Frequent loss of heterozygosity in two distinct regions, 8p23.1 and 8p22, in hepatocellular carcinoma

An integrative view on glucagon function and putative role in the progression of pancreatic neuroendocrine tumours (pNETs) and hepatocellular carcinomas (HCC)

Cancer metabolism research area evolved greatly, however, is still unknown the impact of systemic metabolism control and diet on cancer. It makes sense that systemic regulators of metabolism can act directly on cancer cells and activate signalling, prompting metabolic remodelling needed to sustain cancer cell survival, tumour growth and disease progression. In the present review, we describe the main glucagon functions in the control of glycaemia and of metabolic pathways overall. Furthermore, an integrative view on how glucagon and related signalling pathways can contribute for pancreatic neuroendocrine tumours (pNETs) and hepatocellular carcinomas (HCC) progression, since pancreas and liver are the major organs exposed to higher levels of glucagon, pancreas as a producer and liver as a scavenger. The main objective is to bring to discussion some glucagon-dependent mechanisms by presenting an integrative view on microenvironmental and systemic aspects in pNETs and HCC biology.

BRIT1 dysfunction confers synergistic inhibition of hepatocellular carcinoma by targeting poly (ADP-ribose) polymerases and PI3K

BRIT1 has emerged as a novel key player in homologous recombination (HR). It is located in 8p23, a locus frequently deleted in hepatocellular carcinoma (HCC). Previously, we found that BRIT1-deficiency triggered genomic instability and tumor formation in our mouse model. Here we aim to determine whether BRIT1 aberrations are implicated in HCC and, if so, whether they can be used for targeted therapy with PARP inhibitors and other agents. We analyzed HCC samples for BRIT1 alterations at DNA, RNA and protein levels. BRIT1 was found deleted and/or downregulated in ~30% of HCC samples; BRIT1 mutant K659fsX10 identified in HCC abolished DNA repair function. Notably, BRIT1 deletion was correlated with poor survival and high recurrence of HCC. To determine the role of BRIT1 deficiency in potentiating the drug response, we subsequently generated BRIT1-deficient HCC cells, determined their HR defects, and assessed their response to the PARPi olaparib and PI3K inhibitor in vitro and in mice. BRIT1-deficient HCC cells were HR defective and hypersensitive to olaparib alone or in combination with PI3K inhibitor BEZ235, both in vitro and in vivo. The cytotoxicity of olaparib alone or in combination with BEZ235 was largely alleviated by ectopic BRIT1. We also found that BEZ235 markedly enhanced the production of poly (ADP-ribose) and the level of double-strand breaks (DSB) and single-strand breaks (SSB) in BRIT1-deficient cells. In summary, our results identify BRIT1 deficiency as a potential driver for HCC development, and BRIT1 status is critical to sensitivity to treatment with olaparib and/or BEZ235. PI3K inhibition induces substantial DNA damage and makes cells more dependent on PARP activity in the context of BRIT1 deficiency, thus, BRIT1 depletion facilitates enhancing synthetic lethality of PARP inhibitors and PI3K inhibitors in HCC. This study provides a new mechanistic foundation for significantly expanding the application of PARPi in HCC therapy.

Loss of heterozygosity at D8S262: an early genetic event of hepatocarcinogenesis

BACKGROUND

Hepatocellular carcinoma (HCC) is a multi-factor, multi-step, multi-gene and complicated process resulting from the accumulation of sequential genetic and epigenetic alterations. An important change among them is from precancerous lesions to HCC. However, only few studies have been reported about the sequential genetic changes during hepatocarcinogenesis.

METHODS

We observed firstly molecular karyotypes of 10 matched HCC using Affymetrix single-nucleotide polymorphism (SNP) 6.0 arrays, and found chromosomal fragments with high incidence (more than 70%) of loss of heterozygosity (LOH). Then, we selected 28 microsatellite markers at some gene spanning these chromosomal fragments, and examined the frequency of LOH of 128 matched HCC and 43 matched precancerous lesions-dysplastic nodules (DN) by a PCR-based analysis. Finally, we investigated the expression of proteins encoded by these genes in HCC, DN and the surrounding hepatic tissues.

RESULTS

The result of Affymetrix SNP6.0 arrays demonstrated that more than 70% (7/10) cases had chromosomal fragment deletion on 4q13.3-35.1, 8p23.2-21.2, 16q11.2-24.3, and 17p13.3-12. Among 28 microsatellite markers selected, LOH frequencies at D8S262 for DN and HCC were found to be the highest, 51.2% and 72.7%, respectively. Immunohistochemically, the positive rate of its adjacent gene CSMD1 in HCC, DN, and the surrounding hepatic tissues were 27.3% (35/128), 75% (33/44), and 82% (105/128), respectively.

CONCLUSIONS

LOH at D8S262 may be associated with an early genetic event of hepatocarcinogenesis, and a predictor for the monitor and prevention of HCC.

VIRTUAL SLIDES

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1557074981159099 .

Genomic losses at 5q13.2 and 8p23.1 in dysplastic hepatocytes are common events in hepatitis B virus-related hepatocellular carcinoma

Chromosomal loci with genomic imbalances are frequently identified in hepatocellular carcinoma (HCC). Greater than two-thirds of hepatitis B virus (HBV)-related HCCs originate from liver cirrhosis following a duration of up to two decades. However, it is unclear whether these genomic imbalances occur and accumulate in dysplastic hepatocytes of the cirrhotic liver during the progression from regenerated nodules to preneoplastic lesions, including dysplastic nodules (DN). In the present study, high-grade DNs (HGDNs) of HBV-related liver cirrhosis were screened to identify loci with genomic imbalances, and the frequency of the identified loci in a group of HCCs was analyzed in order to determine whether there may be a genetic link between liver cirrhosis and HCC. Genomic DNA was extracted from six HGDNs of two cases of HBV-related liver cirrhosis and subjected to array comparative genomic hybridization (CGH) analysis with a NimbleGen 720K microarray. Loci with the most frequently observed genomic imbalances in DNs were further analyzed in 83 cases of HCC by differential polymerase chain reaction (PCR) and quantitative PCR. The array CGH analysis revealed that the majority of genomic imbalances in the HGDNs were genomic losses of small segments, with loss of heterozygosity (LOH) at 5q13.2 and 8p23.1 identified most frequently. Of the 83 HCC cases, 30 (36.1%) cases were identified with LOH at 5q13.2, where known tumor-associated genes are located, including general transcription factor IIH subunit 2 (GTF2H2), baculoviral IAP repeat-containing protein 1 (BIRC1) and occludin (OCLN). LOH frequency at 8p23.1 in HCC was 61.29% (D8S1130) and 68.4% (D8S503) respectively, similar to the results obtained in previous studies. In conclusion, the results of the present study provided evidence that genomic losses at 5q13.2 and 8p23.1 identified in dysplastic hepatocytes of the cirrhotic liver are common events in HCC. HCC-associated chromosomal abnormalities may occur and accumulate in preneoplastic lesions of liver cirrhosis.

A critical role for ZDHHC2 in metastasis and recurrence in human hepatocellular carcinoma

It has been demonstrated that loss of heterozygosity (LOH) was frequently observed on chromosomes 8p22-p23 in hepatocellular carcinoma (HCC) and was associated with metastasis and prognosis of HCC. However, putative genes functioning on this chromosomal region remain unknown. In this study, we evaluated LOH status of four genes on 8p22-p23 (MCPH1, TUSC3, KIAA1456, and ZDHHC2). LOH on ZDHHC2 was associated with early metastatic recurrence of HCC following liver transplantation and was correlated with tumor size and portal vein tumor thrombi. Furthermore, our results indicate that ZDHHC2 expression was frequently decreased in HCC. Overexpression of ZDHHC2 could inhibit proliferation, migration, and invasion of HCC cell line Bel-7402 in vitro. These results suggest an important role for ZDHHC2 as a tumor suppressor in metastasis and recurrence of HCC.

Primary microcephaly gene MCPH1 shows signatures of tumor suppressors and is regulated by miR-27a in oral squamous cell carcinoma

Mutations in the MCPH1 (microcephalin 1) gene, located at chromosome 8p23.1, result in two autosomal recessive disorders: primary microcephaly and premature chromosome condensation syndrome. MCPH1 has also been shown to be downregulated in breast, prostate and ovarian cancers, and mutated in 1/10 breast and 5/41 endometrial tumors, suggesting that it could also function as a tumor suppressor (TS) gene. To test the possibility of MCPH1 as a TS gene, we first performed LOH study in a panel of 81 matched normal oral tissues and oral squamous cell carcinoma (OSCC) samples, and observed that 14/71 (19.72%) informative samples showed LOH, a hallmark of TS genes. Three protein truncating mutations were identified in 1/15 OSCC samples and 2/5 cancer cell lines. MCPH1 was downregulated at both the transcript and protein levels in 21/41 (51.22%) and 19/25 (76%) OSCC samples respectively. A low level of MCPH1 promoter methylation was also observed in 4/40 (10%) tumor samples. We further observed that overexpression of MCPH1 decreased cellular proliferation, anchorage-independent growth in soft agar, cell invasion and tumor size in nude mice, indicating its tumor suppressive function. Using bioinformatic approaches and luciferase assay, we showed that the 3'-UTR of MCPH1 harbors two non-overlapping functional seed regions for miR-27a which negatively regulated its level. The expression level of miR-27a negatively correlated with the MCPH1 protein level in OSCC. Our study indicates for the first time that, in addition to its role in brain development, MCPH1 also functions as a tumor suppressor gene and is regulated by miR-27a.

Germinoma in the basal ganglia with an abnormal karyotype: case report and review of the literature

INTRODUCTION

Germ cell tumor of basal ganglia with abnormal constitutional karyotype has been rarely reported.

CASE REPORT

A 9-year-old boy presented with precocious puberty and right hemiparesis. Magnetic resonance imaging showed high intensity on T1-weighted, T2-weighted, and contrast-enhanced T1-weighted images in the left basal ganglia and ipsilateral cerebral hemiatrophy predominantly in the basal ganglia and midbrain. Germinoma in the left basal ganglia was confirmed by stereotactic biopsy and immunochemical examination. His constitutional karyotype was 46, XY, t (8; 19), (p23.1; p13.1), a novel chromosomal abnormality.

DISCUSSION

Intracranial germinoma, a potentially curable tumor, should be considered in children with nonspecific neurological symptoms, endocrinologic changes, and ipsilateral cerebral hemiatrophy on computed tomography or magnetic resonance. Investigation of chromosomal aberrations in those patients would clarify the tumorigenesis and lead to possibilities for novel disease-specific therapies.

Genetic and epigenetic silencing of SCARA5 may contribute to human hepatocellular carcinoma by activating FAK signaling

The epigenetic silencing of tumor suppressor genes is a crucial event during carcinogenesis and metastasis. Here, in a human genome-wide survey, we identified scavenger receptor class A, member 5 (SCARA5) as a candidate tumor suppressor gene located on chromosome 8p. We found that SCARA5 expression was frequently downregulated as a result of promoter hypermethylation and allelic imbalance and was associated with vascular invasion in human hepatocellular carcinoma (HCC). Furthermore, SCARA5 knockdown via RNAi markedly enhanced HCC cell growth in vitro, colony formation in soft agar, and invasiveness, tumorigenicity, and lung metastasis in vivo. By contrast, SCARA5 overexpression suppressed these malignant behaviors. Interestingly, SCARA5 was found to physically associate with focal adhesion kinase (FAK) and inhibit the tyrosine phosphorylation cascade of the FAK-Src-Cas signaling pathway. Conversely, silencing SCARA5 stimulated the signaling pathway via increased phosphorylation of certain tyrosine residues of FAK, Src, and p130Cas; it was also associated with activation of MMP9, a tumor metastasis-associated enzyme. Taken together, these data suggest that the plasma membrane protein SCARA5 can contribute to HCC tumorigenesis and metastasis via activation of the FAK signaling pathway.

Clonality and allelotype analyses of focal nodular hyperplasia compared with hepatocellular adenoma and carcinoma

AIM: To identify clonality and genetic alterations in focal nodular hyperplasia (FNH) and the nodules derived from it.

METHODS: Twelve FNH lesions were examined. Twelve hepatocellular adenomas (HCAs) and 22 hepatocellular carcinomas (HCCs) were used as references. Nodules of different types were identified and isolated from FNH by microdissection. An X-chromosome inactivation assay was employed to describe their clonality status. Loss of heterozygosity (LOH) was detected, using 57 markers, for genetic alterations.

RESULTS: Nodules of altered hepatocytes (NAH), the putative precursors of HCA and HCC, were found in all the FNH lesions. Polyclonality was revealed in 10 FNH lesions from female patients, and LOH was not detected in any of the six FNH lesions examined, the results apparently showing their polyclonal nature. In contrast, monoclonality was demonstrated in all the eight HCAs and in four of the HCCs from females, and allelic imbalances were found in the HCAs (9/9) and HCCs (15/18), with chromosomal arms 11p, 13q and 17p affected in the former, and 6q, 8p, 11p, 16q and 17p affected in the latter lesions in high frequencies (≥ 30%). Monoclonality was revealed in 21 (40%) of the 52 microdissected NAH, but was not found in any of the five ordinary nodules. LOH was found in all of the 13 NAH tested, being highly frequent at six loci on 8p, 11p, 13q and 17p.

CONCLUSION: FNH, as a whole, is polyclonal, but some of the NAH lesions derived from it are already neoplastic and harbor similar allelic imbalances as HCAs.

Deletion at chromosome arms 6q16-22 and 10q22.3-23.1 associated with initiation of prostate cancer

Loss of heterozygosity (LOH) at 6q16-22 and 10q22.3-23.1 is common chromosomal alteration in advanced prostate cancer and suggests that one or more tumor suppressor genes may lie within these chromosome arms. However, the genetic changes in early stage prostate cancer and premalignant lesions remain to be investigated. We used 11 informative microsatellite markers at 6q16-22 and 10q22.3-23.1 in Japanese patients to compare the frequency of LOH in 53 lesions of high-grade prostatic intraepithelial neoplasia (HGPIN), 38 cases (38 lesions) of incidental prostate cancer (IPC) and 107 cases (168 lesions) of clinical prostate cancer (CPC). The frequency of LOH at 6q16-22 with at least one marker was 38 and 49% in IPC and CPC cases, respectively. Similarly, allelic loss at 10q22.3-23.1 was present in 35 and 39% of IPC and CPC, respectively. High-frequency LOH was detected in both the clinically insignificant and significant prostate cancers at 6q16-22 and 10q22.3-23.1 (P>0.05). However, no allelic loss was detected in any markers at the same regions in HGPIN (0%), which is usually considered a premalignant lesion to prostate cancer. Deletions of both the chromosome regions, 6q16-22 and 10q22.3-23.1, are more likely important events in the initiation and/or promotion of prostate cancer.

Identification of minimal regions of deletion at 8p23.1-22 associated with metastasis of hepatocellular carcinoma

AIMS/BACKGROUND

Loss of heterozygosity (LOH) at 8p is the most frequent chromosomal alteration in tumorigenesis of human cancers. However, the genetic change in metastasis of hepatocellular carcinoma (HCC) still has to be investigated.

METHODS

We used 16 microsatellite markers informative in Japanese patients, selected from among 61 published microsatellite markers at 8p23.2-21 to compare the frequency of LOH in primary tumours (Tps) and metastatic tumours (Tms) in a PCR-based analysis. Sixty-three informative cancerous lesions (26 were Tps, 37 were Tms) from 23 cases of HCC were used.

RESULTS

The frequency of LOH at 8p23.2-21 with at least one marker was 19% in Tps and 68% in Tms. Allelic loss at 8p23.2-21 was significantly more frequent in Tms than in Tps (P=0.0003). More specifically, the frequency of LOH at D8S262, D8S1819, D8S503, D8S1130, D8S552, D8S1109, and D8S261 in Tms was 36-60% respectively.

CONCLUSIONS

In contrast, allelic loss at the same markers in Tp was only detected in 0-17% of the tumour respectively. The significant difference in the frequency of LOH at 8p between primary cancer and metastatic cancer in individual cases of HCC suggests LOH at 8p to be involved in the enhancement of tumour aggressiveness, especially during metastasis.