Silencing PTTG1 curbs retinoblastoma cell growth by lowering c-myc

Pituitary tumor-transforming gene 1, better known in the cancer literature as PTTG1, has long carried a reputation as a molecular troublemaker. First isolated in 1997 from rat pituitary tumor cells, the gene has since been found switched to high gear in a long list of human malignancies, from pituitary and breast tumors to ovarian, uterine and lung cancers. A new study published in the journal Cell Division now adds a childhood eye cancer to that list. Researchers report that PTTG1 is markedly elevated in retinoblastoma tissues and cell lines, and that silencing the gene in laboratory-grown retinoblastoma cells slows their proliferation, pushes them into cell cycle arrest, and triggers apoptosis. The mechanism, according to the team, runs through c-myc, one of the most notorious oncogenic transcription factors in biology: when PTTG1 levels fall, c-myc falls with it, and the malignant behavior of the cells eases off.

Retinoblastoma is a relatively unique form of cancer of childhood and the most prevalent intraocular cancer in pediatric patients. The stakes are particularly high in underdeveloped countries, where mortality rates can reach 50 to 70 percent. Children with the disease face multiple risks, including tumor invasion, malignant transformation of intracranial neuroblastoma, and the later appearance of heterochronous tumors. Although therapy has advanced in recent years, survival remains limited by difficulties of early diagnosis, and the conventional treatments, radiation and chemotherapy, can produce serious side effects such as infections and blindness. That combination of clinical urgency and biological mystery is what motivated the Chinese research team, led by Junli Feng, Yunpeng Ye, Furong Cheng and Yanping Wu, to ask whether PTTG1, so often implicated elsewhere, might also be pulling strings in retinoblastoma.

To find out, the researchers first measured where PTTG1 actually sits in the disease. Using quantitative reverse transcription PCR, they compared PTTG1 mRNA levels in sixteen retinoblastoma tissues against eight normal pediatric retinal samples, all obtained from Cangzhou Central Hospital between June 2018 and December 2021. The tumor samples showed significantly elevated PTTG1 expression compared with the normal retinas. The pattern held in cultured cells as well: four retinoblastoma cell lines, WERHRb1, SO-RB50, Y79 and HOX-RB44, all expressed more PTTG1 than the human retinal epithelial cell line ARPE-19, with Y79 and SO-RB50 showing the highest levels. Those two high-expressing lines became the workhorses for the functional experiments that followed.

The team then used short hairpin RNAs to silence endogenous PTTG1 in Y79 and SO-RB50 cells, confirming the knockdown by western blot. The consequences were swift and consistent across assays. A CCK-8 assay showed that suppression of PTTG1 significantly inhibited cell proliferation in both lines, and colony formation experiments revealed a reduced ability of the treated cells to grow into visible colonies. Flow cytometry added a mechanistic layer: roughly 20 percent more cells accumulated in the G0/G1 phase of the cell cycle compared with a negative control, while the S-phase population shrank. In other words, losing PTTG1 appeared to lock the cells at the checkpoint before DNA replication, a classic signature of impaired cell cycle progression.

Apoptosis assays told the complementary part of the story. Downregulation of PTTG1 resulted in measurable cell death by flow cytometry, and western blotting of apoptosis-related proteins corroborated the shift: the anti-apoptotic protein Bcl-2 decreased, while the pro-apoptotic proteins Bax and cleaved caspase 3 increased in the knockdown group. Taken together with the proliferation and cell cycle data, the results suggested that PTTG1 does double duty in these cells, sustaining their drive to divide while simultaneously shielding them from the self-destruct program that stressed or abnormal cells would otherwise activate. Removing it undermines both protective functions at once.

The next question was how PTTG1 exerts these effects. The researchers turned to c-myc, a transcription factor with a well-documented relationship to PTTG1 in other cancers. In hepatocellular carcinoma, PTTG1 is upregulated by TNF-α and promotes cell proliferation via c-myc induction, with inhibition of c-myc leaving PTTG1 expression untouched, evidence that PTTG1 acts upstream. In breast cancer, PTTG1 directly activates c-myc transcription, and PTTG1 deficiency impairs c-myc-driven mammary cell proliferation. In the retinoblastoma cells, the hypothesis held: silencing PTTG1 produced a noticeable reduction in c-myc protein. Because c-myc governs cell growth and cycle regulation by stimulating genes needed for those processes, the team then examined the cyclin A/CDK2 and cyclin D1/CDK4 axes, which are critical for the G1/S transition. Knockdown of PTTG1 led to a significant decrease in cyclin A, cyclin D1, CDK2 and CDK4 proteins.

The decisive test came in the form of rescue experiments. If c-myc is truly the mediator of PTTG1’s influence, then restoring c-myc should restore the malignant phenotype even without PTTG1. The researchers co-transfected Y79 and SO-RB-50 cells with a c-myc-expressing plasmid and PTTG1-targeting shRNA. The result: expression levels of c-myc, CDK2, CDK4, cyclin A and cyclin D1 in the co-transfection group were significantly higher than in the knockdown-only group. Functionally, the CCK-8 assay showed that c-myc overexpression counteracted the proliferation block caused by PTTG1 silencing, flow cytometry showed it reversed the induced apoptosis, and cell cycle analysis showed it restored the altered distribution of cells across cycle phases. These findings, the authors conclude, indicate that c-myc is essential for PTTG1-mediated retinoblastoma cellular function, and that PTTG1 functions mainly through regulating c-myc expression.

The molecular logic is consistent with what is known about both players. PTTG1 contributes to tumor development through several routes: it triggers chromosomal instability by preventing the separation of sister chromosomes during mitosis, disrupts the non-homologous end-joining double-strand DNA repair pathway, and acts as a global transcription factor that enhances the expression of tumor-associated genes, including vascular endothelial growth factor and matrix metalloproteinase 2, both linked to metastasis. It can also interact with transcription factors such as p53, Sp1 and upstream stimulatory factor 1, potentially activating other tumorigenesis-related genes. Previous work had already identified PTTG1 as a transcription factor that binds to the c-myc promoter and regulates its expression, and c-myc itself is a multifunctional oncoprotein involved in cell growth, cell cycle regulation, apoptosis, angiogenesis and transformation, activated in cancers ranging from breast tumors and hepatocellular carcinoma to retinoblastoma.

The authors are candid about the boundaries of what their data can support. The clinical sample size is small, just sixteen retinoblastoma tissues and eight normal retinal samples, which may limit the generalizability of the findings, and larger cohorts will be needed to validate the clinical significance of the PTTG1-c-myc axis. The work was also primarily based on in vitro cell line experiments, lacking in vivo validation in animal models such as retinoblastoma xenografts that would confirm the oncogenic role of PTTG1 under physiological conditions. Perhaps most importantly, the precise molecular mechanism by which PTTG1 regulates c-myc in retinoblastoma cells, whether through direct binding to the promoter or through intermediate molecules, remains unclear; the team suggests that chromatin immunoprecipitation and co-immunoprecipitation assays will be needed to close that gap. The rescue experiments demonstrate functional dependence, but not yet the physical wiring.

Even with those caveats, the study adds a coherent piece to the expanding map of retinoblastoma biology. It ties a chromosomal instability gene to a master proliferation regulator through a pathway already conserved in liver and breast cancers, and it does so in a disease where new molecular targets are badly needed. The authors suggest that targeting PTTG1 may serve as an adjunctive therapy for retinoblastoma in the future, a possibility that will depend on whether the laboratory findings survive the tests of larger patient cohorts, animal models and mechanistic scrutiny that now lie ahead. For a cancer whose standard treatments can cost children their sight, any lead that points toward a more precise molecular handle is worth following.

Subject of Research: The role of the PTTG1-c-myc axis in retinoblastoma cell proliferation and apoptosis

Article Title: PTTG1-mediated the transcription of c-myc promotes retinoblastoma progression

Article References: Feng, J., Ye, Y., Cheng, F., & Wu, Y. (2026). PTTG1-mediated the transcription of c-myc promotes retinoblastoma progression. Cell Division, 21(1), Article 12. https://doi.org/10.1186/s13008-026-00186-0

Image Credits: AI Generated

DOI: 10.1186/s13008-026-00186-0

Keywords: retinoblastoma, PTTG1, c-myc, oncogene, cell cycle, apoptosis, cyclin A, CDK2, CDK4, transcription factor, pediatric cancer, cell line study