Stem cell gene SALL4 in aggressive hepatocellular carcinoma: a cancer stem cell-specific target?

SALL4 activates PI3K/AKT signaling pathway through targeting PTEN, thus facilitating migration, invasion and proliferation of hepatocellular carcinoma cells

This study aims to explore the specific mechanisms of SALL4 on the migration, invasion and proliferation of HCC. HepG2 and SMMC-7721 cells were transfected with SALL4 NC, mimics and inhibitors. The proliferation capability and cell cycle progression of HCC cells were detected through CCK8 assay and flow cytometry, and their migration and invasion capabilities were detected by wound healing assay and Transwell assay. In SALL4 inhibitor NC group and SALL4 inhibitor group, the PTEN inhibitor SF1670 was added, and the expression levels of PI3K/AKT, migration, invasion and proliferation-related proteins were detected by Western blotting. Results showed that after up-regulation of SALL4, the migration distance of HCC cells increased, the numbers of migrated cells and the number of colonies formed significantly rosed, and there were fewer cells in G1 phase but significantly more cells in S phase, thereby down-regulation of SALL4, the opposite results. The results of Western blotting revealed that after SF1670, the specific PTEN inhibitor was added in SALL4 inhibitor group and SALL4 inhibitor NC group, the protein expression of PTEN in HCC cells significantly declined, while the protein expressions of p-PI3K, p-AKT, MMP2, MMP9, CyclinD, CyclinA1, PCNA and P62 significantly rose. In conclusion, SALL4 activates the PI3K/AKT signaling pathway through targeting PTEN, thereby facilitating the migration, invasion and proliferation of HCC cells.

SALL4: An Intriguing Therapeutic Target in Cancer Treatment

Spalt-Like Transcription Factor 4 (SALL4) is a critical factor for self-renewal ability and pluripotency of stem cells. On the other hand, various reports show tight relation of SALL4 to cancer occurrence and metastasis. SALL4 exerts its effects not only by inducing gene expression but also repressing a large cluster of genes through interaction with various epigenetic modifiers. Due to high expression of SALL4 in cancer cells and its silence in almost all adult tissues, it is an ideal target for cancer therapy. However, targeting SALL4 meets various challenges. SALL4 is a transcription factor and designing appropriate drug to inhibit this intra-nucleus component is challenging. On the other hand, due to lack of our knowledge on structure of the protein and the suitable active sites, it becomes more difficult to reach the appropriate drugs against SALL4. In this review, we have focused on approaches applied yet to target this oncogene and discuss the potential of degrader systems as new therapeutics to target oncogenes.

Expression and clinical value of SALL4 in renal cell carcinomas

The aim of the present study was to investigate the expression of spalt like transcription factor 4 (SALL4) in the three most common types of renal cell carcinomas (RCC) [clear cell RCC (ccRCC), papillary renal cell carcinoma (pRCC) and chromophobe RCC (chRCC)], and the association with the overall survival (OS) of patients. The Cancer Genome Atlas (TCGA) database and RCC samples were used to investigate the expression levels of the SALL4 gene and its association with the OS in the three types of RCC based on the analysis of the transcriptome, copy number and survival data. It was found that SALL4 was highly expressed in ccRCC and pRCC tumor tissue, and low mRNA expression level of SALL4 indicated a prolonged survival in both ccRCC and pRCC. This mRNA expression level was associated with pathological Tumor-Node-Metastasis stage, M and T stages in both ccRCC and pRCC. The analysis of the enriched pathway results suggested that SALL4 may act via translation initiation, and that the related genes promoted the progression of RCC. Moreover, the high expression level of SALL4 was detected in RCC samples and serum from patients. It was demonstrated that SALL4 promotes increased viability in RCC cells. Therefore, the present results suggest that SALL4 may be a sensitive and specific cancer biomarker in ccRCC and pRCC. Furthermore, targeting of SALL4 may improve RCC therapy and prolong the survival of patients with ccRCC or pRCC.

Inflammatory Micro-environment Contributes to Stemness Properties and Metastatic Potential of HCC via the NF-κB/miR-497/SALL4 Axis

Increasing evidence has demonstrated the essential role of inflammatory micro-environment in tumorigenesis and tumor progression. Some cancer cells in tumor maintain typical stemness properties and, with the capacity of self-renewal, are thought to be crucial for the initiation and maintenance of tumors as well as their metastasis. Although both inflammatory micro-environment and stemness properties played crucial roles in tumor initiation and development, currently it is still unclear whether and how the inflammatory micro-environment promotes cancer stemness properties. Here, we show the first evidence that the inflammatory micro-environment promotes the stemness properties and metastatic potential of hepatocellular carcinoma (HCC) via the NF-κB/miR-497/SALL4 axis. We discover that miR-497 directly targets SALL4, negatively regulates its expression, and further inhibits the self-renewal and metastasis of HCC; more importantly, inflammatory factor TNF-α inhibits the expression of miR-497 via NF-kB-mediated negative transcriptional regulation and simultaneously upregulates the expression of SALL4 and promotes the self-renewal and metastasis phenotypes of HCC cells. Moreover, lower expression of miR-497 is significantly associated with poor prognosis in HCC patients. Taken together, our findings not only revealed a novel signaling pathway (NF-κB/miR-497/SALL4 axis) to connect inflammation with stemness properties, and clarified the molecular mechanisms underlying the inflammation-mediated self-renewal and metastasis phenotypes, but also provided novel molecular targets for developing new anticancer strategies.

Upregulation of SALL4 by EGFR activation regulates the stemness of CD44-positive lung cancer

The transcriptional factor SALL4, an important stem cell regulator, is expressed in hematopoietic stem cells and various malignancies, but its role in EGFR-mutated NSCLCs has not been studied yet. Here, we report that the expression of Sal-like protein 4 (SALL4), was significantly higher in EGFR mutated lung tumors than in non-tumor tissue. SALL4-high lung cancer patients had poorer prognosis after surgery than SALL4-low patients. The expression of SALL4 could be induced by the activation of EGFR through the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. The knockdown of SALL4 expression could suppress spheroid formation and the expression of lung cancer stem cell marker CD44. More interestingly, the knockdown of SALL4 expression could suppress the migration, invasion, and metastasis of the lung cancer cells and significantly increase the sensitivity of EGFR mutated cells to Erlotinib. These results suggest that SALL4 may be a novel potential therapeutic target for the diagnosis and treatment of lung cancer.

Acquisition of Cholangiocarcinoma Traits during Advanced Hepatocellular Carcinoma Development in Mice

Past studies have identified hepatic tumors with mixed hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC) characteristics that have a more aggressive behavior and a poorer prognosis than classic HCC. Whether this pathologic heterogeneity is due to a cell of origin of bipotent liver progenitors or the plasticity of cellular constituents comprising these tumors remains debated. In this study, we investigated the potential acquisition of CC-like traits during advanced development of HCC in mice. Primary and rare high-grade HCC developed in a genetic mouse model. A mouse model of highly efficient HCC invasion and metastasis by orthotopic transplantation of liver cancer organoids propagated from primary tumors in the genetic model was further developed. Invasive/metastatic tumors developed in both models closely recapitulated advanced human HCC and displayed a striking acquisition of CC-related pathologic and molecular features, which was absent in the primary HCC tumors. Our study directly demonstrates the pathologic evolution of HCC during advanced tumor development, providing the first evidence that tumors with mixed HCC and CC features, or at least a subset of these tumors, represent a more advanced developmental stage of HCC. Finally, liver cancer organoid-generated high-grade tumors exhibited significantly increased extracellular vesicle secretion, suggesting that identifying tumor-specific extracellular vesicle proteins in plasma may be a promising tool for liver cancer detection.

Human primary liver cancer-derived organoid cultures for disease modeling and drug screening

Human liver cancer research currently lacks in vitro models that can faithfully recapitulate the pathophysiology of the original tumor. We recently described a novel, near-physiological organoid culture system, wherein primary human healthy liver cells form long-term expanding organoids that retain liver tissue function and genetic stability. Here we extend this culture system to the propagation of primary liver cancer (PLC) organoids from three of the most common PLC subtypes: hepatocellular carcinoma (HCC), cholangiocarcinoma (CC) and combined HCC/CC (CHC) tumors. PLC-derived organoid cultures preserve the histological architecture, gene expression and genomic landscape of the original tumor, allowing for discrimination between different tumor tissues and subtypes, even after long-term expansion in culture in the same medium conditions. Xenograft studies demonstrate that the tumorogenic potential, histological features and metastatic properties of PLC-derived organoids are preserved in vivo. PLC-derived organoids are amenable for biomarker identification and drug-screening testing and led to the identification of the ERK inhibitor SCH772984 as a potential therapeutic agent for primary liver cancer. We thus demonstrate the wide-ranging biomedical utilities of PLC-derived organoid models in furthering the understanding of liver cancer biology and in developing personalized-medicine approaches for the disease.

The Recent Advances on Liver Cancer Stem Cells: Biomarkers, Separation, and Therapy

As the third major reason of mortality related to cancer in the world, liver cancer is also the fifth most frequent cancer. Unluckily, a majority of patients succumb and relapse though many progresses have been made in detection and therapy of liver cancer. It has been put forward that in liver cancer, cancer stem cells (CSCs) hold main responsibility for the formation, invasion, metastasis, and recurrence of tumor. Strategies that are intended to target liver CSCs are playing a more and more significant role in supervising the development of liver cancer treatment and assessing new therapeutic methods. Herein, a brief review about molecule markers, signal pathways, separation, and treatment on liver cancer stem cells (LCSCs) is provided in this paper.

The diagnostic and prognostic value of SALL4 in hepatoblastoma

AIMS

To investigate the expression of spalt-like transcription factor 4 (SALL4), a regulator of embryonal development, in three epithelial components of hepatoblastoma (HB) and the relationship between SALL4 expression levels and patients' clinicopathological features.

METHODS AND RESULTS

A total of 115 specimens from 79 patients with HB were selected for immunostaining of SALL4. Nuclear staining was semi-quantified using the immunoreactive score (IS; range: 0-12). SALL4 expression was seen in all embryonal components (mean IS = 8.58) and in 41% of fetal components (mean IS = 0.78). No SALL4 expression was seen in either small cell undifferentiated or mesenchymal components of HB. Neither chemotherapy nor metastasis altered SALL4 expression significantly. High SALL4 expression levels were associated significantly with decreased overall survival (OS) (P = 0.004), event-free survival (EFS) (P = 0.003) and the presence of metastasis (P = 0.049) on univariate analysis. Multivariate analysis identified SALL4 as an independent prognostic predictor for OS (P = 0.029).

CONCLUSIONS

SALL4 is useful for subtyping HB, and high SALL4 expression is associated with decreased survival in HB.

Genetic polymorphism of HLA-DQ confers susceptibility to hepatitis B virus-related hepatocellular carcinoma: a case-control study in Han population in China

Several recent genome-wide studies showed that the genetic polymorphisms in the HLA-DQ region (rs9275572 and rs2856718) were related to chronic hepatitis B virus (HBV) infection and chronic hepatitis C virus (HCV)-associated hepatocellular carcinoma (HCC). We analyzed the two single-nucleotide polymorphisms for major HBV outcomes in Han Chinese. A total of 1291 samples were involved and peripheral blood samples were collected in this study. Matrix-assisted laser desorption/ionization time of flight mass spectrometry were used to genotype the single-nucleotide polymorphisms in the HLA-DQ region. Our study indicated the clear relationship between the HLA-DQ rs9275572 and HBV-related HCC after control for the effects of sex, drinking, and smoking. Health subjects with the HLA-DQ rs9275572 GA genotype would have a 0.641 (95 % CI 0.416, 0.985; P = 0.043) times lower odds of having HCC, and those with the AA genotype would have a 0.256 (95 % CI 0.106, 0.618; P = 0.002) times lower odds of having HCC, whereas the values of the other covariates were fixed. Whereas there was no significant difference found for the HLA-DQ rs2856718 AG and GG genotype. Our study suggested that HLA-DQ loci (rs9275572) were associated with HBV-related HCC as a protective factor in Han Chinese.

Tumour antigen expression in hepatocellular carcinoma in a low-endemic western area

Background:

Identification of tumour antigens is crucial for the development of vaccination strategies against hepatocellular carcinoma (HCC). Most studies come from eastern-Asia, where hepatitis-B is the main cause of HCC. However, tumour antigen expression is poorly studied in low-endemic, western areas where the aetiology of HCC differs.

Methods:

We constructed tissue microarrays from resected HCC tissue of 133 patients. Expression of a comprehensive panel of cancer-testis (MAGE-A1, MAGE-A3/4, MAGE-A10, MAGE-C1, MAGE-C2, NY-ESO-1, SSX-2, sperm protein 17), onco-fetal (AFP, Glypican-3) and overexpressed tumour antigens (Annexin-A2, Wilms tumor-1, Survivin, Midkine, MUC-1) was determined by immunohistochemistry.

Results:

A higher prevalence of MAGE antigens was observed in patients with hepatitis-B. Patients with expression of more tumour antigens in general had better HCC-specific survival (P=0.022). The four tumour antigens with high expression in HCC and no, or weak, expression in surrounding tumour-free-liver tissue, were Annexin-A2, GPC-3, MAGE-C1 and MAGE-C2, expressed in 90, 39, 17 and 20% of HCCs, respectively. Ninety-five percent of HCCs expressed at least one of these four tumour antigens. Interestingly, GPC-3 was associated with SALL-4 expression (P=0.001), an oncofetal transcription factor highly expressed in embryonal stem cells. SALL-4 and GPC-3 expression levels were correlated with vascular invasion, poor differentiation and higher AFP levels before surgery. Moreover, patients who co-expressed higher levels of both GPC-3 and SALL-4 had worse HCC-specific survival (P=0.018).

Conclusions:

We describe a panel of four tumour antigens with excellent coverage and good tumour specificity in a western area, low-endemic for hepatitis-B. The association between GPC-3 and SALL-4 is a novel finding and suggests that GPC-3 targeting may specifically attack the tumour stem-cell compartment.

Genetic polymorphisms in antioxidant enzyme genes and susceptibility to hepatocellular carcinoma in Chinese population: a case-control study

An increased oxidant burden has been implicated in hepatocarcinogenesis, and several antioxidant enzymes counteract potential oxidative damage. So, polymorphisms in the genes encoding antioxidant enzymes may play an important role in the development of hepatocellular carcinoma (HCC). To test this hypothesis, we investigated the association of polymorphisms in antioxidant enzyme genes, including three superoxide dismutases (SODs), catalase (CAT), and glutathione peroxidase (GPx), with HCC in a Chinese population consisting of 434 HCC patients and 480 control subjects. Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Odds ratios (ORs) and 95 % confidence intervals (95 % CIs) were estimated by unconditional logistic regression. For the ECSOD Ala40Thr polymorphism, a significant association was observed between this polymorphism and HCC risk in non-hepatitis B virus (HBV) carriers but not in HBV carriers, and individuals with one 40Thr allele (Ala/Thr genotype) (OR = 2.13, 95 % CI = 1.25-3.64, P = 0.006) or at least one 40Thr allele (Ala/Thr and Thr/Thr genotype) (OR = 1.90, 95 % CI = 1.15-3.15, P = 0.012) showed significantly higher risk to HCC, compared with Ala/Ala genotype. No significant associations were observed between three other polymorphisms (MnSOD Ala16Val, CAT-262C/T, GPx Pro198Leu) and HCC susceptibility in both HBV carriers and non-HBV carriers. Furthermore, no other signs of combined effects, except for a combined effect of ECSOD Ala40Thr and MnSOD Val16Ala in non-HBV carriers, were observed for each combination of these four polymorphisms. In conclusion, our results indicate that the antioxidant enzyme gene polymorphisms at least partially contribute to the susceptibility to HCC.