In human cancers, telomeres are commonly maintained by elevated levels of the ribonucleoprotein enzyme telomerase, which contains an intrinsic templating RNA moiety (human telomerase RNA; hTER) and the core protein (human telomerase reverse transcriptase). We developed a lentiviral system for efficient overexpression of mutant-template human telomerase RNA (MT-hTer) to add mutant DNA to telomeres in cancer cells. We show that such MT-hTer overexpression rapidly inhibits cell growth and induces apoptosis in telomerase-positive precancerous or cancer cells but not in telomerase-negative cells. These rapid effects occurred independent of wild-type p53 and telomere length. Tumor growth and progression were significantly decreased in xenografts of human tumor cells overexpressing MT-hTers. Expression of a hairpin short-interfering RNA that specifically targeted the endogenous wild-type hTER template region, but spared the MT-hTers, also caused p53-independent cell growth inhibition and apoptosis, and when coexpressed with MT-hTer, synergistically killed cancer cells. Hence, anti-wild-type-hTER short-interfering RNA and MT-hTers may act through distinct pathways and, particularly in combination, represent a promising approach to anticancer therapies.

Targeted drug delivery systems that combine imaging and therapeutic modalities in a single macromolecular construct may offer advantages in the development and application of nanomedicines. To incorporate the unique optical properties of luminescent quantum dots (QDs) into immunoliposomes for cancer diagnosis and treatment, we describe the synthesis, biophysical characterization, tumor cell-selective internalization, and anticancer drug delivery of QD-conjugated immunoliposome-based nanoparticles (QD-ILs). Pharmacokinetic properties and in vivo imaging capability of QD-ILs were also investigated. Freeze-fracture electron microscopy was used to visualize naked QDs, liposome controls, nontargeted QD-conjugated liposomes (QD-Ls), and QD-ILs. QD-ILs prepared by insertion of anti-HER2 scFv exhibited efficient receptor-mediated endocytosis in HER2-overexpressing SK-BR-3 and MCF-7/HER2 cells but not in control MCF-7 cells as analyzed by flow cytometry and confocal microscopy. In contrast, nontargeted QD-Ls showed minimal binding and uptake in these cells. Doxorubicin-loaded QD-ILs showed efficient anticancer activity, while no cytotoxicity was observed for QD-ILs without chemotherapeutic payload. In athymic mice, QD-ILs significantly prolonged circulation of QDs, exhibiting a plasma terminal half-life ( t 1/2) of approximately 2.9 h as compared to free QDs with t 1/2 < 10 min. In MCF-7/HER2 xenograft models, localization of QD-ILs at tumor sites was confirmed by in vivo fluorescence imaging.

Targeting of pathways downstream of RAS represents a promising therapeutic strategy for pancreatic cancer, the fourth leading cause of cancer-related death in the USA, since activation of the Raf-MEK-ERK and PI3K-AKT pathways is found frequently in this disease and is associated with poor prognosis. Taking advantage of a panel of human PDAC cell lines and specific inhibitors of PI3K and/or mTOR, we systematically address the question whether dual-targeted inhibition of the PI3K and mTOR pathways offers advantages over single-targeted inhibition of PI3K in PDAC. We observe greater overall susceptibility of cell lines to dual inhibition compared to targeting PI3K alone. However, we find that dual inhibition of PI3K and mTOR induces autophagy to a greater extent than inhibition of each target alone. In agreement with this, we show that combined administration of PI3K/mTOR and autophagy inhibitors results in increased anti-tumor activity in vitro and in vivo in models of pancreatic adenocarcinoma. XL765, a PI3K/mTOR inhibitor used in our in vivo studies, is currently undergoing clinical evaluation in a variety of cancer types, while the autophagy inhibitor chloroquine is a widely used anti-malaria compound. Thus, our studies provide rationale for clinical development of combinations of these compounds for the treatment of pancreatic adenocarcinoma.