Biotin & FBXW7: How Cancer Escapes Glutamine Addiction
Lisci M, Vericel F, Liu Y, Gallart-Ayala H, Ivanisevic J, Skinner OS, Jourdain AA • Molecular Cell, 2026; 86(5):901–916 • DOI: 10.1016/j.molcel.2026.02.002
Many cancers are addicted to the amino acid glutamine. This paper asked: what allows some cells to break free? The answer involves Vitamin B7 and one of the most commonly mutated tumor suppressors in human cancer.
Overview
Through a large-scale genetic and nutritional screen — what the authors call "functional nutrient-genetic profiling" — the researchers discovered two key players:
Biotin (Vitamin B7) — when present, activates a metabolic escape route that lets cells survive without glutamine.
FBXW7 — a tumor suppressor that keeps that escape route open. When FBXW7 is mutated (common in many cancers), the escape route is blocked, locking those cells into glutamine addiction.
Background: Why Glutamine Addiction Matters
Normal cells are metabolically flexible — they can switch between nutrients depending on availability. Cancer cells often lose this flexibility and become dependent on specific fuels. Glutamine addiction is well-known: many tumors consume glutamine at far higher rates than normal cells, using it to fuel growth, build proteins, and generate energy.
This dependency is potentially exploitable as a therapy — starve a cancer of glutamine and you might stop its growth. But cancers can develop workarounds. Understanding those workarounds is critical for designing effective therapies.
What the Researchers Did
The team used three complementary approaches together:
Metabolic tracers — molecules labeled with carbon-13 to track exactly how carbon flows through metabolic pathways.
Nutrient supplementation — systematically testing which nutrients could rescue cells from glutamine deprivation.
Genome-wide CRISPR-Cas9 screening — knocking out every gene, one at a time, in glutamine-deprived conditions to identify essential survival genes.
Key Findings
Biotin activates the escape route
When cells are deprived of glutamine, supplementing with biotin allows them to survive. Biotin activates pyruvate carboxylase (PC), which converts pyruvate into oxaloacetate — replenishing the TCA cycle without needing glutamine. Biotin-powered PC is an alternative on-ramp to the TCA cycle that bypasses the glutamine route entirely.
FBXW7 keeps pyruvate carboxylase active
FBXW7 is a tumor suppressor that degrades the oncogene c-MYC. When FBXW7 is functional, c-MYC is kept low, and the PC gene is expressed normally. When FBXW7 is mutated or lost, c-MYC accumulates — and high c-MYC recruits a transcriptional repressor complex (MAX, MNT, SIN3A) to the PC gene promoter, silencing it. Without PC, cells cannot bypass glutamine dependence.
Clinical relevance for FBXW7-mutant cancers
FBXW7 is one of the most commonly mutated tumor suppressors in human cancer — including colorectal cancer, T-cell leukemia, and cholangiocarcinoma. These cancers, with silenced PC, should be most vulnerable to glutamine-targeting therapies such as CB-839/telaglenastat (currently in clinical trials).
Interactive diagram of the molecular mechanism — how FBXW7 loss blocks the biotin-powered TCA bypass route.
Why This Matters
Mechanism: A detailed molecular explanation for glutamine addiction — the FBXW7 → c-MYC → PC axis is a new piece of the puzzle.
Biomarker: FBXW7 mutation status may predict which tumors are most sensitive to glutamine-targeting therapies.
New role for biotin: Generally considered just a B vitamin, biotin turns out to play an underappreciated role in cancer metabolic flexibility.
Method: "Functional nutrient-genetic profiling" — combining nutrient screens with genome-wide CRISPR screens — is a powerful strategy others can apply broadly.
Glossary of Key Terms
- Glutamine addiction
- Dependence of many cancer cells on glutamine as a primary fuel — a metabolic vulnerability potentially exploitable as therapy.
- Pyruvate carboxylase (PC)
- An enzyme that converts pyruvate to oxaloacetate, replenishing the TCA cycle. Requires biotin to function.
- Anaplerosis
- Reactions that replenish TCA cycle intermediates drained during rapid cell growth. Glutamine and pyruvate are major anaplerotic substrates.
- FBXW7
- A tumor suppressor E3 ubiquitin ligase that tags oncogenes (especially c-MYC) for destruction. Lost in many cancers.
- c-MYC
- A powerful oncogene and transcription factor. Normally kept in check by FBXW7; drives glutamine uptake when overactive.
- MAX / MNT / SIN3A
- A gene-silencing complex recruited by c-MYC to the PC gene promoter, switching it off when FBXW7 is lost.
- CRISPR-Cas9 screening
- Genome-wide technique knocking out every gene across millions of cells to identify genes essential for survival under specific conditions.