Disregulation of p16MTS1/CDK4I protein and mRNA expression is associated with gene alterations in squamous-cell carcinoma of the larynx

Human papillomavirus in laryngeal and hypopharyngeal lymphoepithelial carcinoma

The involvement of human papillomavirus (HPV) in laryngeal and hypopharyngeal lymphoepithelial carcinoma was investigated in a series of ten cases (seven laryngeal and three hypopharyngeal), retrieved from the files of three tertiary hospitals in the 2000-2017 period, through polymerase chain reaction with SPF10 primers and INNO-LiPA HPV Genotyping Extra II (Innogenetics). Epstein-Barr virus (EBV) was tested in all cases with in situ hybridization INFORM EBER Probe (Ventana Medical Systems). p16 and p53 expression were immunohistochemically analyzed. Calculated annual incidence was 0.013/100,000, and prevalence was 0.2% of laryngeal and hypopharyngeal carcinomas. All cases were EBV negative. HPV was detected in five cases, three of which also overexpressed p16. HPV16 was detected in four cases, and HPV58 in one case. Five cases were HPV negative, only one of these five overexpressed p16. No recurrence was observed in nine cases during follow-up. The 5-year disease-specific-survival rate was 100%. Mean overall survival was 87 months. Lymphoepithelial carcinoma of the larynx and hypopharynx are not related to EBV. Simultaneous HPV+/p16+ is consistent with HPV causation in a fraction of laryngeal and hypopharyngeal lymphoepithelial carcinomas.

P16(INK⁴a) overexpression is associated with CDKN2A mutation and worse prognosis in HPV-negative laryngeal squamous cell carcinomas

We studied the expression of p16(INK4a) in a series of HPV-negative laryngeal squamous cell carcinomas and assessed its association with prognosis. Forty-five patients with laryngeal carcinoma were included in the study. Clinicopathological features and prognosis were reviewed. p16(INK4a) protein expression was analysed through immunohistochemistry. We analysed messenger RNA (mRNA) in 25 cases through quantitative reverse transcription polymerase chain reaction. HPV status was assessed by PCR using three different protocols based on MY09/11 and GP5/6 primers. Four out of 45 (9 %) cases overexpressed p16(INK4a) protein and showed a tendency to worse survival that was significant for stages I-III (log-rank p value = 0.001). Expression of p16(INK4a) mRNA was high in 12 out of 25 (48 %) cases using an arbitrary cut-off level. All tumours were HPV negative with all three detection methods. A CDKN2A mutation was found in eight cases. One case with a missense and one with a frameshift mutation showed p16(INK4a) protein expression by immunohistochemistry. Six out of seven (86 %) mutated but only 6 out of 18 (33 %) non-mutated cases presented p16(INK4a) mRNA overexpression (p = 0.03). Our findings suggest that p16(INK4a) overexpression, both at protein and mRNA levels, may reflect CDKN2A genetic alterations in HPV-negative laryngeal squamous cell carcinomas.

Mutational Status of CDKN2A and TP53 Genes in Laryngeal Squamous Cell Carcinoma

Laryngeal squamous cell carcinoma (LSCC) is the second most common tumour of the head and neck. It is characterized by frequent aberrations in two cell-cycle regulators--CDKN2A and TP53. However, LSCC has been often studied as a part of the group of head and neck cancers and not as an individual entity. In the current study we aimed to examine mutation status of CDKN2A and TP53 genes in 108 LSCC patients. DNA was extracted from fresh-frozen tumour tissues; exons 1-3 of CDKN2A and exons 5-8 of TP53 were screened for mutations by direct sequencing. Genetic aberrations in CDKN2A were found in 16 (14.2%) and those in TP53--in 56/108 (51.9%) tumours. Seven mutations (two insertions, three deletions, one missense and one silent) detected in CDKN2A were not described previously. Also, we found seven novel deletions and a novel indel in TP53. No significant associations with clinical features were found. However, TP53 mutations were predominantly observed in smokers with advanced stage tumours. Screening for genetic aberrations in a defined group of LSCC contributes to the knowledge about laryngeal carcinogenesis. Further investigations are required to confirm the observed trends in associations with clinical features.

Epigenetic dysregulation in laryngeal squamous cell carcinoma

Laryngeal carcinoma is a common head and neck cancer with poor prognosis. Patients with laryngeal carcinoma usually present late leading to the reduced treatment efficacy and high rate of recurrence. Despite the advance in the use of molecular markers for monitoring human cancers in the past decades, there are still no reliable markers for use to screen laryngeal carcinoma and follow the patients after treatment. Epigenetics emerged as an important field in understanding the biology of the human malignancies. Epigenetic alterations refer to the dysregulation of gene, which do not involve the alterations of the DNA sequence. Major epigenetic changes including methylation imbalance, histone modification, and small RNA dysregulation could play a role in the development of human malignancies. Global epigenetic change is now regarded as a molecular signature of cancer. The characteristics and behavior of a cancer could be predicted based on the specific epigenetic pattern. We here provide a review on the understanding of epigenetic dysregulation in laryngeal carcinoma. Further knowledge on the initiation and progression of laryngeal carcinoma at epigenetic level could promote the translation of the knowledge to clinical use.

Significance of P16INK4A hypermethylation gene in primary head/neck and colorectal tumors: it is a specific tissue event? Results of a 3-year GOIM (Gruppo Oncologico dell'Italia Meridionale) prospective study

BACKGROUND

Methylation of the p16 promoter is one of the most frequent mechanisms of gene inactivation; its incidence is extremely variable according to the type of tumor involved. Our purpose was to analyze the hypermethylation of the p16 promoter in laryngeal squamous cell carcinomas (LSCC), salivary gland (SG) tumors and in colorectal cancer (CRC), to detect any possible association with the clinicopathological features and to determine the prognostic significance of the p16 gene in the tumors analyzed.

PATIENTS AND METHODS

The hypermethylation of the p16 promoter was prospectively analyzed, by MSP, in a consecutive series of 64 locally advanced LSCC patients, in a consecutive series of 33 SG tumor patients and in a consecutive series of 66 sporadic CRC patients.

RESULTS

Hypermethylation was observed in 9% of the LSCC cases, in all cases of SG cancer and in 21% of the CRC cases. No significant association was observed between p16 hypermethylation and clinicopathological variables in all the tissue samples analyzed. Moreover at univariate analysis p16 mutations were not independently related at disease relapse and death in LSCC and CRC.

CONCLUSIONS

The results of this study suggest that the lack of p16 function could happen in advanced stage of SG tumors.

Association of CDK4 and CCND1 mRNA overexpression in laryngeal squamous cell carcinomas occurs without CDK4 amplification

CDK4 is involved in the control of G1-S phase transition as a part of the CCND1/CDK4 complexes. CCNDI and CDK4 gene alterations have been implicated in the development of different tumors. CCND1 has been associated with progression in laryngeal carcinomas. CDK4 protein overexpression was described associated to CCND 1 overexpression in these tumors. However, the mechanisms implicated were not known. We analyzed CDK4 gene alterations and mRNA expression in a series of carcinomas of the larynx, and the results were compared to CCND1 expression and clinicopathological characteristics of the patients. CDK4 mRNA was overexpressed in 42 out of 60 tumors (70%) associated with CCND1 mRNA overexpression because 15 out of 16 cases with high CCND1 levels showed simultaneous increased levels of CDK4 mRNA (p = 0.023) and 12 (87%) of the tumors overexpressing both genes were in stage 4. No CDK4 gene amplifications, rearrangements, or mutations were detected in any of the tumors, including 24 overexpressed cases. These findings confirm that CDK4 overexpression is a frequent phenomenon in laryngeal carcinomas, which occurs at the transcriptional level but is related neither to gene amplification nor to gene mutation, and suggest that cooperation with CCND1 may be involved in the progression of laryngeal tumors.

The prognostic relevance of p16 inactivation in head and neck cancer

The inactivation of the tumor suppressor gene p16 plays an important role in the development of malignant tumors. p16 loss can result from point mutations, loss of heterozygosity (LOH) or methylation of the promoter region. A total of 67 samples of tumor tissue from squamous cell carcinoma of the oral cavity, the pharynx and the larynx were analyzed for an inactivation of p16. The results of the molecular-biological investigations were correlated with the known clinical prognostic parameters after a follow-up period of approximately 3 years. Methylation of the promoter region and LOH were the main mechanisms of p16 inactivation. Point mutations presented as rare events. An inactivation of p16 did not have any statistical influence on tumor prognosis. Patients with a p16 gene inactivated by promoter methylation appeared to have a slightly lower tendency for local and regional recurrences. The inactivation of the tumor suppressor gene p16 plays a role in the carcinogenesis of head and neck cancer.

Inactivation of the cyclin-dependent kinase inhibitor 2A (CDKN2A ) gene in squamous cell carcinoma of the larynx

Defects in the system controlling the cell cycle can lead an increased proliferation of cancer cells. The aim of our study was to analyze the relationship between genetic changes leading to inactivation of the CDKN2A gene and subsequent alteration of protein expression in squamous cell cancer of the larynx (SCCL) in connection with the clinical and histopathological course of the disease. Analysis was carried out on DNA isolated from the blood and primary larynx cancer cells of 62 patients. To investigate loss of heterozygosity (LOH), PCR fragment analysis was applied. The size and quantity of fluorescent PCR products were evaluated in an automated sequencer. Specific chemical methylation with sodium bisulfite in a sequential PCR reaction (MSP) was applied to analyze promoter methylation. Cancer tissue sections served to determine the level of protein expression with immunohistochemical (IHC) staining and commercial antibodies. LOH at the CDKN2A locus was observed in 55.35% of the informative cases. Aberrant methylation was found in 37.5% and a decreased level of protein expression observed in 45% of all informative cases. Whenever P16 expression was decreased, LOH and promoter hypermethylation at CDKN2A were observed with a frequency of 73.33% and 80.95%, respectively (Fisher's test, P<0.005). Sixty-nine percent of G3 tumors had at least one genetic alteration at CDKN2A, compared with 40.9% of G1 cancers. The results indicate that CDKN2A inactivation played a significant role in the development of squamous cell carcinoma of the larynx.

Interruption of p16 gene expression in adult T-cell leukaemia/lymphoma: clinical correlation

We previously reported that p16 gene deletion is involved in the development and progression of adult T-cell leukaemia/lymphoma (ATLL). To further investigate the significance of this gene in ATLL, we examined its expression status in 63 patients. Samples were analysed at DNA, mRNA and protein levels using real-time polymerase chain reaction (PCR), reverse transcription (RT)-coupled real-time PCR and Western blot respectively. Twenty-four patients (38.1%) were p16 gene negative, and they showed significantly shorter survival than p16-gene-positive patients. The expression of p16 mRNA in p16-gene-positive patients varied greatly, and cells from some patients showed up to several hundredfold higher expression than normal lymphocytes. Surprisingly, among 17 patients examined for p16 protein expression, all four patients with unusually high mRNA lacked p16 protein expression, indicating that p16 protein production in these patients was interrupted at the translational level. Moreover, these patients showed significantly shorter survival than p16-protein-positive patients. These results indicate that the presence of p16 gene and p16 mRNA do not necessarily indicate the production of p16 protein in ATLL, and that loss of p16 protein function is involved in progression of ATLL.

Prognostic significance of p16INK4a alterations and 9p21 loss of heterozygosity in locally advanced laryngeal squamous cell carcinoma

The p16INK4a gene, localized within chromosome 9p21, has been identified as a cyclin-dependent kinase inhibitor and may negatively regulate the cell cycle acting as a tumor suppressor. Genetic alterations involving the 9p21 region are common in human cancers. A consecutive series of 64 untreated patients (median of follow up 53 months) undergoing surgical resection for locally advanced laryngeal squamous-cell carcinomas (LSCCs) has been studied prospectively. Our purpose was to investigate p16 alterations (9p21 allelic loss, hypermethylation and point mutations) and their possible association with clinico-pathological data and flow cytometric variables (DNA-ploidy and S-phase fraction (SPF)), and to determine the possible prognostic role of this gene in these tumors. PCR-based techniques were used for investigating 9p21 loss of heterozygosity (LOH) and methylation promoter status of the p16 gene. p16 mutations were detected by PCR-SSCP (single strand conformation polymorphism) and sequencing. 9p21 LOH was detected in 16/62 (26%) informative tumors, point mutations in 5% (3/64) and hypermethylation in 9% (6/64) of the cases. p16 alterations were significantly associated with high SPF and DNA-aneuploidy. By univariate analysis, poor histologic differentiation, stage IV, DNA-aneuploidy and p16 point mutations proved to be significantly related to quicker relapse, whereas these same factors, and in addition high SPF, 9p21 LOH and any p16 alterations were significantly related to shorter overall survival. By Cox proportional hazards analysis only histologic grade (G3) and p16 point mutations were independently related to both disease relapse and death. Our study has identified p16 point mutations as important biomolecular indicators in LSCCs.

Detailed gene expression analysis but not microsatellite marker analysis of 9p21 reveals differential defects in the INK4a gene locus in the majority of head and neck cancers

The INK4a gene locus on chromosome 9p21 encodes two proteins, p16(INK4a) and p14(ARF), which influence cell cycle control regulated by pRb and p53. The objective of this study was to use different methods for the analysis of the incidence of changes at the INK4a locus in head and neck cancer (HNSCC). Primary tumours were analysed for allelic imbalances (AI) with microsatellite markers for chromosome 9, by immunohistochemistry (IHC) and IHC with enhanced sensitivity by tyramide signal amplification (TSA-IHC), and by RT-PCR. No homozygous deletions at 9p21 were detected. AI at 9p21, which was found in approximately 60% of the tumours, completely failed to indicate the functional inactivation of the two INK4a gene products. Immunostaining of normal squamous epithelia revealed very low levels of p16(INK4a), whereas p14(ARF) was readily detectable. In 160 tumours, IHC suggested a loss of p16(INK4a) expression in 90%. However, by TSA-IHC, only 53.7% showed loss of p16(INK4a) expression, and this was consistent with the RT-PCR analyses. In 100 tumours analysed for both proteins, selective loss of p16(INK4a) occurred in 37%; loss of p14(ARF) was found in only 15%, and selective loss in only 4%; 11% of the tumours had lost both proteins. We conclude that only IHC with high sensitivity and the combined expression analysis of mRNAs and proteins is suitable for studying the role of INK4a in HNSCC. The INK4a gene expression defects are frequent but not universal and primarily affect p16(INK4a). Their clinical impact is still not clear.

INK4a/ARF locus alterations in human non-Hodgkin's lymphomas mainly occur in tumors with wild-type p53 gene

INK4a/ARF locus codes for two different proteins, p16(INK4a) and p14(ARF), involved in cell cycle regulation. p14(ARF) is considered an upstream regulator of p53 function. To determine the role of these genes in the pathogenesis of human non-Hodgkin's lymphomas we have analyzed exon 1beta, 1alpha, and 2 of the INK4a/ARF locus and p53 gene aberrations in 97 tumors previously characterized for p16(INK4a) alterations. p53 alterations were detected in four of 51 (8%) indolent lymphomas but in 15 of 46 (33%) aggressive tumors. Inactivation of p14(ARF) was always associated with p16(INK4a) alterations. Exon 1beta was concomitantly deleted with exon 1alpha and 2 in eight tumors. One additional lymphoblastic lymphoma showed deletion of exon 1alpha and 2 but retained exon 1beta. No mutations were detected in exon 1alpha and 1beta in any case. Two of the three mutations detected in exon 2 caused a nonsense mutation in the p16(INK4a) reading frame and a missense mutation in the ARF reading frame involving the nucleolar transport domain of the protein. The third mutation was a missense mutation in the p16(INK4a) reading frame, but it was outside the coding region of p14(ARF). Aggressive lymphomas with p14(ARF) inactivation and p53 wild type showed a significantly lower p53 protein expression than tumors with no alteration in any of these genes. In this series of tumors, inactivation of the INK4a/ARF locus mainly occurred in tumors with a wild-type p53 gene because only two lymphomas showed simultaneous aberrations in these genes. Tumors with concomitant alterations of p16(INK4a) and p14(ARF)/p53 genes seem to exhibit a worse clinical behavior than lymphomas with no alterations or isolated inactivation of any of these genes. These findings indicate that p14(ARF) genetic alterations occur in a subset of aggressive NHLs, but they are always associated with p16(INK4a) aberrations. Concomitant disruption of p16(INK4a) and p14(ARF)/p53 regulatory pathways may have a cooperative effect in the progression of these tumors.

Immunohistochemical p16INK4a analysis of archival tumors with deletion, hypermethylation, or mutation of the CDKN2/MTS1 gene. A comparison of four commercial antibodies

The MTS1/CDKN2/p16 gene encoding the p16INK4a tumor-suppressor protein is commonly inactivated by homozygous deletion or hypermethylation of the promoter in a wide range of human malignancies. In select tumor types, including pancreatic adenocarcinomas, intragenic mutations are found in a significant percentage of cases. The immunoreactivity of mutant p16 proteins has not been comprehensively studied. Moreover, the immunohistochemical properties of commercially available antibodies have not been described in detail. We studied 35 pancreatic adenocarcinomas with a molecularly defined p16 status (16 homozygous deletions, 3 hypermethylated cases, and 16 tumors with an intragenic mutation in one allele associated with loss of the second allele). In addition, we studied nine cell lines (three homozygous deletions, three hypermethylated lines, and three intragenic mutations). Paraffin sections of the tumors and cell blocks were reacted with four different anti-p16 antibodies: polyclonal and monoclonal (clone G175-405) antibodies from PharMingen, monoclonal antibody DCS-50 from Oncogene Science, and monoclonal antibody ZJ11 from Neo-Markers. Optimal staining conditions were established for each antibody. The pancreatic carcinomas with homozygous p16 deletions were largely devoid of nuclear staining (admixed nonneoplastic cells served as internal positive controls); only one adenocarcinoma each reacted with DCS-50 and the polyclonal antibody, and five were positive with ZJ11, suggesting that nonspecific nuclear staining can occur under certain conditions. Antibody DCS-50 produced nuclear staining in all three hypermethylated carcinomas, whereas G175-405 stained none of them. Three of the four antibodies produced nuclear immunoreactivity in 7 to 14 of the 16 carcinomas carrying p16 mutations; G175-405 showed only weak reactivity in one case. Cytoplasmic staining was present in all carcinomas and cell lines and with all antibodies and therefore cannot be considered specific; it was strongest with G175-405. Thus, we found antibody G175-405 to be the most specific, and monoclonals DCS-50 and ZJ11 the least specific for wild-type p16. However, the former tends to give stronger cytoplasmic background staining. For tumor types in which p16 mutations are uncommon, the PharMingen polyclonal antibody may be a suitable alternative.