A recent study published in Scientific Reports unveils a groundbreaking approach in cancer research that addresses the challenge of tumour resistance to treatment by focusing on the heterogeneous nature of cancer cells within a tumour.
Led by Nafiseh Moghimi and a multidisciplinary team of researchers from the University of Waterloo in Canada, Harvard Medical School and Brigham and Women’s Hospital in the United States, and Yeditepe University in Turkey, this innovative research effort involves the bioengineering of in vitro models of breast cancer tumour microenvironments using co-cultured cells embedded in a hydrogel matrix. The resulting well-regulated architecture allows for the development of model tumour heterogeneity, shedding light on cancer behaviour and treatment resistance.
The team’s primary hypothesis revolved around representing a tumour using a cancer cell-laden co-culture hydrogel construct. They achieved this by meticulously modelling the microenvironment of interest within a microfluidic chip, which facilitated the creation of a chemical gradient. To construct these model tumour microenvironments, the researchers employed breast cancer cells and non-tumorigenic mammary epithelial cells embedded in alginate-gelatine hydrogels. The innovative technology of multi-cartridge extrusion bioprinting was instrumental in their endeavour.
The outcomes of this pioneering study enabled precise control over cell positions and arrangements within a cell co-culture system, resulting in the design of various patient-mimetic tumour architectures. The team accomplished tumour heterogeneity by randomly mixing and positioning cells in sequential layers, an approach that mimics the diverse cellular composition found within real tumours. This allowed them to create a chemical environment for chemo-attraction, providing an excellent platform to study the behaviour of cancer cells with remarkable space-time resolution.
Breast cancer is a prevalent disease among women, with over 2 million new cases reported in 2018. Its aggressiveness is attributed to the heterogeneity of breast tumours, which poses significant challenges for effective treatment. Conventional models often fail to capture this cellular heterogeneity, hindering our ability to study their response to external stimuli, formation, and physiology.
Microfluidic platforms have emerged as invaluable tools for in vitro modelling, allowing researchers to mimic physical and chemical stimuli during cell migration. Furthermore, bioprinting has gained attention for its capacity to construct tissue-like structures by precisely positioning cells and biomaterials layer by layer. Moghimi’s research team capitalized on these technologies to bridge the gap, creating model microenvironments that faithfully emulate the complex tumour architectures often absent in traditional methods.
The critical aspect of this study involved maintaining the viability of the bioprinter cells within the constructs. By experimenting with various hydrogel compositions and nozzle sizes during bioprinting, the researchers achieved high-resolution constructs while preserving cell viability. Cell viability proved to be an essential factor in successfully fabricating these cell-printed constructs.
To visualize the distribution of cells within the printed constructs, the scientists used green, fluorescent membrane markers, pre-staining cell membranes before printing and imaging them immediately afterwards using a confocal microscope. The results showed homogeneous cell distribution within the constructs, validating their approach.
The research team combined two diverse types of breast cancer cells, MCF7 and MDA-MB-231, in their experiments. They pre-stained these cells with red and green biomarkers prior to printing, allowing them to track and distinguish the two cell types. Sequential printing of these cells in separate bioinks revealed an innovative approach: the first layer of the printed structure contained red-stained cells, with the second layer consisting of green-stained cells. This method ensured the mixture of the two cell types, and subsequent experiments demonstrated that the staining procedure did not affect cell growth.
The researchers meticulously studied cell growth and aggregation within the bioprinter co-cultures and compared them to separately printed 3D constructs containing each cell type. Over a 10-day experimental timeline, they observed cellular behaviour in tumour-like constructs composed of alginate-gelatine hydrogels. By using epithelial growth factor as a chemoattractant material, they were able to monitor cell migration within the co-cultures of the microfluidic device.
In summary, Nafiseh Moghimi and her team have successfully demonstrated tumour heterogeneity by bioengineering a tumour microenvironment on a microfluidic chip. They created a tumour-on-a-chip model using 3D bioprinting that incorporated two distinct breast cancer cell lines and non-tumorigenic mammary epithelial cells. This model offers valuable insights into the molecular and cellular mechanisms underlying tumour heterogeneity and treatment resistance, with direct implications for tumour diagnostics and therapeutic strategies.
The interactions between tumour cells and the tumour microenvironment play a pivotal role in tumour progression and invasion. This innovative, heterogeneous tumour-on-a-chip model holds significant promise for advancing cancer treatment research. By building in vitro models of tumour microenvironments composed of diverse co-cultured cell types, this approach opens new avenues for the development of more effective personalized medicine and provides a powerful tool for understanding cancer behaviour at the cellular level.
