Molecular genetic analysis of the von Hippel-Lindau and human peroxisome proliferator-activated receptor gamma tumor-suppressor genes in adenocarcinomas of the gastroesophageal junction

Tumor immune microenvironment in therapy-naive esophageal adenocarcinoma could predict the nodal status

BACKGROUND

Currently, preoperative staging of esophageal adenocarcinoma (EAC) has modest reliability and accuracy for pT and pN stages prediction, which heavily affects overall survival. The interplay among immune checkpoints, oncogenes, and intratumoral and peritumoral immune infiltrating cells could be used to predict loco-regional metastatic disease in early EAC.

METHODS

We prospectively evaluated immune markers expression and oncogenes status as well as intratumoral and peritumoral immune infiltrating cells populations in esophageal mucosa samples obtained from neoadjuvant therapy-naïve patients who had esophagectomy for EAC.

RESULTS

Vascular invasion and high infiltration of lamina propria mononuclear cells resulted associated with nodal metastasis. Low infiltration of activated CD8⁺ CD28⁺ T cells was observed in both intratumoral and peritumoral mucosa of patients with nodal metastasis. Low levels of CD69, MYD88, and TLR4 transcripts were detected in the intratumoral specimen of patients with lymph node involvement. Receiver operating characteristic curve analysis showed good accuracy for detecting nodal metastasis for all the markers tested. Significant lower infiltration of CD8 T cells and M1 macrophages and a lower expression of CD8A, CD8B, and TBX21 were found also in Esophageal Adenocarcinoma TCGA panCancer Atlas in the normal tissue of patients with nodal metastasis.

CONCLUSIONS

Our data suggest that immune surveillance failure is the main driver of nodal metastasis onset. Moreover, nodal metastasis containment also involves the immune microenvironment of the peritumoral healthy tissue.

Telmisartan prevents proliferation and promotes apoptosis of human ovarian cancer cells through upregulating PPARγ and downregulating MMP‑9 expression

The mortality rate of ovarian cancer is the highest of all gynecological malignancies. Telmisartan is a commonly used clinical angiotensin receptor blocker, which has antihypertensive, anti‑inflammatory and antithrombotic effects. In the present study, it was investigated whether telmisartan could exert anticancer effects on ovarian cancer cells through upregulating peroxisome proliferator‑activated receptor γ (PPARγ) and downregulating matrix metalloproteinase‑9 (MMP‑9) expression. A 3.3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was conducted to analyze the proliferation of HEY cells. A Caspase‑3 Activity Assay kit and an Annexin V‑fluorescein isothiocyanate/propidium iodide kit were used to analyze the apoptosis of HEY cells. In addition, a gelatin zymography assay and reverse trancription‑quantitative polymerase chain reaction were included to analyze the expression of PPARγ and MMP‑9 in HEY cells. The data showed that telmisartan could significantly decrease cell viability and induce the apoptosis of HEY cells in a time‑ and dose‑dependent manner. Furthermore, telmisartan could also dose‑dependently increase the expression of PPARγ and decrease the expression of MMP‑9 in HEY cells. In addition, downregulation of the expression of PPARγ by small interfering (si)RNA could reduce the effect of telmisartan on ovarian cancer cells and increase the expression of MMP‑9. In conclusion, the results indicated that telmisartan prevents proliferation and promotes apoptosis of human ovarian cancer cells by upregulating PPARγ and downregulating MMP‑9 expression.

Analysis of succinate dehydrogenase subunit B gene alterations in gastric cancers

Recently, the succinate dehydrogenase subunit B gene, SDHB, has emerged as a novel tumor suppressor. In this study, we have examined the genetic and epigenetic alterations of the SDHB gene in sporadic gastric adenocarcinomas in order to investigate if the SDHB gene is involved in gastric carcinogenesis. The expression of SDHB proteins was also examined with immunohistochemistry and Western blot in 184 and eight gastric cancers, respectively. There was loss or reduced expression of SDHB in 45 (24.5%) of the 184 gastric cancers. Statistically, altered expression of SDHB was not associated with clinicopathological parameters, including tumor differentiation, location, depth of invasion, and lymph node metastasis (P > 0.05). Western blot analysis showed a reduced expression of SDHB in four (50.0%) of the eight paired gastric cancer tissues. Genetic analysis showed one missense mutation, GCC --> ACC (Ala --> Thr) at codon 29. In addition, promoter hypermethylation was not detected in the gastric cancer samples. This is the first investigation of the genetic and protein expression analysis of the SDHB gene in gastric cancers. Our results suggest that genetic, epigenetic, and protein expression pattern alterations of the SDHB gene might play a minor role in the development or progression of gastric cancers.

Genetic and epigenetic analysis of the VHL gene in gastric cancers

The von Hippel-Lindau tumor suppressor gene (VHL), which is located on chromosome 3p25, plays an important role in tumorigenesis, particularly in tumor growth and vascularization. Mutations of the VHL gene have been observed in the hereditary VHL syndrome and a variety of other sporadic cancers. In this study, in order to investigate whether the VHL gene is involved in gastric carcinogenesis, we have examined the genetic alterations, including somatic mutations and allelic loss, with the two microsatellite markers, D3S1038 and D3S1110, as well as promoter hypermethylation of the VHL gene in 88 sporadic gastric adenocarcinomas. No mutation was detected in the coding region of the VHL gene. Allelic loss was found in 20 (33.9%) of 59 informative cancer cases at one or both markers. In addition, promoter hypermethylation was not detected in the gastric cancer samples. This is the first investigation of the genetic and epigenetic alterations of the VHL gene in gastric cancers. Our results suggest that genetic and epigenetic alterations of the VHL gene may be not involved in the development or progression of gastric cancers. The findings also provide evidence for the presence of another gastric cancer specific tumor suppressor gene at the 3p25 region.

Loss of heterozygosities in Barrett esophagus, dysplasia, and adenocarcinoma detected by esophageal brushing cytology and gastroesophageal biopsy

BACKGROUND

Esophageal brushing cytology (EBC) and gastroesophageal biopsy (GEB) are complementary procedures for the evaluation of gastroesophageal lesions that help guide surveillance and treatment.

METHODS

The authors investigated loss of heterozygosity (LOH) of 17 microsatellite repeat markers near tumor suppressor genes in gastroesophageal lesions on 34 concomitant EBCs and GEBs.

RESULTS

The results indicated that there was progressive accumulation of LOHs toward malignant transformation. EBC samples a greater area than GEB, and more LOHs are detected by EBC than GEB. The combination of cytomorphology and detection of LOHs can improve diagnostic accuracy and is a more useful methodology with which to evaluate gastroesophageal lesions than either EBC or GEB alone. The authors also found that LOHs at 1p36, 9p21, and 17p13 may play an important role in Barrett esophagus (BE), LOHs at 10q23, 17p13, and 17q12 in low-grade dysplasia (LGD), LOHs at 5q23 and 17q21 in high-grade dysplasia (HGD), and LOHs at 5q23 and 21q22 in adenocarcinoma.

CONCLUSIONS

Detection of LOHs targeting tumor suppressor genes can be useful in evaluating gastroesophageal lesions, studying oncogenesis of gastroesophageal adenocarcinoma, and, in combination with EBC and GEB, determining surveillance for BE and LGD and/or treatment for HGD and adenocarcinoma.

Genome-wide analysis of genetic alterations in Barrett's adenocarcinoma using single nucleotide polymorphism arrays

We performed genome-wide analysis of copy-number changes and loss of heterozygosity (LOH) in Barrett's esophageal adenocarcinoma by single nucleotide polymorphism (SNP) microarrays to identify associated genomic alterations. DNA from 27 esophageal adenocarcinomas and 14 matching normal tissues was subjected to SNP microarrays. The data were analyzed using dChipSNP software. Copy-number changes occurring in at least 25% of the cases and LOH occurring in at least 19% were regarded as relevant changes. As a validation, fluorescence in situ hybridization (FISH) of 8q24.21 (CMYC) and 8p23.1 (SOX7) was performed. Previously described genomic alterations in esophageal adenocarcinomas could be confirmed by SNP microarrays, such as amplification on 8q (CMYC, confirmed by FISH) and 20q13 or deletion/LOH on 3p (FHIT) and 9p (CDKN2A). Moreover, frequent gains were detected on 2p23.3, 7q11.22, 13q31.1, 14q32.31, 17q23.2 and 20q13.2 harboring several novel candidate genes. The highest copy numbers were seen on 8p23.1, the location of SOX7, which could be demonstrated to be involved in amplification by FISH. A nuclear overexpression of the transcription factor SOX7 could be detected by immunohistochemistry in two amplified tumors. Copy-number losses were seen on 18q21.32 and 20p11.21, harboring interesting candidate genes, such as CDH20 and CST4. Finally, a novel LOH region could be identified on 6p in at least 19% of the cases. In conclusion, SNP microarrays are a valuable tool to detect DNA copy-number changes and LOH at a high resolution. Using this technique, we identified several novel genes and DNA regions associated with esophageal adenocarcinoma.

The molecular biology of esophageal adenocarcinoma

BACKGROUND

Barrett's esophagus is an acquired metaplastic change that occurs in the distal esophagus secondary to chronic gastroesophageal reflux. This premalignant condition forms the most important risk factor for developing esophageal adenocarcinoma, which is an extremely aggressive tumor with a 5-year survival rate of less than 25%. Carcinomas that arise in the setting of Barrett's esophagus are thought to develop as part of the metaplasia-dysplasia-carcinoma sequence.

OBJECTIVE

To review the current knowledge on the genomic alterations involved in the development of Barrett's esophagus and its progression to dysplasia and/or cancer.

RESULTS

Several changes in gene structure, gene expression, and protein structure are associated with the progression of Barrett's esophagus to adenocarcinoma. Accumulation of these changes seems to be essential, rather than the exact sequence of these changes. Multiple molecular pathways are involved and interact with each other. Alterations in tumor suppressor genes, amongst which p53 and p16, are early events in the metaplasia-dysplasia-adenocarcinoma sequence, followed by loss of cell cycle checkpoints. Ongoing genomic instability leads to cumulative genetic errors and thereby the generation of multiple clones of transformed cells.

CONCLUSIONS

Within the multistep process of esophageal adenocarcinogenesis, to date no single molecular marker came forward able to predict who will and who will not develop cancer in the setting of Barrett's esophagus. Instead, panels of markers need to be developed in the future allowing to indicate disease progression. Identification of crucial molecular pathways involved in esophageal adenocarcinogenesis would ultimately improve therapy and facilitate development of new treatment strategies.

Epidermal growth factor receptor regulates aberrant expression of insulin-like growth factor-binding protein 3

Epidermal growth factor receptor (EGFR) is frequently overexpressed in esophageal carcinoma and its precursor lesions. To gain insights into how EGFR overexpression affects cellular functions in primary human esophageal cells, we performed gene expression profiling and identified insulin-like growth factor-binding protein (IGFBP)-3 as the most up-regulated gene. IGFBP-3 regulates cell proliferation through both insulin-like growth factor-dependent and independent mechanisms. We found that IGFBP-3 mRNA and protein expression was increased in EGFR-overexpressing primary and immortalized human esophageal cells. IGFBP-3 was also up-regulated in EGFR-overexpressing cells in organotypic culture and in EGFR transgenic mice. Furthermore, IGFBP-3 mRNA was overexpressed in 80% of primary esophageal squamous cell carcinomas and 60% of primary esophageal adenocarcinomas. Concomitant up-regulation of EGFR and IGFBP-3 was observed in 60% of primary esophageal squamous cell carcinomas. Immunohistochemistry revealed cytoplasmic localization of IGFBP-3 in the preponderance of preneoplastic and neoplastic esophageal lesions. IGFBP-3 was also overexpressed in esophageal cancer cell lines at both mRNA (60%) and protein (40%) levels. IGFBP-3 secreted by cancer cells was capable of binding to insulin-like growth factor I. Functionally, epidermal growth factor appeared to regulate IGFBP-3 expression in esophageal cancer cell lines. Finally, suppression of IGFBP-3 by small interfering RNA augmented cell proliferation, suggesting that IGFBP-3 may inhibit tumor cell proliferation as a negative feedback mechanism. In aggregate, we have identified for the first time that IGFBP-3 is an aberrantly regulated gene through the EGFR signaling pathway and it may modulate EGFR effects during carcinogenesis.

Peroxisome proliferator-activated receptor-gamma activated by ligands can inhibit human lung cancer cell growth through induction of apoptosis

To study the expression of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) in lung cancer cells, and to testify if the PPAR-gamma agonists can inhibit human lung cancer cell growth through induction of apoptosis, PPAR-gamma was detected in two lung cancer cell lines by RT-PCR and immunohistochemistry, the inhibition of human lung cancer cell growth was investigated by MTT and cell counts, and the apoptosis was assessed by TUNEL. The results showed that: (1) PPAR-gamma expressed on two lung cancer cell lines; (2) PPAR-gamma activated by ligands could inhibit human lung cancer cell growth remarkably; (3) PPAR-gamma agonists could induce apoptosis to inhibit lung cancer cell growth. It was concluded that PPAR-gamma expressed in lung cancer cell can be activated by ligands and can inhibit lung cancer cell growth through induction of apoptosis.

VHL down-regulation and differential localization as mechanisms in tumorigenesis

BACKGROUND

The von Hippel-Lindau (VHL) gene has been widely analyzed in many tumors. Early studies in animal tumors suggest that changes in VHL protein level and localization may be also important in tumorigenesis. In this study, we determined the role of VHL protein in human renal cell carcinomas.

METHODS

Seventy-five human renal cell carcinomas, predominantly of clear cell type (60 of 75), were examined for VHL protein by immunohistochemistry. The level and pattern of protein expression were then compared to VHL mutations and tumor characteristics.

RESULTS

An apparent decline of VHL level (positive in <50% of tumor cells) was observed in 49 (65%) tumors, a change more frequent than VHL mutations (28 of 75) (37%). In tumors, VHL was localized to the cytoplasm and/or the cell membrane. The occurrence of a predominantly membranous signal was significantly associated with missense mutations (9 of 14 tumors with missense mutations versus 14 of 61 tumors with no or nonmissense mutations, P = 0.0025) and tumor stage (23 of 60 tumors with stage TI versus 0 of 15 tumors with TII and TIII, P = 0.0034).

CONCLUSION

This study provides the first evidence of the role of VHL protein level and intracellular localization in tumorigenesis in humans.

Expression of tumor related genes NGX6, NAG-7, BRD7 in gastric and colorectal cancer

AIM: NGX6, NAG-7 and BRD7 genes are tumor related genes, which have been newly cloned by positional candidate cloning strategy. This study was designed to investigate the expression levels of NGX6, NAG-7 and BRD7 genes in human gastric and colorectal cancer tissues, and their corresponding normal tissues, and to investigate whether these genes play a role in the pathogenesis of gastric and colorectal cancers.

METHODS: Reverse transcription-polymerase chain reaction (RT-PCR), dot hybridization and Northern blot analysis were used to compare the expression levels of NGX6, NAG-7 and BRD7 genes in 34 gastric cancer tissues and 34 colorectal cancer tissues with their corresponding normal tissues of the same patients, respectively.

RESULTS: Among the 34 colorectal cancer specimens and the 34 gastric cancer specimens, the expression of NGX6 in 25 colorectal cancer tissues was absent or very weak (73.5%) by RT-PCR analysis. The down-regulation rate of NGX6 in colorectal cancer tissues was significantly higher than that in corresponding normal tissues (26.5%,9/34) (P < 0.005). Moreover, the down-regulation of NGX6 was significantly correlated with lymph node and/or distance metastases. Patients with lymph node and/or distance metastasis had much higher down-regulation rate of NGX6 than patients without metastases (93.8% vs 55.6%, P < 0.05). However no correlation was found between the expression of NGX6 and pathologic type of colorectal cancer in this study, and also the expression of NGX6 did not display any difference between gastric cancer and corresponding normal tissues (58.8% vs 70.6%, P > 0.25). Dot hybridization and Northern blot analysis confirmed the results of RT-PCR. Furthermore, NAG-7 and BRD7 mRNA was not up- or down-regulated in gastric and colorectal cancers compared with their corresponding normal tissues in our study.

CONCLUSION: The down-regulation of NGX6 may be closely associated with tumorigenesis and metastasis of colorectal carcinoma. However, it may not contribute to the development and progression of gastric carcinoma. In addition, the expression levels of NAG-7, and BRD7 did not alter in gastric and colorectal cancers. This seems to suggest that NAG-7 and BRD7 genes may not play a role in gastric and colorectal carcinogenesis.

Von Hippel-Lindau gene alterations in sporadic benign and malignant pheochromocytomas

The Von Hippel-Lindau (VHL) gene product has a wide spectrum of tissue-specific functions, and specific germline mutations are associated with clinical phenotypes in VHL disease. In particular, missense mutations are correlated with the susceptibility to pheochromocytomas. An association between VHL aberrations and prognosis has been suggested in renal clear cell carcinoma but has not been studied in pheochromocytomas. We studied the frequency and spectrum of VHL alterations in apparently sporadic pheochromocytomas in relation to the clinical behavior in 72 patients, including 48 patients with clinically benign and 24 patients with malignant pheochromocytomas. Single-strand conformation polymorphism (SSCP) analysis followed by DNA sequencing, loss of heterozygosity analysis of the VHL locus and immunohistochemistry for VHL protein expression were used to investigate somatic VHL gene alterations. In 2 patients, 1 with a malignant tumor, germline mutations were identified in the stop codon. Tumor-specific intragenic VHL mutations and accompanying loss of heterozygosity were identified in 2 (4.3%) of 47 sporadic benign pheochromocytomas compared to 4 (17.4%) of 23 malignant tumors (p = 0.064). Only one of these mutations has been previously described, in a renal clear cell carcinoma. Expression of the VHL protein was observed in all pheochromocytomas. No distinction in the nature of VHL alterations between benign and malignant pheochromocytomas and no correlation with histopathologic or clinical features was observed. We report novel VHL mutations in sporadic pheochromocytomas, which are slightly correlated with malignancy. VHL mutations may have some impact on the malignant transformation of pheochromocytomas.