Hello Nature readers,

This week, we learn that a chemical produced by gut bacteria might boost chemotherapy in pancreatic cancer, hear that antibiotics might have a dampening effect on immunotherapy, hear the case for opportunistic fallopian tube removal and find out which animals are immune to cancer — and why!

Metabolite boosts chemo in pancreatic cancer

A chemical produced through the breakdown of the amino acid tryptophan by bacteria in the gut — indole-3-acetic acid (3-IAA) — could make chemotherapy for pancreatic cancer more effective. People with pancreatic cancer who responded to chemotherapy had higher levels of 3-IAA than people who did not respond to treatment, researchers found. Chemotherapy was also more effective in mice that had their levels of 3-IAA artificially boosted through faecal microbiota transplantation, dietary manipulation or oral 3-IAA administration. People can easily increase the amount of tryptophan in their diet — many foods, including dairy products, chicken, egg whites, soya beans and peanuts, contain it. However, treating people directly with 3-IAA supplements would be ideal for future clinical trials because differences in the gut microbiome affect how well people metabolize tryptophan into 3-IAA.

Antibiotics dampen immunotherapy benefit

People with cancer were at a higher risk of death if they had taken antibiotics up to one year before being treated with an immunotherapy called immune checkpoint inhibitors, found a study. Fluoroquinolones were the class of antibiotic associated with the worst outcomes. The population-based study of more than 2,700 people is "particularly provocative" in suggesting that antibiotics might affect treatment even before the clinical diagnosis of cancer, two physicians write in an accompanying editorial.

Opportunistic removal of fallopian tubes

Women who are not planning to get pregnant and are undergoing pelvic surgery anyway might choose to have their fallopian tubes removed to reduce the risk of ovarian cancer. The procedure — called a salpingectomy — is relatively simple and safe, and does not trigger menopause because the fallopian tubes do not make hormones. Ovarian cancer mostly affects postmenopausal women and is difficult to detect early; fewer than half of women diagnosed with it live for more than five years.

The role of the mind in physical illness

In a yet-to-be-published study, mice that had heart attacks were less likely to end up with cardiac scar tissue if researchers had stimulated a region of the brain involved in positive emotion. The reward centre of the brain might be triggering a protective immune response, the researchers surmised. "In the beginning we were sure that it was too good to be true," says neuroimmunologist Hedva Haykin. The study is part of a growing field that is investigating how mental states affect how ill we get and how quickly we recover. There seem to be multiple lines of communication between the nervous system and the immune system, and cracking this secret could help treat a range of diseases, even cancer, says neuroimmunologist Asya Rolls.

The wave of fraud in medical research

Out of 750 scientific papers flagged by Ben Mol and his colleagues as containing potential errors or fraud, only 80 have been retracted. Mol, an obstetrician and gynaecologist, is one of several specialists who are concerned by the volume of dodgy papers being published. Almost 19,000 biomedical-science papers have been retracted, according to a database maintained by scientific-integrity blog Retraction Watch. And the problem is getting worse: there were twice as many retractions in 2022 as in 2018. Many of these papers are coming from prolific fraudsters and 'paper mills', which churn out nonsense research.