From the left. Standing: Nuria Ajenjo (Biobank), María Casanova-Acebes and Alba de Juan (Cancer Immunity Group), Cecilia Sobrino and Sergio Fernández (Biobank), Virginia López del Alcázar (AETCP). Seated: Daniel Alba (Biobank), David J. Quesada (AETCP), María Jesús Artiga (Biobank). Credit: Laura M. Lombardía /CNIO
The Biobank of the National Cancer Research Centre (CNIO) has created the first collection of biological samples for this population group, and makes it available to the scientific community
Cabin crew members subject the body to chronic jet lag due to their work.
CNIO researchers María Casanova-Acebes and Alba de Juan are using these samples to study the relationship between circadian rhythms, the immune system and cancer
The International Agency for Cancer Research classifies work which alters circadian rhythms as ‘probably carcinogenic’
Once a year, more than a hundred flight attendants come to donate blood and saliva to the National Cancer Research Centre (CNIO) in Madrid. They bring with them samples of urine, faeces and nail clippings collected at home in special test tubes provided by CNIO. These samples are taken to the CNIO Biobank, which stores them and manages their transfer to the international scientific community.
The biological samples from this group allow us to investigate the effect of being subjected to constant jet lag on the body. The body has an internal clock to adapt to day and night conditions; when the circadian rhythms become out of synch over a prolonged period of time, there may be an impact on health.
The International Agency for Research on Cancer classifies work that alters circadian rhythms as “probably carcinogen” (the category for carcinogens in which there is “sufficient experimental evidence ” in experimental animals, but “limited evidence” in humans).
Scientific support for an occupational risk
Virginia López del Alcázar, Head of Professional Health at the Spanish Association of Cabin Crew Members (AETCP), explains why they agreed with the CNIO Biobank to start this collection in early 2021: “we needed to prove scientifically that our health is affected by our profession; only then could we ask for recognition of our occupational risk, which is actually considered in other professions in the sector, such as pilots and aerial photographers.”
“Alongside the samples, donors provide detailed information about their clinical and family history, diet, exercise, smoking habits, and hours and type of flight, among other data,” says María Jesús Artiga, acting director of the CNIO Biobank. “This information makes the sample extraordinary valuable for different types of research.”
In addition, the fact that the collection is longitudinal (samples are collected every year from the same donors) makes it a valuable tool to study early markers of different diseases. In the Biobank, the identity of the donor is replaced by a code, ensuring the confidentiality of data and samples.
A distorted clock that disarms the defences
The first request for access to the samples came immediately from CNIO itself, specifically from its Cancer Immunity Group. María Casanova-Acebes and Alba de Juan are investigating the influence of circadian rhythms on the immune system and its relationship with cancer, also taking metabolism into account.
“Our immune system has a cycle of 24 hours, with one stage of rest and another active stage, in which there are more leukocytes – white blood cells – in the tissues,” explains de Juan. “We think that when people are constantly subjected to jet lag or shift changes that cycle gets out of synch, and the number and functions of their leukocytes are no longer optimal,” she adds.
These hypotheses, already verified in animal models, will be tested with the cohort of flight attendants.
For this purpose, they have established three groups: crews of long-haul flights, short-haul flights (covering less distance, but in more variable and shorter shifts), and a control group with individuals who do not fly and lead a life with regular schedules and habits.
“In March 2023, we started collecting samples every six months, to include variability due to seasonal changes,” says Casanova-Acebes. “We will follow them for four years.” To detect changes, they will study the number of immune system cells in their blood “and whether they have a profile more favourable to inflammation,” adds de Juan.
Inflammation and risk
The initial mismatch of circadian rhythms is not only caused by the perception of natural light. There are other external stimuli that condition the body to behave in ‘day mode’ or ‘night mode’: heavy meals, artificial light, noise or interaction with screens can be an activating factor. We know that when these external activation stimuli are not in tune with biorhythms, they can trigger inflammatory distortions.
Casanova-Acebes seeks to “establish which changes in the immune system perpetuated over time will be responsible for inflammatory diseases, including cancer.”
An investigation made possible thanks to donations to CNIO made by the Spanish Association of Cabin Crew Members (AETCP).