Tumors also have microbiota (and even scientists don't know how it behaves)

Microbiota has been a familiar term for some time now. This group of microorganisms, which includes bacteria, fungi, archaea, viruses, and parasites , resides in our bodies.

An alteration of this balance , a condition known as dysbiosis , goes hand in hand with symptoms such as urinary tract infections , food intolerances, abdominal distension or flatulence.

Now, science has gone a step further, and there are already studies that discuss the intratumoral microbiota . For example, a 2023 Nature publication explains that intratumoral microbial components are found in multiple tumor tissues and are "closely related" to cancer initiation and development.

Furthermore, they emphasize its connection with therapeutic efficacy : "The intratumoral microbiota can contribute to the initiation and progression of cancer through DNA mutations , the activation of carcinogenic pathways, the promotion of chronic inflammation, the complement system and the initiation of metastasis ."

Álvaro Pinto , a urological oncologist and researcher at the La Paz Hospital Research Institute (IdiPAZ), is the lead author of a publication that delves into this topic. "The first studies conducted on microbiota and its influence on treatment response have been with the digestive tract , for example, in feces. Our research focuses on its presence within or around the tumor and its influence on treatment," he explains to this newspaper.

Although he admits the study is "very preliminary," he adds that they have demonstrated the presence of detectable bacteria around the tumor. "It's a longer-term project. In relation to bladder tumors , our area of ​​exploration, there is a group of bacteria that could be linked to a lower response to chemotherapy; this is what we want to continue investigating . The goal is to predict which patients will respond better or worse to treatments."

A little-studied approach

Regarding the limited knowledge that exists about this intratumoral microbiota , the oncologist explains that there are more working groups dedicated to its observation: "The tumor is not alone; it is surrounded by vessels or non-tumor cells ."

He also explains that over the years, targeted therapies such as immunotherapy have been developed , which "were promising" and have become standard options: "This is a different approach , understanding the bacteria that might modulate the immune response in the future."

However, he insists, we must first see if the microbiota "plays any role beyond just being there." "If confirmed, it would be another way of acting. For example, if we saw bacterial populations that confer resistance to certain treatments , we would look for other alternatives or ways to modify those bacteria. The more information we have, the better the outcomes for patients ," he states.

How they conducted the research

In the analysis led by Dr. Pinto, published in the Journal of Clinical Oncology , they studied 58 formalin-fixed, paraffin-embedded (FFPE) tissue samples from patients with muscle-invasive bladder cancer (MIBC) obtained by transurethral resection [a surgical procedure used to treat problems in the urethra, bladder, and prostate by accessing them with an endoscope through the urethra].

The proteins they extracted for the microbiota examination were added to a database that included the human proteome and the proteomes of identified bacterial genera . In total, they obtained treatment response information for 56 patients , of whom 24 achieved a complete pathological response (43%), with a median disease-free survival of 22 months and a median overall survival of 29.23 months.

Additionally, 151 bacterial genera were added to the database. Hierarchical clustering analysis identified three groups with distinct microbiota protein profiles: Microbiota 1, Microbiota 2, and Microbiota 3, which showed significant differences in response to neoadjuvant chemotherapy [a treatment given before surgery to shrink tumors].

"The number of bacteria is not as important as the types . We have looked at whether the predominance of some populations over others correlates with the response to treatment. This is the first finding and it needs to be validated by conducting a larger study, with a broader sample of patients . It will take approximately two or three years to obtain the results," concludes the oncologist .