The Link Between Microbiome And Cancer

Can We Prevent Some Types Of Cancer By Changing Our Microbiome?

The term “microbiome” applies to the combination of all of the gene sequences from a population of microbes in the human body. High-throughput DNA amplification and sequencing technologies of the microbial communities provide data that implies the association of microbiome and various human diseases.

Microbiome Health And Balance

Variations in the interactions among the gut microbiome, intestinal epithelium, and host immune system are connected with multiple diseases, including cancer. Environmental factors can influence this interaction throughout oncogenesis and tumor progression.

Microbiomes influence human health in various ways and are likely to impact cancer growth and patients’ response to therapy.

The effects of microbiomes on cancer formation and growth may be direct or indirect. The interactions between microbiomes and cancers still lack a systems biology approach.

Treatments that change the microbiome composition of cancer patients are already under research in tests.

The collection of microbes that live in and on the human body – the human microbiome – can impact cancer initiation, progression, and response to therapy. 

The methods by which microbiomes impact cancers can yield new diagnostics and treatments, but much remains unknown. The interactions between microbes, diet, host factors, drugs, and cell-cell interactions within cancer itself likely involve intricate feedback, and no single component can explain all the behavior of the system.

Understanding the role of host-associated microbial communities in cancer systems will require a multidisciplinary approach combining microbial ecology, immunology, cancer cell biology, and computational biology – a systems biology approach.

How Far Are We In Understanding The Microbiome?

While microbiome study has increased vastly over the past couple of years, conclusions have been difficult to extrapolate. The variability produced by sample collection and approach has not been systematically evaluated.

A statistic often cited says that infectious agents cause 20% of cancers worldwide. That fact perhaps explains why cancer biology tends to view microbes such as viruses and bacteria as carcinogens to be eliminated. The microbial communities that make up the human microbiome impact many aspects of host biology: nutrient uptake, drug metabolism, inflammation, and even behavior.

They most likely also influence cancer progression and treatment, and in ways that can range from harmful to beneficial. Understanding how microbiomes impact cancers – directly and indirectly, harmfully and beneficially – could bring new possibilities for cancer prevention, treatment, and management.

Interaction Between Microbiome And Cancer Therapy

Culturing of bacterial strains has been fundamental to classical microbiology and has enabled the study of individual pathogens. For most commensal bacteria, culture methods had not been optimized for their in vitro isolation and study. With recent advancements in methodology, a large proportion of commensal bacteria is now considered culturable.

During cancer therapy, the gut microbiota interacts in a two-way fashion. On the one hand, several interventions currently used for the management of neoplastic diseases exercise cytotoxic effects on intestinal bacteria. Because of this, radiation therapy and allogeneic stem cell transplantation can be toxic for the gut microbiota—and hence alter its composition—either directly or by activating an immune response.

Furthermore, these therapeutic interventions exert unwanted side effects on the abdominal barrier. On the other hand, growing evidence shows that the gut microbiota influences both the therapeutic activity and the side effects of anticancer agents.

Much More Research Is Needed In This Field

But, many knowledge gaps remain to be filled: microbiomes are a complex ecosystem with dynamics that emerge from interactions between microbes and with the cells of their host. Each cancer is itself an ecosystem in which cancer cells interact with each other in intricate, dynamic ways.

General factors such as circulating metabolites, systemic immunity, etc. can affect the two types of ecosystems concurrently. The relevant links between microbiomes and cancers may be difficult to reduce to a single component. Examining the role of microbiomes in cancer will likely demand a systems biology approach.

Incorporating Microbiome Research Into Personalized Cancer Therapy

Without better ways to prevent, detect, and treat cancer at an early stage, the number of new people diagnosed with cancer will continue to outpace the treatments available. This means many of us could, sadly, need to learn to live with cancer in our lifetime. It is possible that the answer for prolonging quality and fulfilling lives, even when a cancer cure is unavailable, resides in our future ability to leverage the human microbiome, and use it to help to contribute to sustainable, long-term control of the disease.

This could help reduce incurable cancers to chronic but controllable diseases. Once it’s better understood, the homeostasis between microbes and cancer systems may eventually provide healthier and longer lives.

Looking forward, it is essential to understand that the microbiome provides only one dimension to the many aspects that dictate the interface between cancer and the host immune response. Cancer cells grow and evolve under the selective pressure of therapy, and molecular evolution of the tumor could still occur when the microbiome is formed to maximize immunotherapy efficacy.

Also, it is likely that the composition of the microbiome may evolve throughout cancer progression and therapy administration. This variation offers additional research challenges, but with this pliability also comes exciting promise for intervention and exploiting the host-microbiome interdependency to deliver better therapy. In the future, it will be relevant to consider the microbiota as one of many parameters to be incorporated into considerations of personalized cancer therapy.