Lin28 promotes Her2 expression and Lin28/Her2 predicts poorer survival in gastric cancer

Exploring Lin28 proteins: Unravelling structure and functions with emphasis on nervous system malignancies

Cancer and stem cells share many characteristics related to self-renewal and differentiation. Both cell types express the same critical proteins that govern cellular stemness, which provide cancer cells with the growth and survival benefits of stem cells. LIN28 is an example of one such protein. LIN28 includes two main isoforms, LIN28A and LIN28B, with diverse physiological functions from tissue development to control of pluripotency. In addition to their physiological roles, LIN28A and LIN28B affect the progression of several cancers by regulating multiple cancer hallmarks. Altered expression levels of LIN28A and LIN28B have been proposed as diagnostic and/or prognostic markers for various malignancies. This review discusses the structure and modes of action of the different LIN28 proteins and examines their roles in regulating cancer hallmarks with a focus on malignancies of the nervous system. This review also highlights some gaps in the field that require further exploration to assess the potential of targeting LIN28 proteins for controlling cancer.

LIN28 expression and function in medulloblastoma

Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Current treatment modalities are not completely effective and can lead to severe neurological and cognitive adverse effects. In addition to urgently needing better treatment approaches, new diagnostic and prognostic biomarkers are required to improve the therapy outcomes of MB patients. The RNA-binding proteins, LIN28A and LIN28B, are known to regulate invasive phenotypes in many different cancer types. However, the expression and function of these proteins in MB had not been studied to date. This study identified the expression of LIN28A and LIN28B in MB patient samples and cell lines and assessed the effect of LIN28 inhibition on MB cell growth, metabolism and stemness. LIN28B expression was significantly upregulated in MB tissues compared to normal brain tissues. This upregulation, which was not observed in other brain tumors, was specific for the aggressive MB subgroups and correlated with patient survival and metastasis rates. Functionally, pharmacological inhibition of LIN28 activity concentration-dependently reduced LIN28B expression, as well as the growth of D283 MB cells. While LIN28 inhibition did not affect the levels of intracellular ATP, it reduced the expression of the stemness marker CD133 in D283 cells and the sphere formation of CHLA-01R cells. LIN28B, which is highly expressed in the human cerebellum during the first few months after birth, subsequently decreased with age. The results of this study highlight the potential of LIN28B as a diagnostic and prognostic marker for MB and open the possibility to utilize LIN28 as a pharmacological target to suppress MB cell growth and stemness.

RNA-binding protein LIN28A upregulates transcription factor HIF1α by posttranscriptional regulation via direct binding to UGAU motifs

Hypoxia-inducible factor 1α (HIF1α) is a transcription factor that regulates angiogenesis under hypoxic conditions. To investigate the posttranscriptional regulatory mechanism of HIF1α, we performed a cell-based screening to reveal potential cis-elements and the regulatory RNA-binding proteins that act as trans-factors. We found that LIN28A promoted HIF1α protein expression independently of the downregulation of microRNA let-7, which is also directly mediated by LIN28A. Transcriptome analysis and evaluation of RNA stability using RNA-seq and SLAM-seq analyses, respectively, revealed that LIN28A upregulates HIF1A expression via mRNA stabilization. To investigate the physical association of LIN28A with HIF1A mRNA, we performed enhanced crosslinking immunoprecipitation in 293FT cells and integrally analyzed the transcriptome. We observed that LIN28A associates with HIF1A mRNA via its cis-element motif "UGAU". The "UGAU" motifs are recognized by the cold shock domain of LIN28A, and the introduction of a loss-of-function mutation to the cold shock domain diminished the upregulatory activities performed by LIN28A. Finally, the microvessel density assay showed that the expression of LIN28A promoted angiogenesis in vivo. In conclusion, our study elucidated the role of LIN28A in enhancing the HIF1α axis at the posttranscription layer.

RNA-binding proteins: Underestimated contributors in tumorigenesis

mRNA export, translation, splicing, cleavage or capping determine mRNA stability, which represents one of the primary aspects regulating gene expression and function. RNA-binding proteins (RBPs) bind to their target mRNAs to regulate multiple cell functions by increasing or reducing their stability. In recent decades, studies of the role of RBPs in tumorigenesis have revealed an increasing number of proteins impacting the prognosis, diagnosis and cancer treatment. Several RBPs have been identified based on their interactions with oncogenes or tumor suppressor genes in human cancers, which are involved in apoptosis, the epithelial-mesenchymal transition (EMT), DNA repair, autophagy, cell proliferation, immune response, metabolism, and the regulation of noncoding RNAs. In this review, we propose a model showing how RBP mutations influence tumorigenesis, and we update the current knowledge regarding the molecular mechanism by which RBPs regulate cancer. Special attention is being devoted to RBPs that represent prognostic and diagnostic factors in cancer patients.

Long noncoding RNA ZNFX1-AS1 promotes the invasion and proliferation of gastric cancer cells by regulating LIN28 and CAPR1N1

BACKGROUND

Long noncoding RNA (lncRNA) ZNFX1-AS1 (ZFAS1) is a newly discovered lncRNA, but its diagnostic value in gastric cancer is unclear.

AIM

To investigate the potential role of ZFAS1 in gastric cancer and to evaluate the clinical significance of ZFAS1 as a biomarker for gastric cancer screening.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to screen for gastric cancer-associated lncRNAs in gastric cancer patients, gastric stromal tumor patients, gastritis or gastric ulcer patients, and healthy controls. Correlations between ZFAS1 expression and clinicopathological features were analyzed. The biological effects of ZFAS1 on the proliferation, migration, and invasion of gastric cancer cells were studied by MTT, colony formation, and transwell mi-gration assays. The potential mechanism of ZFAS1 was demonstrated using enzyme-linked immunosorbent assay and qRT-PCR. The relationship between ZFAS1 and tumorigenesis was demonstrated using in vivo tumor formation assays.

RESULTS

The plasma level of lncRNA ZFAS1 was significantly higher in preoperative patients with gastric cancer than in individuals in the other 4 groups. Increased expression of ZFAS1 was significantly associated with lymph node metastasis, advanced TNM stage, and poor prognosis. ZFAS1 regulated the proliferation, migration, and invasion of gastric cancer cells and regulated the growth of gastric cancer cells in vivo. LIN28 and CAPRIN1 were identified as key downstream mediators of ZFAS1 in gastric cancer cells.

CONCLUSION

LncRNA ZFAS1 promoted the invasion and proliferation of gastric cancer cells by modulating LIN28 and CAPRIN1 expression, suggesting that ZFAS1 can be used as a potential diagnostic and prognostic biomarker in gastric cancer.

Prognostic value of Lin28A and Lin28B in various human malignancies: a systematic review and meta-analysis

Background

The mammalian homologs of Lin-28, Lin28 (also called Lin28A) and Lin28B, are promising cancer biomarkers. This meta-analysis was performed to evaluate the prognostic values of Lin28A and Lin28B in multiple human malignancies.

Methods

Systematic searches of the PubMed, Web of Science and Embase were used to identify relevant studies. Pooled hazard ratios (HRs) with 95% confidence intervals (CI) for overall survival (OS), recurrence-free survival (RFS), disease-free survival (DFS), or progression-free survival (PFS) were respectively calculated.

Results

3772 Lin28A-associated patients and 1730 Lin28B-related cases were ultimately enrolled in this meta-analysis. The elevated expression level of Lin28A was significantly associated with poor OS (HR = 1.60, P < 0.001) and poor RFS/DFS/PFS (HR = 1.62, P < 0.001) in patients with malignancies. Lin28B overexpression significantly correlated with unfavorable OS (HR = 1.72, P < 0.001) and RFS/DFS/PFS (HR = 2.35, P < 0.001) of human malignancies.

Conclusions

Lin28A and Lin28B possess significant prognostic values in various human malignancies. Overexpression of Lin28A or Lin28B suggests poor prognosis for cancer patients.

Expression of Lin28 is correlated with prognosis and expression of HER-2 and steroid receptors in breast cancer

Objective

Cumulative data from clinical trials suggest that Lin28 may contribute to poor survival in breast cancer patients. The purpose of this study was to investigate the relationship between Lin28 expression and breast cancer patients’ clinicopathological parameters.

Methods

Data from a total of 291 breast cancer patients were collected in this study. The expression level of Lin28 was assessed by immunohistochemical staining. The correlation of Lin28 expression and clinicopathological parameters was statically evaluated and the prognostic significance of Lin28 expression was assessed by univariate and multivariate analyses.

Results

One hundred and eight out of 291 (37.1%) breast cancer specimens showed Lin28 protein positive expression, while the remaining 183 specimens showed negative expression. Positive expression of Lin28 was associated with lymph node metastases (P<0.001), HER-2 (P=0.024), estrogen receptor (P=0.039), and progesterone receptor (P=0.027). Kaplan–Meier analysis showed that Lin28 positive expression showed lower overall survival rates compared with Lin28 negative patients (P=0.019). In the multivariate analysis, Lin28 remained a significant independent prognostic factor (P=0.038) for overall survival rates.

Conclusion

Lin28 expression was associated with advanced disease stage and subtype in breast cancer patients, and Lin28 expression may serve as an independent prognostic factor. These data indicate that Lin28 may play a major role in the therapeutic management of breast cancer.

Human Epidermal Growth Factor Receptor-2 in Sri Lankan Gastric Carcinoma Patients with Clinicopathological Association and Survival

BACKGROUND

HER2 protein expression indicates adverse prognosis in gastric adenocarcinoma (GCa). GCa HER2 positivity ranges from 10 to 22.8%. Similar data are scarce in South Asia and unavailable in Sri Lanka.

AIM

To evaluate HER2 protein expression, its clinicopathological relationship and survival in a Sri Lankan GCa cohort.

METHODS

One hundred consecutive GCa patients were recruited prospectively for 2 years. Histological diagnosis was confirmed on endoscopic biopsies/gastrectomy specimens. Clinicopathological and overall survival data were collected. HER2 expression was assessed using immunohistochemistry. 2+ and 3+ scores were considered positive. HER2 expression and clinicopathological parameters were analyzed by Chi-squared test and multivariate analysis with logistic regression using SPSS-21. Kaplan-Meier method and log-rank test were used for survival analysis.

RESULTS

Study includes 56 biopsies and 44 resections. Male/female ratio was 1.9:1. Mean age of diagnosis was 61.1 years (range 32-82). Majority tumors were proximally located (58%). HER2 positivity was 9%. Even though intestinal subtype predominated HER2 positivity was mostly among diffuse variant (14.8%). In multivariate analysis, mitotic count >5/hpf, high nuclear grade and tumor necrosis were significantly associated with HER2 positivity, while poor differentiation, signet cells, extracellular mucin, perineural invasion and pathological nodal metastasis (all p < 0.05) showed a correlation in univariate analysis. Mean follow-up duration was 37.4 weeks (range 0-104). HER2 positivity was associated with a significantly lower median overall survival (p = 0.046).

CONCLUSION

GCa HER2 positivity was 9%, associated with a lower median overall survival. Adverse histological features had a positive correlation with HER2 positivity. These histological features could direct patients for confirmatory HER2 testing in limited resource settings.

Tumor and serum gamma-glutamyl transpeptidase, new prognostic and molecular interpretation of an old biomarker in gastric cancer

BACKGROUND

Gastric Cancer is one of the most lethal malignancies worldwide. Gamma-glutamyl transpeptidase (GGT) is an enzyme mainly involved in cellular glutathione homeostasis. We aim to explore the clinical value of GGT in gastric cancer.

RESULTS

Among 322 patients enrolled, 65/82 patients were determined as GGT positive in serum/tumor, respectively. High tumor GGT expression is significantly associated with lymph node metastasis, histological subtype, and Her2 expression. Kaplan-Meier curve shows that high tumor GGT patients have shorter overall survival (P log-rank=0.001) and progress-free survival (P log-rank =0.001). Patients with both high tumor and serum GGT have the poorest prognosis. The multivariable Cox analysis shows that the hazard ratio of overall survival for high tumor GGT is 1.69 (95% CI 1.19-2.37). High serum GGT is a poor prognostic factor in adjuvant chemotherapy hazard ratio=2.18, 95%CI (1.15-4.47). These findings were further validated in six online datasets. Gene Sets Enrichment Analysis showed that GGT promotes cancer progression through EMT, KRAS, SRC and PKCA pathways.

METHODS

Tumor GGT and serum GGT levels were evaluated with immuno-histochemistry staining and enzymatic assay, respectively. Kaplan-Meier curve and Cox regression model were used to test the association between GGT and gastric cancer prognosis. Independent datasets from Gene Expression Omnibus and Gene Sets Enrichment Analysis were applied to validate the findings and explore the potential mechanisms.

CONCLUSION

Both tumor GGT and serum GGT are poor prognostic factors in gastric cancer. Patients with high tumor and serum GGT levels require more intense treatment and follow-up.

Expression and associations of TRAF1, BMI-1, ALDH1, and Lin28B in oral squamous cell carcinoma

Tumor necrosis factor receptor-associated factor 1, an adaptor protein of tumor necrosis factor 2, is involved in classical nuclear factor (NF)-κB activation and lymphocyte recruitment. However, less is known about the expression and association of tumor necrosis factor receptor-associated factor 1 with cancer stem cell markers in oral squamous cell carcinoma. This study aimed to investigate the expression of tumor necrosis factor receptor-associated factor 1 and stem cell characteristic markers (lin28 homolog B, B cell-specific Moloney murine leukemia virus integration site 1, and aldehyde dehydrogenase 1) in oral squamous cell carcinoma and analyze their relations. Paraffin-embedded tissues of 78 oral squamous cell carcinomas, 39 normal oral mucosa, and 12 oral dysplasia tissues were employed in tissue microarrays, and the expression of tumor necrosis factor receptor-associated factor 1, B cell-specific Moloney murine leukemia virus integration site 1, aldehyde dehydrogenase 1, and lin28 homolog B was measured by immunohistostaining and digital pathological analysis. The expression of tumor necrosis factor receptor-associated factor 1 was higher in the oral squamous cell carcinoma group as compared with the expression in the oral mucosa (p < 0.01) and oral dysplasia (p < 0.001) groups. In addition, the expression of tumor necrosis factor receptor-associated factor 1 was associated with those of B cell-specific Moloney murine leukemia virus integration site 1, aldehyde dehydrogenase 1, and lin28 homolog B (p = 0.032, r² = 0.109; p < 0.0001, r² = 0.64; and p < 0.001, r² = 0.16) in oral squamous cell carcinoma. The patient survival rate was lower in the highly expressed tumor necrosis factor receptor-associated factor 1 group, although the difference was not significant. The clustering analysis showed that tumor necrosis factor receptor-associated factor 1 was most related to aldehyde dehydrogenase 1. These findings suggest that tumor necrosis factor receptor-associated factor 1 has potential direct/indirect regulations with the cancer stem cell markers in oral squamous cell carcinoma, which may help in further analysis of the cancer stem cell characteristics.

The LIN28/let-7 Pathway in Cancer

Among all tumor suppressor microRNAs, reduced let-7 expression occurs most frequently in cancer and typically correlates with poor prognosis. Activation of either LIN28A or LIN28B, two highly related RNA binding proteins (RBPs) and proto-oncogenes, is responsible for the global post-transcriptional downregulation of the let-7 microRNA family observed in many cancers. Specifically, LIN28A binds the terminal loop of precursor let-7 and recruits the Terminal Uridylyl Transferase (TUTase) ZCCHC11 that polyuridylates pre-let-7, thereby blocking microRNA biogenesis and tumor suppressor function. For LIN28B, the precise mechanism responsible for let-7 inhibition remains controversial. Functionally, the decrease in let-7 microRNAs leads to overexpression of their oncogenic targets such as MYC, RAS, HMGA2, BLIMP1, among others. Furthermore, mouse models demonstrate that ectopic LIN28 expression is sufficient to drive and/or accelerate tumorigenesis via a let-7 dependent mechanism. In this review, the LIN28/let-7 pathway is discussed, emphasizing its role in tumorigenesis, cancer stem cell biology, metabolomics, metastasis, and resistance to ionizing radiation and several chemotherapies. Also, emerging evidence will be presented suggesting that molecular targeting of this pathway may provide therapeutic benefit in cancer.

Association of HER2 status with prognosis in gastric cancer patients undergoing R0 resection: A large-scale multicenter study in China

AIM: To determine whether the positive status of human epidermal growth receptor 2 (HER2) can be regarded as an effective prognostic factor for patients with gastric cancer (GC) undergoing R0 resection.

METHODS: A total of 1562 GC patients treated by R0 resection were recruited. HER2 status was evaluated in surgically resected samples of all the patients using immunohistochemical (IHC) staining. Correlations between HER2 status and clinicopathological characteristics were retrospective analyzed. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazard model, stratified by age, gender, tumor location and tumor-node-metastasis (TNM) stage, with additional adjustment for potential prognostic factors.

RESULTS: Among 1562 patients, 548 (positive rate = 35.08%, 95%CI: 32.72%-37.45%) were HER2 positive. Positive status of HER2 was significantly correlated with gender (P = 0.004), minority (P < 0.001), tumor location (P = 0.001), pathological grade (P < 0.001), TNM stage (P < 0.001) and adjuvant radiotherapy (74.67% vs 23.53%, P = 0.011). No significant associations were observed between HER2 status and disease free survival (HR = 0.19, 95%CI: 0.96-1.46, P = 0.105) or overall survival (HR = 1.19, 95%CI: 0.96-1.48, P = 0.118) using multivariate analysis, although stratified analyses showed marginally statistically significant associations both in disease free survival and overall survival, especially among patients aged < 60 years or with early TNM stages (I and II). Categorical age, TNM stage, neural invasion, and adjuvant chemotherapy were, as expected, independent prognostic factors for both disease free survival and overall survival.

CONCLUSION: The positive status of HER2 based on IHC staining was not related to the survival in patients with GC among the Chinese population.

LIN28: A Stem Cell Factor with a Key Role in Pediatric Tumor Formation

Differentiation and development are normally unidirectional processes in which progenitor/stem cells differentiate into more mature cells. Transformation of adult cells into cancer cells is accompanied in many cases by dedifferentiation of the adult cell, while differentiation failure of progenitor cells can result in the formation of unique type of cancers called pediatric cancer. LIN28A and its paralog LIN28B are pluripotent genes that are expressed mainly in stem/progenitor cells. Since the first identification of LIN28 in mammals, numerous studies demonstrated the general oncogenic features of these genes. In this review, we emphasize the unique role of LIN28 in pediatric tumor formation. We show, based on comprehensive literature screen and analysis of published microarray data, that LIN28 expression in pediatric tumors is even more common than in adult tumors, and discuss the possibility that in the case of pediatric cancers, LIN28 acts by preventing normal development/differentiation rather than by transformation of mature cells into cancer cells. Overall, this review highlights the role of LIN28 as a bridge point between embryonic development, stem cell biology, and cancer.

Lin28: an emerging important oncogene connecting several aspects of cancer

RNA-binding protein Lin28 was originally found as a heterochronic gene which played a significant role in the development of Caenorhabditis elegans. The tumor suppressor let-7 is a downstream target of Lin28, which has a wide variety of target genes which are involved in many aspects of cellular activities. By inhibition of let-7 and directly binding the target RNAs, Lin28 plays an important role in different biological and pathological processes including differentiation, metabolism, proliferation, pluripotency, and tumorigenesis. Overexpression of Lin28 has been reported in several kinds of cancers and is correlated with poor outcomes. It has been shown that Lin28 could affect the progression of cancers in several ways, such as promoting proliferation, increasing glucose metabolism, and inducing epithelial-mesenchymal transition (EMT) and cancer stem cells. Decrease of Lin28 expression or reactivation of let-7 in cancer cells could induce a reverse effect, indicating their therapeutic values in developing novel strategies for cancer treatment. Here, we will overview the regulatory mechanisms and functions of Lin28 in cancers.