Hello Nature readers,
This week, we discover that cancer's addiction to extra chromosomes is an exploitable weakness, hear that cancer is no match for macrophages in a low-protein environment, and learn that pills containing human faeces could boost immunotherapy for advanced skin cancer.

Exploiting cancer's addiction to aneuploidy

Having an abnormal number of chromosomes — known as aneuploidy — helps tumours grow quickly, but also makes them more vulnerable to certain drugs. When Cancer Cells with an extra arm on chromosome 1 were injected into mice, they grew 25 times larger than cancer cells in which the extra chromosome had been removed using CRISPR–Cas9 gene editing. Two drugs known to be activated by chromosome 1 killed more of the cancer cells that had these extra chromosome arms. The study "is important, it's novel, and it was carried out in a very elegant way", says cell biologist Uri Ben-David.

Faecal tablets for advanced skin cancer

Taking donated human faeces in tablet form might help people with advanced melanoma respond better to immunotherapy. In a world-first trial, 20 people with advanced skin cancer swallowed dozens of pills containing frozen faecal matter. "They're tasteless. They have no smell. They're not unsightly. There's nothing. You just have to get past thinking it might be kind of gross," says physician Michael Silverman. Most people in the trial (65%) responded to anti-PD-1 immunotherapy, with tumours melting away entirely for four people. Normally, only around one-third of people with advanced melanoma respond to immunotherapy.

Cancer is no match for macrophages

If nutrients in tumours are scarce, immune cells called macrophages can compete with cancer cells for resources — and win. When mice were given a low-protein diet, macrophages outcompeted breast cancer cells by inhibiting the signalling of a protein complex called mTORC1, stalling cancer growth. This finding could lead to a new form of immunotherapy.

Treatment 'perversely' triggers resistance

People with lung cancer who take targeted treatments for longer seem to be more likely to develop mutations that can lead to drug-resistant cancer. Long-term treatment with tyrosine kinase inhibitors drove the expression of an enzyme called APOBEC3A that wreaked havoc on DNA, causing mutations and therefore drug resistance. "Targeted therapies might perversely increase the adaptive mutability of cancer cells," report the researchers.