MicroRNAs (miRNAs/miRs) are concise, endogenous non-coding RNAs, typically ~22 nucleotides in length, which serve a crucial role in the orchestration of gene expression within multicellular organisms, exerting influence over mRNA stability and translation (1). The dysregulation of miRNAs is frequently implicated in the malignant transformation of cells, as highlighted in previous research (2). miRNAs contribute significantly to biological processes underpinning cancer progression, metastasis, and the development of resistance to treatment (3).

One such miRNA of interest is miR-325, which resides in the first sub-band of region 2 on the short arm of the X chromosome (1). miR-325 has garnered attention due to its aberrant expression across >10 types of cancer. Given its location on the sex chromosomes, there is a hypothesis that the regulation of miR-325 expression may be linked to sex differences. However, prior investigations have often overlooked sex differences in the selection of cell lines, prompting the need for more comprehensive exploration in this area (2,4).

Further analysis of miR-325 regulation has unveiled its interaction with six competing endogenous RNAs (ceRNAs), comprising one circular RNA (circRNA), four long non-coding RNAs (lncRNAs) and one additional miRNA. miR-325 exerts its regulatory influence by targeting and inhibiting 20 protein-coding genes (PCGs), thereby modulating key cancer cell behaviors, including the cell cycle, proliferation, epithelial-mesenchymal transition (EMT), apoptosis, invasion and migration (5–7). The present review also revealed a notable association between diminished expression of miR-325 and shortened overall survival (OS) and progression-free survival (PFS) across various types of cancer. Furthermore, miR-325 has been implicated in resistance to three anticancer drugs, and may actively participate in the molecular mechanisms of action associated with oxaliplatin (8), cisplatin (CDDP) (9,10) and doxorubicin (DOX) (11).

The aim of this review was to systematically examine the current state of research surrounding miR-325, including its abnormal expression, molecular mechanisms and clinical implications. By providing a consolidated overview of the knowledge on miR-325, this review seeks to offer valuable insights to guide future investigations in this field.

As illustrated in Table I, miR-325 exhibits consistent downregulation in both cellular and tissue contexts across eight distinct cancer types. Notably, miR-325 is downregulated in colorectal cancer (CRC) (4,5,11), gastric cancer (GC) (12,13), HCC (8,14,15), bladder urothelial carcinoma (BLCA) (6,16,17), non-small cell lung cancer (NSCLC) (18,19), oral squamous cell carcinoma (OSCC) (20) and papillary thyroid cancer (PTC) (21). In addition, miR-325 expression is downregulated in a T-cell acute lymphoblastic leukemia (T-ALL) cell line (5). Notably, miR-325 demonstrates heightened expression levels in glioblastoma multiforme and lower-grade glioma (GBM/LGG) (22) and nasopharyngeal carcinoma (NPC) (23). Meanwhile, the status of miR-325 expression in breast cancer (BC) (23,24) appears to be contentious.

As shown in Table I and Fig. 1, a comprehensive analysis was conducted by comparing the expression differences of miR-325 between cancer tissues and corresponding para-cancerous tissues, as well as between cancer cells and para-cancerous cells, across 11 cancer types.

As shown in Fig. 1 and Table II, miR-325 is considered a potent regulator that can inhibit 20 PCGs, thereby exerting control over various cancer cell behaviors, such as proliferation, EMT, apoptosis, invasion and migration.

Cell cycle orchestration involves a complex interplay of proteins, enzymes, cytokines and signaling pathways, which are crucial for cell proliferation and repair (25). In NSCLC, miR-325 has been shown to impede the progression of the cell cycle S phase or G₂/M phase in the HCT116 cell line by targeting the gene kinesin family member 2C (KIF2C) (7).

Cancer proliferation signifies a dysregulated balance between cell gain and loss, where mutant tumor cells proliferate faster than they die (26). miR-325 has been reported to curtail cancer cell proliferation in NSCLC, CRC, BLCA, HCC, skin cutaneous melanoma (SKCM), T-ALL, NPC, BC, PTC, GC and GBM/LGG by targeting 14 genes, including high mobility group box 1 (HMGB1) (8,18), glutathione peroxidase 2 (GPX2) (10), tripartite motif containing 14 (TRIM14) (5), metallothionein 3 (MT3) (27), C-X-C motif chemokine ligand 17 (CXCL17) (15), dolichyl-phosphate N-acetylglucosaminephosphotransferase 1 (DPAGT1) (10,12), aquaporin 5 (AQP5) (16), mitogen-activated protein kinase kinase kinase 2 (MAP3K2) (28), BAG cochaperone 2 (BAG2) (5), cell division cycle associated 5 (CDCA5) (23), lipocalin 15 (LCN15) (29), DEAD-box helicase 5 (21), human antigen R(HuR) (14) and forkhead box M1 (FOXM1) (22).

Apoptosis, a well-known form of programmed cell death, serves as a key physiological mechanism limiting cell population expansion (26). miR-325 has been shown to enhance cancer cell apoptosis in HCC, T-ALL and GC by targeting four genes, namely DPAGT1 (10,12), AQP5 (16), BAG2 (5) and HuR (14).

EMT, a critical cell biological program, is implicated in development and wound healing, and its activation is associated with the formation of normal and cancer stem cells (30). It has been demonstrated that miR-325 impedes EMT progression in BLCA by targeting the gene MT3 (27). By contrast, in BC, miR-325 may promote EMT progression by targeting the gene S100 calcium binding protein A2 (S100A2) (24).

Cancer metastasis, the primary cause of cancer-related death, is reliant on an increase in cell migration during tumor progression, enabling tumor cells to escape the primary tumor and invade adjacent tissues to form metastases (31). miR-325 has been shown to inhibit the invasion and migration of cancer cells in NSCLC, CRC, BLCA, HCC, SKCM, NPC, BC and GBM/LGG by targeting 12 genes: KIF2C (7), HMGB1 (8,18), GPX2 (10), TRIM14 (5), MT3 (27), acid phosphatase 5 (ACP5) (32), HMGB1 (12), CXCL17 (15), MAP3K2 (28), CDCA5 (23), LCN15 (29), and FOXM1 (22). By contrast, miR-325 can promote the invasion and migration of BC cancer cells by targeting the gene S100A2 (24).

ceRNAs competitively bind to miRNA, thereby attenuating its inhibitory influence on target mRNA and regulating cellular activity at the post-transcriptional level (31). The ceRNA regulatory network of miR-325, as shown in Table III and Fig. 2, involves circRNAs and lncRNAs serving pivotal roles in cellular biology.

circRNAs exert diverse biological functions by serving as transcriptional regulators, miRNA sponges and protein templates (33). As depicted in Table III, the inhibitory impact of miR-325 on target genes was competitively counteracted by Circ_0069313. In OSCC, the Circ_0069313/miR-325/FOXP3 axis was implicated in inducing OSCC cell immune escape (20).

lncRNAs are RNA molecules exceeding 200 nucleotides in length, which are central to cellular regulation (34). The regulatory interplay involving four lncRNAs, AR, FOXD3-AS1, LINC01515 and MSC-AS1, has been shown to competitively inhibit miR-325 (11,22,26,30) (Table III; Fig. 2).

The lncRNA/miR-325/PCG axis has emerged as a potent regulator hindering cancer progression, including its inhibitory role in HCC. Notably, the AR/miR-325/ACP5 axis has been shown to exhibit the capability to impede invasion and migration of HCC cells (32). Additionally, three distinct lncRNA/miR-325/PCG axes have been implicated in promoting cancer progression. In SKCM, the FOXD3-AS1/miR-325/MAP3K2 axis can promote proliferation, migration and invasion of cancer cells (28). In NPC, the LINC01515/miR-325/CDCA5 axis has been shown to foster proliferation, migration and invasion, while inhibiting apoptosis (23). Similarly, in CRC, the MSC-AS1/miR-325/TRIM14 axis may stimulate proliferation, invasion and migration of cancer cells (5).

The base sequence of miR-325 is 3′-UGUGAAUGACCUGUGGAUGAUCC-5′ (5) (Fig. 3A and C). Four target genes have been observed to bind to this sequence. Specifically, miR-325 forms a binding interaction with CDCA5 through the 3′-UgUGGAUGAUC-5′ sequence (23), TRIM14 and MAP3K2 through the 3′-GAUGAUC-5′ sequence (11,26), and BAG2 through the 3′-AUGAUC-5′ sequence (5) (Fig. 3A). In addition, three lncRNAs have been shown to bind to the base sequence of miR-325. The binding interactions are as follows: miR-325 binds to LINC01515 through the 3′-UgAAuGA-CCU-gUgGAUGAUC-5′ sequence (23), MSC-AS1 through the 3′-UgAAUgACCugUgGAUGAUC-5′ sequence (5), and FOXD3-AS1 through the 3′-GAUGAUC-5′ sequence (27).

As shown in Fig. 3B, the pre-miR-325 sequence has 13 target genes, and its base sequence is 3′-AACUAUCCCUCCAGGAGUUAUUUGUUUAAUA-5′ (6). Pre-miR-325 forms specific binding interactions with the following genes: MT3 through the 3′-CCUCCagaaGUUAUU-5′ sequence, heat shock protein family A member 12B (HSPA12B) through the 3′-CUCCAggaGUUAUUU-5′ sequence, ACP5 and LCN15 through the 3′-AGUUAUU-5′ sequence, LNX1, CXCL17, S100 calcium binding protein A4 (S100A4), S100A2 and HuR through the 3′-AGUUAUUU-5′ sequence, and FOXP3, AOP5, GPX2, KIF2C and HuR through the 3′-GUUAUUU-5′ sequence. Additionally, pre-miR-325 binds to FOXM1 through the 3′-GAGUUAUU-5′ sequence. Furthermore, as shown in Fig. 3D, pre-miR-325 forms a binding interaction with Circ-0069313 through the 3′-GUUAUUU-5′ sequence.

As illustrated in Table IV, the prognostic significance of miR-325 is underscored by its dysregulation, and is associated with the pathological state of cancer tissues and diagnostic risk, influencing patient prognosis. In GC, HCC, NSCLC and BLCA, diminished miR-325 expression has been reported to be associated with adverse patient outcomes. In GC, reduced miR-325 expression has been shown to align with a shorter OS (9). Similarly, in HCC, low miR-325 expression corresponded to earlier TNM stage, and shorter OS and PFS, alongside factors such as tumor size and metastasis (12). Patients with NSCLC with low miR-325 expression exhibited shorter OS and PFS (15) (19). In addition, in BLCA, diminished miR-325 expression was associated with a shorter OS (17). Notably, miR-325 has been reported to target and inhibits KIF2C expression in NSCLC, with high KIF2C expression linked to shorter OS (7). In NPC, elevated LINC01515 expression, suppressing miR-325, has been shown to be associated with poor prognosis and OS in patients (23). Similarly, in NSCLC, heightened GPX2 expression, directly targeted by miR-325, was negatively associated with miR-325 expression, and associated with poor prognosis and OS (10). In OSCC, hsa_circ_0069313 can bind to miR-325, inhibiting its expression, and was thus revealed to be associated with poor prognosis and OS (20). Furthermore, in SKCM, FOXD3-AS1, targeted by miR-325, was upregulated and negatively associated with miR-325 expression, contributing to poor prognosis and OS in patients (28)

The development of drug resistance in tumor cells significantly contributes to the ineffectiveness of chemotherapy (35). As shown in Fig. 4A, miR-325 may serve a crucial role in modulating the response of cancer cells to various anticancer drugs. Oxaliplatin is a highly effective chemotherapy agent in CRC treatment. This third-generation platinum compound induces DNA cross-linking in cancer cells, resulting in apoptotic cell death. In CRC, miR-325 sensitized cancer cells to oxaliplatin-induced cytotoxicity by modulating the HSPA12B/PI3K/AKT/Bcl-2 pathway (8). CDDP, which is employed in treating diverse types of human cancer, such as bladder, head and neck, lung, ovarian and testicular cancer (36), has been shown to encounter regulatory influence from miR-325. In GC, SNHG6 can bind to miR-325-3p, interacting directly with GITR to regulate CDDP resistance. GITR, in turn, promotes CDDP resistance in GC cell lines, primarily by modulating Bcl2-mediated apoptosis (9). Notably, in NSCLC, GPX2 has been reported to drive malignant progression and CDDP resistance in KRAS-driven lung cancer (10). DOX is a standard systemic chemotherapy adjuvant drug for transarterial chemoembolization. Chemosensitivity to DOX has been reported to be markedly increased in cells overexpressing miR-325, and the inhibitory effects of miR-325 on chemoresistance have been shown to be diminished upon artificially restoring DPAGT1 expression. Meanwhile, miR-325 inhibits the expression of DPAGT1 gene in HCC. This regulatory mechanism has been shown to phenotypically mimic the effects of DPAGT1 silencing both in vitro and in vivo, consequently reducing the survival rate of DOX-resistant cells (11).

The CADDIE database (https://www.exbio.wzw.tum.de/caddie/) was used to search potential targeted drugs of PCGs, and the obtained results are shown in Fig. 4B. Among these, MAP3K2 has associations with bosutinib and fostatinib, HMGB1 with chloroquine, MT3 with zinc acetate and zinc chloride, GPX2 with glutathione, S100A4 with trifluoperazine, and S100A2 with zinc chloride, zinc acetate and olopatadine. Future investigations are warranted to elucidate the potential interactions between miR-325 and these drugs.

The findings of the present study underscore the potential utility of miR-325 as a biomarker in various types of cancer. In NSCLC (7), miR-325 has emerged as a promising diagnostic and treatment target. Similarly, in HCC (15), miR-325 may hold promise as a biomarker for treatment. In NPC (23), LINC01515 has been shown to act as a molecular sponge for miR-325, influencing cell division cycle-related expression, and showcasing potential as a prognostic biomarker or therapeutic target. In BLCA (16,26), low-level expression of miR-325 has emerged as a biomarker for adverse clinicopathological characteristics and poor prognosis. In GBM/LGG (22), miR-325 was identified as a promising prognostic biomarker.

Collectively, these findings highlight the potential role of miR-325 as a diagnostic, therapeutic and prognostic biomarker across different types of cancer. However, the existing research on miR-325 has certain limitations. Notably, the expression of miR-325 in BC appears controversial. One dataset indicated the upregulation of miR-325 in the primary BC tissues of 30 patients compared with in non-cancerous tissues (24), whereas another dataset suggested it was downregulated in the BC tissues of 15 patients compared with in adjacent tissues (29). Discrepancies in the choice of cell lines, small sample sizes and inconsistent tumor stages among patient samples may contribute to these variations in miR-325 expression patterns in BC.

Addressing these disparities, future research should delve into sex-specific differences in miR-325, explore the relationship between miR-325 and resistance to various anticancer drugs, and investigate how abnormal miR-325 expression in tumors is related to the efficacy of drug treatments. These areas of research will provide a more comprehensive understanding of the role of miR-325 in cancer, contributing to its potential as a robust biomarker in diagnosis, treatment and prognosis across diverse cancer types.

The present study comprised a comprehensive examination of miR-325, offering a review that highlights its potential as a potential focal point in cancer research. The review not only identified the promise of miR-325, but also provided valuable insights and directions for subsequent investigations into its various facets. Simultaneously, it addressed existing controversies and shortcomings within the current landscape of miR-325 research. Future endeavors in this field may concentrate on elucidating the aberrant molecular regulation of miR-325, identifying its molecular mechanisms associated with antitumor drug resistance and efficacy. An intriguing aspect is the chromosomal location of miR-325 on the X chromosome. Nevertheless, the existing literature has only described sex differences in miR-325 expression in specific tumor types, signifying a lack of emphasis on sex-specific cell line selection in ongoing research. To correct for this, forthcoming studies should aim to amass gene expression profiles from patient tissues of diverse sexes, integrating comprehensive statistical analyses with clinical data from both male and female patients with cancer. Such an approach promises to establish a robust theoretical foundation for the clinical application of miR-325 in tumor research.