Cancer spheroids in drug screening

Spheroids are three-dimensional structures that can be used as 3D cell culture models. It has been extensively shown that they mimic both architectural and structural property of human tissues. Spheroids play an increasingly crucial role in the context of drug development for cancer treatment. There is increasing evidence that spheroids represent a better model for the investigation of drug resistance as compared to monolayers. This is probably due to the fact that cancer cells are cultivated in an environment which closely mimic their natural microenvironment (1,2). 

Cultivation of spheroids under In vitro conditions  

The maintenance of spheroids does not need special culturing conditions. They can be cultivated at 37°C with 5% CO2. Universal growth media containing factors required for cell growth and proliferation are usually used for the maintenance of spheroids in culture and foetal calf serum (FBS) can be added as a supplement. Cells undergo process of self-assembly to constitute multi-cellular spheroids. Self-assembly is a natural process that happens during embryogenesis, morphogenesis, and organogenesis. It is indeed affected by various factors, such as gradients of nutrients, oxygen, and growth factors in cell culture medium.  

Spheroids are usually formed and cultivated in ultralow attachment (ULA) 96 well plates. BIOFLOAT 96-well plates (faCellitate GmbH, Germany) outperforms other products available on the market by speed, robustness, reliability, and reproducibility. A single perfectly round-shaped spheroid forms in every well with a high reproducibility and even challenging types of cells reliably form spheroids in BIOFLOAT 96-well plates.  

Cancer-cell spheroids and drug resistance studies  

Emerging clinical evidence supports a higher efficacy of combined drug protocols compared to monotherapies for the treatment of cancer patients. Accordingly, combinatorial therapeutic approaches show higher toxicity in cancer spheroids as compared to monotherapies. The degree of cancer cell death in spheroid models better correlates with the clinical outcomes compared to drug testing in 2D monolayer cultures. Therefore, spheroids are of great therapeutic relevance and a good alternative to animal testing in the context of drug development and screening. In order to study drug toxicity, spheroids are treated with a range of drug concentrations. The un-treated spheroids (without drug treatment) are used as a control. The field of toxicological research can open doors for testing tumour-targeted drugs in spheroid models (2,3,4).  

REFERENCES:  

1. Aas T, Børresen AL, Geisler S, Smith-Sørensen B, Johnsen H, Varhaug JE, et al. Specific P53 mutations are associated with de novo resistance to doxorubicin in breast cancer patients. Nat Med. 1996;2:811–4. doi: 10.1038/nm0796-811 

1. Desoize B, Jardillier J. Multicellular resistance: a paradigm for clinical resistance? Crit Rev Oncol Hematol. 2000;36:193–207. doi: 10.1016/S1040-8428(00)00086-X. 

1. Mellor HR, Callaghan R. Accumulation and distribution of doxorubicin in tumour spheroids: the influence of acidity and expression of P-glycoprotein. Cancer Chemother Pharmacol. 2011;68:1179–90. doi: 10.1007/s00280-011-1598-8. 

1. Dunkern TR, Mueller-Klieser W. Quantification of apoptosis induction by doxorubicin in three types of human mammary carcinoma spheroids. Anticancer Res. 1999;19(4B):3141–6.