Cancer researchers have uncovered an unexpected molecular system that helps explain how the MYC gene drives some of the most aggressive and difficult-to-treat tumors. In two studies published back-to-back in Genes & Development, teams led by Anindya Bagchi of Sanford Burnham Prebys Medical Discovery Institute show that a region of DNA long regarded mainly as a neighboring noncoding locus is actually a powerful regulatory hub. The region, known as PVT1, produces two previously unrecognized proteins with opposing effects: one strengthens MYC-driven cancer growth, while the other restrains a major cancer-signaling pathway. Together, the findings reveal a “dual-hit” mechanism that may help tumors amplify MYC activity while simultaneously removing an important molecular brake.
MYC is one of the most influential genes in human cancer. It encodes a transcription factor, a protein that binds DNA and controls the activity of many other genes involved in cell growth, division, metabolism and survival. MYC is deregulated in more than half of human cancers and can push cells into a state of sustained proliferation. In tumors, excessive MYC activity allows malignant cells to manufacture proteins and energy at an accelerated rate, evade normal growth controls and tolerate conditions that would kill healthy cells. MYC is implicated in cancers ranging from breast and lung tumors to leukemia and brain cancer. Yet despite its central role, MYC has traditionally been considered “undruggable” because its structure lacks the deep binding pockets commonly exploited by conventional small-molecule medicines.
The new work shifts attention from MYC itself to the genetic neighborhood that supports its activity. PVT1 lies adjacent to MYC on chromosome 8q24, one of the most frequently altered regions of the cancer genome. In many tumors, MYC and PVT1 are amplified together, and earlier research from the Bagchi laboratory established that PVT1 is required for the growth of MYC-dependent cancers. The biological explanation, however, remained unclear. PVT1 had generally been classified as a long noncoding RNA, meaning an RNA molecule not thought to serve as a template for producing proteins. The paired studies now show that this description is incomplete. Alternative forms of PVT1 can generate both a circular RNA that encodes a protein and a separate transcript containing the instructions for a tiny regulatory peptide.
The first study identifies the circular RNA product of PVT1, called CircPVT1, as the source of a novel protein named Firefox. Circular RNAs are formed when an RNA strand bends back on itself and its ends are joined, creating a closed molecular loop. Because they lack the exposed ends found on conventional messenger RNAs, circular RNAs can be unusually stable inside cells. Some circular RNAs regulate gene activity by binding other RNAs or proteins, but the researchers found that CircPVT1 also contains a translatable coding sequence. Cellular machinery uses that sequence to produce Firefox, establishing that a molecule previously categorized as noncoding can directly generate a functional cancer-associated protein.
Experiments showed that Firefox is essential for the full oncogenic effect of MYC. When researchers reduced Firefox levels in cancer cells, the amount of MYC protein fell and the transcriptional program controlled by MYC became less active. This distinction is important because MYC activity is regulated at several levels. A tumor may contain abundant MYC messenger RNA, yet the resulting protein can still be rapidly destroyed or fail to activate its target genes. Firefox appears to support the stability or functional output of MYC, although the precise molecular contacts that produce this effect remain a subject for further investigation. In animal models of MYC-driven cancer, experimentally induced depletion of Firefox significantly slowed tumor growth, indicating that the protein is not merely a molecular bystander but a functional dependency of malignant cells.
The second study reveals an opposing product of the same genomic region. The researchers examined structural rearrangements involving PVT1, in which breaks in DNA cause segments of chromosomes to exchange positions. They found that a recurring translocation removes a section of PVT1 containing the instructions for a previously unknown micropeptide. The team named this peptide Honeybadger. Micropeptides are generally much shorter than conventional proteins, but their size does not prevent them from exerting major biological effects. Many micropeptides interact with larger proteins embedded in membranes or operating within signaling networks, acting as molecular switches, stabilizers or inhibitors.
Honeybadger directly binds KRAS, a central signaling protein that controls cell proliferation and survival through the RAS–MAPK pathway. KRAS normally transmits signals from cell-surface receptors to a chain of intracellular proteins, ultimately activating MAP kinases that alter gene expression. Mutated KRAS can become permanently active and is responsible for driving approximately one-quarter to one-third of human cancers. The Sanford Burnham Prebys researchers found that Honeybadger functions as a restraint on this pathway by binding KRAS and dampening downstream RAS–MAPK signaling under normal conditions. When a PVT1 translocation deletes the Honeybadger-encoding region, that restraint disappears. Even wild-type, or nonmutated, KRAS can then produce excessive signaling.
This increase in RAS–MAPK activity has consequences for MYC. The pathway stabilizes MYC protein, allowing it to remain active for longer and intensifying the transcriptional program that promotes tumor growth. This mechanism could explain how tumors lacking KRAS mutations nevertheless acquire abnormally strong KRAS signaling and elevated MYC output. At the same time, the rearranged PVT1 locus retains or enhances the production of Firefox, the MYC-supporting oncoprotein. The resulting combination is particularly damaging: the tumor gains a factor that helps MYC function and loses a micropeptide that normally suppresses upstream signaling. According to the researchers, these two changes converge on the same cancer-driving program and may account for the poor prognosis associated with certain PVT1-rearranged tumors.
The findings also challenge the conventional way scientists interpret cancer-associated DNA regions. A genomic locus positioned beside a powerful oncogene may not be passive, and an RNA labeled “noncoding” may contain hidden instructions for producing biologically important peptides. PVT1 now appears to operate as a flexible regulatory platform whose effects depend on which transcripts are produced and which portions of the locus are disrupted. Structural changes at the site can therefore alter cancer behavior in more than one way at once. This framework may help researchers revisit other genomic regions that have been dismissed because they do not resemble classical protein-coding genes. It also illustrates why cancer genomes cannot be understood solely by cataloging mutations in familiar oncogenes and tumor suppressors; rearrangements, transcript architecture and small translated products can be equally consequential.
The therapeutic implications remain preliminary, but the work opens several possible routes toward controlling MYC-driven disease without directly blocking MYC. Firefox could become a target for drugs or molecular degraders designed to eliminate the protein or interrupt its interaction with the MYC machinery. Honeybadger, or a molecule that reproduces its effect on KRAS, could potentially restore suppression of RAS–MAPK signaling in tumors where the micropeptide has been lost. Patients might also be classified according to PVT1 amplification, transcriptional status or structural rearrangement, creating biomarkers for therapies aimed at these dependencies. Such strategies will require extensive validation in additional cancer types, careful assessment of toxicity and a clearer understanding of how Firefox and Honeybadger function at the molecular level. The research team plans to examine their roles across more tumors and work with collaborators on prototype therapeutic approaches. For cancers in which MYC has remained beyond the reach of direct drug development, the PVT1 locus may provide a new set of vulnerabilities surrounding the master regulator.
Subject of Research: Molecular mechanisms that regulate MYC-driven cancer through the PVT1 genomic locus, including the Firefox oncoprotein and Honeybadger micropeptide.
Article Title: “Firefox, a Protein Encoded by Circular PVT1, Is Essential for MYC-Driven Oncogenesis”; “Honeybadger, a Micropeptide Encoded by an Alternative PVT1 Transcript, Is a Critical Negative Regulator of RAS–MAPK Signaling in MYC-Driven Tumors”
News Publication Date: 19-Aug-2026
Web References: https://genesdev.cshlp.org/content/early/2026/08/10/gad.353355.125; https://genesdev.cshlp.org/content/early/2026/08/11/gad.353356.125; https://sbpdiscovery.org/scientists/anindya-bagchi-phd/
References: DOI 10.1101/gad.353355.125; DOI 10.1101/gad.353356.125
Image Credits: Sanford Burnham Prebys Medical Discovery Institute
Keywords: Cancer, MYC, PVT1, CircPVT1, Firefox protein, Honeybadger micropeptide, KRAS, RAS–MAPK signaling, oncogenesis, tumor suppressors, cancer genomics, targeted therapy
