Francesca Falcetta

Synthesis of surfactant free PCL-PEG brushed nanoparticles with tunable degradation kinetics

A delivery system based on polymer nanoparticles (NPs) is developed and tested in relevant biological conditions for breast cancer treatment. ɛ-Caprolactone (CL) and polyethylene glycol (PEG) copolymers have been used for the one pot synthesis of surfactant free PEGylated NPs which are monodispersed, stable in physiological conditions and have size in the range 90-250 nm. The degradation behavior of these NPs has been investigated in cell medium and a relation between degradation time and molecular weight of the starting CL-based material has been established. This allows producing NPs with controlled degradation kinetics. Finally, selected NPs have been tested in 4T1 breast cancer cells to check their toxicity and to investigate the uptake process, in order to validate their use as targeted vectors for breast cancer treatment.

Chemotherapeutic activity of silymarin combined with doxorubicin or paclitaxel in sensitive and multidrug-resistant colon cancer cells

PurposeThe milk thistle extract silymarin, alone or in combined chemotherapy, is now under investigation in anticancer research, with particular interest for its possible employ in the treatment of chemoresistant tumours. So far, the consequences of a silymarin pre-treatment have not been thoroughly investigated. We studied whether silymarin pre-treatment synergized with chemotherapy, exploring the dose-dependence of the interaction in sensitive and multidrug-resistant cells.MethodsWe studied cell cycle perturbations induced by silymarin in two colon carcinoma cell lines, LoVo and the multidrug-resistant isogenic LoVo/DX. Synergism/additivity/antagonism of silymarin–doxorubicin silymarin–paclitaxel combined treatments were evaluated by isobologram/combination index analysis, in the whole spectrum of active and sub-active concentrations of all drugs. The mechanisms of silymarin interaction with the other drugs were investigated by measuring drug uptake and cell cycle perturbations.ResultsSilymarin had similar antiproliferative activity against both cell lines. Pre-treatment with low silymarin concentrations synergised with both doxorubicin and paclitaxel in LoVo but not in LoVo/DX. Higher silymarin concentrations were additive with doxorubicin and paclitaxel in both cell lines. Silymarin favourably interfered with uptake and cell cycle effects of the chemotherapeutics in LoVo but not in LoVo/DX.ConclusionThese findings confirm activity of silymarin against colon carcinoma, including multidrug-resistant types, at relatively high but clinically achievable concentrations. In view of its low toxicity, two schedules based on low- and high-dose silymarin pre-treatment might offer a valuable option for combined treatment.

Integrated multiplatform method for in vitro quantitative assessment of cellular uptake for fluorescent polymer nanoparticles

Studies of cellular internalization of nanoparticles (NPs) play a paramount role for the design of efficient drug delivery systems, but so far they lack a robust experimental technique able to quantify the NP uptake in terms of number of NPs internalized in each cell. In this work we propose a novel method which provides a quantitative evaluation of fluorescent NP uptake by combining flow cytometry and plate fluorimetry with measurements of number of cells. Single cell fluorescence signals measured by flow cytometry were associated with the number of internalized NPs, exploiting the observed linearity between average flow cytometric fluorescence and overall plate fluorimeter measures, and previous calibration of the microplate reader with serial dilutions of NPs. This precise calibration has been made possible by using biocompatible fluorescent NPs in the range of 20-300 nm with a narrow particle size distribution, functionalized with a covalently bonded dye, Rhodamine B, and synthesized via emulsion free-radical polymerization. We report the absolute number of NPs internalized in mouse mammary tumor cells (4T1) as a function of time for different NP dimensions and surface charges and at several exposure concentrations. The obtained results indicate that 4T1 cells incorporated 10(3)-10(4) polymer NPs in a short time, reaching an intracellular concentration 15 times higher than the external one.

A biodistribution study of PEGylated PCL-based nanoparticles in C57BL/6 mice bearing B16/F10 melanoma

One of the major drawbacks that limits the clinical application of nanoparticles is the lack of preliminary investigations related to their biocompatibility, biodegradability and biodistribution. In this work, biodegradable PEGylated polymer nanoparticles (NPs) have been synthesized by using macromonomers based on poly(ε-caprolaconte) oligomers. More in detail, NPs have been produced by adopting a surfactant-free semibatch emulsion polymerization process using PEG chains as a stabilizing agent. The NPs were also labeled with rhodamine B covalently bound to the NPs to quantitatively study their biodistribution in vivo. NPs were investigated in both in vitro and in vivo preclinical systems to study their biodistribution in mice bearing B16/F10 melanoma, as well as their biocompatibility and biodegradability. The NP concentration was evaluated in different tissues at several times after intravenous injection. The disappearance of the NPs from the plasma was biphasic, with distribution and elimination half-lives of 30 min and 15 h, respectively. NPs were retained in tumors and in filter organs for a long time, were still detectable after 7 d and maintained a steady concentration in the tumor for 120 h. 48 h after injection, 70 ± 15% of the inoculated NPs were excreted in the feces. The favorable tumor uptake, fast excretion and absence of cytotoxicity foster the further development of produced NPs as drug delivery carriers.

HPLC-MS/MS method to measure trabectedin in tumors: preliminary PK study in a mesothelioma xenograft model.

BACKGROUND Trabectedin is an anticancer agent registered for the second-line treatment of soft tissue sarcoma and ovarian cancer. No preclinical data are available on its tumor distribution, so a method for quantification in neoplastic tissues is required. METHODS/RESULTS We validated an LC-MS/MS assay determining the recovery, sensitivity, linearity, precision and accuracy in mouse tumor and liver samples. The limit of quantification was 0.10 ng/ml with a curve range of 0.10-3.00 ng/ml (accuracy 96.1-102.1%). Inter-day precision and accuracy of QCs were 6.0-8.2 and 97.0-102.6% respectively. The method was applied in mesothelioma xenografts treated with therapeutic doses. CONCLUSION The method was validated for measuring trabectedin in tissues. In a mesothelioma xenograft model, trabectedin distributed preferentially in tumor compared with liver.

Dynamic rendering of the heterogeneous cell response to anticancer treatments.

The antiproliferative response to anticancer treatment is the result of concurrent responses in all cell cycle phases, extending over several cell generations, whose complexity is not captured by current methods. In the proposed experimental/computational approach, the contemporary use of time-lapse live cell microscopy and flow cytometric data supported the computer rendering of the proliferative process through the cell cycle and subsequent generations during/after treatment. The effects of treatments were modelled with modules describing the functional activity of the main pathways causing arrest, repair and cell death in each phase. A framework modelling environment was created, enabling us to apply different types of modules in each phase and test models at the complexity level justified by the available data. We challenged the method with time-course measures taken in parallel with flow cytometry and time-lapse live cell microscopy in X-ray-treated human ovarian cancer cells, spanning a wide range of doses. The most suitable model of the treatment, including the dose-response of each effect, was progressively built, combining modules with a rational strategy and fitting simultaneously all data of different doses and platforms. The final model gave for the first time the complete rendering in silico of the cycling process following X-ray exposure, providing separate and quantitative measures of the dose-dependence of G1, S and G2M checkpoint activities in subsequent generations, reconciling known effects of ionizing radiations and new insights in a unique scenario.

Integrated experimental and simulation study of the response to sequential treatment with erlotinib and gemcitabine in pancreatic cancer

The combination of erlotinib with gemcitabine is one of the most promising therapies for advanced pancreatic cancer. Aiming at optimizing this combination, we analyzed in detail the response to sequential treatments with erlotinib → gemcitabine and gemcitabine → erlotinib with an 18 h interval, adopting a previously established experimental/computational approach to quantify the cytostatic and cytotoxic effects at G1, S and G2M checkpoints. This assessment was achieved by contemporary fits of flow cytometric and time-lapse experiments in two human pancreatic cancer cell lines (BxPC-3 and Capan-1) with a mathematical model reproducing the fluxes of cells through the cycle during and after treatment. The S-phase checkpoint contributes in the response to erlotinib, suggesting that the G1 arrest may hamper S-phase cytotoxicity. The response to gemcitabine was driven by the dynamics of the progressive resumption from the S-phase arrest after drug washout. The effects induced by single drugs were used to simulate combined treatments, introducing changes when required. Gemcitabine → erlotinib was more than additive in both cell lines, strengthening the cytostatic effects on cells recovering from the arrest induced by gemcitabine. The interval in the erlotinib → gemcitabine sequence enabled to overcome the antagonist effect of G1 block on gemcitabine efficacy and improved the outcome in Capan-1 cells.

Challenges in the Integration of Flow Cytometry and Time-Lapse Live Cell Imaging Data Using a Cell Proliferation Model

Multicellular systems are currently studied both in vitro and in vivo using different platforms, providing high throughput data of different types. Mathematical modelling is now called to interpret this reality and has to face more and more with quantitative data. This requires a connection between the basic theoretical model and the data structures, taking account of the processes of measure. Working on the response to anticancer treatment, we considered the data provided by flow cytometry (FC) and time-lapse live cell imaging (TL) in time-course experiments in vitro with untreated and treated cell populations. We created a flexible cell cycle simulator including subsequent cell generations to achieve a full reconstruction in silico of the cell cycle progression under a variety of treatment effects. Unperturbed growth was modelled taking into account intercellular variability of G1,S and G2M transit times, quiescent cells and natural cell loss. The effect of treatment was modelled by “perturbation modules” associated to each cell cycle phase and cell generation, containing a submodel of the checkpoint activity in that phase. Upon input of a set of parameters associated to unperturbed growth and perturbation modules, the program reproduced the time course of cell cycling through subsequent generations, providing outputs comparable with both TL and FC measures. The challenges to fit the data of specific experiments were discussed, indicating a feasible procedure for model building and identification. This lead to a dynamic rendering of proliferation midway between the macroscopic data level and the underlying molecular processes.

Application of 3D Mass Spectrometry Imaging to TKIs

Mass spectrometry imaging (MSI) allows visualization of endogenous and exogenous compound in tissue sections based on its molecular mass. The 3D reconstruction by MSI provides a more informative description of the tumor drug distribution compared to the high‐performance liquid chromatography method, highlighting the heterogeneity of intratumor drug concentration. This additional information can be important in understanding chemoresistance to target agents. Here, we present the 3D visualization of the tyrosine kinase inhibitor (TKI), imatinib, in a xenograft model of resistant malignant pleural mesothelioma.

Tumor progression and metastatic dissemination in ovarian cancer after dose-dense or conventional paclitaxel and cisplatin plus bevacizumab

The efficacy of therapeutic regimens incorporating weekly or every‐3‐weeks paclitaxel (PTX) for ovarian cancer is debated. We investigated the addition of bevacizumab in regimens of chemotherapy with different PTX doses and schedules in preclinical models. Treatments were cisplatin (DDP) with weekly PTX (conventional), or dose‐dense‐equi (every other day to the conventional cumulative dose), or dose‐dense‐high (total dose 1.5 times higher), with or without bevacizumab. Treatment efficacy was evaluated analyzing tumor growth in different time‐windows in two patient‐derived ovarian cancer xenografts with different sensitivity to cisplatin. Tumor progression, metastasis and survival were studied in ovarian cancer models growing orthotopically and disseminating in the mouse peritoneal cavity. Short‐term effects on cell cycle, tumor cell proliferation/apoptosis and vasculature were evaluated by flow cytometry and immunohistochemistry. PTX dose‐dense (with/without DDP) was superior to the conventional scheme in a dose‐dependent manner; the high efficacy was confirmed by the lower ratio of tumor to normal cells. All schemes benefited from bevacizumab, which reduced tumor vessels. However, DDP/PTX dose‐dense‐high (only chemotherapy) was at least as active as DDP/PTX conventional plus bevacizumab. DDP/PTX dose‐dense‐high plus bevacizumab was the most effective in delaying tumor progression, though it did not prolong mouse survival and the continuous treatment with bevacizumab was associated with a malignant disease. These findings indicate that the effect of bevacizumab in combination with chemotherapy may depend on the schedule‐dose of the treatment and help to explain the unclear benefits after bevacizumab.