The compound interrupts cancer cell replication and triggers their destruction
From the humble onion, researchers at the University of Granada have drawn a compound that, in laboratory settings, disrupts the very machinery by which colorectal cancer grows, spreads, and survives. The substance, known as PTSO, does not merely attack tumor cells directly — it also quiets inflammation, rebalances gut microbiota, and enlists the immune system as an ally. Published in Phytotherapy Research, the findings remind us that nature's most ordinary gifts sometimes carry extraordinary latent power, though the long road from laboratory promise to human healing has yet to be walked.
- Colorectal cancer claims over 44,000 new diagnoses each year in Spain alone, pressing researchers to find treatments that go beyond conventional approaches.
- PTSO, extracted from common onions, reduced tumor size and number in laboratory models by halting cancer cell replication and triggering their destruction through oxidative stress.
- The compound simultaneously attacks multiple tumor survival pathways — STAT3, PI3K/mTOR, and Wnt/β-catenin — while calming inflammation and restoring gut microbiota balance.
- Encapsulating PTSO proved critical: the protective shell prevents premature breakdown in the digestive tract, delivering the compound precisely where it is needed in the colon.
- Despite striking early results, the research remains preclinical — human clinical trials are the essential and still-absent next step before any therapeutic use can be considered.
Researchers at the University of Granada, working alongside Germany's Deutsches Zentrum Immuntherapie and other international partners, have found that a compound derived from ordinary onions shows remarkable anti-tumor properties against colorectal cancer in laboratory models. The substance, propyl propane thiosulfonate — or PTSO — was the focus of a study published in Phytotherapy Research, motivated by the disease's heavy toll: more than 44,000 new cases are diagnosed annually in Spain alone.
In laboratory settings, PTSO proved effective through several simultaneous mechanisms. It interrupted cancer cell replication, induced oxidative stress to destroy tumor tissue, and blocked key molecular pathways — including STAT3, PI3K/mTOR, and Wnt/β-catenin — that tumors depend on to grow and develop blood supply. Crucially, the compound also addressed the inflammatory environment that often accompanies colorectal cancer linked to chronic bowel disease: it suppressed pro-inflammatory immune cells, activated tumor-fighting T lymphocytes, strengthened the intestinal barrier, and helped restore a healthier gut microbiota.
Delivery method emerged as a decisive factor. Encapsulated PTSO significantly outperformed its unencapsulated form, as the protective shell prevented premature degradation in the upper digestive tract and ensured the compound reached the colon intact and in concentrated form.
The researchers have been careful to frame their findings within their limits. The study succeeded in animal models and human cell cultures, but no clinical trials in living patients have yet been conducted. Confirming whether PTSO is safe and effective in people remains the necessary — and still distant — next chapter of this work.
Researchers at the University of Granada have identified a compound in ordinary onions that shows striking promise against colorectal cancer in laboratory studies. The work, published in the journal Phytotherapy Research and conducted by a multidisciplinary team led by the university's pharmacology department in partnership with Germany's Deutsches Zentrum Immuntherapie and other international centers, focused on a substance called propyl propane thiosulfonate, or PTSO, derived from common onion tissue.
Colorectal cancer accounts for more than 44,000 new diagnoses annually in Spain alone, making it a significant public health burden. The Granada team set out to understand whether PTSO could address this disease at the cellular level. In laboratory models, the compound performed remarkably: it reduced both the number and volume of colon tumors through multiple mechanisms. PTSO interrupts the replication cycles of cancer cells, preventing them from multiplying, and triggers their destruction by inducing oxidative stress within tumor tissue. Beyond these direct effects, the compound also blocks critical molecular signaling pathways—including STAT3, PI3K/mTOR, and Wnt/β-catenin—that tumors rely on to expand and establish blood supply.
One of the most challenging aspects of treating colorectal cancer, particularly when it accompanies chronic inflammatory bowel disease, is the inflammatory environment and degraded gut bacteria that fuel malignant cell growth. The Granada study demonstrated that PTSO addresses both problems. It dramatically reduces localized inflammation and suppresses pro-inflammatory immune cells while simultaneously activating T lymphocytes, which are essential for attacking tumors. The compound also strengthens the intestinal barrier by reducing endotoxins in the bloodstream, improving the integrity of the colon's mucous lining, and helping restore balance to the gut microbiota.
How the compound is delivered matters enormously. The researchers found that encapsulated PTSO significantly outperforms the unencapsulated form. The capsule protects the substance from degrading prematurely as it passes through the upper digestive tract, ensuring controlled release directly in the colon where it is needed. This targeted delivery multiplies the compound's stability and absorption in affected tissues.
Yet the researchers have urged caution. The work remains in the preclinical phase—successful in animal models and human cell cultures, but not yet tested in living patients. The logical next step is to design and conduct human clinical trials to determine whether PTSO is safe, tolerable, and actually effective in people with colorectal cancer. Until those trials are completed and their results published, the promise shown in the laboratory cannot be translated into clinical practice. The path from promising laboratory findings to approved therapy is long and uncertain, and this research, for all its encouraging early signals, is still at its beginning.
Notable Quotes
The researchers urged caution, noting the study remains in preclinical phase and human clinical trials are necessary to validate safety and efficacy in patients— University of Granada research team
The Hearth Conversation Another angle on the story
What makes this compound different from other experimental cancer treatments we've heard about?
Most cancer drugs are synthetic—designed in labs to target specific pathways. PTSO is natural, already present in something we eat. The real difference is the mechanism. It doesn't just kill cancer cells; it also quiets the inflammatory environment that allows tumors to thrive and restores the gut bacteria that fight back against malignancy.
Why does the encapsulation matter so much?
Without it, PTSO breaks down in your stomach and small intestine before reaching the colon, where the cancer is. The capsule is like a delivery vehicle—it keeps the compound intact until it arrives at its destination, where it can actually do work.
If this works in lab models, why can't we start giving it to patients now?
Because lab models are controlled environments. We don't know yet if human bodies will tolerate it, if it will work the same way in living tissue, or if there are side effects we haven't seen. Clinical trials exist precisely to answer those questions before we expose patients to something untested.
How long until we might see this as a treatment option?
That depends entirely on how the clinical trials go. If they're successful, we're looking at years of regulatory review. If they fail or show safety concerns, the research stops. There's no timeline yet—only the next necessary step.
Does this mean people should start eating more onions to prevent colon cancer?
Not based on this research. The compound in the study is concentrated and encapsulated in a specific form. Eating onions is healthy for many reasons, but it's not the same as receiving a controlled dose of PTSO. That's precisely why the clinical trials matter.