Spheroid-based engineering of a human vasculature in mice.

The complexity of the angiogenic cascade limits cellular approaches to studying angiogenic endothelial cells (ECs). In turn, in vivo assays do not allow the analysis of the distinct cellular behavior of ECs during angiogenesis. Here we show that ECs can be grafted as spheroids into a matrix to give rise to a complex three-dimensional network of human neovessels in mice. The grafted vasculature matures and is connected to the mouse circulation. The assay is highly versatile and facilitates numerous applications including studies of the effects of different cytokines on angiogenesis. Modifications make it possible to study human lymphangiogenic processes in vivo. EC spheroids can also be coimplanted with other cell types for tissue engineering purposes.

Mouse-Derived Isograft (MDI) In Vivo Tumor Models II. Carcinogen-Induced cMDI Models: Characterization and Cancer Therapeutic Approaches.

In this second study, we established syngeneic in vivo models named carcinogen-induced mouse-derived isografts (cMDIs). Carcinogen-induced tumors were obtained during short-term observation (3⁻9 months) of CBA/J mice treated with various administration routes with 3-methylcholanthrene (MCA) or N-methyl-N-nitrosourea (MNU) as carcinogens. During necropsy, primary tumors and suspicious tissues were assessed macroscopically and re-transplanted (in PDX-like manner) into sex-matched syngeneic animals. Outgrowing tumors were histologically characterized as either spinocellular carcinoma (1/8) or various differentiated sarcomas (7/8). Growth curves of four sarcomas showed striking heterogeneity. These cMDIs were further characterized by flow cytometry, RNA sequencing, or efficacy studies. A variable invasion of immune cells into the tumors, as well as varying expression of tyrosine kinase receptor, IFN-γ signature, or immune cell population marker genes could be observed. Immune checkpoint inhibitor treatment (anti-mPD-1, anti-mCTLA-4, or a combination thereof) showed different responses in the various cMDI models. In general, cMDI models are carcinogen-induced tumors of low passage number that were propagated as tissue pieces in mice without any tissue culturing. Therefore, the tumors contained conserved tumor characteristics and intratumoral immune cell populations. In contrast to the previously described spontaneous MDI, carcinogen induction resulted in a greater number of individual but histologically related tumors, which were preferentially sarcomas.

Mouse-Derived Isograft (MDI) In Vivo Tumor Models I. Spontaneous sMDI Models: Characterization and Cancer Therapeutic Approaches.

Syngeneic in vivo tumor models are valuable for the development and investigation of immune-modulating anti-cancer drugs. In the present study, we established a novel syngeneic in vivo model type named mouse-derived isografts (MDIs). Spontaneous MDIs (sMDIs) were obtained during a long-term observation period (more than one to two years) of naïve and untreated animals of various mouse strains (C3H/HeJ, CBA/J, DBA/2N, BALB/c, and C57BL/6N). Primary tumors or suspicious tissues were assessed macroscopically and re-transplanted in a PDX-like manner as small tumor pieces into sex-matched syngeneic animals. Nine outgrowing primary tumors were histologically characterized either as adenocarcinomas, histiocytic carcinomas, or lymphomas. Growth of the tumor pieces after re-transplantation displayed model heterogeneity. The adenocarcinoma sMDI model JA-0009 was further characterized by flow cytometry, RNA-sequencing, and efficacy studies. M2 macrophages were found to be the main tumor infiltrating leukocyte population, whereas only a few T cells were observed. JA-0009 showed limited sensitivity when treated with antibodies against inhibitory checkpoint molecules (anti-mPD-1 and anti-mCTLA-4), but high sensitivity to gemcitabine treatment. The generated sMDI are spontaneously occurring tumors of low passage number, propagated as tissue pieces in mice without any tissue culturing, and thus conserving the original tumor characteristics and intratumoral immune cell populations.

Development of novel bisphosphonate prodrugs of doxorubicin for targeting bone metastases that are cleaved pH dependently or by cathepsin B: synthesis, cleavage properties, and binding properties to hydroxyapatite as well as bone matrix.

Bone metastases are a frequent cause of morbidity in cancer patients. The present palliative therapeutic options are chemotherapy, hormone therapy, and the administration of bisphosphonates. The affinity between bisphosphonates and the apatite structure of bone metastases is strong. Thus, we designed two low-molecular-weight and water-soluble prodrugs which incorporate a bisphosphonate group as a bone targeting ligand, doxorubicin as the anticancer agent, and either an acid-sensitive bond (1) or a cathepsin B cleavable bond (3) for ensuring an effective release of doxorubicin at the site of action. Cleavage studies of both prodrugs showed a fast release of doxorubicin but sufficient stability over several hours in human plasma. Effective binding of prodrug 1 and 3 was demonstrated with hydroxyapatite and with native bone. In orientating toxicity studies in nude mice, the MTD of 1 was 3-fold higher compared to conventional doxorubicin, whereas 3 showed essentially the same MTD as doxorubicin.

Development of a novel prodrug of paclitaxel that is cleaved by prostate-specific antigen: an in vitro and in vivo evaluation study.

In developed countries, prostate cancer is the third most common cause of death from cancer in men. Unfortunately, whilst accumulating clinical data have suggested that taxanes may prolong the survival in a subset of men with prostate carcinoma, the dose and duration of administration of these drugs are limited by their significant systemic toxicities due to a lack of tumour selectivity. In an attempt to improve both the water solubility and tumour-targeting properties of paclitaxel (Taxol®), we set out to develop a water soluble paclitaxel prodrug that is activated specifically by prostate-specific antigen (PSA) which is almost exclusively expressed in prostate tissue and prostate carcinoma making it an ideal molecular target for prodrug strategies. Using albumin as a drug carrier, we describe a novel albumin-binding prodrug of paclitaxel, EMC-Arg-Ser-Ser-Tyr-Tyr-Ser-Leu-PABC-paclitaxel [EMC: ε-maleimidocaproyl; PABC: p-aminobenzyloxycarbonyl] that was synthesised by reacting EMC-Arg-Ser-Ser-Tyr-Tyr-Ser-OH with H-Leu-PABC-paclitaxel. This prodrug was water soluble and was bound to endogenous and exogenous albumin. Moreover, incubation studies with PSA demonstrated that the albumin-bound form of the prodrug was cleaved rapidly at the P1-P1' scissile bond releasing the paclitaxel-dipeptide H-Ser-Leu-PABC-paclitaxel. Last but not least, due to the incorporation of a PABC self-eliminating linker, this dipeptide was rapidly degraded to liberate paclitaxel as a final cleavage product within a few hours in prostate tumour tissue homogenates. Of note was that the albumin-bound form of the prodrug was approximately three-fold more active in killing PSA-positive LNCaP cells than paclitaxel. In addition, orientating toxicity studies in mice showed that the maximum tolerated dose of the novel paclitaxel prodrug was twice that of conventional paclitaxel. When tested in vivo in an orthotopic mouse model of human prostate cancer using luciferase-transduced LNCaP LLN cells, both paclitaxel and the new paclitaxel prodrug showed distinct antitumour efficacy on the primary tumour and metastases that was significantly better than the effect of doxorubicin which was used as a comparison and showed no antitumour efficacy. The new paclitaxel prodrug (3 × 24 mg paclitaxel equivalents) showed comparable antitumour activity on the primary tumour to paclitaxel at its maximum-tolerated dose (3 × 12mg/kg), reduced circulating PSA levels and demonstrated a better antitumour effect on lung metastases but not on bone metastases.