The Future of Breast Cancer Treatment, feat. Synthetic Biology

So far, in our article series, you have encountered all the aspects of breast cancer treatment using synthetic biology — from understanding different types of cancer through robust disease modelling systems, novel diagnosis methods which utilise different aspects of synthetic biology and work with much higher efficiency, to developing and accurately delivering drugs to target cells without affecting neighbouring cells. It’s natural to be in awe of such speedy developments in the field of breast cancer treatment, but don’t be surprised yet; synthetic biology is just getting started in revolutionising the field of therapeutics. With the current pace of ongoing research, we will witness massive developments fueled by synthetic biology in ways of treating breast cancer. Let’s delve into a few such groundbreaking research endeavours.

An innovative approach in disease modelling has been the advancement of CRISPR/Cas9 technology and the development of new Cas9 variants to modulate gene expression and/or epigenetic status, significantly increasing our capability to study genes in vivo. This will help further disease modelling in many ways, like reducing the number of test animals required, which is a considerable advantage from the bioethical aspect, and reducing the time needed to validate gene functions in complex disease models. Also, it will help us to investigate multiple genes at once in vivo, aiding in the discovery of new targets specific to certain conditions like cancer, and not easily identifiable through traditional genetic analysis. With the help of such technologies, more efficient Genetically Engineered Mouse Models (GEMMs) have been developed, which have been used to study oncogenes in vivo. Another cost-effective option for disease modelling using the same technology has been the development of Somatically Engineered Mouse Models (SEMMs), which are based on the postnatal introduction of oncogenes in desired somatic cells of organs to study their effects rather than needing to modify embryonic cells as in GEMMs. Lastly, the latest developments in patient-derived mice xenografts have proven to be much better in testing therapeutics as these retain all the intricate features of the patient’s tumour.

Regarding therapeutics, traditional chemical therapies like chemotherapy are proving to be increasingly inefficient because breast cancer tumours undergo rapid changes due to the clonal evolution of cancer stem cells. Moreover, patients exhibit different side effects and cancer cells develop resistance to chemo drugs after a few rounds of application. So, the future of breast cancer treatment or, as a matter of fact, any kind of cancer treatment lies in specificity. Rather than implementing chemotherapy or hormonal therapy for an entire area of tissues, transferring drugs or nucleic acids only to the cancer cells using cellular-level targeting mechanisms without affecting neighbouring tissues, is the ultimate goal researchers are trying to achieve.

Recent advances in synthetic biology have made cancer treatment possible using gene therapy. DNA therapeutics like plasmid DNA (pDNA), oligodeoxynucleotide, DNA aptamers and RNA therapeutics like microRNA (miRNA), short interfering RNA (siRNA), ribozymes, or circular RNA can be used to selectively kill cancer cells by disrupting their cellular processes, or by prompting the immune response to tumour antigens, or by inhibiting their growth. RNA interference therapies and DNA vaccination against overexpressed tumour antigens are some such breast cancer gene therapies utilising the above nucleic acids. All of these endeavours are under clinical trials. Previous methods like electroporation, sonoporation or laser irradiation for the transfer of plasmid DNA without the use of viral vectors have now been replaced by multifunctional envelope-type nanodevices, which are much more efficient and also transfer more significant amounts of nucleic acids. Zhu et al. proposed a novel translation method for CRISPR-Cas9 therapeutic systems, aiming to enhance gene editing in living organisms by applying a magnetic field. Their study utilised recombinant baculovirus vectors combined with nanomagnets to achieve improved transduction in target cells and specific tissue delivery. The objective was to minimise genotoxicity and maximise therapeutic efficacy, particularly in tumour-bearing mouse models. The utilisation of this technology for breast cancer treatment is under research.

Nanoparticles developed for drug or nucleic acid delivery to target cells can completely bypass all immune barriers of the body and reach the target cells. These may be inorganic molecules, organic molecules or even specially engineered small nucleic acid particles, synthesised to reach target cells. These nanoparticles can serve several purposes, from drug delivery to molecular diagnosis. With the help of synthetic biology, specific ligands, mainly antibodies, are synthesised, which can actively target cancer cells, utilising specific overexpressed biomarkers in tumour cells such as luteinising hormone-releasing hormone receptors (LHRH), oestrogen and progesterone receptors (ER & PR), human epidermal growth factor receptor 2 (HER2), transferrin receptors, etc. Nanotechnology also has its applications in diagnostics, where smart nanoprobes coupled with ligands can detect even the smallest molecular changes at the cellular level at very early stages, even before morphological signs appear. Thus, having a superior edge over traditional diagnostic techniques. The utilisation of the ligand-biomarker interactions in cancer cells with certain overexpressed receptors and proteins, for example, mammaglobin on breast cancer cells, has been a groundbreaking approach in the delivery of nanoparticles and molecular probes. This approach has also enabled researchers to create nanotechnology-based death-induced gene therapy, which transfers pDNA containing apoptosis or toxin-inducing genes to target cells without any degradation. Nanomedicines reduce systemic toxicity to a great extent and also ensure the entrapment of water-soluble drugs, sustained drug release, and internalisation of drugs into tumour cells via endocytosis. This reduces drug resistance and also facilitates the co-delivery of different drugs or molecular probes along with drugs. Hopefully, all these technologies will be seen in mainstream therapeutics within the next decade.

Micro RNA(miRNA) are found in quite insubstantial regions of the genome, thus facing frequent alterations in breast cancer cells. miRNA participates in critical cellular functions such as cell growth, cell signalling, and apoptosis, so its upregulation is often associated with a poorer prognosis of tumours. Thus, this can be utilised as an effective biomarker for both cancer detection and drug delivery in the future. Subsequently, gene therapy targeting miRNA aberrations can help restore the normal functioning of certain cellular processes in cancer cells. Nanoparticle-mediated gene therapy for the p53 tumour suppressor gene is also under research.

Triple negative breast cancer (TNBC) is one of the few cancer subgroups still lacking effective therapeutic options. Cells of this subtype of cancer lack expression of oestrogen and progesterone receptors (ER & PR) and also lack the amplification of the human epidermal growth factor receptor 2 (HER2) gene. The absence of these three factors makes TNBC the only immunopathological subtype of breast cancer that does not respond to common therapeutic options like hormonal therapies targeting signalling pathways of these genes. Characterised by aggressive metastasis and high relapse rates, TNBC proves to be one of the worst subtypes of breast cancer. Moreover, most TNBC tumours lack the abnormal features of breast cancer, so traditional imaging techniques prove to be futile in diagnosis. Novel diagnosis methods developed with the help of synthetic biology provide accurate detection of TNBC tumours at quite early stages. Signalling or contrast agents with molecular imaging capabilities, i.e., functioning as molecular probes, have been developed, which bind to overexpressed or upregulated receptors in the tumours with the help of specific ligands. Molecular imaging allows the examination of tumour cells from a molecular approach which allows much early detection of tumours as molecular changes show up much earlier than morphological changes. The ligands are specifically designed for the target receptor with the help of synthetic biology techniques.

Coming to therapeutic outcomes, synthetic biology has provided much more potent options than traditional methods like radiotherapy and chemotherapy, which have wide-spectrum action, sometimes causing harm to non-cancerous cells in the process. Furthermore, the transfer of nanomedicines by local injection fails to achieve the required target cell delivery accuracy. This is where active targeting comes into play, which uses specially synthesised monoclonal antibodies, peptides or aptamers. These molecules are bound to the surface of nanocarriers and are designed to target the cancer cells, thus ensuring effective medicine delivery. TNBC cells are characterised by high levels of Epidermal Growth Factor Receptor (EGFR), which is a predictive biomarker for worse prognosis in TNBC tumours. Biological therapy with cetuximab and panitumumab monoclonal antibodies targeting EGFR is also under trial. Gene therapies for the BRCA1 gene are also under research, as mutations in the BRCA1 gene, which controls DNA repair, are common in TNBC cells. In aggressive TNBC, TP53 is the most commonly mutated gene but lacks druggable targets. However, the neighbour gene POLR2A represents a viable alternative target due to its hemizygous loss in TNBC cases with copy number loss of TP53. Partial deletion of POLR2A frequently occurs in TNBC, providing a potential option for targeted therapy. A recently patented nano-bomb has been developed to target POLR2A. This nano-bomb is triggered by low pH, expands about a hundred times in size inside TNBC cells, and selectively kills only cancer cells through controlled release. Lastly, with the help of synthetic biology, prognostic biomarkers coupled with targeting antibodies have been developed, which help to study the effect of medicines in different patients and facilitate personalised drug response analysis. This will facilitate more accurate treatment for every patient. All of the above-mentioned processes are under clinical trials to be implemented for TNBC treatment, and with rapid developments in synthetic biology techniques, therapeutic options for all TNBC patients will soon be available.

Synthetic biology has also helped to revolutionise immunotherapy for cancer. A recent advancement has been the development of CAR (chimeric antigen receptors) T-cell therapy. This method utilises our body’s natural guardians, T cells, to kill cancer cells. T cells are extracted from a patient's bloodstream and engineered to specifically target the type of cancer cells present in the patient by studying the surface antigens present on those cells. The chimeric antigen receptors, bound to the T cells, help them locate the cancer cells. These engineered cells are then amplified and reintroduced into the patient’s bloodstream, which lets the T cells do their only job, kill, but just on the cancer cells. This therapy has to be customised for each patient as cancer tumours exhibit tumour heterogeneity, i.e., the tumours are different for each patient. Research to develop CAR T-cell therapy for breast cancer is underway.

Looking at the future prospects, this field, just like every other, seems to be somewhat intertwined with the advent of Artificial Intelligence (AI). So let’s learn how AI is helping to pave a better future for breast cancer treatment.

AI has already demonstrated its capabilities in diagnostics. Analysis of scans of tumours by AI can reveal disease characters and affected spots that were impossible to be detected by the naked eye, thus proving to be much more efficient than humans in the visual analysis of scans. The fusion of AI and synthetic biology has opened quite a promising new avenue for cancer treatment. When AI is fed data from thousands of cancer patients and their treatment procedures, it displays the capability to design the perfect drug or nucleic acid with exact molecular capabilities to treat that specific type of cancer. To tackle tumour heterogeneity, an artificial intelligence-assisted medical system has been created which can predict a drug selection framework for cancer patients. This personalised system analyses all the genetic and molecular data about the patient’s tumours and predicts the effectiveness of any drug for that patient, or deduces which drug would be most effective for them. It also takes into account the economic cost associated with using that drug. By considering both effectiveness and cost, the system aims to assist doctors, researchers, and patients in making informed decisions about the most appropriate and efficient use of targeted drugs. This approach helps balance the drug’s potential benefits with the economic implications, ensuring that resources are used effectively to achieve the best possible patient outcomes while considering financial constraints. This system would soon be incorporated into breast cancer treatment models.

As a concluding note to the article, I would like to mention that, while developing such promising technologies for breast cancer treatment, abiding by bioethics principles must be one of our priorities. The toxicity and biodegradability of nanoparticles remain one of such concerns. Providing informed choices to patients should also be another prime concern. Furthermore, there are deeply rooted ethical concerns regarding Genetically Modified Organisms (GMOs) used for research, like contamination of natural gene pools due to escape of GMOs, animal welfare, and cruelty. Newly developed disease modelling systems like Somatically Engineered Mouse Models (SEMMs) greatly help to mitigate such concerns. Special attention must be paid to aspects such as safety, toxicity, immunogenicity, germ-line modification capabilities, long-term effects and lastly, environmental impacts of any drugs, nanoparticles or nucleic acids developed for treatment so that something created to help cure a breast cancer patient doesn’t end up harming them or anyone else.

With these ideals in mind, we hope synthetic biology will usher in a bright era in treating breast cancer and help save millions of lives worldwide. A big thanks to all our readers for staying with us till the end of this article series.

References:

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3. Arnold, C. Inside the nascent industry of AI-designed drugs. Nat Med 29, 1292–1295 (2023). https://doi.org/10.1038/s41591-023-02361-0
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CAR T Cells: Engineering Patients’ Immune Cells to Treat Their Cancers was originally published by the National Cancer Institute.

7. AUTHOR=Lima Anthony, Maddalo Danilo

TITLE=SEMMs: Somatically Engineered Mouse Models. A New Tool for In Vivo Disease Modeling for Basic and Translational Research

JOURNAL=Frontiers in Oncology

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/articles/10.3389/fonc.2021.667189