Epigenetic modification is notably relevant to differential gene expression, while dysregulation in these processes can lead to the development of several cancer types (14). Previous studies clearly showed that lncRNAs participate in this process (15,16) (Fig. 1A).

Mediated by various DNA methyltransferases (DNMTs), DNA methylation is a basic epigenetic modification to alter gene transcription (17). Phenotypic variations in cancer cells are directly regulated by aberrant DNA methylation, which influences the expression levels of essential oncogenes or tumor suppressor genes (TSGs), thereby impacting cancer progression (18). Numerous studies have identified that lncRNAs could interact with DNMTs and regulate DNMTs-mediated methylation on promoters, particularly on CpG island, thus affecting tumor-related gene expression (19,20) (Fig. 1A-a).

As aforementioned, lncRNAs can be scaffolds or decoys to interact with epigenetic factors, such as enhancer of Zeste homolog 2 (EZH2), DNMT1, to affect gene expression. Cai et al (21) found that oncogenic lncRNA UCA1 could promote GBC growth and metastasis by recruiting EZH2 to the promoter of p21 and E-cadherin, and epigenetically regulating their transcription. Similarly, Lin et al (22) reported that lncRNA MALAT1 was able to recruit EZH2 to the promoter of ABI family member 3 binding protein, thus inhibiting GBC cell senescence and potentiating cell proliferation. Gao et al (23) revealed that lncRNA FOXD2-AS1 could also recruit DNMT1 to the promoter of mutL homolog 1 (MLH1) and promote its methylation, leading to the transcriptional repression of MLH1, which was verified as a TSG involved in the DNA mismatch repair pathway. FOXD2-AS1 affects GBC malignant phenotypes (23). Jin et al (24) observed that, with the assistance of EZH2, lncRNA PVT1 recruited DNMT1 to the promoter region of microRNA-18b-5p (miR-18b-5p), and decreased miR-18b-5p transcription epigenetically. As a target of miR-18b-5p, the level of hypoxia inducible factor 1α (HIF1α), a well-known cancerous factor, was increased, which promoted GBC growth. Mechanistically, the PVT1/miR-18b-5p/HIF1α axis facilitated GBC progression in a non-competing endogenous RNA (ceRNA) manner (24). Li et al (25) demonstrated that MEG3 could bind to EZH2 and activate EZH2-mediating trimethylation of histone 3 on lysine-27 (H3K27me3) of the CXC motif chemokine ligand 3 (CXCL3) promoter region. Subsequently, MEG3 attenuated GBC cells malignant behavior via inhibition of CXCL3 expression (25).

In addition to DNA methylation, chromatin structure can be altered via histone modifications (26), while lncRNAs have been found to cooperate with histone-modifying enzymes. Generally, lncRNAs function as molecular scaffolds or decoys to affect the recruiting of chromatin remodeling complexes, such as histone modifying enzymes to regulate gene expression in close proximity (cis-acting) or distant crosstalk (trans-acting) (27), therefore having an impact on tumorigenesis and tumor development (Fig. 1A-b). The most common example is polycomb repressive complexes (PRCs), which functions as a methyltransferase to promote H3K27me3 and leads to chromatin compaction and subsequently transcriptional repression (28,29).

Nucleosome positioning is another important process in epigenetic modulation because the firm interplay of nucleosomes with histone cores can significantly influence DNA accessibility (30). LncRNAs are known to regulate nucleosome positioning mainly by interacting with adenosine triphosphatase (ATPase) subunits of chromatin remodeling complexes (31). For example, lncRNA PAPAS interacts with the chromodomain helicase DNA-binding 4 subunit of the nucleosome remodeling and histone deacetylation complex. This complex itself plays a role in chromatin remodeling, while the interaction between lncRNAs and ATPase subunits relocates the nucleosome to target regions, such as the transcriptional ‘off’ position, and finally triggers epigenetic modification (32,33) (Fig. 1A-c).

Transcription is a basic but essential process for gene regulation that changes cell differentiation, cell state and function (34). It has been demonstrated that lncRNAs can regulate transcription in different ways (35) (Fig. 1B). LncRNAs can act as decoys or scaffolds to bind to transcriptional factors (TFs), including transcriptional activators and repressors, subsequently affecting target gene expression (36) (Fig. 1B-a). LncRNAs interact with promoters and influence transcription of target genes by cis- or trans-acting (37,38) (Fig. 1B-b).

Certain lncRNAs were reported to affect transcription by modulating the local chromatin structure (39). Saayman et al (40) demonstrated that lncRNA BGas interacted with high mobility group proteins (HMG) A1 and HMGB1, as well as the partner of Y14 and within benign gonial cell neoplasm homolog, to regulate local chromatin and DNA architecture of intron 11 of the cystic fibrosis transmembrane conductance regulator gene and thereby affecting its transcription.

Since it allows diverse transcripts, post-transcriptional modification remains a key process in controlling protein production. LncRNAs can also control gene expression by acting as post-transcriptional regulators (8,41) (Fig. 1C).

Affected by endo- or exonucleases, multiple mRNA decay or stabilizing factors, mRNA decapping and mRNA deadenylation, the mRNA stability of oncogenes or TSGs was reported to be regulated by lncRNAs through several mechanisms (42) (Fig. 1C-a). The most common mechanism is that lncRNAs, mainly natural antisense transcript (NAT) lncRNAs, can bind to targeted mRNAs due to sequence complementarity, thus preventing its interaction with different mRNA-decay factors and blocking mRNA degradation (43,44). Apart from this mechanism, lncRNAs can also bind to various RNA binding proteins (RBPs) involved in mRNA turnover or decay, thus affecting mRNA stability (45,46). In particular, lncRNAs can bind to N6-methyladenosine (m6A) readers to recognize m6A sites on mRNAs, thus affecting their decay (47–49).

MicroRNAs (miRNAs or miRs) regulate gene expression by binding to a complementary sequence of the target mRNA, which is termed ‘miRNA response element’ (MRE). According to the level of complementarity, miRNAs can facilitate both mRNA decomposition by argonaute 2 (AGO2) endonuclease in cases of full complementarity, and miRNA-induced silencing complexes (miRISCs)-mediated translational repression in cases of partial complementarity (50). LncRNAs can act as ceRNAs to capture their target miRNAs, releasing the downstream target (generally miRNA-targeted mRNAs) to fulfill its intrinsic function (51,52).

To date, the majority of studies on the roles of lncRNAs in GBC have focused on their function as miRNAs sponges to regulate subsequent targets. For example, Wang et al (53,54) revealed that H19 had the ability to sponge miR-194-5p or miR-342-3p separately, thus facilitating AKT2 or forkhead box M1 expression, which contributes to GBC growth. Li et al (55) demonstrated that H19 was upregulated in exosomes in bile acid that derived from cholangiocytes under pathological conditions. In addition, two oncogenic lncRNAs were reported to be able to sponge different miRNAs and subsequently modulate the downstream targets, LINC01694 (56) and SNHG6 (57), respectively, which could be detected in serum samples. These results indicated that detection of pathogenic lncRNAs in body fluids may provide more information for the diagnosis and subsequent monitoring of patients with GBC. Wang et al (58,59) demonstrated that MALAT1 could function as a ceRNA to sponge miR-206 and miR-363-3p in GBC, thus regulating the expression of annexin a2, KRAS, and myeloid cell leukemia-1, which are known oncogenes in human malignancies. Chen et al (60) observed that oncogenic lncRNA PVT1 could act as a ceRNA to sponge miR-143 and upregulate the expression of hexokinase 2, which is considered an oncogene to facilitate glucose utilization. Therefore, PVT1 promoted GBC progression via metabolism reprogramming (60). Similarly, Liu and Xu (61) demonstrated that PVT1 played a tumorigenic role in GBC via directly binding to miR-30d-5p. Notably, overexpression of MALAT1 in GBC tissues was reported to be associated with larger tumor size and positive lymph node metastasis. Furthermore, upregulated PVT1 in GBC tisssues was found to be related to higher TNM stage, which predicted poor overall survival of patients with GBC (62). Apart from these well-known lncRNAs, other oncogenic or tumor-suppressive lncRNAs exist, which can sponge targeted miRNAs, as shown in Table I.

Alternative splicing of precursor mRNA (pre-mRNA) can produce >2 isoforms of the same mRNA, which has an impact on increasing the diversity of proteomics (63). Notably, lncRNAs may be involved in this complex process to support the generation of tumor-related proteins via various mechanisms in cancerous cells (64,65) (Fig. 1C-b). First, lncRNAs can act as decoys and interact with splicing factors (SFs), which results in the physical downregulation of SFs' recruitment to their target pre-mRNAs (66,67). In addition, various lncRNAs contain complementary sequences (named NAT) to be paired with endogenous RNAs, which are able to interplay with cis- or trans-acting elements of pre-mRNAs via base complementary pairing. Such interplay influences the splicing site recognition and the recruitment of SFs, and results in the dysregulation of splicing isoforms expression (68,69). Furthermore, lncRNAs have a restricted potential to encode some micropeptides. These micropeptides can not only modulate the binding of SFs with targeted pre-mRNAs but also affect the differential expression of splicing isoforms, which can affect tumor growth (70). Moreover, lncRNAs can regulate SF expression in direct or indirect ways in cancer. The best example of direct regulation is MALAT1 in ovarian cancer (OC). Overexpressed MALAT1 leads to upregulation of RNA binding fox-1 homolog 2, which is a vital SF in epithelial-to-mesenchymal transition (EMT)-driven alternative splicing, and ultimately leads to OC aggressiveness (71). As for indirect ways, lncRNAs can affect SF expression via post-translational modification, such as cooperating with certain kinases to enhance the phosphorylation of SFs (72,73).

Regulated translation provides cancerous cells the advantage of rapidly adopting to environmental changes (74). Previous studies have suggested that lncRNAs participate in translational modification via indirect or direct methods (75). The indirect method is the lncRNA-mediated modulation of signaling pathways associated with translation (76,77), while the direct methods are as follows (Fig. 1D).

Recent research has shown that lncRNAs influence the translation of oncogenes or TSGs mainly through two mechanisms (Fig. 1D-a). Firstly, lncRNAs can bind to mRNA through base complementary pairing, resulting in decreasing binding sites with ribosomes and inhibition of translation (78). Another mechanism involves the interaction of lncRNAs and translation regulatory proteins (TRPs), such as Y-box binding protein-1, subsequently regulating the binding of TRPs to target mRNAs and thereby modulating translation (79).

Except for the translational modification of mRNA targets, emerging evidence has reported that lncRNAs are capable of modulating ribosome function to affect the translation process (80) (Fig. 1D-b). LncRNAs interfere with ribosome biogenesis in the nucleoli mainly in two ways: By affecting nucleolar structure (81), or by affecting the production (82) or maturation (83) of ribosomal RNA and/or ribosomal protein to modulate ribosome assembly and activity.

Moreover, it could be hypothesized that lncRNAs could be regulators of translation either via recruiting eukaryotic initiation factors to the ribosome, or through regulating other translational stages such as elongation and termination. However, the details of these mechanisms remain unclear.

Compared with normal cells, environmental changes in cancerous cells promote global translation shut down (84), such as decreased cap-dependent translation, while maintaining the biosynthesis of basic proteins for survival via various mechanisms (85). Generally, cap-independent mechanisms include the identification of upstream open reading frames and internal ribosome entry sites (IRES). However, there is little evidence about lncRNA roles in translation reprogramming (86).

For instance, lncRNA Zeb2-NAT physically bound and masked the splicing site of IRES on Zeb2 mRNA, and caused increased translation of Zeb2, which is a transcriptional suppressor of E-cadherin and modulator of EMT (87) (Fig. 1D-c). In this regard, further studies should be conducted to explore the regulatory mechanisms of lncRNAs involved in this dynamic process.

Post-translational modifications are essential for almost all aspects of cell function and are frequently implicated in tumors (88–90). Through participating in post-translational modification, lncRNAs can affect the abundance of proteins that impact cancer development (91,92) (Fig. 1E).

Previous studies suggested that numerous oncogenic lncRNAs prevented various oncoproteins from ubiquitination and subsequent proteasomal degradation mainly through three mechanisms, including i) Recruitment of deubiquitinases (DUBs) to oncoproteins (93); ii) direct interaction with oncoproteins physically (94); and iii) competitively binding to oncoproteins to hinder its degradation mediated by other modulators before (95). Certain oncogenic lncRNAs were found to activate some regulators, which promoted degradation of tumor suppressive factors in a ubiquitin-proteasome-dependent manner, thus releasing the inhibition of tumor growth (96,97).

In contrast to the aforementioned mechanisms, tumor suppressive lncRNAs mediate enhanced ubiquitination and degradation of oncogenic proteins to inhibit tumorigenesis (27). For instance, lncRNA ANCR inhibits aggressive phenotypes of breast cancer by facilitating the interaction between EZH2 and cyclin-dependent kinase 1 (CDK1). CDK1 phosphorylates EZH2 at threonine 345/487, and ultimately increases EZH2 decay via the ubiquitin-proteasome pathway (98) (Fig. 1E-a).

In GBC, studies also reported that several lncRNAs could bind to proteins and modulate protein functions in GBC cells. Ma et al (99) demonstrated that ectopic expression of lncRNA GCASPC in GBC cells could bind to pyruvate carboxylase (PC), a key modulator in the Krebs cycle that provides extra energy for cancer cells, and facilitate PC degradation via the ubiquitin-proteasome pathway. Mechanistically, GCASPC acts as tumor-suppressor by blocking energy supply of GBC cells. It was also found that GCASPC is a target for miR-17-3p. Through binding to GCASPC, miR-17-3p recruits miRISCs and promotes GCASPC degradation via an AGO2-dependent manner, and downregulation of GCASPC is correlated with GBC progression (99). Jin et al (100) revealed that the tumor-suppressive lncRNA MEG3 is capable of promoting EZH2 ubiquitination, which leads to large tumor suppressor homolog 2 transcription and inhibition of GBC cell proliferation and invasion. Cai et al (101) identified an upregulated lncRNA ENST00000425894 named GBCDRlnc1 in doxorubicin-resistant GBC cells. Mechanistically, GBCDRlnc1 could interact with phosphoglycerate kinase 1 and inhibit its ubiquitination in GBC drug-resistant cells, which results in decreased levels of the autophagy-related protein (ATG) 5-ATG12 conjugate. Finally, GBCDRlnc1 mediates the inhibition of autophagy initiation and downregulates sensitivity of GBC cells to doxorubicin (101). Xue et al (102) indicated that lncRNA SSTR5-AS1 is overexpressed in gemcitabine-resistant GBC tissues. Mechanistically, SSTR5-AS1 interacts with non-POU domain containing octamer-binding protein (NONO) and strengthens its stability by prohibiting the proteasome-dependent degrading pathway. It has been reported that NONO is capable of forming a subnuclear body by binding to lncRNAs and promoting nuclear retention of RNA, thus regulating the expression of certain genes in differentiated cells. In the study of Xue et al (102), an interaction between SSTR5-AS1 and NONO was required for chemoresistance of GBC cells. Liu et al (103) identified that lncRNA MNX1-AS1 could serve as a scaffold for the interaction between ubiquitin specific peptidase 16 (USP16) and insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3). USP16 deubiquitinates IGF2BP3, and stabilized IGF2BP3 could increase TEA Domain family member 4 (TEAD4) expression, which could regulate the Hippo pathway function. Additionally, TEAD4 functions as a transcriptional activator to promote MNXA-AS1 formation. Finally, MNX1-AS1 forms a positive feedback loop with the TEAD4/Hippo pathway with the assistance of USP16 and IGF2BP3 (103).

Protein phosphorylation is regarded as an important post-translational modification to regulate intracellular and transmembrane signal transduction (27). Numerous lncRNAs are considered to modulate the phosphorylation of some critical signaling molecules by direct or indirect methods, thereby affecting hallmarks of cancer (104,105). Direct regulation refers to the fact that lncRNAs alter kinase activity by binding to them directly (73,98) (Fig. 1E-b), while the indirect regulation refers to the fact that lncRNAs affect kinase function through other pathways. Typical examples of indirect regulation include lncRNA interaction with G-protein-coupled receptor and phosphatidylinositol-(3,4,5)-trisphosphate (106), and the influenced targets include Janus kinase (JAK) 2 of the JAK2/STAT3 signaling pathway in breast cancer (107), STAT3 of the interleukin-6 (IL-6)/STAT3 signaling pathway in hepatocellular carcinoma (108) and the PI3K/AKT signaling pathway in medulloblastoma (109).

As aforementioned, Zheng et al (110) demonstrated that downregulated lncRNA RP11-147L13.8 was also associated with poor prognosis of patients with GBC. Mechanistically, RP11-147L13.8 can bind to the basic region leucine Zipper of Jun protein, and suppress c-Jun serine 73 phosphorylation by suppressing JNK functions in GBC cells. Therefore, RP11-147L13.8 plays tumor-suppressive roles in GBC (110).

Besides the regulation of the aforementioned post-translational modifications, other types of post-translational modifications, such as lncRNAs-induced non-histone acetylation have been revealed only in cell proliferation and apoptosis pathways (111,112), which indicates that these modifications may also participate in cancer development.

Previous studies found that aberrant expression of lncRNAs in GBC cells was correlated with certain signaling pathways (Table I), but the regulatory mechanisms involved were unclear. In 2014, Wu et al (10) reported for the first time that in GBC tissues, upregulated MALAT1 could promote GBC cell proliferation and metastasis possibly via the ERK/MAPK pathway. Cai et al (113) demonstrated that TF specificity protein 1 upregulates lncRNA LINC00152 in GBC and LINC00152 subsequently interacts with the PI3K/AKT pathway and inhibits GBC cell apoptosis. Yang et al (114) revealed that lncRNA HEGBC could bind to the promoter of IL-11 and facilitate its expression, thus activating the IL-11/STAT3 signaling pathway. STAT3 could also bind to the promoter of HEGBC and activate its expression. Finally, HEGBC formed a positive feedback loop with the IL-11/STAT3 pathway and exerted oncogenic functions in GBC (114). Liang et al (115) demonstrated that lncRNA DILC could facilitate GBC development via the Wnt/β-catenin signaling pathway.

Regarding tumor-suppressive lncRNAs, Bao et al (116) demonstrated that MEG3 is positively correlated with endoplasmic reticulum stress-related proteins. Moreover, downregulation of MEG3 decreases nuclear factor-κB signaling and suppresses GBC cell proliferation (116).

Previous studies have reported the existence of certain pathogenic lncRNAs in GBC cells (Table I). Ma et al (117) found that downregulation of lncRNA LET is positively correlated with the G₀/G₁ phase arrest marker p21, and LET could suppress GBC proliferation not only via mediating G₀/G₁ arrest but also by promoting GBC cell apoptosis (117). Wang et al (118) showed that transforming growth factor-β1 and IL-6 treatment could induce the upregulation of lncRNA H19 in vitro, which is positively associated with GBC lymphatic metastasis and tumor size. Mechanistically, upregulated H19 is able to upregulate Twist1, which could affect the expression of genes related to EMT and tumor invasion, such as E-cadherin and vimentin (118). Similarly to the study by Wu et al, Ma et al (119) found that another lncRNA, namely AFAP1-AS1 can also interact with Twist1, and upregulate GBC cell EMT in a similar manner. Wu et al (120) demonstrated that upregulated lncRNA Loc344887 is able to increase the expression of Twist1, vimentin, and N-cadherin, as well as decrease E-cadherin expression to promote EMT. Ectopic expression of nuclear factor (erythroid-derived2)-like 2 leads to increased Loc344887 expression in vitro, which results in GBC cell malignant phenotypes (120). Various pathogenetic lncRNAs are listed in Table I, including ANRIL (121), ROR (122) and Linc00261 (123). However, the functions and regulatory mechanisms of these lncRNAs in GBC cells remain unknown, and require further research.

In summary, the majority of previous studies have focused on the function of lncRNAs as ceRNAs to sponge miRNAs, and certain RBPs that interacted with lncRNAs were also identified. However, studies on other regulatory mechanisms of lncRNAs in GBC are rare. Therefore, further research on the multiple pathogenetic roles of lncRNAs in GBC is needed.

LNA gapmers are recently employed tools for intractable genes or pathways (153). Structurally, LNA gapmers are able to interact with aimed RNAs using its central DNA gap, which leads to RNase H-mediated degradation (154) (Fig. 2A-b). LNA gapmers exhibit improved stability and efficiency than siRNAs (155). LNA gapmers targeting MALAT1 inhibit multiple myeloma (MM) growth and increase tumor cell apoptosis in an MM patient-derived xenograft model (156). Further studies are needed before LNA gapmers can be applied to clinical practice.

With the exception of siRNAs, ASOs and LNA gapmers, some molecules can promote lncRNA degradation.

As aforementioned, lncRNAs can act as ceRNAs to sponge miRNAs. Contrarily, miRNAs can also bind to MREs of lncRNAs to regulate their stability (157) (Fig. 2A-c). For example, miRNA let7 upregulation results in lincRNA-p21 decay in an AGO2-dependent manner with the assistance of HuR (158). Nevertheless, disadvantages such as diverse miRNA targets and being easily-cleared in vivo limit its application in clinical treatment.

Ribozymes were identified as rare RNA molecules, and their function of degrading specific RNAs drew attention to their potential to target pathological lncRNAs (159). Deoxyribozymes were also found in ex vivo selections unexpectedly, which has similar catalytic activity to ribozymes (160) (Fig. 2A-d). Recently, Chen et al (161) reported that a ribozyme, termed hominin vlincRNA-located, was able to induce the degradation of its source lncRNAs. However, these kinds of molecule are currently difficult to design for aiming at lncRNAs effectively.

Derived from bacteria and archaea, the CRISPR-Cas system guides ribonucleoproteins to specific DNA sites with the assistance of designed guide RNAs (gRNAs) (162). The catalytic activity of Cas proteins then leads to double-stranded breaks, which can be repaired by non-homologous DNA end joining (NHEJ) or homology-directed repair (163,164). Finally, these two repair mechanisms assist to generate needed genome alternation, such as ‘knock-out’ or ‘knock-in’ mutations (165). Due to its specificity and efficiency, the CRISPR-Cas system appears to be a novel method for gene editing, which has great potential for translational medicine (Fig. 2B).

Since NHEJ, the most common repair mode in cells, often results in deletions or frameshift mutations to generate non-functional transcripts (166,167), previous studies suggested that the transcription of specific lncRNAs may be blocked via the CRISPR-Cas9 system. In basic research, CRISPR-Cas9 has been used to explore the functional role of various lncRNAs in neoplasms, examples including lncRNA CCAT2 in colorectal cancer (CRC) (168), and lncRNA LINC-ROR in breast cancer (169). The application of the CRISPR-Cas system is currently limited to ex vivo research. Addressing ethical considerations is as important as overcoming technical problems and enabling safety in human subjects. Thus, it can be proposed that the CRISPR-Cas system may be an attractive method for the treatment of patients with GBC.

As aforementioned, lncRNAs have multiple functions in cancer mainly via binding to other molecules, including other types of RNA or proteins. Aiming at these interactions, small molecule inhibitors have been developed to suppress the binding of lncRNAs to other cellular components mainly via the following two mechanisms (Fig. 2C): i) Inhibitors bind to target domains of lncRNAs to alter lncRNAs' spatial structure directly (170); or ii) inhibitors occupy the docking sites for DNA, RNA, proteins or lipids to suppress the interaction of lncRNAs with these sites (171).

For instance, the small molecule inhibitor AC1NOD4Q can inhibit the interaction between lncRNA HOTAIR and EZH2 in glioma (172). Isolated form plants, curcumin is a well-known anticancer drug (173), which can downregulate lncRNA ROR and release miR-145 to significantly inhibit prostate cancer development (174). Another compound, 5-azathioprine-2-deoxycytidine, can inhibit the methylation of the imprinted control region of H19 and decrease H19 expression (175). The concomitant use of high throughput technologies and computational analysis to develop specific compounds provides a rationale for the identification of new drugs, and well-designed inhibitors may become important breakthroughs for GBC management.

Previous studies indicated that rigorous folding of the lncRNA secondary structure remains essential for its function. Certain lncRNAs are invalidated to siRNAs, ASOs, and ribozymes due to their complex secondary structures (176). To solve this problem, short DNAs, oligonucleotide RNAs or polypeptides with specific structures were produced as aptamers, which aimed to recognize special structures of lncRNAs and facilitate their degradation or block their interaction with other molecules (177,178) (Fig. 2C). For example, Wang et al (179) revealed that chimeric aptamer targeting epithelial growth factor receptor (EGFR) leads to the downregulation of lncRNA HOTAIR in EGFR-expressing triple-negative breast cancer (TNBC) cell and inhibits TNBC cell malignant phenotypes.

Compared with each other, all the aforementioned methods are mainly used in vitro. Therefore, breakthroughs are hardly reported without the assistance of a reliable delivery system to facilitate the transport of these targeted molecules to tumor tissues safely and precisely. Although the CRISPR-Cas system is the most accurate and radical method to knockout pathological lncRNAs, it still requires further investigation to resolve aforementioned problems before being applied in clinical management. To block the interaction of lncRNAs with other functional molecules, aptamers need to be well designed individually, which may be expensive in practice. Small molecule inhibitors are limited at present, but Chinese herbal medicine may shed new light on the research and development of novel drugs. As for methods to promote dysregulated lncRNAs decay, ASOs and LNA gapmers appear to be more specific and safer than siRNAs; however, some drugs based on siRNAs are applied in therapy or in clinical trials. In addition, there are certain disadvantages of miRNAs and ribozymes/deoxyribozymes that cannot be ignored. For miRNAs, numerous studies reported its interaction with lncRNAs, but miRNAs are easily-cleared like siRNAs and are not sufficiently specific. As for ribozymes/deoxyribozymes, they are rare in nature and difficult to design artificially.

As one of the most lethal abdominal tumors, GBC tends to develop resistance to current treatments. Therapy targeting tumorigenesis lncRNAs may provide new opportunities for GBC clinical practice. Although different methods function through various mechanisms, novel therapeutic tools should focus on targeted and rapid delivery systems and avoid their degradation in vivo after guaranteeing their safety.