Tumors develop before birth. Somewhere in the developing fetus, neural crest cells that were supposed to mature into adrenal tissue or sympathetic ganglia may take a wrong turn and a child is born with a malignant tumor that may not declare itself for several months. Neuroblastoma accounts for approximately 28% of all cancers diagnosed in infants in Europe and the United States. In its mildest form, it is a fire that regresses on its own and goes out on its own. In the most brutal cases, it spreads so quickly that oncologists reach for words they don’t want to use in front of parents. The 5-year survival rate for high-risk neuroblastoma is approximately 40%. This number has hardly changed in one generation.
Now, a study has been published in a peer-reviewed journal. brain medicine (Genomic Press) provides what has been missing. It’s a mechanistic explanation of how this cancer persists and how to cut the wire.
A messenger who became a mercenary
Nitric oxide is one of the oldest signaling molecules in biology. Dilates blood vessels. It conveys messages between neurons. At physiological concentrations, a quiet civil servant is essential. However, at higher concentrations, it becomes more reactive, producing nitrogen species that chemically modify proteins through a process called S-nitrosylation. This modification is involved in every step of cancer progression.
The relationship between nitric oxide and tumors is not simple. Very high concentrations can damage DNA and cause apoptosis. Sustained lower levels appear to have the opposite effect, promoting survival and metastasis. Professor Haitham Amal of the Hebrew University of Jerusalem and his colleagues previously demonstrated that nitric oxide accelerates the progression of glioblastoma. The remaining questions were whether the same enzyme, neuronal nitric oxide synthase, had a similar effect on neuroblastoma, and if so, which downstream pathway.
The answer turned out to be mTOR.
Two paths leading to the same silence
The team attacked nNOS from two directions. They treated human SH-SY5Y neuroblastoma cells with BA-101, a selective pharmacological inhibitor, at 100 μM for 24 hours. Separately, they silenced the nNOS gene using small interfering RNA. This logic was intentional. If drugs and genetic tools produce the same results, you’re looking at biology rather than pharmacological noise.
they gave the same result.
BA-101 reduced NADPH diaphorase activity, a standard measure of NOS function, by 35 to 40 percent. Gene silencing reduced it by 45 to 50 percent. Nitrite levels, a stable surrogate for nitric oxide production, were reduced by 65 to 70 percent with BA-101 and 55 to 60 percent with siRNA. Colony formation, the most direct measure of proliferative capacity, was significantly reduced after both BA-101 treatment (p < 0.001) and nNOS silencing (p < 0.01). Cells were losing their ability to proliferate.
Signal cascade collapses from the top
What followed downstream was systematic. Protein tyrosine nitration, as measured by 3-nitrotyrosine immunoreactivity, was sharply reduced after BA-101 treatment (p<0.01) and nNOS silencing (p<0.001). The chemical signature of nitrosative stress was disappearing.
Then dominoes. AKT phosphorylation was decreased (p < 0.01 for BA-101, p < 0.05 for siRNA), but total AKT was unchanged. Phosphorylation of mTOR itself was decreased under both conditions (p < 0.01, respectively). The downstream mTORC1 substrate ribosomal protein S6 followed (p < 0.05 for BA-101; p < 0.01 for siRNA). And this was the most important detail. TSC2, a major negative regulator of mTOR signaling, was significantly elevated under both treatments (p < 0.05). Removing the nitric oxide signal allowed the cell's own braking system to reactivate, much like someone taking their foot off a gas pedal wired in the floor.
Synaptophysin, a neuroendocrine tumor marker used to assess the malignancy of neuroblastoma cells, was significantly decreased with BA-101 (p < 0.01) and nNOS knockdown (p < 0.05). Tumor cells didn't just grow slower; At the molecular level, cancerous properties were becoming less recognized.
mirror experiment
Good science asks the opposite question. If blocking nitric oxide suppresses mTOR signaling, injecting nitric oxide into cells should amplify mTOR signaling. The researchers exposed SH-SY5Y cells to the nitric oxide donor SNAP at 200 μM for 24 hours.
All the needles swung in the opposite direction. 3-Nitrotyrosine was elevated (p < 0.05). TSC2 was decreased (p < 0.01). Phosphorylation of AKT, mTOR, and RPS6 were all increased (p < 0.05 each). A converse experiment yielded the opposite result. This is the kind of symmetry that distinguishes discoveries from flukes.
From food to animals
Cell culture can teach us a lot. We don’t know if tumors in vivo will respond in the same way. The research team established neuroblastoma xenografts by injecting SH-SY5Y cells subcutaneously into the flanks of 6-week-old NOD-SCID mice, waited until the tumors were palpable, and then administered BA-101 intraperitoneally at 80 mg/kg/day for 22 days. Control animals received vehicle only. 6 mice per group.
Control tumors grew to approximately 1.5 cm in greatest dimension. The treated tumors were not. The final tumor volume and weight were dramatically reduced in the BA-101 group (both p < 0.001). Body weights were not significantly different between groups, suggesting that the compound was tolerated without severe systemic toxicity. The in vivo data did what in vivo data should do. This confirms that the mechanism observed in the dish works throughout the organism.
“The magnitude of the suppression in vivo caught our attention,” said the study’s corresponding author, Professor Haitham Amal, of the Hebrew University of Jerusalem’s School of Medicine, School of Pharmacy, Institute for Pharmaceutical Research, and the Rosamund Stone Zander and Hanschelg Wyss Center for Translational Neuroscience at Harvard Medical School and Boston Children’s Hospital. “While we have previously demonstrated a role for nitric oxide in glioblastoma, the consistency of our results in neuroblastoma across all assays, from protein phosphorylation to colony formation to xenograft growth, indicates that nNOS is more than a contributor. nNOS appears to be a central driving force in the signaling that maintains this tumor.”
“What convinced me was that the pharmacological and genetic approaches were consistent,” said Dr. Shashank Kumar Ojha, lead author of the study and a researcher at the Institute of Pharmaceutical Sciences at the Hebrew University of Jerusalem. “If BA-101 and siRNA independently produce the same pattern of effects across NADPH-diaphorase activity, nitrosative stress markers, mTOR pathway phosphorylation, and clonogenic growth, we can be confident that the biology is real. Their reproducibility provides a therapeutic hypothesis worth further testing.”
what remains unknown
The author is frank about the limitations. This in vitro study relies on a single cell line, SH-SY5Y, and cannot fully capture the genetic heterogeneity of neuroblastoma and the complexity of the tumor microenvironment. The chemical identity of BA-101 is currently unpublished pending patent issuance, meaning it must await independent replication by other laboratories. Whether nitrosative stress directly underlies the dysfunction or whether intermediate mechanisms are involved remains an open question, which the authors explicitly flag for future investigation.
These are honest warnings and they are important. However, they do not undermine the central finding. The nNOS-mTOR axis is real, druggable, and responds to intervention with such force that it warrants further study in mice.
mTOR inhibitors, such as rapalogs and catalytic mTOR inhibitors, are compromised by feedback activation and resistance mechanisms and have shown limited efficacy as monotherapy in neuroblastoma. The current study suggests another form of attack. In other words, rather than targeting mTOR with the lock, we intervene upstream to turn the key. nNOS inhibition may circumvent compensatory pathways that prevented direct mTOR blockade by reducing nitric oxide-dependent mTOR activation.
There is a long distance between the rat’s flank and the child’s bedside. Researchers know this better than anyone. But previously invisible doors are now identified, measured, and shown to open. Subsequent research will determine what happens next.
sauce:
Reference magazines:
Oja, South Carolina others. (2026). Targeting nNOS suppresses AKT-TSC-mTOR signaling and inhibits neuroblastoma growth. brain medicine. DOI: 10.61373/bm026a.0027. https://genomicpress.kglmeridian.com/view/journals/brainmed/aop/article-10.61373-bm026a.0027/article-10.61373-bm026a.0027.xml
