Bioprinting Spheroids for High-Throughput Applications: Advancing Cancer Research

Understanding Spheroids

What Are Spheroids?

Spheroids are 3D cell aggregates that closely resemble the tissue microenvironment of the human body and functionality. In contrast to conventional?2D cell cultures , which cultivate cells on plane surfaces, spheroids permit cell clustering. This promotes cell-cell and cell-matrix interactions, which creates a more physiologically relevant microenvironment for research on disease progression studies, drug testing, cellular mechanisms and so on. In general, spheroids are spherical-shaped having a diameter of around 200 μm. Furthermore, spheroids exhibit three concentric zones: an internal zone of necrotic cells, a middle zone of quiescent cells, and an exterior zone of strongly proliferating and moving cells. These zones offer insights into the complex interplay between cells and the surrounding matrix.

Spheroids in cancer research

Spheroids in Drug Testing and Disease Research

High throughput growth inhibition screening campaigns is the general technique to find anti-cancer therapeutic leads. These campaigns are carried out on panels of tumour cell lines that are analysed in 2D cell culture models. Despite large investments in cancer research and drug discovery, the majority of advanced stage metastatic tumours are still incurable. Furthermore, new cancer treatment approval rates are ≤5%—much lower than for other therapeutic areas.

The poor success rate of anticancer drugs can be attributed to a number of factors. These include the inability of preclinical models to represent human cancers’ complexity and heterogeneity accurately, frequent use of poorly defined proliferation or angiogenesis endpoints in place of distinct molecular targets and pathways, and inadequate translational research to the clinic.?

As a result, there is a growing trend to recreate 3D tumour microenvironment? in vitro . Tumour cells grown in 3D microenvironments respond differently to stimuli. This is because they get distinct biological cues as opposed to 2D monolayer cultures. For instance, researchers expose 3D tumor cell cultures to dramatically different adhesion, topographical, and mechanical cues. These cues are absent in 2D cultures. Studies have shown that cancer cells can spontaneously aggregate into spheroids. Hence, cancer spheroids resemble the natural microenvironment of avascular tumours. According to the literature, spheroids with sizes between 300 – 500 μm best replicate the hypoxia and proliferation gradients found in?in vivo?malignancies.?

Additionally, a permeability barrier that therapeutic medicines must pass through is created by the interactions between cells in 3D tumour spheroids. This permeability barrier creates a physiologically relevant microenvironment for drug screening. As a result, there is now general agreement that?in vitro?3D tumour cell cultures offer better preclinical models for assessing the efficacy of cancer drug leads. Moreover, using these models could increase the success rate of drug candidates moving forward into clinical trials.

High throughput fabrication of breast cancer tumour models

The Role of 3D Bioprinting in Breast Cancer Models

The GLOBOCAN 2020 WHO reports indicate that breast cancer incidence rates are at an all-time high and will continue to rise. Projections show new cases increasing from 2.26 million in 2020 to 3.19 million by 2040. Additionally, experts expect breast cancer mortality rates to climb as well, rising from nearly 685 thousand deaths in 2020 to around 1.04 million by 2040.

Novel Techniques for Developing Immunocompetent Models

Cancer is a disease that is progressively changing, with recent research showing cancer cells exhibiting chemoresistance. As a result, clinicians and physicians who treat patients must regularly update and review their chemotherapy regimens. This draws attention to the FDA’s drug approval procedure for anti-cancer medications, which involves a significant financial outlay.

One way to tackle this problem is to fabricate a drug screening platform that is physiologically similar and can close the gap between animal and?in vitro?cancer models. They can help in reducing the overall cost of the procedure. This eliminates the need for animal models and reduces the time required for translational research.

In recent years, there has been significant research in high throughput fabrication of spheroids. Spheroids can generate reliable data that clarifies issues related to therapeutic efficacy, disease progression, and personalised medicine. As a result, drug discovery has transformed by the addition of spheroids to high throughput fabrication platforms, especially in the field of oncology. This helps in screening hundreds of tumours and drugs at once, offering a more thorough assessment of the toxicity and efficacy of possible medications.

Bioprinting and Spheroids

The advent of 3D bioprinting enables the fabrication of highly reproducible, high-throughput testing platforms. Researchers have widely applied 3D bioprinting in tissue engineering and regenerative medicine . Recently, they have also used it in 3D cancer modeling, creating physiologically relevant drug testing platforms. Furthermore, bioprinting allows cancer models to replicate dynamic tumor microenvironments. By modifying biomaterials, researchers can replicate distinct phases of carcinogenesis.

In breast cancer models, researchers frequently observe p53 gene mutations as one of the most common genetic abnormalities. These mutations appear in 60–80% of triple-negative breast cancer (TNBC) cases. Since p53 is mutated in 50% of human malignancies, its role in carcinogenesis is highly significant. Mutant p53 in TNBC patients results in a poorer prognosis.

Furthermore, for patients in their earliest N-stage, immunohistochemically detected WT p53 tumors were linked to improved survival. This survival is specific to breast cancer. Therefore, it is crucial to create prospective anticancer medicines. These medicines should target mutant p53 and have as few side effects as possible

Looking into utilising 3D bioprinting for high throughput fabrication of physiologically relevant TNBC models is Dr Falguni Pati ’s paper on ‘Assessment and process optimization of high throughput biofabrication of immunocompetent breast cancer model for drug screening applications ’. This research focuses on utilising a novel detergent-free method of developing decellularized adipose tissue (DAT) hydrogel for creating bioinks with immunocompetent breast cancer models. The team developed a high-throughput 3D bioprinting protocol using the?Trivima Bioprinter ?from?Next Big Innovation Labs? , to bioprint 3D micro tumours in a 96-well plate format in a record time of 7 minutes.

This approach proved to be more efficient compared to manual pipetting and other bioprinting protocols. In addition, the 3D bioprinted model was tested with anticancer drugs like 5-FU and PRIMA-1Met, thus demonstrating the platform’s capability for drug screening applications. The study highlighted the potential for personalised cancer model development and drug testing with high-throughput 3D bioprinting.

For more details, follow the link attached:?https://doi.org/10.1088/1758-5090/ad586b | https://nextbiginnovationlabs.com/bioprinting-winter-school-2024/