Disruption of the Fanconi anemia/BRCA pathway in sporadic cancer

An increasing number of studies provide evidences linking disruption of Fanconi anemia/BRCA cascade with sporadic cancers. Given that this pathway plays essential roles in response to the DNA interstrand cross-links, these cancers are expected to be chemosensitive to cross-link based therapy. In the present mini-review we expand the spectrum of possibilities for FA/BRCA disruption and review some works describing functional upstream and downstream events linking disruption of the FA/BRCA pathway to sporadic cancer. This may involve but not limited to epigenetic silencing of the FA-core complex or BRCA1/2, mutations of one or several FA-BRCA genes or modification of encoded products. All this may serve as a platform for occurrence, development and treatment of sporadic cancers and therefore deserves to be in the focus of new research directions.     

BRCA/Fanconi anemia pathway implicates chemoresistance to gemcitabine in biliary tract cancer

The BRCA/Fanconi anemia (FA) pathway plays a key role in the repair of DNA double strand breaks. We focused on this pathway to clarify chemoresistance mechanisms in biliary tract cancer (BTC). We also investigated changes in the CD24⁺/44⁺ population that may be involved in chemoresistance, as this population likely includes cancer stem cells. We used three BTC cell lines to establish gemcitabine (GEM)‐resistant (GR) cells and evaluated the expression of BRCA/FA pathway components, chemoresistance, and the effect of BRCA/FA pathway inhibition on the CD24⁺/44⁺ population. FANCD2 and CD24 expression were evaluated in 108 resected BTC specimens. GR cells highly expressed the BRCA/FA components. The BRCA/FA pathway was upregulated by GEM and cisplatin (CDDP) exposure. Inhibition using siRNA and RAD51 inhibitor sensitized GR cells to GEM or CDDP. The CD24⁺/44⁺ population was increased in GR and parent BTC cells treated with GEM or CDDP and highly expressed BRCA/FA genes. FANCD2 was related to CD24 expression in resected BTC specimens. Inhibition of the BRCA/FA pathway under GEM reduced the CD24⁺/44⁺ population in MzChA1‐GR cells. Thus, high expression of the BRCA/FA pathway is one mechanism of chemoresistance against GEM and/or CDDP and is related to the CD24⁺/44⁺ population in BTC.     

The Fanconi anaemia/BRCA pathway

Fanconi anaemia (FA) is a rare genetic cancer-susceptibility syndrome that is characterized by congenital abnormalities, bone-marrow failure and cellular sensitivity to DNA crosslinking agents. Seven FA-associated genes have recently been cloned, and their products were found to interact with well-known DNA-damage-response proteins, including BRCA1, ATM and NBS1. The FA proteins could therefore be involved in the cell-cycle checkpoint and DNA-repair pathways. Recent studies implicate the FA proteins in the process of repairing chromosome defects that occur during homologous recombination, and disruption of the FA genes results in chromosome instability--a common feature of many human cancers.     

Promoter methylation of tumor suppressor genes in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma(ESCC) is a prevalent and fatal cancer in China and other Asian countries.Epigenetic silencing of key tumor suppressor genes(TSGs) is critical to ESCC initiation and progression.Recently,many novel TSGs silenced by promoter methylation have been identified in ESCC,and these genes further serve as potential tumor markers for high-risk group stratification,early detection,and prognosis prediction.This review summarizes recent discoveries on aberrant promoter methylation of TSGs in ESCC,providing better understanding of the role of disrupted epigenetic regulation in tumorigenesis and insight into diagnostic and prognostic biomarkers for this malignancy.     

Cytogenetic characteristics of oral squamous cell carcinomas in Fanconi anemia

Fanconi anemia (FA) is an autosomal recessive syndrome with a marked predisposition to malignancies, in particular acute myeloid leukemia and squamous cell carcinoma of the oral cavity. We examined oral squamous cell carcinoma tissue from two FA patients (FA-A and FA-C) by comparative genomic hybridization. Both tumors, which were negative for human papilloma as well as Epstein-Barr viral sequences, showed multiple alterations with a high proportion of whole-arm chromosomal gains and losses. This combination of features as well as the sites involved in chromosomal breakage are very similar to what is typically observed in non-FA oral tumors. These results suggest that the process leading to early occurrence of oral cancer in FA patients follows a similar pathway as in non-FA cancer patients, which would support a caretaker function for FA genes in the protection against oral carcinogenesis. Since FA patients are uniquely hypersensitive to DNA cross-linking agents, while oral cancer in the general population is thought to be environmentally induced, these results also suggest that environmental DNA cross-linkers may be causally involved in oral carcinogenesis.     

喉鳞状细胞癌RECK基因甲基化状态与放疗敏感性的关系

  目的  检测原发性喉鳞状细胞癌组织和正常喉黏膜组织的RECK基因启动子甲基化状态,分析患者术后进行放疗后RECK基因甲基化与放疗敏感性的关系。  方法  甲基化特异性PCR检测手术切除的喉鳞状细胞癌标本70例及正常喉黏膜标本15例的RECK基因甲基化情况,放疗6个周期,随访5年,分析RECK基因甲基化与放疗敏感性及治疗效果的关系。  结果  经6个周期放疗后,放疗敏感47例（67.14%）,放疗不敏感23例（32.86%）,放疗敏感组RECK基因甲基化水平低于放疗不敏感组（P＜0.05）;缓解组RECK基因甲基化水平低于未缓解组,RECK基因甲基化可使肿瘤未缓解的危险增高5.010倍（OR=5.010,95%CI:1.616~15.533）。  结论  RECK基因启动子区甲基化是人喉鳞状细胞癌的早期事件,与患者的放疗敏感性和治疗效果具有重要关系,对放疗敏感和放疗效果具有提示和预测作用。      

食管鳞癌DNA甲基化的研究进展

近年来研究结果表明,相关抑癌基因启动子区超甲基化导致的基因表达紊乱已成为食管癌发病机制研究的热点之一.众多研究表明DNA甲基化在食管癌的发生、侵袭和转移过程中发挥了积极的作用,外周血DNA甲基化谱可作为食管癌早期诊断、预后判断及随访的检测指标,有望将抑癌基因去甲基化作为食管癌的治疗靶点.     

Human papillomavirus DNA and p53 polymorphisms in squamous cell carcinomas from Fanconi anemia patients

Fanconi anemia is an autosomal recessive disorder characterized by congenital malformations, bone marrow failure, and the development of squamous cell carcinomas (SCCs) and other cancers. Recent clinicopathologic evidence has raised the possibility that an environmental factor such as human papillomavirus (HPV) may be involved in the pathogenesis of SCCs in Fanconi anemia patients. Given the high prevalence of p53 mutations in SCCs among the general population and the lack of p53 mutations in HPV-related carcinogenesis, we evaluated the role of HPV and p53 mutations and polymorphisms in SCC from Fanconi anemia patients. We used polymerase chain reaction (PCR) screening and real-time PCR to detect and quantify HPV DNA in DNA extracted from microdissected SCCs obtained from 24 Fanconi anemia patients (n = 25 SCCs; case subjects) and 50 age-, sex-, and tumor site-matched SCC patients without Fanconi anemia (n = 50 SCCs; control subjects). We PCR-amplified and sequenced exons 4-9 of the p53 gene from SCC DNA. We detected HPV DNA in 84% of the SCC specimens from the case subjects and in 36% of the SCC specimens from the control subjects (P<.001). The prevalence of p53 mutations in SCCs from the case subjects (0%, 0/25) was statistically significantly lower than that of SCCs from the control subjects (36%, 12/33; P<.001). A greater proportion of patients with Fanconi anemia and SCC were homozygous for Arg72, a p53 polymorphism that may be associated with increased risk for HPV-associated human malignancies, than an ethnically-matched cohort of Fanconi anemia patients without SCC (75% versus 51%; P =.05). These data suggest that Fanconi anemia is associated with increased susceptibility to HPV-induced carcinogenesis.     

Head and neck squamous cell carcinoma in 13 patients with Fanconi anemia after hematopoietic stem cell transplantation

BACKGROUND: Fanconi anemia (FA) is a chromosomal instability disorder with a very high risk of developing head and neck squamous cell carcinoma (HNSCC), most notably after hematopoietic stem cell transplantation (HSCT). METHODS: In the current study, the authors reported 13 cases of HNSCC in FA patients who underwent HSCT at the Saint Louis Hospital between 1976 and 2007. RESULTS: The median age of the patients at time of HSCT was 9.7 years. All patients received irradiation-based conditioning before HSCT and all developed extensive chronic graft versus host disease (GVHD). HNSCC was diagnosed at a median interval of 10 years after HSCT, mainly in numerous sites within the oral cavity (11 patients). Lymph node involvement was diagnosed in 4 patients. The TNM classification was: T1 in 6 patients, T2 in 2 patients, T3 in 2 patients, and T4 in 3 patients. Treatment was comprised of surgery in 10 patients, with clear surgical margins reported in 7 (including cervical lymph node dissection in 6 patients). Surgery was performed in addition to other treatments in only 2 patients (radiotherapy or cryotherapy). For the remaining 3 patients, treatment consisted in radiotherapy (2 patients) or chemotherapy (1 patient). Disease progression while receiving therapy was observed in 5 patients and 5 other patients developed disease recurrence between 3.5 and 23.7 months after treatment. Death occurred in 11 patients. At the time of last follow-up, only 2 patients were alive without any disease between 9 and 23 months after diagnosis. CONCLUSIONS: HNSCC developing in FA patients after HSCT is associated with a very poor prognosis. A systematic surveillance of the oral cavity is essential to permit early surgery, which to the authors' knowledge remains the only curative treatment for a minority of patients. It is very important to attempt to prevent this cancer by reducing chronic GVHD and using conditioning without irradiation.     

Mutated Fanconi anemia pathway in non-Fanconi anemia cancers

An extremely high cancer incidence and the hypersensitivity to DNA crosslinking agents associated with Fanconi Anemia (FA) have marked it to be a unique genetic model system to study human cancer etiology and treatment, which has emerged an intense area of investigation in cancer research. However, there is limited information about the relationship between the mutated FA pathway and the cancer development or/and treatment in patients without FA. Here we analyzed the mutation rates of the seventeen FA genes in 68 DNA sequence datasets. We found that the FA pathway is frequently mutated across a variety of human cancers, with a rate mostly in the range of 15 to 35 % in human lung, brain, bladder, ovarian, breast cancers, or others. Furthermore, we found a statistically significant correlation (p < 0.05) between the mutated FA pathway and the development of human bladder cancer that we only further analyzed. Together, our study demonstrates a previously unknown fact that the mutated FA pathway frequently occurs during the development of non-FA human cancers, holding profound implications directly in advancing our understanding of human tumorigenesis as well as tumor sensitivity/resistance to crosslinking drug-relevant chemotherapy.     

Targeting Fanconi anemia/BRCA2 pathway defects in cancer: the significance of preclinical pharmacogenomic models.

Defects in the Fanconi anemia (FA) pathway occur in subsets of diverse human cancers. The hypersensitivity of FA pathway-deficient cells to DNA interstrand cross-linking and possibly other agents renders these genes attractive targets for a genotype-based, individualized anticancer therapy. A prerequisite before clinical trials is the validation and quantification of this hypersensitivity in suitable preclinical pharmacogenomic models. In addition, the effects of combinational therapy need to be evaluated and novel agents sought. We discuss here the pitfalls and limitations in the interpretation of common FA models when applied to the validation of FA gene defects as therapeutic targets. In general, all preclinical models are prone to certain artifacts and, thus, promising results in a single or few models rarely translate into clinical success. Nevertheless, the extraordinary robustness of FA pathway-deficient cells to interstrand cross-linking agents, which are observable in virtually any model independent of species, cell type, or technique used to engineer the gene defect, in various in vitro and in vivo settings, renders these gene defects particularly attractive for targeted therapy. Clinical trials are now under way.     

DNA methylation in anal intraepithelial lesions and anal squamous cell carcinoma.

PURPOSE: Anal intraepithelial neoplasia is associated with human papillomavirus infection and may progress to invasive squamous cell carcinoma (SCC), which is increasing in immunocompromised patients. We hypothesize that anal intraepithelial neoplasia is associated with abnormal DNA methylation and that detection of these events may be used to improve screening programs. EXPERIMENTAL DESIGN: Seventy-six patients were identified who underwent anal cytology screening and subsequent biopsy at our institution between 1999 and 2004. The specimens from these patients included 184 anal biopsies [normal, n = 57; low-grade squamous intraepithelial lesion (LSIL), n = 74; high-grade squamous intraepithelial lesion (HSIL), n = 41; and invasive SCC, n = 12] and 37 residual liquid-based anal cytology specimens (normal, n = 11; LSIL, n = 12; HSIL, n = 14). The methylation status of the following genes was determined for each biopsy and cytology sample using real-time methylation-specific PCR: HIC1, RASSF1, RARB, CDKN2A, p14, TP73, APC, MLH1, MGMT, DAPK1, and IGSF4. RESULTS: Methylation-specific PCR analysis of biopsy samples revealed that DNA methylation was more common in SCC and HSIL than LSIL and normal mucosa. Specifically, methylation of IGSF4 and DAPK1 was prevalent in SCC (75% and 75% of cases, respectively) and HSIL (59% and 71%, respectively) but was absent in LSIL and normal biopsy samples. Methylation profiles of cytologic samples were similar to those found in the biopsy samples. CONCLUSIONS: Aberrant DNA methylation is a frequent event in anal HSIL and SCC. Methylation of IGSF4 and DAPK1 is specific for HSIL and SCC, and may serve as a useful molecular biomarker.     

Distant metastases in laryngeal squamous cell carcinoma

Distant metastases (DM) is the point of concern and seems to be on the rise with the improved control of the laryngeal cancer in the primary site and neck regions. Prognostic factors must be evaluated to improve the detection of DM at early stage of the disease. Therefore, we have analyzed our cases of laryngeal squamous cell carcinoma with DM to find out the risk factors in these patients. We analyzed the records of laryngeal squamous cell carcinoma patients with DM. The records were evaluated according to distant metastases site, TNM staging, the metastases at the neck, treatment and survival. The incidence of DM was 7.2% in our series. Lung is the most common site of DM in laryngeal squamous cell carcinoma. Staging grouping has been helpful in predicting DM, most of the cases were in stage III and IV (85%). Supraglottic lesions is the most common site in patients with DM. The recurrence in the locoregional site was observed in 47% of cases. The overall survival with DM is 28 months, without DM 22 months. The patients with DM in laryngeal squamous cell carcinoma were from the group with supraglottic lesions, stage 3, 4a and 4b. Stage grouping seems to be a better indicator of DM rather than T or N stage alone. The most common site of metastasis is the lung.     

Activation of the Fanconi anemia/BRCA pathway and recombination repair in the cellular response to solar ultraviolet light

Recombination repair plays an important role in the processing of DNA double-strand breaks (DSB) and DNA cross-links, and has been suggested to be mediated by the activation of the Fanconi anemia (FA)/BRCA pathway. Unlike DNA damage generated by ionizing radiation or DNA cross-linking, UV light-induced DNA damage is not commonly thought to require recombination for processing, as UV light does not directly induce DSBs or DNA cross-links. To elucidate the role of recombination repair in the cellular response to UV, we studied the FA/BRCA pathway in primary skin cells exposed to solar-simulated light. UV-induced monoubiquitination of the FANCD2 protein and formation of FANCD2 nuclear foci confirmed the activation of the pathway by UV light. This was only observed when cells were irradiated during S phase and was not caused by directly UV-induced DSBs. UV-exposed cells did not exhibit FANCD2 nuclear foci once they entered mitosis or when growth-arrested. In addition, UV-induced nuclear foci of the recombination proteins, RAD51 and BRCA1, colocalized with FANCD2 foci. We suggest that in response to UV light, when nucleotide excision repair failed to repair, or when translesional DNA synthesis failed to bypass UV-induced DNA photoproducts, the FA/BRCA pathway mediates the recombination repair of replication forks stalled at DNA photoproducts as a third line of defense.     

Inactivation of the Fanconi anemia/BRCA pathway in lung and oral cancers: implications for treatment and survival

Inactivation of the FANC-BRCA pathway via promoter methylation of the FANCF gene renders cells sensitive to DNA crosslinking agents, and has been identified in ovarian cancer cell lines and sporadic primary tumor tissues. We investigated epigenetic alterations in the FANC-BRCA pathway in head and neck squamous cell carcinomas (HNSCC) and non-small-cell lung cancers (NSCLC) using methylation-specific PCR. Promoter methylation of FANCF occurred in 15% (13/89) of HNSCCs and 14% (22/158) of NSCLCs. Methylation of BRCA1 occurred only in 6/158 NSCLC, and was limited to adenocarcinomas and large-cell carcinomas of the lung. No methylation of BRCA2 was detected. FANCF methylation was associated with a shorter duration of tobacco use (P=0.03) and a younger age of starting smoking (P=0.06) in NSCLC, and with a greater number of years of alcohol drinking (P=0.02) in HNSCC. In adenocarcinomas of the lung, FANCF promoter methylation was a significant predictor of poor survival with a hazard ratio of 3.1 (95% CI 1.2-7.9). This study demonstrates that inactivation of the FANC-BRCA pathway is relatively common in solid tumors and may be related to tobacco and alcohol exposure and survival of these patients.