DNA Deamination Is Required for Human APOBEC3A-Driven Hepatocellular Carcinoma In Vivo.

Although the APOBEC3 family of single-stranded DNA cytosine deaminases is well-known for its antiviral factors, these enzymes are rapidly gaining attention as prominent sources of mutation in cancer. APOBEC3's signature single-base substitutions, C-to-T and C-to-G in TCA and TCT motifs, are evident in over 70% of human malignancies and dominate the mutational landscape of numerous individual tumors. Recent murine studies have established cause-and-effect relationships, with both human APOBEC3A and APOBEC3B proving capable of promoting tumor formation in vivo. Here, we investigate the molecular mechanism of APOBEC3A-driven tumor development using the murine Fah liver complementation and regeneration system. First, we show that APOBEC3A alone is capable of driving tumor development (without Tp53 knockdown as utilized in prior studies). Second, we show that the catalytic glutamic acid residue of APOBEC3A (E72) is required for tumor formation. Third, we show that an APOBEC3A separation-of-function mutant with compromised DNA deamination activity and wildtype RNA-editing activity is defective in promoting tumor formation. Collectively, these results demonstrate that APOBEC3A is a "master driver" that fuels tumor formation through a DNA deamination-dependent mechanism.

SN-38 Conjugated Gold Nanoparticles Activated by Ewing Sarcoma Specific mRNAs Exhibit In Vitro and In Vivo Efficacy.

The limited delivery of chemotherapy agents to cancer cells and the nonspecific action of these agents are significant challenges in oncology. We have previously developed a customizable drug delivery and activation system in which a nucleic acid functionalized gold nanoparticle (Au-NP) delivers a drug that is selectively activated within a cancer cell by the presence of an mRNA unique to the cancer cell. The amount of drug released from sequestration to the Au-NP is determined by both the presence and the abundance of the cancer cell specific mRNA in a cell. We have now developed this technology for the potent, but difficult to deliver, topoisomerase I inhibitor SN-38. Herein, we demonstrate both the efficient delivery and selective release of SN-38 from gold nanoparticles in Ewing sarcoma cells with resulting efficacy in vitro and in vivo. These results provide further preclinical validation for this novel cancer therapy and may be extendable to other cancers that exhibit sensitivity to topoisomerase I inhibitors.

Efficient Synthetic Approach to Linear Dasatinib-DNA Conjugates by Click Chemistry.

A pair of synthetic approaches to linear dasatinib-DNA conjugates via click chemistry are described. The first approach involves the reaction of excess azido dasatinib derivative with 5'-(5-hexynyl)-tagged DNAs, and the second involves the reaction of excess alkynyl-linked dasatinib with 5'-azido-tagged DNA. The second approach using alkynyl-derived dasatinib and 5'-azido-tagged DNA yielded the corresponding dasatinib-DNA conjugates in higher yield (47% versus 10-33% for the first approach). Studies have shown these linear dasatinib-DNA conjugates-derived gold nanoparticles exhibit efficacy against leukemia cancer cells with reduced toxicity toward normal cells compared to that of free dasatinib.

Drug conjugated nanoparticles activated by cancer cell specific mRNA.

We describe a customizable approach to cancer therapy in which a gold nanoparticle (Au-NP) delivers a drug that is selectively activated within the cancer cell by the presence of an mRNA unique to the cancer cell. Fundamental to this approach is the observation that the amount of drug released from the Au-NP is proportional to both the presence and abundance of the cancer cell specific mRNA in a cell. As proof-of-principle, we demonstrate both the efficient delivery and selective release of the multi-kinase inhibitor dasatinib from Au-NPs in leukemia cells with resulting efficacy in vitro and in vivo. Furthermore, these Au-NPs reduce toxicity against hematopoietic stem cells and T-cells. This approach has the potential to improve the therapeutic efficacy of a drug and minimize toxicity while being highly customizable with respect to both the cancer cell specific mRNAs targeted and drugs activated.