p53 protein expression in mammary ductal carcinoma in situ: relationship to immunohistochemical expression of estrogen receptor and c-erbB-2 protein

Prognostic factors in early breast carcinoma

Several investigators, the SEER data, and the ECOG/Intergroup study have shown that patients with small tumors (< 0.5 cm) have a recurrence rate of less than 2%, compared to 20-25% for large tumors (> or = 5 cm). Nuclear grade and tumor differentiation are established indicators; however, the interobserver lack of concordance has thwarted their use in clinical trials. The presence of peritumoral lymphatic and blood vessel invasion (PLBI) is associated with a relative risk of recurrence of 4.7. The predictive value of the presence of hormone receptors in tumors is associated with a favorable disease free and overall survival difference of 8-10%; however, this advantage is being eroded by the early appearance of other factors, such as the epidermal growth factor receptor (EGFR), proliferative capacity (S-phase), nuclear grade, and HER-2/neu oncogene. Concordance among the different methods of hormone-receptor assay (immunocytochemical, sucrose gradient, and dextran-coated charcoal) is essential to refine the true value of these factors. DNA flow cytometry measurements of ploidy (DNA content) and S-phase fraction are the most characterized of the prognostic factors. There are conflicting reports regarding the clinical significance of ploidy status, while measurements of S-phase fraction clearly indicate a robust association with disease free and overall survival. Our data continue to show that S-phase, but not ploidy, can predict time to recurrence significantly in untreated patients, even when data are stratified for tumor size. HER-2/neu oncogene is expressed in about 50% of ductal carcinoma in situ and 14% of invasive ductal carcinoma. The presence of this oncogene at high copy number may be a useful independent marker of poor prognosis and may be associated with drug resistance and correlated with tumor recurrence and shorter survival. EGFR could be measured in most breast tumors, and the level of its expression has inversely correlated with estrogen receptor protein expression. The value of EGFR as a predictor of prognosis remains controversial and is still being investigated. Cathepsin-D provides a provocative biologic rationale but is hindered by different and incongruent methods of analysis. The majority of large studies with more than 3-years' follow-up suggests that high cathepsin-D levels may be predictive of greater recurrence and lower survival. Angiogenesis has been implicated as a critical component of the metastatic process. Early studies show that tumor angiogenesis is an independent and highly significant prognostic indicator, and its presence may suggest the selection of "anti-angiogenic therapy."(ABSTRACT TRUNCATED AT 400 WORDS)

p53 gene mutations and steroid receptor status in breast cancer. Clinicopathologic correlations and prognostic assessment

BACKGROUND

There is increasing evidence linking development and progression of cancer to an accumulation of mutations at the genomic level. The most frequently mutated gene known to date in sporadic breast cancer appears to be the tumor suppressor gene p53. This study was designed to determine the frequency of p53 gene mutations in primary breast cancer, to correlate the presence of p53 mutations with established clinicopathologic parameters, including the estrogen receptor (ER) and progesterone receptor (PR) status, and to assess the prognostic significance of p53 mutations regarding patient survival.

METHODS

We examined the p53 gene in genomic DNA samples from 192 primary breast cancers. Using denaturant gradient gel electrophoresis, the authors analyzed exons 5-9 in all tumors for mutations and performed DNA sequencing in 20 tumors to identify the exact nature of the p53 mutations.

RESULTS

p53 gene alterations were identified in 43 of the 192 tumors (22%), the majority localized in exons 5 and 6. DNA sequencing showed mostly missense mutations resulting from G or C substitutions. p53 mutations were found more often in tumors of younger women (P = 0.002), Afro-American women (P = 0.05), and in tumors lacking ER (P = 0.03), PR (P = 0.04), or both (P = 0.06). There were no significant correlations with family history, tumor size, histologic grade or type, nodal status, or disease stage. The overall survival rates showed no significant difference between patients with mutant and wild-type p53 tumors. The same was true when the comparison was limited to node-negative patients or patients with ER-positive or ER-negative tumors. Finally, there was no significant difference in survival between patients with tumors harboring mutations in exons 5 and 6 versus exons 7-9.

CONCLUSIONS

The results of this and other studies demonstrate a consistent relationship between ER-positive tumors and wild-type p53 on one hand and ER-negative cancers and p53 mutations on the other. Our data do not support a significant prognostic role for p53 mutations in predicting survival.

Immunohistochemical studies of early breast cancer evolution

Despite modern therapy, one third to one half of patients who get breast cancer will eventually die from it. This disconcerting circumstance has focused attention on prevention, and preventing breast cancer will require a much better understanding of the biological abnormalities underlying its development and progression. Many studies into the mechanisms of invasive breast cancer evolution have evaluated presumed precursor lesions (e.g. proliferative disease without atypia, atypical ductal hyperplasia, and ductal carcinoma in-situ) for genetic alterations known to occur in fully developed invasive carcinomas. This approach has shed some light on events which may be important in early malignant transformation, including the observations that overexpression of the c-erbB-2 oncogene and mutations of the p53 tumor suppressor gene are present in significant subsets of DCIS, but not PDWA or ADH. Although this approach is limited by our incomplete knowledge of cancer genetics, there is still a great deal to learn about breast cancer evolution by evaluating cancer-associated genes in potential precursor lesions using established techniques such as immunohistochemistry and in situ hybridization.

Biomarkers in early breast neoplasia

Early breast neoplasia may be defined in many ways. Any non-invasive or invasive but nonmetastatic breast cancer qualifies as early neoplasia in the sense that they are non-lethal. Before we can prevent lethal breast cancer, we must gain a better understanding of the biological abnormalities underlying its development and progression. Many studies into the mechanisms of breast cancer evolution have evaluated potential precursor lesions (e.g., proliferative disease without atypia [PDWA], atypical ductal hyperplasia [ADH], and ductal carcinoma in situ [DCIS]) for genetic alterations known to occur in fully developed invasive carcinomas. This approach has shed some light on events which may be important in early malignant transformation, including the observations that overexpression of the c-erbB-2 oncogene and mutations of the p53 tumor suppressor gene are present in significant subsets of DCIS, but not PDWA or ADH. This approach is limited by our incomplete knowledge of cancer genetics. However, there is more to learn by evaluating known cancer-associated genes in potential precursor lesions using established techniques such as immunohistochemistry and in situ hybridization. Until recently, technology could not detect unknown genetic abnormalities in microscopic lesions such as PDWA, ADH, or DCIS. Now, PCR-based techniques have the theoretical ability to detect novel tumor promoter and suppressor genes in clinical samples of these very small lesions. For example, suppressor-type genes may be detected using comprehensive mapping probes to identify loss of heterozygosity in PCR-amplified DNA extracted from a few hundred cells microdissected from either fresh or archival tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Oncogenes, breast cancer, and chemoprevention

Perturbations of oncogenes in breast carcinoma include amplifications of the HER-2/neu and PRAD1 genes, as well as p53 mutations. Some of these lesions frequently appear in early cancers such as ductal carcinoma in situ and are stable as the tumors become invasive and metastasize. Thus these findings suggest that oncogene mutations may define a point of origin for a given breast cancer, and are fixed lesions during tumor progression. Such germline abnormalities may occur at the BRCA1, H-RAS VNTR, and p53 loci. The rational use of genetics may be to identify women at high risk for the development of breast cancer so that they may be enrolled in future chemoprevention trials.