Alterations of p16-pRb Pathway and Chromosome Locus 9p21–22 in Sporadic Invasive Breast Carcinomas

P16 Expression in Human Breast Carcinoma and its Relationship to Clinicopathological Parameters

Background

p16 is a cyclin-dependent kinase inhibitor and a cardinal regulator of the cell cycle. The relationship between p16 overexpression and poor prognosis of breast cancer has been reported in some studies. This study aimed to evaluate p16 expression in breast cancer in comparison to normal breast tissue and determine the association between p16 expression and clinicopathological parameters in breast cancer.

Materials and Methods

Paraffin blocks of 110 samples were studied. These included 40 invasive breast carcinoma (tumor group) and normal tissue adjacent to the tumor (tumor control), as well as 30 normal mammoplasty specimens (normal control). Samples were from the pathology archive of Alzahra Hospital, Isfahan, Iran, from 2016 to 2020. p16 expression was studied and compared in these three groups using the immunohistochemistry technique. Moreover, the relationship between p16 expression and age, tumor size, carcinoma subtype, tumor grade, and lymph node involvement was investigated in the tumor group. SPSS version 16 was used to analyze data.

Results

p16 expression showed a significant difference between the tumor group and the two control groups with a significantly higher expression in the tumor group. There was a significant direct relationship between the intensity of p16 expression and the number of involved lymph nodes (P < 0.001). No significant relationship was detected between p16 expression and other clinicopathological factors.

Conclusion

p16 seems to have a rather significant expression in breast cancer in comparison to normal breast parenchyma. However, among clinicopathological parameters, we found only a direct relationship between lymph node involvement and intensity of p16 expression.

Association between genetic variants at 9p21 locus with risk of breast cancer: A systematic review and meta-analysis

Breast cancer (BC) is the most frequent tumor in women and genetic factors are among the main risk factors contributing to this malignancy. Chromosome 9p21 contains important regulatory non-coding RNAs and is associated with multiple malignancies including BC. The current meta-analysis aimed to investigate the association between genetic variants within the 9p21 locus and risk of breast cancer. A literature search was performed using PubMed, Web of Science, Embase, MEDLINE, Scopus and Clinical key databases. Nine studies containing 23,726 subjects were eligible for the final analysis and specific odds ratios (OR) and confidence intervals (95% CI) were evaluated to assess the strength of the associations. In the pooled analysis, there was an association between the genetic variations in 9p21 locus (CDKN2A/2B) with risk of breast cancer with a standard OR of 1.22 (95% CI: 1.04-1.45, P = 0.016; random-effects model), supporting the significance of this locus as a novel risk factor for breast cancer patients. In conclusion, our results showed that 9p21 region is positively associated with risk of BC and its polymorphisms may be a candidate marker for BC susceptibility.

Integrating the DNA damage and protein stress responses during cancer development and treatment

During evolution, cells have developed a wide spectrum of stress response modules to ensure homeostasis. The genome and proteome damage response pathways constitute the pillars of this interwoven 'defensive' network. Consequently, the deregulation of these pathways correlates with ageing and various pathophysiological states, including cancer. In the present review, we highlight: (1) the structure of the genome and proteome damage response pathways; (2) their functional crosstalk; and (3) the conditions under which they predispose to cancer. Within this context, we emphasize the role of oncogene-induced DNA damage as a driving force that shapes the cellular landscape for the emergence of the various hallmarks of cancer. We also discuss potential means to exploit key cancer-related alterations of the genome and proteome damage response pathways in order to develop novel efficient therapeutic modalities. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Differential expression of breast cancer-associated genes between stage- and age-matched tumor specimens from African- and Caucasian-American Women diagnosed with breast cancer

Background

Recent studies suggest that the poorer breast cancer outcome observed in African-American women (AAW) may, in part, result from underlying molecular factors. The purpose of this study was to investigate gene expression differences between Caucasian-American women (CAW) and AAW that may contribute to this poorer prognosis.

Methods

The expression of 84 genes involved in breast carcinoma prognosis, response to therapy, estrogen signaling, and tumor aggressiveness was assessed in age- and stage-matched CAW and AAW paraffin-embedded breast cancer specimens. The Wilcoxon–Mann–Whitney Test was used to identify genes with a significant difference in expression between CAW and AAW. To determine if the differentially expressed genes could segregate between the CAW and AAW, we performed semi-supervised principal component analysis (SSPCA).

Results

Twenty genes were differentially expressed between AAW and CAW. SSPCA incorporating these 20 genes segregated AAW and CAW into two distinct groups. AAW were significantly (p < 0.05) more likely to display aberrations in G₁/S cell-cycle regulatory genes, decreased expression of cell-adhesion genes, and low to no expression of ESR1, PGR, ERBB2 and estrogen pathway targets.

Conclusions

The gene expression differences identified between AAW and CAW may contribute to more aggressive disease, resistance to therapy, enhanced metastatic potential and poor clinical outcome. These findings support the hypothesis that breast cancer specimens collected from AAW display distinct gene expression differences compared to similar tissues obtained from CAW. Additional population-based studies are necessary to determine if these gene expression variations contribute to the highly aggressive and treatment-resistant breast cancer phenotype frequently observed in AAW.

Surrogate tissue telomere length and cancer risk: shorter or longer?

Telomeres play a critical role in chromosome stability. Telomere length (TL) shortening is a risk factor for cancers. Measuring TL in surrogate tissues that can be easily collected may provide a potential tool for early detection of cancers. A number of studies on surrogate tissue TL and cancer risks have been conducted and results are inconsistent, including positive, negative, or null associations. In this article, we reviewed the published data on surrogate tissue TL in relation to cancer risks, discussed the possible reasons for the differences in the results and future directions and challenges for this line of research.

Shortened telomere length is associated with increased risk of cancer: a meta-analysis

BACKGROUND

Telomeres play a key role in the maintenance of chromosome integrity and stability, and telomere shortening is involved in initiation and progression of malignancies. A series of epidemiological studies have examined the association between shortened telomeres and risk of cancers, but the findings remain conflicting.

METHODS

A dataset composed of 11,255 cases and 13,101 controls from 21 publications was included in a meta-analysis to evaluate the association between overall cancer risk or cancer-specific risk and the relative telomere length. Heterogeneity among studies and their publication bias were further assessed by the χ(2)-based Q statistic test and Egger's test, respectively.

RESULTS

The results showed that shorter telomeres were significantly associated with cancer risk (OR = 1.35, 95% CI = 1.14-1.60), compared with longer telomeres. In the stratified analysis by tumor type, the association remained significant in subgroups of bladder cancer (OR = 1.84, 95% CI = 1.38-2.44), lung cancer (OR = 2.39, 95% CI = 1.18-4.88), smoking-related cancers (OR = 2.25, 95% CI = 1.83-2.78), cancers in the digestive system (OR = 1.69, 95% CI = 1.53-1.87) and the urogenital system (OR = 1.73, 95% CI = 1.12-2.67). Furthermore, the results also indicated that the association between the relative telomere length and overall cancer risk was statistically significant in studies of Caucasian subjects, Asian subjects, retrospective designs, hospital-based controls and smaller sample sizes. Funnel plot and Egger's test suggested that there was no publication bias in the current meta-analysis (P = 0.532).

CONCLUSIONS

The results of this meta-analysis suggest that the presence of shortened telomeres may be a marker for susceptibility to human cancer, but single larger, well-design prospective studies are warranted to confirm these findings.

DNA copy number aberrations and disruption of the p16Ink4a/Rb pathway in radiation-induced and spontaneous rat mammary carcinomas

Chromosomal amplifications and deletions are thought to be important events in spontaneous and radiation-induced carcinogenesis. To clarify how ionizing radiation induces mammary carcinogenesis, we characterized genomic copy number aberrations for gamma-ray-induced rat mammary carcinomas using microarray-based comparative genomic hybridization. We examined 14 carcinomas induced by gamma radiation (2 Gy) and found 26 aberrations, including trisomies of chromosomes 4 and 10 for three and one carcinomas, respectively, an amplification of the chromosomal region 1q12 in two carcinomas, and deletions of the chromosomal regions 3q35q36, 5q32 and 7q11 in two, two and four carcinomas, respectively. These aberrations were not observed in seven spontaneous mammary carcinomas. The expression of p16Ink4a and p19Arf, which are located in the chromosomal region 5q32, was always up-regulated except for a carcinoma with a homozygous deletion of region 5q32. The up-regulation was not accounted for by gene mutations or promoter hypomethylation. However, the amounts of Rb and its mRNA were down-regulated in these carcinomas, indicating a disruption of the p16Ink4a/Rb pathway. This is the first report of array CGH analysis for radiation-induced mammary tumors, which reveals that they show distinct DNA copy number aberration patterns that are different from those of spontaneous tumors and those reported previously for chemically induced tumors.

Telomere deficiencies on chromosomes 9p, 15p, 15q and Xp: potential biomarkers for breast cancer risk

Although telomere dysfunction is a characteristic of breast cancer cells, the relationship between deficiency on individual chromosomal telomeres in normal somatic cells and breast cancer risk has not been characterized. A case-control study was conducted to examine the associations between individual lengths of 92 telomeres in the human genome and the risk of breast cancer in 204 newly diagnosed breast cancer patients and 236 healthy controls. Chromosome arm-specific telomere lengths were measured by telomere quantitative fluorescent in situ hybridization. Unconditional logistic regression was used to estimate the risk associations. This genome-wide screen identified that shorter telomere lengths on chromosomes Xp and 15p were associated with breast cancer risk in pre-menopausal women, with adjusted odds ratios (aORs) of 2.5 (95% CI = 1.3, 4.8) and 2.6 (1.3, 5.0), respectively. The study also revealed that greater length differences between homologous telomeres on chromosomes 9p, 15p and 15q were associated with breast cancer risk in pre-menopausal women, with aORs of 4.6 (2.3, 9.2), 3.1 (1.6, 6.0) and 2.8 (1.4, 5.4), respectively. When the subjects were categorized into quartiles, a dose-response relationship was observed for all of the above telomeres (P-for-trend ≤ 0.005). This study revealed that telomere deficiencies on chromosomes 9p, 15p, 15q and Xp were associated with breast cancer risk in pre-menopausal women. If confirmed in future studies, chromosomal arm-specific telomeres are likely to be a useful panel of blood-based biomarkers for breast cancer risk assessment, given their strong associations with breast cancer risk.

Premalignant breast neoplasia: a paradigm of interlesional and intralesional molecular heterogeneity and its biological and clinical ramifications

As is well established in invasive breast disease, it is becoming increasingly clear that molecular heterogeneity, both between and within lesions, is a prevalent, distinct phenotype of premalignant lesions of the breast. Key pathways of tumorigenesis modulate critical features of premalignant lesions such as proliferation, differentiation, stress response, and even the generation of diversity. Current studies show that evaluation of these lesions may provide clinically useful information on future tumor formation as well as biological insights into the origin and functional significance of this distinct phenotype.

Exploring the gain of function contribution of AKT to mammary tumorigenesis in mouse models

Elevated expression of AKT has been noted in a significant percentage of primary human breast cancers, mainly as a consequence of the PTEN/PI3K pathway deregulation. To investigate the mechanistic basis of the AKT gain of function-dependent mechanisms of breast tumorigenesis, we explored the phenotype induced by activated AKT transgenes in a quantitative manner. We generated several transgenic mice lines expressing different levels of constitutively active AKT in the mammary gland. We thoroughly analyzed the preneoplastic and neoplastic mammary lesions of these mice and correlated the process of tumorigenesis to AKT levels. Finally, we analyzed the impact that a possible senescent checkpoint might have in the tumor promotion inhibition observed, crossing these lines to mammary specific p53(R172H) mutant expression, and to p27 knock-out mice. We analyzed the benign, premalignant and malignant lesions extensively by pathology and at molecular level analysing the expression of proteins involved in the PI3K/AKT pathway and in cellular senescence. Our findings revealed an increased preneoplastic phenotype depending upon AKT signaling which was not altered by p27 or p53 loss. However, p53 inactivation by R172H point mutation combined with myrAKT transgenic expression significantly increased the percentage and size of mammary carcinoma observed, but was not sufficient to promote full penetrance of the tumorigenic phenotype. Molecular analysis suggest that tumors from double myrAKT;p53(R172H) mice result from acceleration of initiated p53(R172H) tumors and not from bypass of AKT-induced oncogenic senescence. Our work suggests that tumors are not the consequence of the bypass of senescence in MIN. We also show that AKT-induced oncogenic senescence is dependent of pRb but not of p53. Finally, our work also suggests that the cooperation observed between mutant p53 and activated AKT is due to AKT-induced acceleration of mutant p53-induced tumors. Finally, our work shows that levels of activated AKT are not essential in the induction of benign or premalignant tumors, or in the cooperation of AKT with other tumorigenic signal such as mutant p53, once AKT pathway is activated, the relative level of activity seems not to determine the phenotype.

Electron microscopy evidence that cytoplasmic localization of the p16INK4A“nuclear” cyclin-dependent kinase inhibitor (CKI) in tumor cells is specific and not an artifact. A study in non-small cell lung carcinomas

It is well established that p16(INK4A) protein acts as a cell cycle inhibitor in the nucleus. Therefore, cytoplasmic localization of p16 (INK4A) usually is disregarded by investigators as nonspecific. Three recent studies reported findings that differ from the current view concerning p16(INK4A) immunohistochemical localization. All three demonstrated that breast and colon cancers expressing cytoplasmic p16(INK4) represent distinct biological subsets. We previously detected in a percentage of non-small cell lung carcinomas simultaneous nuclear and cytoplasmic p16(INK4A) staining. In view of the reports concerning breast and colon carcinomas, we conducted an ultrastructural re-evaluation of our cases to clarify the specificity of p16(INK4A) cytoplasmic expression. We observed p16 (INK4A) immunolocalization in both the nucleus and the cytoplasm of a proportion of tumor cells. Diffuse dense nuclear staining was detected in the nucleoplasm, whereas weaker granular immunoreactivity was observed in the cytoplasm near the rough endoplasmic reticulum. Negative tumor cells also were visible. In the tumor-associated stromal, cells p16(INK4A) immunoreactivity was detected only in the nuclei. We have demonstrated that p16(INK4A) cytoplasmic staining is specific and suggest that it represents a mechanism of p16(INK4A) inactivation similar to that observed in other tumor suppressor genes.

Telomere length in blood cells and breast cancer risk: investigations in two case-control studies

Telomere dysfunction, which leads to genomic instability, is hypothesized to play a causal role in the development of breast cancer. However, the few epidemiologic studies that assessed the relationship between telomere length in blood cells and breast cancer risk have been inconsistent. We conducted two case-control studies to further understand the role of telomere length and breast cancer risk. Overall telomere lengths were measured by telomere quantitative fluorescent in situ hybridization (TQ-FISH) and telomere quantitative real-time PCR (TQ-PCR). The associations between telomere length in blood leukocytes and risk of breast cancer were examined in two breast cancer case-control studies that were conducted at Roswell Park Cancer Institute (RPCI) and Lombardi Comprehensive Cancer Center (LCCC). Using the 50th percentile value in controls as a cut point, women who had shorter telomere length were not at significantly increased risk of breast cancer compared with women who had longer telomere length in the RPCI study (odds ratio [OR] = 1.34, 95% confidence interval [CI] = 0.84-2.12), in the LCCC study (OR = 1.18, 95% CI = 0.73-1.91), or in the combined RPCI and LCCC studies (OR = 1.23, 95% CI = 0.89-1.71). There was no significant dose-response relationship across quartiles of telomere length and no significant difference when comparing women in the lowest to highest quartile of telomere length. Overall telomere length in blood leukocytes was not significantly associated with the risk of breast cancer.

Chromosome 9 arm-specific telomere length and breast cancer risk

BACKGROUND

Telomere dysfunction is involved in the development of breast cancer and very short telomeres are frequent genetic alterations in breast tumors. However, the influence of telomere lengths of specific chromosomal arms on the breast cancer risk is unknown.

METHODS

We conducted a case-control study of breast cancer to examine the associations of the telomere length on chromosome 9 short arms (9p) and long arms (9q) with risk of breast cancer. Chromosome 9 arm-specific telomere lengths were measured by quantitative fluorescent in situ hybridization using cultured blood lymphocytes.

RESULTS

Telomere length on chromosome 9p was significantly shorter in breast cancer patients than in control subjects (P < 0.001). Using the 50th percentile value in controls as a cut point, women who have short 9p telomeres had an increased risk of breast cancer [adjusted odds ratio (OR) = 2.6; 95% confidence interval (CI) = 1.5-4.3]. When the 9p telomere length was divided into quartiles, a significant inverse dose-response relationship between 9p telomere length and breast cancer risk was observed (P(trend) < 0.001), with a quartile ORs of 3.0 (95% CI = 1.2-7.5), 3.9 (95% CI = 1.6-9.5) and 6.6 (95% CI = 2.8-15.9) for third, second and first quartile, respectively, when compared with women in the fourth quartile.

CONCLUSIONS

Short telomere length on chromosome 9p is strongly associated with the risk of breast cancer. If confirmed by future studies, chromosome 9p telomere length has the potential to be incorporated into the current prediction models to significantly enhance breast cancer risk prediction.

Novel presentation of a familial pancreatic cancer syndrome

INTRODUCTION

Earlier detection of pancreatic cancer may help identify patients for whom surgical intervention could provide cure or prolong life. In this article, we report the occurrence of breast cancer, melanoma, squamous cell carcinoma of the alveolar ridge, colon cancer, a desmoid tumor of the abdominal wall, and pancreatic adenocarcinoma in a 65-year-old woman. She was identified as having the familial atypical multiple mole melanoma-pancreatic cancer syndrome (FAMMM-PC) with a germline p16 mutation at amino acid position 15.

DISCUSSION

Patients with this syndrome traditionally present with multiple nevi and melanoma, and a subset also present with other cancers, including pancreatic cancer; however, no FAMMM-PC patient has yet been described with this constellation of cancers, including squamous cell carcinoma of the alveolar ridge and a desmoid tumor. Recognition of the tumors this population of patients is susceptible to developing and their genetic associations can help guide the surgeon in screening, surveillance, and eventually prevention of many of these cancers.

The functional loss of the retinoblastoma tumour suppressor is a common event in basal-like and luminal B breast carcinomas

Introduction

Breast cancers can be classified using whole genome expression into distinct subtypes that show differences in prognosis. One of these groups, the basal-like subtype, is poorly differentiated, highly metastatic, genomically unstable, and contains specific genetic alterations such as the loss of tumour protein 53 (TP53). The loss of the retinoblastoma tumour suppressor encoded by the RB1 locus is a well-characterised occurrence in many tumour types; however, its role in breast cancer is less clear with many reports demonstrating a loss of heterozygosity that does not correlate with a loss of RB1 protein expression.

Methods

We used gene expression analysis for tumour subtyping and polymorphic markers located at the RB1 locus to assess the frequency of loss of heterozygosity in 88 primary human breast carcinomas and their normal tissue genomic DNA samples.

Results

RB1 loss of heterozygosity was observed at an overall frequency of 39%, with a high frequency in basal-like (72%) and luminal B (62%) tumours. These tumours also concurrently showed low expression of RB1 mRNA. p16^INK4a was highly expressed in basal-like tumours, presumably due to a previously reported feedback loop caused by RB1 loss. An RB1 loss of heterozygosity signature was developed and shown to be highly prognostic, and was potentially a predictive marker of response to neoadjuvant chemotherapy.

Conclusions

These results suggest that the functional loss of RB1 is common in basal-like tumours, which may play a key role in dictating their aggressive biology and unique therapeutic responses.

Abrogated response to cellular stress identifies DCIS associated with subsequent tumor events and defines basal-like breast tumors

Approximately 15%-30% of women diagnosed with ductal carcinoma in situ (DCIS) develop a subsequent tumor event within 10 years after surgical lumpectomy. To date, little is known about the molecular pathways that confer this differential risk for developing subsequent disease. In this study, we demonstrate that expression of biomarkers indicative of an abrogated response to cellular stress predicts DCIS with worse outcome and is a defining characteristic of basal-like invasive tumors. Mechanistic studies identify the Rb pathway as a key regulator of this response. Conversely, biomarkers indicative of an intact response to cellular stress are strongly associated with a disease-free prognosis. Assessment of these biomarkers in DCIS begins to allow prediction of tumor formation years before it actually occurs.

Analysis of p16 expression and allelic imbalance / loss of heterozygosity of 9p21 in cutaneous squamous cell carcinomas

Deletions of the short arm of chromosome 9 have been reported in different types of malignancies. This chromosomal region contains a number of known tumour suppressor genes, including the p16^INK4A (CDKN2A), p15^INK4B and MTAP tumour suppressor genes located at 9p21. In this study twenty-two paraffin embedded invasive cutaneous SCC were examined for allelic imbalance/ loss of heterozygosity (AI/LOH) of the 9p region (in particular 9p21), and for p16 protein expression. DNA was isolated from microdissected sections of normal and tumour cells and analysed for AI/LOH by using six fluorescently labelled microsatellite markers that map to the 9p region. P16 protein expression was examined by immunohistochemistry. At each of the six microsatellite markers the majority of SCC analysed showed AI/LOH. Overall both AI/LOH within the CDKN2A locus and absence of p16 protein expression were frequent among the cutaneous SCC analysed, suggesting that p16 inactivation may play a role in cutaneous SCC development. The majority of the SCC analysed also had AI/LOH of the marker within the MTAP gene, and at markers flanking the CDKN2A gene; thus further investigation as to a possible role for these genes in the development of cutaneous SCC is warranted.

CDKN2A-positive breast cancers in young women from Poland

PURPOSE

To investigate the contribution of CDKN2A A148T common variant to early-onset breast cancer in Poland, and to establish the characteristic features of these cancers.

EXPERIMENTAL DESIGN

We studied 3,069 women diagnosed with breast cancer under the age of 51 and 3,493 population controls. CDKN2A variant were detected using RFLP-PCR and confirmed by genomic sequencing. Clinical and pathological features of CDKN2A-positive cases and CDKN2A-negative cases were compared.

RESULTS

A148T variant was identified in 157 of 3,069 women with breast cancer (5.1%). Overall, the odds ratio for early-onset breast cancer, given a CDKN2A variant was 1.4 (95% CI 1.075-1.725; P = 0.012). Breast tumors in women with the CDKN2A variant were more commonly intraductal cancers (DCIS) with micro-invasion (14.8% vs. 8.5%; P = 0.035). Carriers and non-carriers were similar with respect to tumor size, laterality, multicentricity, nodal status, family history and estrogen-receptor status.

CONCLUSION

The CDKN2A A148T variant seems to contribute to early-onset breast cancer in Poland. Breast tumors which arise in carriers of A148T variant appear to be similar to those of breast cancers in the population at large.

Tumor suppressive role of a 2.4 Mb 9q33-q34 critical region and DEC1 in esophageal squamous cell carcinoma

The key genes involved in the development of esophageal squamous cell carcinoma (ESCC) remain to be elucidated. Previous studies indicate extensive genomic alterations occur on chromosome 9 in ESCC. Using a monochromosome transfer approach, this study provides functional evidence and narrows down the critical region (CR) responsible for chromosome 9 tumor suppressing activity to a 2.4 Mb region mapping to 9q33-q34 between markers D9S1798 and D9S61. Interestingly, a high prevalence of allelic loss in this CR is also observed in primary ESCC tumors by microsatellite typing. Allelic loss is found in 30/34 (88%) tumors and the loss of heterozygosity (LOH) frequency ranges from 67 to 86%. Absent to low expression of a 9q32 candidate tumor suppressor gene (TSG), DEC1 (deleted in esophageal cancer 1), is detected in four Asian ESCC cell lines. Stably expressing DEC1 transfectants provide functional evidence for inhibition of tumor growth in nude mice and DEC1 expression is decreased in tumor segregants arising after long-term selection in vivo. There is 74% LOH in the DEC1 region of ESCC primary tumors. This study provides the first functional evidence for the presence of critical tumor suppressive regions on 9q33-q34. DEC1 is a candidate TSG that may be involved in ESCC development.

Racial differences in the expression of cell cycle-regulatory proteins in breast carcinoma

BACKGROUND

African-American (AA) women are more likely to be diagnosed with an advanced stage of breast carcinoma than are white women. After adjustment for disease stage, many studies indicate that tumors in AA women are more likely than tumors in white women are to exhibit a high level of cell proliferation and features of poor prognosis. The purpose of the current study was to compare tumor characteristics and cell cycle alterations in AA women and white women that might affect the aggressiveness of breast carcinoma.

METHODS

The study included 124 AA and 397 white women, ages 20-54 years. These women were enrolled in a case-control study in Atlanta, Georgia, between 1990 and 1992. Breast tumor specimens obtained from these women were centrally reviewed for histologic characteristics and evaluated for expression of estrogen and progesterone receptors (ER/PR), c-ErbB-2, Ki-67, p53, cyclin E, cyclin D1, p27, p16, pRb, and p21 by immunohistochemistry. Logistic regression models were used to assess the age- and stage-adjusted associations of various tumor characteristics with race.

RESULTS

The odds of a breast carcinoma diagnosis at a younger age and at a later stage were higher for AA women than for white women. After adjustment for disease stage and age at diagnosis, AA women also were found to have increased odds of having a higher-grade tumor, a higher mitotic index, marked tumor necrosis, ductal histology, loss of ER and PR, overexpression of cyclin E, p16, and p53 and low expression of cyclin D1 at diagnosis.

CONCLUSIONS

The observed differences between tumor specimens obtained from AA women and tumor specimens obtained from white women, independent of stage and age at diagnosis, indicated that race may be a determinant, or a surrogate for other determinants, of aggressive breast carcinoma and specific cell cycle defects.

High expression levels of p27 correlate with lymph node status in a subset of advanced invasive breast carcinomas: relation to E-cadherin alterations, proliferative activity, and ploidy of the tumors

BACKGROUND

The cyclin-dependent kinase inhibitor p27 plays a central role in cell cycle progression and is deregulated in breast carcinomas. Although its levels are inversely associated with tumor proliferation, overexpression of p27 has been reported in a subset of rapidly proliferating breast carcinoma cell lines.

METHODS

p27 levels were determined by immunohistochemistry in a series of 52 sporadic invasive breast carcinomas consisting of 47 ductal, 2 lobular, and 3 mixed; most tumors were Grade 2 or 3 (46 of 52) and Tumor Node Metastasis (TNM) Stage II-IV (46 of 52). E-cadherin expression and its gene alterations at 16q22.1 were also studied, because in vitro evidence suggests a biologic association between p27 and E-cadherin-mediated growth suppression.

RESULTS

The mean p27 labeling index (LI; percentage of p27 positive tumor cells) was 33.3% +/- 25.3% (range, 0.1-85%). High p27 levels (p27 LI, > 50%) were observed in 14 (26.9%) of 52 carcinomas and were significantly associated with metastatic disease in axillary lymph nodes (14 of 33 vs. 0 of 19; P = 0.0007 by Fisher exact test). In addition, p27 LI was higher in the group of lymph node positive vs. lymph node negative tumors (mean p27 LI, 40.9% vs. 20.1%; P = 0.008 by Mann-Whitney test). Reduced or absent E-cadherin expression was found in 27 of 45 (60%) informative cases. Allelic imbalance of the 16q22.1 locus was found in 14 (27.5%) of 51 cases by using the microsatellite markers D16S503, D16S752, and D16S512. p27 LI and E-cadherin alterations were not statistically related.

CONCLUSIONS

In summary, high p27 levels detected in a subset of advanced breast carcinomas correlate with lymph node metastasis, suggesting that other mechanisms may bypass the cell cycle inhibitory role of p27 and provide growth advantage in these tumors.

Additional characterization of a hexanucleotide polymorphic site in the first intron of human H-ras gene: comparative study of its alterations in non-small cell lung carcinomas and sporadic invasive breast carcinomas

Intron 1 of the human H-ras gene possesses a polymorphism consisting of repetitions of the GGGCCT consensus. Three alleles have been reported at this locus. We confirmed that two, P1 and P2, display four and two repeats, respectively, with their internal sequence structure similar to that previously described. The third, P3, previously assigned as a three-unit repetition allele according to its electrophoretic mobility and with no other information regarding its internal structure, was also found. Sequence analysis of the P3 allele revealed that it consists of three perfect repeats of the GGGCCT consensus. This polymorphism is present only in human c-H-ras gene, although single hexanucleotide repeats are found scattered within intron 1 of this gene in rodents. Analysis of this locus in matched tumor/distant normal samples from: (i) 38 patients with non-small-cell lung carcinoma (NSCLC), and (ii) 35 patients with sporadic invasive breast carcinoma, revealed: (1) 6.6% and 19% loss of heterozygosity (LOH) respectively, and (2) 10.5% and 2.9% hexanucleotide instability (HI) respectively, detected by the presence of shifted in length alleles. Shifted alleles exhibited altered internal sequence structure in comparison to normal ones, suggesting complex mutational events. The same pattern of alterations was also detected in tissues adjacent to lung adenocarcinomas and dysplasias adjacent to squamous cell carcinomas (7.7% LOH, 5.9% HI), implying that abnormalities at this locus may be early events in lung carcinogenesis. The frequency of alterations (LOH vs. HI) was significantly different among NSCLC and breast cancer (P=.005), probably due to the different tumor biology of each system. Finally, altered mRNA expression of H-ras gene was detected in all cases with HI, but this finding was also observed in samples without HI. In view of reports showing that elements in intron 1 of H-ras gene potentially influence its transcriptional regulation, from our results we cannot exclude that the hexanucleotide locus could be an element with possible involvement in expressional regulation of this gene.

Methylation of the p16(Ink4a) tumor suppressor gene 5'-CpG island in breast cancer

Methylation of the p16(Ink4a) tumor suppressor gene 5'CpG island was analyzed in 104 primary breast cancer specimens using Southern blotting and methylation specific polymerase chain reaction (PCR) (MSP). Eight and four tumors, respectively, showed methylation, and all MSP positive tumors were detected by Southern blotting. To investigate possible methylation not detectable by these methods, bisulphite genomic sequencing was performed in 220 clones from 14 selected tumors. Absent methylation or methylation of single CpG dinucleotides prevailed in all tumors, but of the MSP positive tumors, three contained alleles with methylation of 31 or 32 of the 32 analyzed CpG dinucleotides in the island. Partially methylated alleles were also observed. In a group with low p16(Ink4a) expression determined by Western blotting, four randomly selected tumors contained several identical clones with methylation of 15 CpG dinucleotides by bisulphite genomic sequencing but with a methylation pattern that did not support detection by either Southern blotting or MSP, increasing the potential significance of p16(Ink4a) methylation in breast cancer.

Genetic heterogeneity in ductal carcinoma of the breast

Genetic heterogeneity in breast cancer has been observed both by cytogenetic and loss of heterozygosity (LOH) analyses; however, the frequency with which genetically heterogeneous clones arise is unknown. In this study, a panel of 115 breast carcinomas was analyzed to determine the extent of clonal divergence in tumor foci at progressive stages of tumor evolution. Intraductal, infiltrating, and metastatic tumor components were microdissected from each tumor and tested for LOH at 20 microsatellite markers on seven chromosomal arms. Of these cases, 24 (21%) demonstrated genetically divergent clones during tumor progression. Clonal divergence, inferred from discordant LOH patterns, was observed most commonly between intraductal and infiltrating tumor (18 cases), but was also demonstrated between infiltrating and metastatic tumor (11 cases). Discordant LOH was observed with markers on one chromosomal arm in 16 cases, on two in 7 cases, and on four in 1 case, and was observed most commonly with markers on 17p, 17q, and 16q. More detailed microdissection of four cases provided evidence for a specific chronology of genetic alterations occurring during the progression of each tumor. The results indicate that the different tumor components observed microscopically in breast cancer specimens often represent genetically divergent clones.