3D multicellular models to study the regulation and roles of acid–base transporters in breast cancer

Abstract

As a result of elevated metabolic rates and net acid extrusion in the rapidly proliferating cancer cells, solid tumours are characterized by a highly acidic microenvironment, while cancer cell intracellular pH is normal or even alkaline. Two-dimensional (2D) cell monocultures, which have been used extensively in breast cancer research for decades, cannot precisely recapitulate the rich environment and complex processes occurring in tumours in vivo. The use of such models can consequently be misleading or non-predictive for clinical applications. Models mimicking the tumour microenvironment are particularly pivotal for studying tumour pH homeostasis, which is profoundly affected by the diffusion-limited conditions in the tumour. To advance the understanding of the mechanisms and consequences of dysregulated acid–base homeostasis in breast cancer, clinically relevant models that incorporate the unique microenvironment of these tumours are required. The development of three-dimensional (3D) cell cultures has provided new tools for basic research and pre-clinical approaches, allowing the culture of breast cancer cells under conditions that closely resemble tumour growth in a living organism. Here we provide an overview of the main 3D techniques relevant for breast cancer cell culture. We discuss the advantages and limitations of the classical 3D models as well as recent advances in 3D culture techniques, focusing on how these culture methods have been used to study acid–base transport in breast cancer. Finally, we outline future directions of 3D culture technology and their relevance for studies of acid–base transport.

Crosstalk between tumor acidosis, p53 and extracellular matrix regulates pancreatic cancer aggressiveness

“…To mimic the architecture and microenvironment conditions of tumor tissue, 33 , 34 we cultured Panc02 cells as 3D spheroids and monitored spheroid growth over 9 days (Figure 1C ). Under control conditions, p53KO spheroids grew to more than twice the area and were more viable compared to WT cells at day 9 (Figure 1C‐E ).…”

Pyrazine ring-based Na+/H+ exchanger (NHE) inhibitors potently inhibit cancer cell growth in 3D culture, independent of NHE1

“…The use of physiologically-relevant in vitro models can reduce costs and save animal lives by allowing three-dimensional (3D) in vitro drug efficacy screening prior to in vivo testing. Screening in 3D spheroids, which mimic tumour oxygen, pH-and nutrient gradients, as well as drug permeability and -response 3,19,20 , is a key element in studies of anticancer drugs 3,19,21,22 . Such studies are particularly important for drugs that are weak acids (cariporide, eniporide) and weak bases (pyrazinoylguanidines such as EIPA and amiloride), as pH will profoundly impact drug charge and hence distribution between cytosol, extracellular space, and acidic compartments 12,23 .…”

Adaptation to an acid microenvironment promotes pancreatic cancer organoid growth and drug resistance in a p53-dependent manner

“…Since it is not possible to control cellular diversity, pH and other environmental factors in tumors in vivo , and thereby establish causality, we adapted corresponding in vitro organoids models over time from a physiologically normal pH (7.4) to an acidic pH relevant to that of acidic tumor niches. Because they are stem cell based, organoids retain the properties of the native tissue better than cultured cell lines (Czaplinska et al, 2019). We used four organoid lines for adaptation experiments - mN10, corresponding to normal pancreatic cells, and a set of KRAS-mutated (mP) organoids with either intact p53, p53KO or the pH sensitive p53 mutant R273H.…”