This study strictly adhered to PRISMA guidelines, with literature searches performed by two independent investigators across three databases: PubMed, Embase, and Web of Science (Moher et al., 2010). The search strategy was formulated as follows: “ST8SIA6-AS1” AND (“cancer” OR “tumor” OR “neoplasm” OR “carcinoma”), with a retrieval cutoff date of 31 May 2025. Simultaneously, we conducted a retrospective analysis of the literature by examining the reference lists of the selected studies and conducting manual screenings to identify further eligible publications.

The criteria for literature selection were defined as follows: Inclusion Criteria: (1) Studies investigating the correlation between ST8SIA6-AS1 expression levels and clinicopathological parameters or prognostic indicators in patients with malignant tumors; (2) Provision of quantitative detection data for ST8SIA6-AS1 in human malignant solid tumor tissues; (3) Survival analyses must report hazard ratios (HR) with 95% confidence intervals (95% CI) or allow for reconstruction from survival curve data; (4) Publications must be restricted to English; (5) Explicit methodological description of ST8SIA6-AS1 detection techniques. Exclusion Criteria: (1) Duplicate publications (retaining the version with the most comprehensive data and largest sample size); (2) Non-primary research publications (such as reviews, case reports, conference abstracts, etc.); (3) Studies lacking extractable clinical outcome metrics; (4) Secondary analysis studies (e.g., systematic reviews or meta-analyses); (5) Research involving benign tumors or precancerous lesions; (6) Studies that include cohorts receiving therapeutic interventions (e.g., chemotherapy or targeted therapy). Two independent researchers performed the literature screening in strict adherence to the established criteria, with any discrepancies being resolved through arbitration by a third senior researcher.

Two investigators independently conducted data extraction and quality assessment following standardized protocols. Key variables were extracted from selected studies based on inclusion criteria, including the first author, publication year, patient cohort size, cancer type, detection methodology, HR, 95% CI for overall survival (OS) or progression-free survival (PFS), and recorded clinicopathological parameters. For studies that provided only Kaplan-Meier survival curves, Engauge Digitizer 4.1 software, along with spreadsheet calculations, was utilized for curve digitization and reconstruction of HR/CI (Wen et al., 2019). Study quality was assessed using the Newcastle-Ottawa Scale (NOS), with two independent investigators scoring each included study. Studies that achieved a total score of ≥6 were classified as high quality. Discrepancies in assessments were reconciled through discussion, with any unresolved controversies adjudicated by a third investigator to ensure objectivity (Wen Y. et al., 2018).

Using GEPIA 2 (http://gepia2.cancer-pku.cn), which includes RNA sequencing data from 492 PCa tissues and 152 normal tissues sourced from the TCGA and GTEx databases, we analyzed the expression characteristics of ST8SIA6-AS1 in these samples. Additionally, we examined ST8SIA6-AS1 expression in a cohort of 49 paired tumor and adjacent non-cancerous tissue samples from the TCGA. The raw RNA-seq transcriptome data were log2 (x +1) transformed for normalization using R (version 4.0.2).

The human prostate cancer cell line PC-3 used in this study was obtained from the American Type Culture Collection (ATCC). All cell lines were routinely cultured at 37 °C in a humidified incubator with 5% CO₂. RWPE-1, LNCaP, PC-3, and 22Rv1 cells were maintained in RPMI 1640 medium, while DU 145 cells were cultured in high-glucose DMEM, both supplemented with 10% heat-inactivated fetal bovine serum (FBS; Gibco, Grand Island, NY, United States). To investigate the functional mechanisms of ST8SIA6-AS1, Lipofectamine 2000 transfection reagent (Invitrogen, United States) was employed to deliver ST8SIA6-AS1-specific siRNA (si-ST8SIA6-AS1) and scrambled negative control siRNA (si-NC; both synthesized by Invitrogen) into PC-3 cells. Transfection efficiency was evaluated 48 h post-transfection through qRT-PCR analysis of ST8SIA6-AS1 expression levels.

RNA analysis was conducted following standardized molecular biology protocols. Total RNA was extracted from tissues and cultured cells using TRIzol reagent (Invitrogen). Reverse transcription was performed strictly according to the manufacturer’s instructions (PrimeScript RT Reagent Kit, TaKaRa) to generate complementary DNA (cDNA). Quantitative real-time polymerase chain reaction (PCR) was carried out using SYBR Premix Ex Taq reagents (TaKaRa), with thermal cycling parameters configured according to the manufacturer’s protocol. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as the endogenous reference for normalizing ST8SIA6-AS1 expression levels.

Cell proliferation activity in prostate cancer cells was assessed using the KFluor 488 Click-iT EdU Imaging Detection Kit (KeyGen Biotech, Jiangsu, China). The experimental procedures were conducted as follows: Prostate cancer cells seeded in 24-well plates were treated with 50 μM EdU for 2 h, fixed with 4% formaldehyde, and subsequently incubated with the Click-iT reaction mixture to label EdU-positive cells. Nuclei were counterstained with Hoechst 33342 (blue fluorescence). Following image acquisition using an inverted fluorescence microscope, the proportion of EdU-positive cells (EdU-positive cells/total Hoechst-stained cells) was quantified using ImageJ software (National Institutes of Health, United States) to determine cellular proliferation rates.

Cell motility was quantitatively assessed using a Transwell chamber system (24-well plate, 8 μm pore size polycarbonate membrane; BD Biosciences) following a previously standardized protocol (Wen YA. et al., 2018). For invasion assays, the upper chambers were pre-coated with 0.33 mg/mL Matrigel matrix (Corning) for 2 h prior to experimentation to establish a basement membrane invasion model, while migration assays utilized uncoated membranes. Prostate cancer cells were resuspended in serum-free medium and seeded into the upper chambers at a density of 5 × 10⁴ cells per well, with the lower chambers filled with complete medium containing 10% FBS as a source of chemoattractant. After a 24-h incubation, non-migrated or non-invaded cells were removed from the upper chambers. The migrated or invaded cells on the lower membrane surface underwent methanol fixation followed by staining with 0.1% crystal violet for 15 min. Cell quantification was performed by counting the cells in five randomly selected microscopic fields under bright-field illumination, with the mean value serving as the quantitative metric.

A prostate cancer xenograft model was established using male BALB/c nude mice (4 weeks old, weighing 20–22 g; Experimental Animal Center of Fujian Medical University, Fuzhou, China). A stable knockdown of ST8SIA6-AS1 was achieved in PC-3 cells using lentiviral vectors containing shRNA specifically targeting ST8SIA6-AS1 (GenePharma, Shanghai, China). Subsequently, sh-ST8SIA6-AS1-transfected cells and control PC-3 cells were subcutaneously inoculated into the right flank of the mice (Wen YA. et al., 2018). Twenty-five days post-inoculation, euthanasia was performed via intraperitoneal injection of sodium pentobarbital (250 mg/kg), followed by dissection for tumor tissue collection and gravimetric analysis. All experimental procedures strictly adhered to protocols approved by the Institutional Animal Care and Use Committee of Fujian Medical University, ensuring compliance with the principles of the 3Rs (Replacement, Reduction, Refinement).

Meta-analysis was conducted using STATA 12.0 software (StataCorp LP, TX, United States) to calculate pooled effect sizes, including odds ratios (ORs) and hazard ratios (HRs) along with 95% confidence intervals (CIs). Publication bias was assessed using Begg’s rank correlation test, and sensitivity analysis was performed to validate the robustness of the results. Heterogeneity was evaluated using Cochran’s Q-test (significance threshold: p < 0.10) and quantified using the I ² statistic. A fixed-effects model was applied when I ² < 50% or Q-test p > 0.05; otherwise, a random-effects model was adopted. Continuous variable differences were analyzed using Student’s t-test, while categorical variables were compared via chi-square tests. All supplementary statistical analyses were conducted in SPSS 25.0 (IBM), with results expressed as mean ± standard error of the mean (S.E.M). Statistical significance was defined as two-tailed p < 0.05.

The literature screening process is illustrated in Figure 1. This study conducted a systematic search and screening in accordance with PRISMA guidelines. Initial searches across three databases (PubMed, Web of Science, and Embase) yielded 82 relevant articles, from which 25 duplicates and 1 retracted article were excluded through deduplication. Subsequent title and abstract screening of the remaining 56 articles resulted in the exclusion of 43 studies that did not meet the predefined inclusion criteria. Full-text evaluation of 13 potentially eligible articles further excluded 2 study due to critical data deficiencies. Following this rigorous screening process, 11 clinical studies that satisfied the methodological quality criteria were ultimately included for meta-analysis.

This meta-analysis ultimately incorporated 11 clinical studies (Table 1), encompassing a total of 2,392 patients with malignant tumors, covering the period from 2020 to 2024. It included distinct analyses from the same study Luo et al. (2020) for breast cancer (BC) and lung cancer (LC), as well as separate analyses from Wang et al. (2023) for LC and colorectal cancer (CRC). These distinct analyses were incorporated into their respective outcome assessments. All included studies extracted survival data based on Kaplan-Meier survival curves. The research covered five tumor types: liver cancer (n = 4), bile duct cancer (n = 1), breast cancer (n = 4), colorectal cancer (n = 1), and lung cancer (n = 3).

Among the 11 studies that met the eligibility criteria, 8 studies (n = 2,024) reported analyses of the correlation between ST8SIA6-AS1 expression levels and OS. Heterogeneity testing revealed no significant statistical heterogeneity across the studies (I ² = 0.0%, p = 0.931), confirming the consistency among results. A fixed-effects model was consequently employed to pool the effect sizes. The meta-analysis demonstrated that high ST8SIA6-AS1 expression was significantly associated with poorer OS (HR = 1.48, 95% CI: 1.31–1.65, p < 0.001; Figure 2).

To investigate the potential relationship between ST8SIA6-AS1 and OS, stratified subgroup analyses were conducted based on tumor type and sample size. (1) In the digestive system tumor subgroup (HR = 1.55, 95% CI: 1.22–1.88, p < 0.001) and the non-digestive system tumor subgroup (HR = 1.46, 95% CI: 1.26–1.65, p < 0.001), high ST8SIA6-AS1 expression was significantly correlated with worse OS (Figure 3A). (2) When stratified by sample size, both large-sample studies (≥100 cases, HR = 1.47, 95% CI: 1.29–1.64, p < 0.001) and small-sample studies (<100 cases, HR = 1.62, 95% CI: 1.08–2.17, p < 0.001) revealed a significant relationship between ST8SIA6-AS1 and poor OS (Figure 3B). As well, no significant heterogeneity was detected among these subgroups.

Aggregate analysis of clinicopathological parameters across included studies (Table 2) revealed a significant positive association between high ST8SIA6-AS1 expression and tumor malignant progression. Specifically: (1) TNM stage (n = 471): Higher expression levels of ST8SIA6-AS1 were associated with worse TNM staging (OR = 2.83, 95% CI: 1.77–4.52, p < 0.001). (2) Tumor size (n = 358): The high-expression cohort demonstrated significantly elevated risk for large tumor size (OR = 2.07, 95% CI: 1.35–3.18, p = 0.001). (3) Lymph node metastasis (n = 224): High-expression status showed borderline association with lymph node metastasis (OR = 2.44, 95% CI: 0.98–6.07, p = 0.055), warranting further validation.

Publication bias in studies investigating the association between ST8SIA6-AS1 expression and OS was systematically assessed through Begg’s funnel plot (Figure 4A) along with rank correlation testing (z = 1.68, Pr > |z| = 0.093). The results suggested no significant publication bias. A sensitivity analysis was performed utilizing the leave-one-out method (Figure 4B). This analysis revealed that after excluding any individual study, the combined HR generally remained stable within the range of 1.31–1.65. This consistency suggests that the results are reliable.

Transcriptomic data analysis based on the TCGA and GTEx databases revealed significantly differential expression patterns of ST8SIA6-AS1 in PCa tissues. Compared to normal prostate tissues, PCa samples exhibited a statistically significant upregulation of ST8SIA6-AS1 expression (Figures 5A,B). To further validate this finding, we measured expression profiles in four PCa cell lines (LNCap, 22Rv1, PC-3, and DU145) and normal human prostate epithelial cells (RWPE-1) using qRT-PCR. The findings indicated that the levels of ST8SIA6-AS1 were markedly increased in PCa cell lines in comparison to normal control samples, with the differences reaching statistical significance (Figure 5C).

Experiments utilizing gene silencing technology have demonstrated the critical role of ST8SIA6-AS1 in the malignancy of prostate cancer. Following shRNA-mediated specific knockdown, qRT-PCR confirmed an approximately 80% reduction in ST8SIA6-AS1 expression (Figure 6A), and demonstrated a significant downregulation of ST8SIA6-AS1 expression in sh-ST8SIA6-AS1 group compared to the sh-NC control group (Figure 6F). EdU proliferation assays revealed suggestively decreased EdU-positive rates in PC-3 cells after the knockdown of ST8SIA6-AS1 (Figures 6B,C). Transwell Matrigel invasion assays showed significantly fewer invasive and migratory cells in the experimental groups (Figures 6D,E).

To investigate the effects of ST8SIA6-AS1 knockdown in vivo, subcutaneous allograft tumor models were established by injecting PCa cells with stable ST8SIA6-AS1 knockdown. Compared to the control group, tumors in the sh-ST8SIA6-AS1 group exhibited significantly smaller and lighter (Figures 7A–C).