In patients with CCNE1 amplification (n = 28), TP53 mutations (n = 23, 82.1%) and ERBB2 amplification (n = 8, 28.6%) were the most frequent concurrent genetic alterations.
Of note, human genomic databases (TCGA, METABRIC etc.) show a high degree of p53 LOH in all examined tumor types that carry missense p53 mutations, including sarcomas and breast carcinomas (with and without HER2 amplification).
The association between TP53 mutation and ERBB2 amplification was confirmed in a wider DCIS cohort using p53 immunohistochemistry as a surrogate marker for TP53 mutations (P=0.03).
Together, resistance to HER2 blockade should be indicated during treatment if any of the following situations applies: 1) recurrence or persistence of HER2 amplification in the blood; 2) emergence or ≥20% increase in the fraction of mutations in any of these resistance-related genes including TP53/PIK3CA/MTOR/PTEN.
TP53 mutations (15/27, 56%), PTEN loss (11/29, 38%, including 2 cases with PTEN mutation), PIK3CA hotspot mutations (10/30, 33%), HRAS hotspot mutations (10/29; 34%), and ERBB2 amplification (9/29, 31%, including 1 case with mutation) represented the 5 most common abnormalities.
In IBC, Alu hypomethylation correlated with negative estrogen receptor (ER) status, and LINE-1 hypomethylation was associated with negative ER status, ERBB2 (HER2) amplification and p53 overexpression.
Additional FISH studies that use probes to the SMS, RARA, and TP53 genes are an effective way to determine the true HER2 amplification status in patients with polysomy 17 and they have important potential implications for guiding HER2-targeted therapy in breast cancer.
In this study, we now show that p53 positivity in unamplified 17 polysomy identifies cases that are associated with an even higher Nottingham score and greater hormone receptor negativity that is similar to cases with HER2 amplification.
Patients carrying a TP53 mutation showed a significantly higher likelihood of developing a breast cancer with Human Epidermal growth factor Receptor (HER2) amplification (83%) when compared to the cohort of young onset breast cancer cases (16%); ER and PR status were equivalent between groups.
TP53 mutational status (exons 2-10) and ERBB2 amplification status were determined in tumor specimens from a prospective cohort of 543 women with node-negative breast cancer.
While TOP2alpha and p53 gene amplification was detected in no case, 5 cases (8%) showed HER2 gene amplification, which was related to HER2 3+ score in 4 cases.
By conventional light microscopy, HER-2/neu amplification (>/=6 copies >50% cancer cells) was detected in 14% (8/59) tumours, HER-2/neu overexpression (>10% cells moderate/strong complete membrane staining) in 22% (13/60) for A0485, and 18% (11/60) for TAB250, p53 (>10% +cells) in 61% (36/59), and Ki-67 (>50% +cells) in 50% (30/60).
We found elevated risks of disease recurrence and overall mortality in patients with both p53 mutation and neu/erbB-2 amplification in their tumor compared with patients with neither or only one of the alterations.
i) HER-2 gene amplification did not seem to be correlated with response to anthracyclines. ii) Both topo-II gene amplification and protein overexpression seem to correlate with response to anthracyclines, although other factors, such as p53 and cell proliferation, are most likely to be involved. iii) The role of combined evaluation of several relevant markers and of potential 'molecular signatures' are currently being evaluated in prospective randomized clinical trials.
Heterogeneous gene alterations in primary breast cancer contribute to discordance between primary and asynchronous metastatic/recurrent sites: HER2 gene amplification and p53 mutation.
In EOBC, c-erbB-2 amplification and p53 over-expression were not associated with high tumor grade or high cell-proliferation rate, in contrast to the significant associations of these markers in tumors in older women.
Appropriate combinations of conventional factors with nuclear p53 immunoreaction and c-erbB-2 amplification would help to identify highly aggressive node-positive breast carcinomas and would aid stratification of patient groups in randomized clinical trials of adjuvant systemic therapies.