharmacokinetic and antitumour evaluations of the formulation were done. RESULTS: TPT-SLNs have uniformly distributed particles with mean size in nanorange (174 nm) and IE of ~90%. TPT-SLNs-TRHS demonstrated suitable gelation properties upon administration into the rat's rectum. Moreover, drug release was exhibited in a control manner over an extended period of time for the incorporated TPT. Pharmacokinetic studies showed enhanced bioavailability of the TPT with improved plasma concentration and AUC. Further, it showed significantly enhanced antitumour effect in tumour-bearing mice as compared to the test formulations. CONCLUSION: It can be concluded that SLNs incorporated in TRHS could be a potential source of the antitumour drug delivery with better control of the drug release and no toxicity.

The miR-17∼92 cluster contributes to MLL leukemia through the repression of MEIS1 competitor PKNOX1.

Mixed lineage leukemias have a relatively poor prognosis and arise as a result of translocations between the MLL(KMT2A) gene and one of multiple partner genes. Downstream targets of MLL are aberrantly upregulated and include the developmentally important HOX genes and MEIS1, as well as multiple microRNAs (miRNAs), including the miR-17∼92 cluster. Here we examined the contribution of specific miRNAs to MLL leukemias through knockdown studies utilizing custom anti-microRNA oligonucleotides. Combinatorial treatment against miR-17-5p and miR-19a-3p of the miR-17∼92 cluster dramatically reduces colony forming ability of MLL-fusion containing cell lines relative to non-MLL acute myeloid leukemia (AML) controls. To determine the mechanism by which these miRNAs contribute to leukemia, we validated PKNOX1 as a target of both miR-17-5p and miR-19a-3p. MEIS1 and PKNOX1 are TALE domain proteins that participate in ternary complexes with HOX and PBX partners. Here we establish the competitive relationship between PKNOX1 and MEIS1 in PBX-containing complex formation and determine the antagonistic role of PKNOX1 to leukemia in a murine MLL-AF9 model. These data implicate the miR-17∼92 cluster as part of a regulatory mechanism necessary to maintain MEIS1/HOXA9 -mediated transformation in MLL leukemia, indicating that targeting multiple non-homologous miRNAs may be utilized as a novel therapeutic regimen.

MicroRNAs in leukemias: emerging diagnostic tools and therapeutic targets.

MicroRNAs (miRNA) are small non-coding RNAs of approximately 22 nucleotides that regulate the translation and stability of mRNA to control different functions of the cell. Misexpression of miRNA has been linked to disruption of normal cellular functions, which results in various disorders including cancers such as leukemias. MicroRNA involvement in disease has been the subject of much attention and is increasing our current understanding of disease biology. Such linkages have been determined by high-throughput studies, which provide a framework for characterizing differential miRNA expression levels correlating to different cytogenetic abnormalities and their corresponding malignancies. In addition, functional studies of particular miRNAs have begun to define the effects of miRNA on predicted mRNA targets. It is clear that miRNAs can serve as molecular markers of leukemias and the hope is that they can also serve as new therapeutic targets. Studies are beginning to elucidate how to deliver therapeutic antagonists to attenuate overexpressed miRNAs and to replace underexpressed miRNAs. In this review, we: i) discuss the current understanding of miRNA function and expression in normal hematopoiesis, ii) provide examples of miRNAs that are misregulated in leukemias, and iii) evaluate the current status and potential future directions for the burgeoning field of antisense oligonucleotides and other therapeutic attempts to intervene in miRNA disregulation in leukemias.