p53 mutations and histologic type of invasive breast carcinoma. A polymerase chain reaction-single-strand conformation polymorphism and immunohistochemical analysis

Different prognostic roles of mutations in the helical and kinase domains of the PIK3CA gene in breast carcinomas

PURPOSE

In breast cancer, the PIK3CA gene is frequently mutated at "hotspots" in exons 9 and 20, corresponding to the helical and kinase domains, respectively. We decided to investigate the association of PIK3CA mutations with pathologic features and clinical outcome in a large series of patients with breast cancer.

EXPERIMENTAL DESIGN

Frozen samples from 163 consecutive patients were analyzed for PIK3CA mutations using PCR single-strand conformation polymorphism and sequence analyses.

RESULTS

We identified 46 missense mutations, 24 (53%) in exon 9, and 21 (47%) in exon 20. Twelve (50%) of the 24 mutations in exon 9 were of the E542K type and 11 (46%) were of the E545K type. Twenty (95%) of the 21 mutations in exon 20 were H1047R substitutions. Mutations in exon 9 were more frequent in lobular carcinomas (42% of cases) than in ductal carcinoma (11% of cases; P = 0.002). At univariate survival analysis, PIK3CA exon 20 mutations were associated with prolonged overall and disease-free survival, whereas mutations in exon 9 were associated with significantly worse prognosis. At multivariate analysis, exon 9 PIK3CA mutations were the strongest independent factor to predict poor prognosis for disease-free survival (P = 0.0003) and overall survival (P = 0.001).

CONCLUSION

Our data show that exon 9 PIK3CA mutations are typical of infiltrating lobular carcinomas. In addition, they indicate that PIK3CA mutations in different exons are of different prognostic value: exon 9 mutations are independently associated with early recurrence and death, whereas exon 20 PIK3CA mutations are associated with optimal prognosis.

Breast cancer, serum antioxidant vitamins, and p53 protein overexpression

Although several studies have suggested that the relationship between the various risk factors and breast cancer may differ according to the breast cancer subtypes, it is not clear whether the p53 protein expression status of breast cancer represents an etiologically distinct form of the disease with different risk factor profiles. This study was carried out to investigate whether the relationship between breast cancer and serum antioxidant vitamins would differ according to p53 expression status (p53-positive and p53-negative). Breast cancer cases (n = 92) and controls (n = 122) were recruited between January 1993 and April 1994 at the Asan Medical Center. p53 overexpression in tissue sections from 92 women with breast cancer was determined using immunohistochemistry. The serum concentrations of the carotenoids and alpha-tocopherol were measured using liquid chromatography. For serum antioxidant vitamins, odds ratios with respect to the common control group for breast cancers of different p53 protein overexpression status were compared using multiple polytomous logistic regression. Serum concentrations of beta-carotene and zeaxanthin + lutein were significantly associated with the risk of breast cancer in p53-positive and p53-negative cancers. The adjusted odds ratios for the highest compared with the lowest quartile were 0.19 [95% confidence interval (CI) = 0.01-2.51] for beta-carotene and 0.34 (95% CI = 0.06-1.87) for zeaxanthin + lutein in p53-positive cancer cases and 0.05 (95% CI = 0.00-0.57) for beta-carotene and 0.06 (95% CI = 0.01-0.40) for zeaxanthin + lutein in p53-negative cancer cases. However, none of these associations differed significantly between p53-positive and p53-negative cancers. The results of this study showed that the relationship of antioxidant vitamins with breast cancer does not differ according to the presence or absence of the p53 mutation.

Hereditary breast cancer: a review

Breast cancer is the most common female malignancy and a major cause of death in middle-aged women. A positive family history of breast cancer is one of the strongest risk factors for the disease. In addition, many afflicted breast cancer families are characterized by early onset and bilateral tumors, and also, in some cases, associated malignancies, most commonly ovarian cancer. It is estimated that 5-10% of all breast cancer cases are due to autosomal dominant genes segregating with the disease. Mutations in the BRCA1 and BRCA2 genes are known to predispose to breast and ovarian cancer in many families. Other genes are only involved in very rare syndromes, and additional genes remain to be disclosed.

Enriched SSCP: a highly sensitive method for the detection of unknown mutations. Application to the molecular diagnosis of lung cancer in sputum samples

Detection of gene mutations by sensitive polymerase chain reaction (PCR)-based methods can allow to identify occult neoplastic cells in a great excess of nonmalignant cells. These molecular approaches have an enormous potential in terms of early diagnosis, detection of occult micrometastases of solid tumors, and minimal residual disease in patients with hematopoietic malignancies. Currently, the applications of such methods are limited, mainly because the high sensitivity required for the identification of rare mutated alleles can be achieved only in cases in which mutations occur in few specific codons of a gene or when the mutation is already known. No methods are available by which few alleles with unknown mutations in tumor genes can be recognized in a great excess of wild-type alleles. We have developed an extremely sensitive method, termed enriched single-strand conformational polymorphism (E-SSCP), which permits detection of a rare alleles with unknown mutations. The method is based on the observation that after a conventional SSCP analysis the vast majority of mutated bands migrate close to the wild-type bands. The area of the gel having the highest chance to hold mutated alleles is physically isolated and is used as substrate for a second round of SSCP. Serially diluted DNA samples containing gene mutations demonstrated detection of 1 mutant/10(6) normal alleles. The E-SSCP assay was first applied to six sputum samples of patients affected by lung cancers with known p53 mutations showing in sputa the same mutations observed in tumors. The technique was then applied to eight cytologically negative sputum samples obtained from patients who later developed a clinically manifested lung carcinoma. In three cases, harboring a p53 mutation in tumor tissue, the E-SSCP analysis allowed the detection of the mutations in sputa months before clinical diagnosis. In conclusion, we have presented a general, highly sensitive technique for the detection of unknown mutations that may have several potential applications and may hold considerable promise for the early detection and study of cancer.