Somatic mutation analysis of p53 and ST7 tumor suppressor genes in gastric carcinoma by DHPLC

Systematic Review and Meta-analysis of TP53, HER2/ERBB2, KRAS, APC, and PIK3CA Genes Expression Pattern in Gastric Cancer

Background: With a global prevalence of about 10%, gastric cancer is among the most prevalent cancers. Currently, there has been an ongoing trend toward investigating genetic disruptions in different cancers because they can be used as a target-specific therapy. We aimed to systemically review some gene expression patterns in gastric cancer. Methods: The current systematic review was designed and executed in 2020. Scopus, PubMed, Cochrane Library, Google Scholar, web of knowledge, and Science Direct were searched for relevant studies. A manual search of articles (hand searching), reference exploring, checking for grey literature, and seeking expert opinion were also done. Results: In this review, 65 studies were included, and the expression pattern of HER2/ ERBB2, ER1/Erb1/EGFR, PIK3CA, APC, KRAS, ARID1A, TP53, FGFR2 and MET was investigated. TP53, APC, KRAS, and PIK3CA mutation cumulative frequency were 24.8 (I²=95.05, Q value=525.53, df=26, P<0.001), 7.2 (I²=89.79, Q value=48.99, df=5, P<0.001), 7.8 (I²=93.60, Q value=140.71, df=9, P=0.001) and 8.6 (I²=80.78, Q value=525.53, df=9, P<0.001) percent, respectively. Overexpression was investigated for HER1/ Erb1/EGFR, PIK3CA, APC, KRAS, ARID1A, TP53, CCND1, FGFR2, MET and MYC. The frequency of TP53 and HER2/ERBB2 were 43.1 (I²=84.06, Q value=58.09, df=9, P<0.001) and 20.8 (I²=93.61, Q value=234.89, df=15, P<0.001) percent, respectively. Conclusion: More research is encouraged to investigate the genes for which we could not perform a meta-analysis.

MIB1 upregulates IQGAP1 and promotes pancreatic cancer progression by inducing ST7 degradation

Despite recent progress in cancer treatment, the prognosis of patients with pancreatic cancer still remains poor. Pancreatic tumors are reported to display high molecular heterogeneity. Elucidating the molecular mechanisms underlying pancreatic cancer progression is essential for improving patient treatment and survival. The overexpression of E3 ubiquitin ligase mind bomb 1 (MIB1) was previously described in pancreatic cancer cells, where it enhanced tumor cell proliferation. However, the role of MIB1 in pancreatic cancer progression remains elusive. In the present study, we confirmed that MIB1 expression is elevated in pancreatic cancer tissues and that high levels of MIB associate with unfavorable prognosis. Overexpression of MIB1 enhanced proliferation and invasion of pancreatic cancer cells both in vitro and in vivo. We further investigated the molecular mechanisms downstream of MIB1 and observed for the first time that MIB1 targets suppressor of tumorigenicity 7 protein (ST7), previously described as suppressor of tumorigenicity, for proteasomal degradation. Furthermore, we found that ST7 suppressed tumor growth by downregulating IQ motif containing GTPase activating protein 1 (IQGAP1) in pancreatic tumor cells. Thus, these data show that MIB1 promotes pancreatic cancer progression by inducing ST7 degradation followed by downregulation of IQGAP1 in pancreatic cancer cells. In conclusion, our research shows that the MIB1/ST7/IQGAP1 axis is essential for pancreatic cancer progression, and MIB1 inhibition may serve as a novel therapeutic strategy in patients with pancreatic cancer.

The long noncoding RNA ST7-AS1 promotes laryngeal squamous cell carcinoma by stabilizing CARM1

The laryngeal squamous cell carcinoma (LSCC) represents a malignant cancer and contributes largely to head and neck tumorigenesis. The molecular mechanisms for LSCC progression are poorly understood. In current work, we identified long non-coding RNA (lncRNA) termed suppressor of tumorigenicity 7 antisense RNA 1 (ST7-AS1) as an oncogenic factor in LSCC. ST7-AS1 is frequently overexpressed in LSCC tissues and cell lines. ST7-AS1 is required for the malignancy of LSCC cells through migration, tumor sphere formation assay and in vivo implantation. Mechanistically, ST7-AS1 could interact with CARM1, a well characterized protein arginine methyltransferase and protect CARM1 from ubiquitin-dependent degradation. CARM1 can methylate Sox-2, a pluripotent transcription factor. Thus, ST7-AS1 might mediate its oncogenic effect by signaling through CARM1-Sox-2 axis to enhance Sox-2 self-association and transactivation activity. Collectively, we have unraveled a ST7-AS1/CARM1/Sox-2 signaling axis in LSCC and may have created novel interconnections between noncoding RNAs and cancer development.

Denaturing HPLC for mutation screening

Denaturing High-Performance Liquid Chromatography (dHPLC) is probably the most versatile and one of the most widely used mutation screening technologies. It benefits from a combination of relative technical simplicity and a very high sensitivity (mutation detection rate), approaching 100%. DHPLC can reliably detect single-base mismatches in fragments between 150 and 500 bp, although detection in fragments up to 1,500 bp has been reported. The ability of dHPLC to detect both known and unknown mutations/SNPs, and its' high sensitivity and specificity (reproducibility) has put this technology at the forefront of genetic analysis for a wide variety of diseases.

Localization and characterization of ST7 in cancer

PURPOSE

ST7 has been proposed to be a tumor suppressor gene in the chromosome region 7q31.1-q31.2. In order to gain some insight into its role in cancer, the localization and verification of the ST7 expression levels were determined.

METHODS

Various types of ST7 expression vectors tagged with the sequences of GFP, YFP or V5 were created using a gateway cloning system and full-length ST7 cDNA isolated from a human adult brain cDNA library. Cell cycle synchronization was also performed to analyze the expression of endogenous ST7 and its potentially related genes at each stage of the cell cycle.

RESULTS

Cytosolic ST7 expression in HCT-116, MCF-7 and PC-3 cancer cell lines was detected via the fluorescence signal of the fusion proteins. ST7 translocation from the cytoplasm to the nucleus has not been observed in any of the conditions assayed. A cell cycle synchronization study demonstrated that both ST7 and SERPINE1 were overexpressed when cells were arrested. Expression of these genes was found to be diminished when the cells re-entered cell division status. In addition, we also found that Survivin, MMP-13 and Cyclin D1 were differentially expressed during the cell cycle.

CONCLUSION

Our findings suggest that ST7 mediates tumor suppression through the regulation of the genes involved in maintaining the cellular structure of the cell and involved in oncogenic pathways.

Enhanced detection of TP53 mutations using a GC-clamp in denaturing high performance liquid chromatography

Although denaturing gradient gel electrophoresis (DGGE) is a highly effective technique for screening for TP53 mutations, the use of denaturing high performance liquid chromatography (DHPLC) is a growing methodology. This report describes a comparison between DHPLC and DGGE in the detection of TP53 mutations in hematopoietic cell lines and lymphomas. In addition, the improved effectiveness of guanine cytosine (GC)-clamped DHPLC for TP53 screening is detailed. Thirty DNA samples with known TP53 mutations in the hotspot region of codons 5-8, previously identified by DGGE, were analyzed by DHPLC. We found 100% concordance in mutation detection by DHPLC with DGGE. Similar to the improved efficacy observed in DGGE, the addition of 40 nucleotide GC-clamps composed of guanine and cytosine bases at one end of the product enhanced the detection of a mutation pattern by DHPLC. DHPLC of GC-clamped products is a viable and faster alternative method for screening TP53 mutations.

Is there a role for PCR-SSCP among the methods for missense mutation detection of TP53 gene?

Mutation analysis methods have increased in variety during the past years. High-throughput microarray methods have especially increased in popularity. However, new methods require reference points, and not all of the methods are equal in sensitivity and specificity. Furthermore, the detection of unknown missense mutations, such as unknown TP53 mutations in human tumors, for clinical purposes requires great accuracy, which may be difficult to acquire with the current high-throughput methods. For these reasons, the classical methods, such as PCR-manual sequencing and PCR-SSCP, are still valuable and necessary.

No association between p53 gene intron 7 polymorphism and chronic atrophic gastritis in Han Chinese of Jiangsu province

AIM: To explore whether the polymorphism of p53 gene intron 7 is associated with the occurrence of chronic atrophic gastritis (CAG) in Han Chinese of Jiangsu province.

METHODS: The genome DNA was extracted from tissues of 80 CAG patients and 76 healthy controls, and the exon 7 and 8 as well as the intron 7 within exon 7 and 8 of p53 gene were amplified by polymerase chain reaction (PCR). The products were sequenced after purification. The polymorphism of p53 gene intron 7 was comparatively analyzed with the standard sequences. The genotypes and allelic frequencies compared between the two groups using chi-square test.

RESULTS: In CAG cases, the allelic frequencies of the 72^th base pair (bp) and the 92^th bp in p53 gene intron 7 were 32.5% (T-G) and 67.5% (C-T), and the frequencies of genotype T-G/T-G, C-T/T-G, and C-T/C-T were 11.3%, 42.5%, and 46.3%, respectively. Meanwhile in the controls, the allelic frequencies of T-G and C-T were 29.6% and 70.4%, and the frequencies of genotype T-G/T-G, C-T/T-G, and C-T/C-T were 9.2%, 40.8%, and 50.0%, respectively. There were no significant differences in the allelic frequencies and genotypic distributions between the two groups (P > 0.05). The risk of CAG occurrence was not significantly different between the individuals with T-G and C-T allele (OR = 1.14).

CONCLUSION: There is no direct association between the polymorphism of p53 gene intron 7 and epigenetic penetrance of CAG in Han Chinese of Jiangsu province.

ST7-mediated suppression of tumorigenicity of prostate cancer cells is characterized by remodeling of the extracellular matrix

Multiple lines of evidence have provided compelling evidence for the existence of a tumor suppressor gene (TSG) on chromosome 7q31.1. ST7 may be the target of this genetic instability but its designation as a TSG is controversial. In this study, we show that, functionally, ST7 behaves as a tumor suppressor in human cancer. ST7 suppressed growth of PC-3 prostate cancer cells inoculated subcutaneously into severe combined immunodeficient mice, and increased the latency of tumor detection from 13 days in control tumors to 23 days. Re-expression of ST7 was also associated with suppression of colony formation under anchorage-independent conditions in MDA-MB-231 breast cancer cells and ST7 mRNA expression was downregulated in 44% of primary breast cancers. Expression profiling of PC-3 cells revealed that ST7 predominantly induces changes in genes involved in re-modeling the extracellular matrix such as SPARC, IGFBP5 and several matrix metalloproteinases. These data indicate that ST7 may mediate tumor suppression through modification of the tumor microenvironment.

Expression of tumor metastasis-related gene protein in the same syndromic classification of gastric carcinoma on traditional Chinese medicine

AIM: To explore the entity of gastric carcinoma under the same syndromic classification based on traditional Chinese medicine from the angle of gene protein expression.

METHODS: Patients with gastric carcinoma were collected and then classified before operation according to dialectic criterion of traditional Chinese medicine. Samples of gastric carcinoma from all the patient were collected after operation. EnVision two step immuhistochemical method was used to observe the expession of E-cadherin, C-erbB-2, P53, nm23, ICAM-1, VEGF, KDR, MMP-2, TIMP-2 in the cancerous samples.

RESULTS: The preceding 9 gene proteins were differently expressed in each type. There was significant difference (P = 0.0 001 < 0.01) in the expression of the 9 gene proteins between different syndromic types. Several genes had different expression in the same syndromic type. The rates of VEGF, E-cad, nm23 expression were higher (94%, 90% and 92% respectively) than other proteins. E-cad expression in the stagnation of phlegm-damp type is the highest expression (average rank = 63.09). E-cad expression was lower in the types of the stasis and endogenous toxics and the discordance of liver-stomach.

CONCLUSION: Metastasis of gastric carcinoma in the types of the stasis and endogenous toxics and the discordance of liver-stomach may relate to the loss of E-cadherin expression. However, both cancer gene and anti-oncogene are expressed at a high level in the two types.