A phenocopy signature of TP53 loss predicts response to chemotherapy

In preclinical studies, p53 loss of function impacts chemotherapy response, but this has not been consistently validated clinically. We trained a TP53-loss phenocopy gene expression signature from pan-cancer clinical samples in the TCGA. In vitro, the TP53-loss phenocopy signature predicted chemotherapy response across cancer types. In a clinical dataset of 3003 breast cancer samples treated with neoadjuvant chemotherapy, the TP53-loss phenocopy samples were 56% more likely to have a pathologic complete response (pCR), with a significant association between TP53-loss phenocopy and pCR in both ER positive and ER negative tumors. In an independent clinical validation in the I-SPY2 trial (N = 987), we confirmed the association with neoadjuvant chemotherapy pCR and found higher rates of chemoimmunotherapy response in TP53-loss phenocopy tumors compared to non-TP53-loss phenocopy tumors (64% vs. 28%). The TP53-loss phenocopy signature predicts chemotherapy response across cancer types in vitro, and in a proof-of-concept clinical validation is associated with neoadjuvant chemotherapy response across multiple clinical breast cancer cohorts.

GBP5 Serves as a Potential Marker to Predict a Favorable Response in Triple-Negative Breast Cancer Patients Receiving a Taxane-Based Chemotherapy

Pre-operative (neoadjuvant) or post-operative (adjuvant) taxane-based chemotherapy is still commonly used to treat patients with triple-negative breast cancer (TNBC). However, there are still no effective biomarkers used to predict the responsiveness and efficacy of taxane-based chemotherapy in TNBC patients. Here we find that guanylate-binding protein 5 (GBP5), compared to other GBPs, exhibits the strongest prognostic significance in predicting TNBC recurrence and progression. Whereas GBP5 upregulation showed no prognostic significance in non-TNBC patients, a higher GBP5 level predicted a favorable recurrence and progression-free condition in the TNBC cohort. Moreover, we found that GBP5 expression negatively correlated with the 50% inhibitory concentration (IC₅₀) of paclitaxel in a panel of TNBC cell lines. The gene knockdown of GBP5 increased the IC₅₀ of paclitaxel in the tested TNBC cells. In TNBC patients receiving neoadjuvant or adjuvant chemotherapy, a higher GBP5 level strongly predicted a good responsiveness. Computational simulation by the Gene Set Enrichment Analysis program and cell-based assays demonstrated that GBP5 probably enhances the cytotoxic effectiveness of paclitaxel via activating the Akt/mTOR signaling axis and suppressing autophagy formation in TNBC cells. These findings suggest that GBP5 could be a good biomarker to predict a favorable outcome in TNBC patients who decide to receive a taxane-based neoadjuvant or adjuvant therapy.

Distinguishing Low-Risk Luminal A Breast Cancer Subtypes with Ki-67 and p53 Is More Predictive of Long-Term Survival

Overexpression of p53 is the most frequent genetic alteration in breast cancer. Recently, many studies have shown that the expression of mutant p53 differs for each subtype of breast cancer and is associated with different prognoses. In this study, we aimed to determine the suitable cut-off value to predict the clinical outcome of p53 overexpression and its usefulness as a prognostic factor in each subtype of breast cancer, especially in luminal A breast cancer. Approval was granted by the Institutional Review Board of Samsung Medical Center. We analyzed a total of 7,739 patients who were surgically treated for invasive breast cancer at Samsung Medical Center between Dec 1995 and Apr 2013. Luminal A subtype was defined as ER&PR + and HER2- and was further subclassified according to Ki-67 and p53 expression as follows: luminal A (Ki-67-,p53-), luminal A (Ki-67+, p53-), luminal A (Ki-67 -, p53+) and luminal A (Ki-67+, p53+). Low-risk luminal A subtype was defined as negative for both Ki-67 and p53 (luminal A [ki-67-, p53-]), and others subtypes were considered to be high-risk luminal A breast cancer. A cut-off value of 10% for p53 was a good predictor of clinical outcome in all patients and luminal A breast cancer patients. The prognostic role of p53 overexpression for OS and DFS was only significant in luminal A subtype. The combination of p53 and Ki-67 has been shown to have the best predictive power as calculated by the area under curve (AUC), especially for long-term overall survival. In this study, we have shown that overexpression of p53 and Ki-67 could be used to discriminate low-risk luminal A subtype in breast cancer. Therefore, using the combination of p53 and Ki-67 expression in discriminating low-risk luminal A breast cancer may improve the prognostic power and provide the greatest clinical utility.

Outcome of triple-negative breast cancer in patients with or without markers regulating cell cycle and cell death

Purpose

The genes p53 and B-cell lymphoma (bcl)-2 play an important role in regulating the mechanisms of apoptosis. In this paper, we retrospectively applied these factors to our series of triple negative breast cancer (TNBC) patients, in conjunction with an evaluation of the prognostic significance of these factors' influence on TNBC survival rate. Particular focus was placed on the role of bcl-2, p53, Ki-67.

Methods

The study subjects, 94 women with TNBC, were a subset of patients operated at Kosin University Gospel Hospital from January 2000 to December 2005. Chi-squared tests were used for statistical analysis.

Results

Positive staining for cytokeratin (CK)5/6 in 23 cases (24.5%), epidermal growth factor receptor in 15 cases (16.0%), bcl-2 in 26 cases (27.7%), p53 in 55 cases (58.5%) and Ki-67 in 74 cases (78.7%) was determined. Lymph node status, tumor size and expression of CK5/6 or Ki-67 were independent prognostic factors for patients with TNBC.

Conclusion

Markers regulating cell cycle and cell death such as p53 and bcl-2 cannot be used to classify TNBCs into two subtypes with differing disease-free survival. But because our study is small in size, more abundant patient data will be needed to evaluate the factors' predictive role in regulating cell cycle and cell death.

Biomarkers predicting clinical benefit: fact or fiction?

Preoperative therapy is increasingly used in operable disease to improve the chance for breast-conservative surgery. Moreover, this strategy allows for a better definition of patient prognosis. Independently from stage at diagnosis and breast cancer subtype, the achievement of a pathological complete response (pCR) is a surrogate marker for long-term outcome. The likelihood of pCR depends on tumor biology, being poorly differentiated tumors with ductal histology, absence of hormone receptors, and high proliferation rate those with a higher chance of achieving a CR. However, pCR is a late efficacy parameter that can be evaluated at the end of the preoperative treatment; moreover, a pCR is achieved in a minority of patients and is not an appropriate efficacy measure for neoadjuvant endocrine therapy. The predictive role of tumor biomarkers such as p53, microtubule-associated tau protein, and poly (ADP-ribose) polymerase will be reviewed along with potential markers of early treatment effect.