Biophysical and Biomechanical Effect of Low Intensity US Treatments on Pancreatic Adenocarcinoma 3D Cultures

Current developments in medical technology have focused on therapeutic treatments that selectively and effectively address specific pathological areas, minimizing side effects on healthy tissues. In this regard, many procedures have been developed to provide non-invasive therapy, for example therapeutic ultrasound (US). In the medical field, in particular in cancer research, it has been observed how ultrasounds can cause cell death and inhibit cell proliferation of cancer cells, while preserving healthy ones with almost negligible side effects. Various studies have shown that low intensity pulse ultrasound (LIPUS) and low intensity continuous ultrasound (LICUS) regulate the proliferation, cell differentiation and cavitation phenomena. Nowadays, there are poorly known aspects of low intensity US treatment, in terms of biophysical and biomechanical effects on target cells. The aim of this study is to set up an innovative apparatus for US treatment of pancreatic ductal adenocarcinoma (PDAC) cells, monitoring parameters such as acoustic intensity, acoustic pressure, stimulation frequency and treatment protocol. To this purpose, we have developed a custom-made set up for the US stimulation at 1.2 and 3 MHz of tridimensional (3D) cultures of PDAC cells (PANC-1, Mia Paca-2 and BxPc3 cells). Images of the 3D cultures were acquired, and the Calcein/PI assay was applied to detect US-induced cell death. Overall, the setup we have presented paves the way to an innovative protocol for tumor treatment. The system can be used either alone or in combination with small molecules or recombinant antibodies in order to propose a novel combined therapeutic approach.

Prostaglandin F2 and EP2 Agonists Exert Different Effects on 3D 3T3-L1 Spheroids during Their Culture Phase

To elucidate the effects of switching a PGF2α agonist, bimatoprost acid (BIM-A), to an EP2 agonist (Omidenepag—OMD; butaprost—Buta) or reversing the switching on adipose tissue, two-dimensional (2D) and three-dimensional (3D) cultures of 3T3-L1 cells were analyzed by lipid staining and according to the mRNA expression of adipogenesis-related genes (Pparγ, Ap2, and Leptin), components of the extracellular matrix (ECM; collagen1 (Col1), Col4, Col6, and fibronectin (Fn)), and the sizes and stiffness of the 3D spheroids. Switching from BIM-A to EP2 agonists caused (1) suppression of lipid staining and downregulation of most adipogenesis-related genes, (2) smaller and stiffer 3D spheroids, and (3) upregulation of Col1 and Fn, downregulation of Col4 (2D), or up-regulation of all ECM genes (3D, BIM-A to OMD), as well as downregulation of Col6 (3D, BIM-A to Buta). In contrast, reversing the switching resulted in (1) an enhancement in lipid staining (2D) and a significant upregulation of adipogenesis-related genes (2D, 3D Buta to BIM-A), (2) larger and slightly stiffer 3D spheroids, and (3) upregulation of Col1 and Fn (2D). These collective findings indicate that the switching orders of BIM-A and EP2 agonists have a significant effect on lipid metabolism, ECM expression, and the physical stiffness of 3T3-L1 cells.

Pre-Clinical In Vitro Models Used in Cancer Research: Results of a Worldwide Survey

To develop and subsequently get cancer researchers to use organotypic three-dimensional (3D) models that can recapitulate the complexity of human in vivo tumors in an in vitro setting, it is important to establish what in vitro model(s) researchers are currently using and the reasons why. Thus, we developed a survey on this topic, obtained ethics approval, and circulated it throughout the world. The survey was completed by 101 researchers, across all career stages, in academia, clinical or industry settings. It included 40 questions, many with multiple options. Respondents reported on their field of cancer research; type of cancers studied; use of two-dimensional (2D)/monolayer, 2.5D and/or 3D cultures; if using co-cultures, the cell types(s) they co-culture; if using 3D cultures, whether these involve culturing the cells in a particular way to generate spheroids, or if they use additional supports/scaffolds; techniques used to analyze the 2D/2.5D/3D; and their downstream applications. Most researchers (>66%) only use 2D cultures, mainly due to lack of experience and costs. Despite most cancer researchers currently not using the 3D format, >80% recognize their importance and would like to progress to using 3D models. This suggests an urgent need to standardize reliable, robust, reproducible methods for establishing cost-effective 3D cell culture models and their subsequent characterization.

Functional analysis of N-acetylglucosaminyltransferase-I knockdown in 2D and 3D neuroblastoma cell cultures

Tumor development can be promoted/suppressed by certain N-glycans attached to proteins at the cell surface. Here we examined aberrant neuronal properties in 2D and 3D rat neuroblastoma (NB) cell cultures with different N-glycan populations. Lectin binding studies revealed that the engineered N-glycosylation mutant cell line, NB_1(-Mgat1), expressed solely oligomannose N-glycans, and verified that the parental cell line, NB_1, and a previous engineered N-glycosylation mutant, NB_1(-Mgat2), expressed significant levels of higher order N-glycans, complex and hybrid N-glycans, respectively. NB_1 grew faster than mutant cell lines in monolayer and spheroid cell cultures. A 2-fold difference in growth between NB_1 and mutants occurred much sooner in 2D cultures relative to that observed in 3D cultures. Neurites and spheroid cell sizes were reduced in mutant NB cells of 2D and 3D cultures, respectively. Cell invasiveness was highest in 2D cultures of NB_1 cells compared to that of NB_1(-Mgat1). In contrast, NB_1 spheroid cells were much less invasive relative to NB_1(-Mgat1) spheroid cells while they were more invasive than NB_1(-Mgat2). Gelatinase activities supported the ranking of cell invasiveness in various cell lines. Both palladin and HK2 were more abundant in 3D than 2D cultures. Levels of palladin, vimentin and EGFR were modified in a different manner under 2D and 3D cultures. Thus, our results support variations in the N-glycosylation pathway and in cell culturing to more resemble in vivo tumor environments can impact the aberrant cellular properties, particularly cell invasiveness, of NB.

Erlotinib Promotes Ligand-Induced EGFR Degradation in 3D but Not 2D Cultures of Pancreatic Ductal Adenocarcinoma Cells

The epithelial growth factor receptor (EGFR) is a tyrosine kinase receptor that participates in many biological processes such as cell proliferation. In addition, EGFR is overexpressed in many epithelial cancers and therefore is a target for cancer therapy. Moreover, EGFR responds to lots of stimuli by internalizing into endosomes from where it can be recycled to the membrane or further sorted into lysosomes where it undergoes degradation. Two-dimensional cell cultures have been classically used to study EGFR trafficking mechanisms in cancer cells. However, it has been widely demonstrated that in 2D cultures cells are exposed to a non-physiological environment as compared to 3D cultures that provide the normal cellular conformation, matrix dimensionality and stiffness, as well as molecular gradients. Therefore, the microenvironment of solid tumors is better recreated in 3D culture models, and this is why they are becoming a more physiological alternative to study cancer physiology. Here, we develop a new model of EGFR internalization and degradation upon erlotinib treatment in pancreatic ductal adenocarcinoma (PDAC) cells cultured in a 3D self-assembling peptide scaffold. In this work, we show that treatment with the tyrosine kinase inhibitor erlotinib promotes EGFR degradation in 3D cultures of PDAC cell lines but not in 2D cultures. We also show that this receptor degradation does not occur in normal fibroblast cells, regardless of culture dimensionality. In conclusion, we demonstrate not only that erlotinib has a distinct effect on tumor and normal cells but also that pancreatic ductal adenocarcinoma cells respond differently to drug treatment when cultured in a 3D microenvironment. This study highlights the importance of culture systems that can more accurately mimic the in vivo tumor physiology.