Inactivation of tumor suppressor genes p15(INK4b) and p16(INK4a) in primary cutaneous B cell lymphoma

Primary cutaneous B cell lymphomas represent a distinct group of lymphoproliferative disorders that can be distinguished from systemic lymphoma by their good response to local treatment and favorable prognosis. In systemic B cell lymphoma, inactivation of p15(INK4b) and p16(INK4a) is frequently observed and may be associated with a poor prognosis. There have been no comprehensive studies in primary cutaneous B cell lymphomas, however. Mechanisms of p15/p16 inactivation include loss of heterozygosity, homozygous deletion, promotor region hypermethylation, and point mutation. We analyzed DNA from 36 cases of primary cutaneous B cell lymphomas, four systemic B cell lymphomas, and six benign B cell lymphoproliferative infiltrates for abnormalities of p15 and p16 using microsatellite markers for 9p21, methylation specific polymerase chain reaction, and polymerase chain reaction/single stranded conformational polymorphism analysis with exon specific primers. Expression of both p15 and p16 protein was assessed by immunohistochemistry. Loss of heterozygosity at 9p21 was identified in 2 out of 36 primary cutaneous B cell lymphomas. Hypermethylation of p15 and p16 promotor regions was identified in 8 of 35 (23%) and 15 of 35 (43%) cases, respectively. In two cases p16 hypermethylation was identified in recurrent disease but not in the initial tumor. No point mutations were identified. In seven patients, however, a polymorphism was observed in exon 3 of the p16 gene. In primary cutaneous B cell lymphomas with allelic loss or promotor hypermethylation of either p15 or p16, loss of expression in tumor cells was identified in 5 of 8 and 9 of 10 cases, respectively. Our findings suggest that p15(INK4b) and p16(INK4a) biallelic gene abnormalities are common in primary cutaneous B cell lymphomas, most frequently as a result of promotor hypermethylation. The presence of abnormalities in recurrent disease in some cases suggests that inactivation of p15 and p16 may be involved in disease progression.     

p14ARF hypermethylation is common but INK4a-ARF locus or p53 mutations are rare in Merkel cell carcinoma

Although the exact molecular mechanisms of Merkel cell carcinoma (MCC) tumorigenesis are unknown, they likely involve complex genetic alterations and mutations similar to those seen in many other cancers. In this study, we obtained MCCs from 21 elderly patients (19 women, 2 men) and analyzed their DNA for mutation of exons of interest in several tumor-suppressor genes or oncogenes known to be frequently mutated in skin cancer: p53 (exons 4-8), Ras (exons 1 and 2), c-Kit (exon 11), and the INK4a-ARF locus (encoding p14 and p16) (exons 1 and 2). Direct sequence analysis revealed p53 mutations (that is, at codons 224, 234, and 294) in three tumors (14%) and p16INK4a mutations (that is, at codon 6) in one (5%). No mutations were detected in Ha-Ras, Ki-Ras, N-Ras, c-Kit, or p14ARF. On the other hand, methylation-specific PCR revealed methylation of p14ARF promoter DNA in eight of 19 analyzable tumor samples (42%) and p16INK4a promoter DNA in one of 19 analyzable tumor samples (5%). Together, these findings suggest that p14ARF silencing may be an important mechanism in MCC tumorigenesis, and thus a potential target for therapeutic intervention in this highly aggressive tumor type.     

p14ARF与皮肤恶性肿瘤的关系

p14ARF是近年来发现的抑癌基因之一,其通过p53、Rb及促分裂原活化蛋白激酶这3条相互独立的通道在细胞周期的调控中发挥作用。研究表明,p14ARF在包括皮肤恶性肿瘤在内的多种恶性肿瘤中的表达均有显著下调。p14ARF的功能失活的机制主要包括基因的甲基化、基因缺失和突变,其中以甲基化最为常见。目前科学家将p14ARF作为治疗恶性肿瘤的靶向之一进行了有益的探索,并取得了初步成果。     

p16和pRb在皮肤鳞癌中的表达及其意义

目的：探讨p16、pRb蛋白在皮肤鳞癌中的表达及他们的相互关系和意义。方法：应用免疫组织化学SP法检测40例原发性皮肤鳞癌绀织中p16、pRb的表达：结果：p16、pRb阳性表达率分别为37．5％和52．5％。两者在皮肤鳞癌中的表达呈显著负相关（P=0．011）。结论：在原发性皮肤鳞癌中存在p16和pRb的异常表达现象，两者的表达相互抑制，呈显著负相关。     

Human papillomavirus-associated increase in p16INK4A expression in penile lichen sclerosus and squamous cell carcinoma.

BACKGROUND: Human papillomaviruses (HPVs) are sexually transmitted human carcinogens that may play a role in the oncogenesis of penile cancer. OBJECTIVES: To investigate the role of HPV infection and expression of the tumour suppressor protein p16INK4A in the pathogenesis of penile cancer. METHODS: By means of polymerase chain reaction amplification and reverse hybridization line probe assay to detect HPV infection, and immunohistochemical staining for p16INK4A and Ki67, we analysed 26 penile squamous cell carcinomas (SCCs) and 20 independent penile lichen sclerosus (LS) lesions from 46 patients. RESULTS: HPV DNA was found in 54% of penile SCCs and 33% of penile LS cases in single and multiple infections. High-risk HPV 16 was the predominant HPV type detected. No relationship between Ki67 expression and HPV infection was observed. Strong immunostaining for p16INK4A correlated with HPV 16/18 infection in both penile LS and penile SCC. In our penile SCC series the cancer margins were also associated with penile LS in 13 of 26 lesions, and HPV was detected in seven of the 13 SCC cases associated with LS and in six of the 11 SCC lesions not involving LS. CONCLUSIONS: Our study shows a high prevalence of HPV 16 and p16INK4A expression in penile lesions, consistent with an active role for HPV in interfering with the retinoblastoma pathway. High-risk HPV infection could be involved in the tumorigenic process in 50% of penile cancers, and the use of prophylactic HPV vaccines has the potential to prevent these cancers.     

p16INK4a与HPV感染相关疾病

p16是抑制CDK4和6的肿瘤抑制蛋白。高危型HPV中的致癌基因E7可使p16^INK4a失去pRb的反馈性抑制而过度表达且功能异常。低危型HPV感染相关的尖锐湿疣中p16^INK4a免疫活性表现为离散、点状分布的阳性。中高危HPV感染相关的鲍恩样丘疹病中p16^INK4a免疫活性表现为弥漫强阳性。p16^INK4a较HPV型别能更客观地推测尖锐湿疣、鲍恩样丘疹病恶变的可能。     

p63 is a useful marker for cutaneous spindle cell squamous cell carcinoma

BACKGROUND: Cutaneous spindle cell squamous cell carcinoma (SCSCC) is a rare variant of SCC. This lesion is sometimes difficult to diagnose based purely on morphologic features. p63 is a member of the p53 gene family that can be identified in epithelial malignancies. METHODS: Thirteen cases of spindle SCC were stained with p63, CK34betaE12, MNF116, vimentin, and S100. Control cases included desmoplastic melanoma (eight cases), atypical fibroxanthoma (AFX) (10 cases), dermatofibrosarcoma protuberans (eight cases), and cutaneous leiomyosarcoma (LMS) (four cases). RESULTS: p63 was expressed diffusely in the nuclei of 100% (13/13) of SCSCCs. Of controls, p63 showed focal labeling of two LMS and two AFX. MNF116 and CK34betaE12 were positive in 13/13 SCSCCs. Of controls, one LMS was focally positive for MNF116. All SCSCCs and all control cases were positive for vimentin. CONCLUSIONS: In the given differential diagnosis, p63 appears relatively specific to SCSCC and adds a useful nuclear marker to the available repertoire. The findings also suggest that cytokeratins MNF116 and CK34betaE12 may be more useful than standard cytokeratins in labeling SCSCC.     

皮肤鳞状细胞癌的研究进展

皮肤鳞状细胞癌(CSCC)是世界范围内最常见的非黑色素瘤皮肤癌之一。研究显示,近年来CSCC的发病率呈不断增高的趋势,其临床表现多样,具有侵袭性,可通过淋巴、血液途径进行转移,晚期患者具有较高的复发率和致死率,对生命造成极大的威胁。本文结合近几年国内外有关CSCC的研究进展进行综述,以期对CSCC的早期诊断、治疗选择和预防提供帮助。     

E-钙黏蛋白与皮肤鳞状细胞癌

E-钙黏着蛋白是介导上皮细胞间粘连的最重要的一种钙依赖性的细胞黏附分子.近年来研究发现E-钙黏着蛋白异常表达与多种上皮恶性肿瘤的分化、浸润生长、转移和预后有着密切的关系.研究E-钙黏着蛋白的结构功能、在肿瘤侵袭转移中的作用机制、与皮肤鳞状细胞癌的相关性及临床意义,以期对皮肤鳞状细胞癌的早期诊断、治疗选择和预后预测提供一定依据.     

p16INK4a expression in actinic keratosis and Bowen's disease

BACKGROUND: Progression of cutaneous squamous neoplasms from actinic keratosis (AK) to Bowen's disease (BD; squamous cell carcinoma in situ) has important implications for clinical management and treatment, thus requiring accurate diagnosis. p16INK4a is a cell cycle regulatory tumour suppressor protein that negatively regulates D-type cyclins in the G1 cell cycle phase via intimate interplay with the retinoblastoma gene. Expression of a paraffin-reactive p16INK4a marker has recently been shown to increase in cervical squamous neoplasms as lesions progress from low-grade dysplasia to squamous cell carcinoma in situ. p16INK4a expression in the progression of squamous cutaneous neoplasia, however, has not been evaluated. OBJECTIVES: To evaluate p16INK4a expression in the progression of squamous cutaneous neoplasia. METHODS: Biopsies of 203 squamous cutaneous neoplasms with unequivocal features of AK (n = 87) and BD (n = 116) as well as a benign squamous control group (verruca vulgaris: n = 10; seborrhoeic keratosis: n = 11; scar tissue: n = 8) obtained between January and December 2001 at Henry Ford Hospital (Detroit, MI, U.S.A.) were immunostained for p16INK4a (Dako; clone E6H4; dilution 1 : 50) using large core (1.5 mm) tissue microarray analysis. Nuclear/cytoplasmic immunoreactivity in > 10% of neoplastic cells was considered positive. RESULTS: Of 203 cases, 166 (81.8%) were interpretable (AK 59; BD 107). Mean patient age was 71.0 years (range 33-93); 57% were male. Sites of involvement were: head and extremities 75.9%, trunk/buttocks 21.7%, genital region 2.4%. p16INK4a immunostaining was positive in 90 of 107 (84.1%) BD cases, four of 59 (6.8%) AK cases and none of 29 benign squamous controls. The sensitivity and specificity of p16INK4a for a diagnosis of BD (vs. benign squamous controls/AK) was 84.1% and 95.5%, respectively (P < 0.0001, Fisher's exact test, two-sided). CONCLUSIONS: p16INK4a is a sensitive and specific marker for distinguishing BD from AK/benign squamous cutaneous lesions and may be helpful as an adjunct to histomorphology in the diagnosis and appropriate clinical management of these lesions.     

Overexpression of RNA helicase p68 protein in cutaneous squamous cell carcinoma

Background. RNA helicase p68 is a prototypic DEAD‐box RNA helicase. Recent studies indicate that p68 plays important role in cancer development and progression. However, the role of p68 protein expression in cutaneous squamous cell carcinoma (SCC) remains unknown. Aim. To elucidate the expression of p68 protein in cutaneous SCC. Methods. The level of p68 protein was examined by double immunofluorescent staining in 24 samples of human cutaneous SCC tissue specimens and their adjacent tissues and in 6 normal foreskin samples to compare the expression of p68 with that of Ki‐67. Results. Overexpression of p68 protein was seen in all 24 SCC cases (100%), whereas very low expression of p68 was detected in normal foreskin. Moreover, p68 protein expression was higher in cases of cutaneous SCC with metastasis than in cases without metastasis. Additionally, p68 had a similar expression pattern to that of Ki‐67. Conclusion. The high frequency of p68 expression in cutaneous SCC indicates that p68 might be involved in the development and progression of cutaneous SCC.     

Deregulation of the tumour suppressor genes p14ARF, p15INK4b, p16INK4a and p53 in basal cell carcinoma

Background  Basal cell carcinoma (BCC) is a locally aggressive slowly growing tumour that rarely metastasizes and is mostly seen in older members of the population.
Objectives  To determine the involvement of the tumour suppressor genes p14^ARF, p15^INK4b, p16^INK4a and p53 in BCC.
Methods  We investigated the integrity of the CDKN2A locus in 15 BCC samples by analysing the presence of allelic imbalance/loss of heterozygosity (LOH). Moreover, we studied the mRNA expression levels of the tumour suppressor genes p14^ARF, p15^INK4b, p16^INK4a and p53 in the BCC samples and compared them with mRNA levels in the corresponding normal tissue. The presence of mutations was examined by sequencing for exons 1a and 2 of p16^INK4a.
Results  We found LOH in one BCC sample for the marker D9S1748. A polymorphism (G442A) of exon 2 was detected in three cases. p14^ARF, p15^INK4b and p53 presented high expression levels, whereas p16^INK4a exhibited low mRNA levels compared with the corresponding normal tissue. Significant correlations were detected among the genes studied.
Conclusions  Our results demonstrate a different expression profile between p16^INK4a and p14^ARF, p15^INK4b and p53 in BCC. Moreover, we found a low percentage of LOH and of a polymorphic sequence variant (Ala148Thr) for the CDKN2A locus.     

erbB4和PTEN在皮肤鳞状细胞癌组织中的表达

目的 观察并探讨erbB4和PTEN在皮肤鳞状细胞癌（鳞癌）组织中的蛋白表达及其临床意义。方法 采用免疫组化Elivision法,检测52例皮肤鳞癌（其中11例伴有淋巴结转移,41例无转移）、10例正常人皮肤标本中erbB4和PTEN蛋白表达。结果 皮肤鳞癌组中39例erbB4蛋白呈阳性表达,阳性率为75%;对照组中仅1例阳性表达,两组阳性率比较,χ2 = 12.77,P < 0.01;皮肤鳞癌患者中在有淋巴结转移组erbB4蛋白阳性表达率（100%）明显高于无淋巴结转移组（68.29%）,两组阳性率比较,P < 0.05。PTEN蛋白在皮肤鳞癌组中25例阳性表达,阳性率为48.08%,对照组10例均为阳性表达,两组阳性率比较,χ2 = 9.20,P < 0.01;在鳞癌高分化组及中低分化组中的阳性率分别为78.57%、36.84%,两组差异有统计学意义（P < 0.05）;有淋巴结转移组PTEN阳性率（9.09%）明显低于无转移组（58.54%）（P < 0.01）。皮肤鳞癌erbB4蛋白与PTEN蛋白表达呈负相关（r = -0.42,P < 0.01）。结论 erbB4与PTEN可能参与了皮肤鳞癌的发生、恶性进展及转移。     

High frequency of loss of heterozygosity on chromosome region 9p21-p22 but lack of p16INK4a/p19ARF mutations in greek patients with basal cell carcinoma of the skin

Basal cell carcinoma of the skin is the most common neoplasia in humans. Previous studies have shown the existence of allelic imbalance (loss of heterozygosity and microsatellite instability) in BCC on several human chromosomes. Chromosome region 9p21-p22 harbors the CDKN2a/p16INK4a, p19ARF, and p15INK4b tumor suppressor genes. To determine the contribution of these genes to the development of basal cell carcinomas we looked for evidence of allelic imbalance in 67 sporadic basal cell carcinoma specimens from Greek patients and screened 28 of them presenting loss of heterozygosity at 9p21-p22 for germline mutations in p16INK4a and p19ARF genes. Chromosome regions 17q21 and 17p13 were also screened for allelic imbalance in all the 67 basal cell carcinoma specimens. Overall, 69% (46 of 67) of the specimens displayed loss of heterozygosity in at least one microsatellite marker, whereas only six of the 67 (9%) exhibited microsatellite instability. For the 9p21-p22 locus the overall frequency of loss of heterozygosity reached 55% (37 of 67) and is the highest reported. The overall frequency of loss of heterozygosity for the 17q21 locus is 34% (22 of 64) and for the 17p13 locus is 11% (seven of 65). Two of the 28 loss of heterozygosity positive cases were heterozygous for a previously described polymorphism, Ala148Thr, in exon 2 of the CDKN2a gene. This is the first demonstration of polymorphism in the CDKN2a gene in human basal cell carcinomas. No sequence variation in exon 1beta of the p19ARF gene was found. Our results provide evidence of a significantly high occurrence of loss of heterozygosity for the 9p21-p22 locus; however, lack of p16INK4a/p19ARF mutation suggests that these genes seem not to be implicated by mutational inactivation in the development of basal cell carcinoma. Other(s), yet unidentified, tumor suppressor gene(s) located in this locus may be related to this specific type of skin cancer.