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We describe herein non-integrating minimally sized nano-S/MAR DNA vectors, which can be used to genetically modify dividing cells in place of integrating vectors. They represent a unique genetic tool, which avoids vector-mediated damage. Previous work has shown that DNA vectors comprising a mammalian S/MAR element can provide persistent mitotic stability over hundreds of cell divisions, resisting epigenetic silencing and thereby allowing sustained transgene expression. The composition of the original S/MAR vectors does present some inherent limitations that can provoke cellular toxicity. Herein, we present a new system, the nano-S/MAR, which drives higher transgene expression and has improved efficiency of establishment, due to the minimal impact on cellular processes and perturbation of the endogenous transcriptome. We show that these features enable the hitherto challenging genetic modification of patient-derived cells to stably restore the tumor suppressor gene SMAD4 to a patient-derived SMAD4 knockout pancreatic cancer line. Nano-S/MAR modification does not alter the molecular or phenotypic integrity of the patient-derived cells in cell culture and xenograft mouse models. In conclusion, we show that these DNA vectors can be used to persistently modify a range of cells, providing sustained transgene expression while avoiding the risks of insertional mutagenesis and other vector-mediated toxicity., Graphical Abstract, Bozza and et al. describe minimally sized DNA vectors that can be used to generate genetically modified isogenic human cells that produce persistent transgene expression while avoiding insertional mutagenesis and vector-mediated toxicity. They show the restoration of the tumor suppressor gene SMAD4 into patient-derived pancreatic cells reversing the cellular and molecular phenotype.

Pancreatic adenocarcinoma is a highly aggressive malignancy with dismal prognosis and limited curative options. We investigated the influence of organ environments on gene expression in RNU rats by orthotopic and intraportal infusion of Suit2-007luc cells into the pancreas, liver and lung respectively. Tumor tissues from these sites were analyzed by chip array and histopathology. Generated data was analyzed by Chipster and Ingenuity Pathway Analysis (±1.5 expression fold change and p

Endothelial to hematopoietic transition (EHT) is a crucial step in the formation of definitive hematopoietic stem cells during embryonic development. Holding such a critical developmental role not many details regarding molecular changes and cell surface marker (CSM) expression on these transitional cells are known. We think that sub-segregating the process of EHT holds great therapeutic potential by giving new indications to understand the hematopoietic stem cell maturation. We generated embryonic stem (ES) cell lines from Hoxb4-YFP reporter mice (Hills, 2011), in which YFP expression marks functional HSCs in adult and embryonic mice. When these cell lines were subject to embryoid body differentiation assays, we observed a transient Hoxb4/YFP+ cell population, which corresponded to the emergence of hemogenic endothelial cells in culture. We then analyzed the gene expression profile of the Hoxb4+ cells and compared it to immediate precursor (Hoxb4-Flk1+) and daughter (Hoxb4-CD41+) cell populations. As well as documenting the expression of numerous molecular markers previously associated with EHT, we also observed an elevated inflammatory gene expression signature that has previously been characterized as a mediator of hematopoietic specification in vivo. We were additionally able to identify 45 novel cell surface markers that could potentially be used to prospectively isolate and sub segregate cells undergoing EHT. 26 of these targets were subsequently verified using MRM mass spectrometry. To establish if any of these markers were functionally relevant, we generated knockout (KO) cell lines using CRISPR/Cas9. Upon EB differentiation, we observed a profound block in hematopoietic differentiation for ES cells that were KO for the membrane proteins Evi2a and Lyve1. This block was manifest at the EHT stage, as verified by time-lapse video imaging, and was equivalent in magnitude to Runx1 KO, suggesting a crucial role of Evi2a and Lyve1 during the EHT stage of hematopoietic development. Notably, this defect could be rescued by genetic replacement of the deleted gene. When comparing our data to human fetal liver data sets Evi2a is highly expressed in fetal liver, as well as in HSCs isolated from murine AGM and fetal liver.

Cutaneous beta human papillomavirus (HPV) types are suspected to be involved, together with ultraviolet (UV) radiation, in the development of non-melanoma skin cancer (NMSC). Studies in in vitro and in vivo experimental models have highlighted the transforming properties of beta HPV E6 and E7 oncoproteins. However, epidemiological findings indicate that beta HPV types may be required only at an initial stage of carcinogenesis, and may become dispensable after full establishment of NMSC. Here, we further investigate the potential role of beta HPVs in NMSC using a Cre-loxP-based transgenic (Tg) mouse model that expresses beta HPV38 E6 and E7 oncogenes in the basal layer of the skin epidermis and is highly susceptible to UV-induced carcinogenesis. Using whole-exome sequencing, we show that, in contrast to WT animals, when exposed to chronic UV irradiation K14 HPV38 E6/E7 Tg mice accumulate a large number of UV-induced DNA mutations, which increase proportionally with the severity of the skin lesions. The mutation pattern detected in the Tg skin lesions closely resembles that detected in human NMSC, with the highest mutation rate in p53 and Notch genes. Using the Cre-lox recombination system, we observed that deletion of the viral oncogenes after development of UV-induced skin lesions did not affect the tumour growth. Together, these findings support the concept that beta HPV types act only at an initial stage of carcinogenesis, by potentiating the deleterious effects of UV radiation., Author summary Many epidemiological and biological findings support the hypothesis that beta HPV types cooperate with UV radiation in the induction of NMSC, the most common form of human cancer. We have previously shown that K14 HPV38 E6/E7 Tg mice, when exposed to long-term UV radiation, developed NMSC, whereas WT animals subjected to identical treatments did not develop any type of skin lesions. Here, we show that the high skin cancer susceptibility of these Tg animals tightly correlates with their tendency to accumulate UV-induced mutations in genes that are frequently mutated in human NMSC. Importantly, deletion of the HPV38 E6 and E7 genes in existing skin lesions did not affect the further growth of the cancer cells. Together, these findings support the model that beta HPV infection is a co-factor in skin carcinogenesis, facilitating the accumulation of the UV-induced DNA mutations.