Microsatellite instability is a late event in the carcinogenesis of uterine cervical cancer

Assessment of the frequency of genetic alterations (LOH/MSI) in patients with intraepithelial cervical lesions with HPV infection: a pilot study

In the present study, we analyzed (1) the type of HPV infection and (2) the frequency of loss of heterozygosity and microsatellite imbalance (LOH/MSI) in normal cytology and cervical intraepithelial neoplasia (CIN1-3). The cytological material included: low-grade squamous intraepithelial lesions (CIN1, n = 11), high-grade lesions (CIN2 and CIN3, n = 13), and cytologically normal cells from non-neoplastic cervical samples (n = 8). HPV genotyping was done using RealLine HPV 16/18 kit. We used 20 microsatellite markers from: 1p31.2, 3p14.3, 3p21.3, 3p22.2, 3p24.2, 3p25.3, 7q32.2, 9p21.3, 11p15.5, 12q23.2, and 16q22.1. LOH/MSI was correlated with clinicopathological parameters. The presence of HPV DNA was revealed in 78.13 % samples, including normal cytology. LOH/MSI was the most frequent for: 3p25.3 (39 %), 3p22.2 (20.83 %), 3p24.2 (20 %), and 3p14.3 (16.67 %). It was demonstrated that D3S1234 (FHIT; 3p14.3), D3S1611 (MLH1; 3p22.2), D3S1583 (RARB; 3p24.2), D3S1317 and D3S3611 (VHL; 3p25.3) could differentiate patients with CIN2/CIN3 versus CIN1, showing significantly higher frequency in CIN2/CIN3. LOH/MSI frequency for other than 3p markers was lower, 10-22.2 %. The simultaneous occurrence of LOH/MSI for several markers (OFAL) was higher in CIN2/CIN3. Significant differences in OFAL were found between samples with versus without HPV infection. In HPV-positive patients, significant differences in OFAL were found between normal cytology, CIN1 and CIN2/CIN3. HPV infection influences the increase in LOH/MSI frequency, especially in tumor suppressor gene loci. Several studied microsatellite markers seem to be useful for CIN grading. Hopefully, the obtained results, if confirmed on larger patient cohort, would allow creating a panel of markers supporting clinical diagnosis in patients with HPV infection.

Prevalence of micronuclei in exfoliated uterine cervical cells from patients with risk factors for cervical cancer

CONTEXT AND OBJECTIVE

Pap smears are the most common and inexpensive screening method for cervical cancer. We analyzed micronucleus prevalence in exfoliated cervical mucosa cells, to investigate associations between increased numbers of micronuclei and risk factors for cervical cancer.

DESIGN AND SETTING

Analytical cross-sectional study, at Instituto de Pesquisa em Oncologia (IPON).

METHODS

Exfoliated cervical cells were obtained from 101 patients between September 2004 and November 2005. Patients' ages, habits (passive or active smoking, alcoholism and numbers of sexual partners), age at first sexual intercourse, contraceptive methods used, histories of sexually transmitted diseases, use of hormone replacement therapy, numbers of pregnancies and abortions, inflammatory cytology and cervical intraepithelial neoplasia (CIN) were obtained. Cells were collected using Ayre spatulas, transferred to vials containing 0.9% saline solution for micronucleus tests and analyzed at 1000x magnification. The number of micronuclei in 1,000 epithelial cells per patient sample was counted.

RESULTS

Comparisons between groups with active (7.9 +/- 7.8) and passive (7.2 +/- 10.6) smoking versus no smoking (3.7 +/- 5.1); with/without alcoholism (7.8 +/- 1.4 and 6.9 +/- 10.1); with/without inflammatory cytology (10.7 +/- 10.5 and 1.3 +/- 1.7); and with CIN I, II and III and no CIN (respectively 4.3 +/- 4.3, 10.6 +/- 5.3, 22.7 +/- 11.9 and 1.3 +/- 1.4) found elevated micronucleus prevalence (P < 0.05).

CONCLUSIONS

We concluded that the prevalence of micronuclei in exfoliated uterine cervical cells was greater in patients with one or more risk factors for uterine cervical cancer than in patients without risk factors.

Loss of MSH2 protein expression is a risk factor in early stage cervical cancer

BACKGROUND

Loss of mismatch repair (MMR) gene expression has been associated with fewer metastases and improved prognosis in various tumour types.

AIMS

To evaluate the predictive and prognostic significance of loss of MMR protein MSH2 in early stage cervical cancer.

METHODS

Specimens from 218 consecutive patients with early stage, surgically treated cervical cancer were analysed. Median age was 42 years (interquartile range 35-53). International Federation of Gynecology and Obstetrics (FIGO) stages were IB1 (57%), IB2 (25%) and IIA (18%). Histology was 70% squamous cell, 6% adenosquamous and 24% adenocarcinoma. Pelvic lymph node metastasis was present in 66 (30%) patients. Median follow-up was 5.2 years (interquartile range 2.5-7.9). Tissue microarrays (TMAs) were constructed containing three cores of paraffin-embedded tumour per case. MSH2 expression was assessed by immunohistochemistry on TMAs and full sections.

RESULTS

In TMAs MSH2 expression could be analysed in 184/218 (84%) tumours. Loss of MSH2 was observed in 58/184 (32%) tumours, with a moderately strong concordance between TMAs and full sections (kappa = 0.47). In tumours with loss of MSH2, pelvic lymph node metastasis and cancer invasion beyond 10 mm were more frequent (48% vs 25%, and 59% vs 37%, respectively). However, loss of MSH2 expression was not related to recurrence or survival.

CONCLUSION

TMAs are powerful tools for high throughput screening of biological markers for prognostic value in cervical cancer. Absence of MSH2 expression is associated with a high-risk profile in early stage cervical cancer, but does not predict lymph node status with sufficient accuracy to be used in the clinic.

X chromosomal and autosomal loss of heterozygosity and microsatellite instability in human cervical carcinoma

The study analyzes tumor material and normal tissue from 27 patients with pure squamous cell carcinoma of the uterine cervix for loss of heterozygosity (LOH) and microsatellite instability (MSI) on 14 autosomal and 11 X chromosomal loci. Overall, 4-40% of the informative cases showed LOH at autosomal regions with the highest frequency at 3p (21-40%) and a marked frequency at 2q35-q37.1 (12.5%) and 17p13.3 (10%), representing regions with putative tumor suppressor gene (TSG) function. The frequency of X chromosomal LOH ranged from 4% to 20%, with a maximum at Xq28 (20%) and Xq11.2-q12 (17%), again indicating alterations in TSG. A 12% LOH was seen at Xq21.33-q22.3, a region encoding a protein with a regulatory function in the cell cycle via cyclin-dependent kinases. MSI was detected in autosomal regions in up to 7% in regions linked to the X chromosome in up to 11%, probably indicating alterations of mismatch repair mechanisms. Our results and those obtained from the literature suggest that autosomal LOH and MSI in carcinomas of the cervix uteri are predominantly found at regions with putative TSG function. Beside TSG alterations, X chromosomal LOH is probably more strongly connected to disturbances in cell cycle regulation.

Combined array-comparative genomic hybridization and single-nucleotide polymorphism-loss of heterozygosity analysis reveals complex genetic alterations in cervical cancer

Background

Cervical carcinoma develops as a result of multiple genetic alterations. Different studies investigated genomic alterations in cervical cancer mainly by means of metaphase comparative genomic hybridization (mCGH) and microsatellite marker analysis for the detection of loss of heterozygosity (LOH). Currently, high throughput methods such as array comparative genomic hybridization (array CGH), single nucleotide polymorphism array (SNP array) and gene expression arrays are available to study genome-wide alterations. Integration of these 3 platforms allows detection of genomic alterations at high resolution and investigation of an association between copy number changes and expression.

Results

Genome-wide copy number and genotype analysis of 10 cervical cancer cell lines by array CGH and SNP array showed highly complex large-scale alterations. A comparison between array CGH and SNP array revealed that the overall concordance in detection of the same areas with copy number alterations (CNA) was above 90%. The use of SNP arrays demonstrated that about 75% of LOH events would not have been found by methods which screen for copy number changes, such as array CGH, since these were LOH events without CNA. Regions frequently targeted by CNA, as determined by array CGH, such as amplification of 5p and 20q, and loss of 8p were confirmed by fluorescent in situ hybridization (FISH). Genome-wide, we did not find a correlation between copy-number and gene expression. At chromosome arm 5p however, 22% of the genes were significantly upregulated in cell lines with amplifications as compared to cell lines without amplifications, as measured by gene expression arrays. For 3 genes, SKP2, ANKH and TRIO, expression differences were confirmed by quantitative real-time PCR (qRT-PCR).

Conclusion

This study showed that copy number data retrieved from either array CGH or SNP array are comparable and that the integration of genome-wide LOH, copy number and gene expression is useful for the identification of gene specific targets that could be relevant for the development and progression in cervical cancer.

Laterally spreading type of colorectal adenoma exhibits a unique methylation phenotype and K-ras mutations

BACKGROUND & AIMS

Laterally spreading tumors (LST), characterized by superficial extension along the colonic lumen, have recently been detected by colonoscopy. However, genetic and epigenetic characteristics of these tumors were scarcely reported.

METHODS

A total of 205 sporadic colorectal adenoma tissues (157 protruded-type, 23 granular-type LST (G-LST), 12 flat-type LST (F-LST), and 13 flat-type smaller than 1 cm) were collected. CpG island methylator phenotype (CIMP) was determined by examination of methylation status at p16, methylated in tumor (MINT) 1, 2, 12, and 31 loci. K-ras codon 12 and 13 point mutations were also examined. The relationship between macroscopic appearance and CIMP status or K-ras mutations was analyzed.

RESULTS

Among adenomas larger than 1 cm, CpG island methylation involving 2 or more loci (CIMP-high) was more likely to be observed in G-LST (14/23, 61%) than in protruded-type adenomas (18/73, 25%) (P = .002). The prevalence of K-ras mutations in G-LST (18/23, 78%) was significantly higher than that in protruded-type adenomas (18/73, 25%) (P < .0001). Moreover, the prevalence of CIMP-high and K-ras mutations in G-LST located in the proximal colon was much higher (11/13, 85%; and 12/13, 92%, respectively). In contrast, F-LST exhibited low prevalence of CIMP-high (1/12, 8%) and K-ras mutations (2/12, 16%).

CONCLUSIONS

High prevalence of CIMP-high and K-ras mutations in G-LST, especially in the proximal colon, could strongly suggest that G-LST appearance is associated with a unique carcinogenic pathway.

Invasive potency related to RCAS1 expression in uterine cervical cancer

OBJECTIVES

RCAS1 expression is significantly associated with clinical prognosis in various human cancers, which suggests that RCAS1 may be involved in acquisition of malignant phenotypes. To investigate the relationship between RCAS1 and one such characteristic, tumor invasiveness, we examined RCAS1 expression in cervical neoplasms ranging from the precancerous state to invasive cancer.

METHODS

RCAS1 expression was studied retrospectively via immunohistochemical methods. Samples consisted of biopsy tissue from 90 patients with intraepithelial neoplasia and resected tumor tissue from 154 patients with invasive cancer. Statistical analysis was done to correlate RCAS1 expression and clinicopathologic variables in patients with a depth of cancer cell invasion into stromal tissue of >5 mm.

RESULTS

RCAS1 expression was detected in patients with intraepithelial cancer and invasive cancer but not in patients with dysplasia. The occurrence and degree of RCAS1 expression increased with the depth of invasion. In patients with invasive cancer, RCAS1 overexpression was significantly correlated with invasion of the lymph-vascular space, lymph node metastasis in two or more sites, and tumor volume; RCAS1 expression was not associated with histologic subtype. Overall survival rates for patients with RCAS1 overexpression were significantly shorter than those for patients without RCAS1 overexpression. In connective tissue surrounding tumor cells, the number of cells expressing vimentin significantly decreased in relation to RCAS1 expression level. Moreover, significant associations between expression levels of RCAS1 and those of MMP-1 and laminin-5 were found.

CONCLUSION

RCAS1 may contribute to acquisition of malignant uterine cervical phenotypic characteristics including invasion, metastasis, and tumor growth via connective tissue remodeling.

Loss of heterozygosity analysis in uterine cervical adenocarcinoma

OBJECTIVE

Uterine cervical adenocarcinoma (CAC) is a rare form of cervical cancer, constituting only 5-8% of all cervical epithelial malignancies. Loss of heterozygosity (LOH) analysis of CAC was undertaken to identify alterations of chromosomal loci that may play important roles in the development of this tumor type.

METHODS

We analyzed loss of heterozygosity (LOH) using a total of 50 markers on 20 chromosomal arms in 37 cases of microdissected CAC DNA.

RESULTS

LOH of >40% was observed on 2p (50%), 3p (45%), 9p (45%), 11q (46%), 17p (57%), 17q (44%), 18q (57%), and 19p (44%). LOH of 30-40% was observed on 6p (38%), 6q (40%), and 10q (31%). Overall, mean LOH was 34% and fractional allelic loss (FAL) was 0.34. High-level and low-level microsatellite instability (MSI) was shown in four cases (11%) and six cases (16%), respectively. Frequency of LOH on10q was significantly higher in endometrioid-type than endocervical-type adenocarcinoma (71% versus 20%; P < 0.05). Conversely, 6q LOH was higher in endocervical type than endometrioid type (0% versus 60%; P < 0.05). 19p13.3 has been reported to be frequently deleted in adenoma malignum, a histological subtype of CAC. To define the critical regions of LOH in CAC in general, we further performed deletion mapping of 19p using 13 markers. Unlike adenoma malignum, multiple regions on 19p appeared to be important loci of LOH for CAC.

CONCLUSION

CACs develop with frequent LOH of multiple chromosomal arms, which may be related to its aggressive clinical behavior and poor prognosis. LOH of 10q may be unique to endometrioid-type CAC.

Identifying the combination of genetic factors that determine susceptibility to cervical cancer

Cervical cancer is common among women all over the world. Although infection with high-risk types of human papillomavirus (HPV) has been identified as the primary cause of cervical cancer, only some of those infected go on to develop cervical cancer. Obviously, the progression from HPV infection to cancer involves other environmental and host factors. Recent population-based twin and family studies have demonstrated the importance of the hereditary component of cervical cancer, associated with genetic susceptibility. Consequently, single-nucleotide polymorphism (SNP) markers and microsatellites should be considered genetic factors for determining what combinations of genetic factors are involved in precancerous changes to cervical cancer. This study employs a Bayesian network and four different decision tree algorithms, and compares the performance of these learning algorithms. The results of this study raise the possibility of investigations that could identify combinations of genetic factors, such as SNPs and microsatellites, that influence the risk associated with common complex multifactorial diseases, such as cervical cancer.

Microsatellite analysis of early stage (Ia-IIb) uterine cervical squamous carcinoma

Cervical cancer is the most common gynecologic malignancy of the developing world. The oncogenic role of human papilloma virus (HPV) is well known. Attention is now focusing on the complicit genetic changes, which allow progression of these tumors. Regarding these changes, deletion of tumor suppressor genes (loss of heterozygosity [LOH]) is the preferred pathway of progression with only a subset manifesting microsatellite instability (MSI). Implicated loci include 3p14.1-22. Several studies suggest that the mutator phenotype in cervical cancer may correlate with higher grade tumors, more advanced disease stage, and poor outcome. Unlike colorectal cancer, in which an inverse relationship has been demonstrated between microsatellite instability and loss of heterozygosity, cervical cancers expressing MSI have been found to coexpress LOH at other loci. In this study we analyzed 8-microsatellite loci including p53, DCC, APC, the MMR gene hMLH1 and 2 regions of interest on chromosome 3 in a high-risk population group in which HPV infection is endemic.

The role of microsatellite instability in cervical intraepithelial neoplasia and squamous cell carcinoma of the cervix

OBJECTIVES

This study was conducted to define the role of microsatellite instability (MSI) in cervical intraepithelial neoplasia (CIN) and squamous cell carcinoma (SCC) of the cervix. We also tested the validity of using markers recommended for MSI study in colonic carcinoma by the National Cancer Institute (NCI) for cervical neoplasm.

METHODS

Twenty normal cervical, 24 low-grade CIN (CIN-L), 59 high-grade CIN (CIN-H), and 93 SCC tissues were examined for MSI after microdissection. A polymerase chain reaction based MSI detection was performed using five markers recommended by the NCI for colonic cancer (panel one) as well as five other markers (panel two) found to be informative in earlier studies. High-frequency MSI (MSI-H) was defined as instability in > or = 2 of 5 loci if one panel was used and > or = 30% of loci when more than five loci were used. Low-frequency MSI (MSI-L) was diagnosed if instability was noted but did not meet the criteria of MSI-H. Findings were correlated with clinicopathologic information.

RESULTS

The combined use of panel one and two markers showed no MSI in normal cervical or CIN-L tissue, MSI-L in 1 CIN-H (1.7%), MSI-L in 16 (17.2%), and MSI-H in 11 (11.8%) SCC, respectively. The NCI-recommended panel alone detected 19 of 27 MSI-positive SCC. MSI-positive was not related to patient age, disease stage, and tumor grade. The overall survival of MSI-positive patients was significantly worse than that of microsatellite stable patients (P = 0.02). An increasing trend of MSI-H rate with higher disease stages was noted (P = 0.035) but MSI-H was not associated with poor prognosis.

CONCLUSIONS

The NCI recommended panel of markers might not be useful in MSI study for SCC and using more than five markers improves the MSI detection. MSI is rare in cervical dysplasia but is present in a subset of SCC. The association between MSI-positivity and prognosis awaits future confirmation.

Frequent loss of heterozygosity in chromosomal region 9pter-p13 in tumor biopsies and cytological material of uterine cervical cancer

Using polymerase chain reaction-based microsatellite analysis we examined 40 cases, tumor biopsies and cytological material, of early stage cervical cancer and 20 healthy donors. Loss of heterozygosity (LOH) was detected in 35 out of 40 cases (87.5%), located on 9pter-p13 (67.5%), 9q32-34 (17.5%), 13q12 (32.5%), 17p13 (0%) and 17q11-q22 (12.5%). Microsatellite instability (MIN) phenotype was found in three out of 40 cases (7.5%). The accuracy in LOH and MIN detection in cytological material compared to tumor biopsies was 91.5 and 86.0%, respectively. None of the specimens of healthy donors exhibited any genetic alteration. Our data suggest that microsatellite analysis in cytological material could be used for the early detection of cervical cancer.