The research, led by Yue Cheng and colleagues at Tongde Hospital in Zhejiang Province, China, began with a straightforward question: which genes distinguish aggressive prostate tumours from healthy prostate tissue? Using the TIMER2.0 pan-cancer database, the team surveyed SURF6 expression across multiple cancer types and found it significantly elevated in a range of malignancies, including bladder, breast, colon, liver, and stomach cancers. Crucially, prostate adenocarcinoma was among the tumour types showing robust SURF6 upregulation. The researchers then validated this finding using data from The Cancer Genome Atlas (TCGA), immunohistochemical staining from the Human Protein Atlas, and their own patient samples—frozen tumour tissues and matched adjacent normal tissue collected from seven patients undergoing primary surgery. Both Western blotting and quantitative reverse-transcription PCR confirmed that SURF6 was consistently more abundant in tumour tissue than in normal prostate.

SURF6 is not a random suspect. It is a highly conserved nucleolar matrix protein that binds nucleic acids, participates in the early steps of pre-ribosomal RNA processing, and contributes to ribosome biogenesis and cell-cycle control. Because rapidly proliferating tumour cells demand an enormous capacity for protein synthesis, dysregulation of nucleolar proteins such as SURF6 has long been viewed as a hallmark of cancer biology. What the new study adds is direct evidence that in prostate cancer, SURF6 is not merely a passenger but an active promoter of malignant behaviour.

The clinical data lent weight to this idea. When the team stratified prostate cancer patients by SURF6 expression, several worrying patterns emerged. Tumours classified as T3 or T4—larger, more locally advanced growths—expressed significantly more SURF6 than earlier T1 and T2 stage tumours. Patients whose cancer had spread to lymph nodes (N1 stage) showed higher SURF6 levels than those without nodal involvement, and men with Gleason scores of 8 or above, indicating poorly differentiated and aggressive disease, carried higher SURF6-associated risk scores than those with scores of 6. Most strikingly, survival analysis using the GEPIA2 platform showed that patients with high SURF6 expression had significantly worse overall survival and disease-free survival than those whose tumours expressed lower levels.

To determine whether SURF6 actually drives these behaviours or merely accompanies them, the researchers manipulated its levels in prostate cancer cell lines. They used small interfering RNA to silence SURF6 in PC3 cells, an aggressive androgen-independent line, and introduced a SURF6 overexpression plasmid into DU145 cells. The results were unambiguous. CCK-8 proliferation assays and colony formation experiments showed that depleting SURF6 markedly slowed the growth of PC3 cells, while boosting SURF6 accelerated the proliferation of DU145 cells. Wound healing and Transwell invasion assays told the same story for motility: silencing SURF6 suppressed migration and invasion, whereas overexpression enhanced them.

Perhaps the most consequential discovery concerns cancer stem cells—the rare, self-renewing subpopulation of tumour cells believed to seed recurrence and resist conventional therapies. Using sphere-formation assays, a standard test of stem-like self-renewal, the researchers found that SURF6 knockdown drastically impaired the ability of PC3 cells to form tumour spheres, while SURF6 overexpression increased sphere formation in DU145 cells. Flow cytometry revealed corresponding shifts in the proportions of cells carrying CD44 and CD133, well-established surface markers of prostate cancer stem cells. Western blotting extended the picture to intracellular stemness factors: levels of SOX4, Nanog, and OCT4 all fell when SURF6 was silenced and rose when it was overexpressed. In short, SURF6 appears to help prostate cancer cells maintain the stem-like identity that makes them so difficult to eradicate.

Having established what SURF6 does, the team turned to how its expression is controlled—and here the study enters one of the most dynamic areas of modern molecular biology: epitranscriptomics. Specifically, the researchers investigated N6-methyladenosine, or m6A, the most abundant internal chemical modification on eukaryotic messenger RNA. m6A marks are installed by a “writer” complex whose catalytic core is the methyltransferase METTL3, and they are interpreted by “reader” proteins such as YTHDF1, which typically enhances the translation or stability of methylated transcripts. Dysregulated m6A signalling has been implicated in numerous cancers, but its role in prostate cancer stemness had remained incompletely understood.

The evidence that SURF6 is an m6A target built up methodically. First, the team measured global m6A levels and found them significantly higher in PC3 and DU145 prostate cancer cells than in the normal prostate epithelial line RWPE-1. Sorting the cancer cells into CD44-positive and CD44-negative fractions by fluorescence-activated cell sorting revealed that the stem-like CD44-positive population carried even higher m6A levels. A computational survey of the SURF6 messenger RNA sequence using the SRAMP prediction tool identified several high-confidence m6A sites, and RNA immunoprecipitation with an anti-m6A antibody confirmed that SURF6 transcripts are indeed methylated—with enrichment strongest in the CD44-positive fraction. TCGA correlation analysis pointed to METTL3 as the relevant writer: knocking down METTL3 in PC3 cells reduced SURF6 at both RNA and protein levels, while overexpressing METTL3 in DU145 cells increased it.

The reader protein fell into place next. YTHDF1 expression correlated with SURF6 across prostate cancer samples, and RNA immunoprecipitation with a YTHDF1 antibody pulled down SURF6 messenger RNA from both cell lines. A reciprocal RNA pull-down experiment, using biotin-labelled SURF6 RNA as bait, retrieved YTHDF1 protein, confirming a physical interaction. Functionally, silencing YTHDF1 lowered SURF6 expression, whereas YTHDF1 overexpression raised it. The decisive experiment came from dual-luciferase reporters carrying either the wild-type SURF6 3′ untranslated region or a mutant version in which the predicted m6A motif had been disrupted. METTL3 and YTHDF1 both enhanced the activity of the wild-type reporter but had little effect on the mutant, demonstrating that this specific m6A site is required for regulation. An actinomycin D chase assay added the final mechanistic detail: in the absence of YTHDF1, SURF6 messenger RNA degraded more rapidly, while YTHDF1 overexpression stabilised the transcript.

With the regulatory circuit defined, the researchers asked how SURF6 exerts its effects downstream. The answer pointed squarely at CDK4, a cyclin-dependent kinase that drives the G1-to-S transition of the cell cycle and is already the target of approved inhibitors in other cancers. SURF6 knockdown reduced CDK4 expression, and the two genes’ expression correlated significantly in TCGA prostate cancer data. Actinomycin D decay assays showed that CDK4 messenger RNA decayed faster when SURF6 was silenced, and RNA pull-down experiments demonstrated that SURF6 physically associates with CDK4 transcripts—suggesting SURF6 may stabilise CDK4 mRNA, a striking role for a protein classically known as a nucleolar component of the ribosome-building machinery.

Rescue experiments sealed the causal chain. When the researchers forced CDK4 overexpression in SURF6-depleted PC3 cells, the accumulation of cells stuck in the G0/G1 phase was relieved, and proliferation, colony formation, migration, and invasion largely recovered. Conversely, knocking down CDK4 in SURF6-overexpressing DU145 cells blunted the pro-tumorigenic effects of SURF6. The same rescue logic applied to stemness: CDK4 overexpression restored sphere formation, the CD44-positive and CD133-positive fractions, and the expression of CD44, SOX4, Nanog, and OCT4 in SURF6-silenced cells, while CDK4 knockdown reversed these gains in SURF6-overexpressing cells.

Finally, the team translated their findings into living animals. They implanted nude mice with PC3 cells engineered to express a short hairpin RNA against SURF6, alongside control cells carrying a non-targeting construct. Tumours in the SURF6-knockdown group grew significantly more slowly, with markedly smaller volumes and lower final weights. Histological examination revealed reduced Ki-67 staining, a sign of diminished proliferation, while immunofluorescence and immunohistochemistry showed lower levels of CD44 and CDK4 in the shrunken tumours—confirming in vivo that the molecular pathway identified in culture operates in actual tumour growth.

Taken together, the study outlines a complete regulatory axis: METTL3 installs m6A marks on the SURF6 transcript, YTHDF1 reads those marks and stabilises the message, elevated SURF6 sustains CDK4 expression, and CDK4 drives both cell-cycle progression and the maintenance of cancer stem cell identity. Each link in this chain represents a potential point of therapeutic intervention. Because CDK4/6 inhibitors are already in clinical use for breast cancer, the prospect of extending such approaches to SURF6-high prostate tumours is an obvious next step, as is the development of m6A-pathway inhibitors capable of turning down SURF6 at the RNA level. The authors caution that their clinical sample size was small and that further validation in large patient cohorts will be needed, but the convergence of bioinformatics, cell biology, and animal modelling makes a compelling case that a nucleolar protein once known mainly for ribosome assembly sits at the heart of prostate cancer’s most dangerous behaviours. Targeting SURF6, the researchers suggest, could one day attack both the growth and the recurrence-seeding stem cell reservoir of the disease simultaneously.