Topoisomerase IIalpha-positive and BRCA1-negative phenotype: Association with favorable response to epirubicin-based regimens for human breast cancers

Prospects of Topoisomerase Inhibitors as Promising Anti-Cancer Agents

Topoisomerases are very important enzymes that regulate DNA topology and are vital for biological actions like DNA replication, transcription, and repair. The emergence and spread of cancer has been intimately associated with topoisomerase dysregulation. Topoisomerase inhibitors have consequently become potential anti-cancer medications because of their ability to obstruct the normal function of these enzymes, which leads to DNA damage and subsequently causes cell death. This review emphasizes the importance of topoisomerase inhibitors as marketed, clinical and preclinical anti-cancer medications. In the present review, various types of topoisomerase inhibitors and their mechanisms of action have been discussed. Topoisomerase I inhibitors, which include irinotecan and topotecan, are agents that interact with the DNA-topoisomerase I complex and avert resealing of the DNA. The accretion of DNA breaks leads to the inhibition of DNA replication and cell death. On the other hand, topoisomerase II inhibitors like etoposide and teniposide, function by cleaving the DNA-topoisomerase II complex thereby effectively impeding the release of double-strand DNA breaks. Moreover, the recent advances in exploring the therapeutic efficacy, toxicity, and MDR (multidrug resistance) issues of new topoisomerase inhibitors have been reviewed in the present review.

lncRNA and breast cancer: Progress from identifying mechanisms to challenges and opportunities of clinical treatment

Breast cancer is a malignant tumor that has a high mortality rate and mostly occurs in women. Although significant progress has been made in the implementation of personalized treatment strategies for molecular subtypes in breast cancer, the therapeutic response is often not satisfactory. Studies have reported that long non-coding RNAs (lncRNAs) are abnormally expressed in breast cancer and closely related to the occurrence and development of breast cancer. In addition, the high tissue and cell-type specificity makes lncRNAs particularly attractive as diagnostic biomarkers, prognostic factors, and specific therapeutic targets. Therefore, an in-depth understanding of the regulatory mechanisms of lncRNAs in breast cancer is essential for developing new treatment strategies. In this review, we systematically elucidate the general characteristics, potential mechanisms, and targeted therapy of lncRNAs and discuss the emerging functions of lncRNAs in breast cancer. Additionally, we also highlight the advantages and challenges of using lncRNAs as biomarkers for diagnosis or therapeutic targets for drug resistance in breast cancer and present future perspectives in clinical practice.

An epirubicin-peptide conjugate with anticancer activity is dependent upon the expression level of the surface transferrin receptor

Epirubicin (EPI) is one of the most widely used anticarcinogens; however, serious side effects, including cardiomyopathy and congestive heart failure, limit its long‑term administration. To overcome this problem, the HAIYPRH peptide ligand was used with EPI in the synthesis of a HAIYPRH‑EPI conjugate. The anticancer activity and cellular uptake of the conjugate were measured and evaluated. The results of the present study indicated that the cytotoxicity of HAIYPRH‑EPI was correlated with the expression of the cell surface transferrin receptor (TfR). The conjugate exerted high cytotoxicity and proapoptotic function when in an LN229 glioma cell line, which overexpresses surface TfR. It was hypothesized that transferrin (Tf) can promote cytotoxicity. Conversely, the conjugate exhibited very low cytotoxicity and proapoptotic function in a U87 glioma cell line, in which surface TfR expression was undetectable. In addition, fluorescence microscopy and flow cytometry methods were used to evaluate cellular uptake, and the results of these methods were consistent with the present hypotheses. The conjugate cellular uptake of the conjugate in LN229 cells was markedly higher compared with that in U87 cells, and it was hypothesized that Tf can enhance the uptake in LN229 cells. The cytotoxicity of HAIYPRH‑EPI was dependent upon the expression of surface TfR. Considering that the majority of cancer cells have high rates of iron uptake and surface TfR is generally overexpressed on cancer cells, it was speculated by the authors that HAIYPRH‑EPI may form part of an effective strategy for increasing the selectivity of EPI for cancer cells, as well as reducing its systemic toxicity. To confirm the hypothesis, the effects of HAIYPRH‑EPI on non‑cancerous cell lines were investigated. A future study will examine the side effects of HAIYPRH‑EPI, using a suitable delivery system in an animal model.

Enriched CD44(+)/CD24(-) population drives the aggressive phenotypes presented in triple-negative breast cancer (TNBC)

The mechanism underlying the aggressive behaviors of triple negative breast cancer (TNBC) is not well characterized yet. The association between cancer stem cell (CSC) population and the aggressive behaviors of TNBC has not been established. We found the CD44(+)/CD24(-) cell population was enriched in TNBC tissues and cell lines, with a higher capacity of proliferation, migration, invasion and tumorigenicity as well as lower adhesion ability. The CD44(+)/CD24(-) cell population with cancer stem cell-like properties may play an important role in the aggressive behaviors of TNBC. This discovery may lead to new therapeutic strategies targeting CD44(+)/CD24(-) cell population in TNBC.

Predictive markers of anthracycline benefit: a prospectively planned analysis of the UK National Epirubicin Adjuvant Trial (NEAT/BR9601)

BACKGROUND

The NEAT/BR9601 trial showed benefit for addition of anthracyclines to cyclophosphamide, methotrexate, and fluorouracil (CMF) as adjuvant treatment for early breast cancer. We investigated prospectively predictive biomarkers of anthracycline benefit including HER2 and TOP2A.

METHODS

1941 tumours from 2391 women recruited to NEAT/BR9601 were analysed on tissue microarrays for HER2 and TOP2A amplification and deletion, HER1-3 and Ki67 expression, and duplication of chromosome 17 centromere enumeration probe (Ch17CEP). Log-rank analyses identified factors affecting relapse-free and overall survival, and regression models tested independent prognostic effect of markers, with adjustment for known prognostic factors (age, nodal status, oestrogen-receptor status, grade, and tumour size). The predictive value of markers was tested by treatment interactions for relapse-free and overall survival.

FINDINGS

1762 patients were analysed. 21% of tumours (n=367) were HER2 amplified, 10% were TOP2A amplified (n=169), 11% showed TOP2A deleted (n=191), 23% showed Ch17CEP duplication (n=406), and 61% had high (>13.0%) Ki67 (n=1136). In univariate analyses, only HER2 amplification and TOP2A deletion were significant prognostic factors for relapse-free (hazard ratio [HR] 1.59, 95% CI 1.32-1.92, p<0.0001; and 1.52, 1.20-1.92, p=0.0006, respectively) and overall survival (1.79, 1.47-2.19, p<0.0001; and 1.62, 1.26-2.08, p=0.0002 respectively). We detected no significant interaction with anthracycline benefit for Ki67, HER2, HER1-3, or TOP2A. By contrast, in multivariate analyses, Ch17CEP duplication was associated with significant improvements in both relapse-free (HR 0.92, 95% CI 0.72-1.18 for tumours with normal Ch17CEP vs 0.52, 0.34-0.81 for tumours with abnormal Ch17CEP; p for interaction=0.004) and overall survival (0.94, 0.72-1.24 vs 0.57, 0.36-0.92; p for interaction=0.02) with anthracycline use.

INTERPRETATION

In women with early breast cancer receiving adjuvant chemotherapy, the most powerful predictor of benefit from anthracyclines is Ch17CEP duplication. In view of the location of HER2/TOP2A on chromosome 17, Ch17CEP duplication might explain the inconsistencies in previous studies of factors predicting benefit from anthracyclines.

FUNDING

Cancer Research UK and the Scottish Breast Cancer Clinical Trials Group.

Predictive factors for anthracycline-based chemotherapy for human breast cancer

Predictive factors for anthracycline-based chemotherapy have yet to be incorporated into daily practice. Meta-analyses of studies using anthracycline-based treatment regimens have shown an improved prognosis for human epidermal growth factor receptor type 2 (HER2)-positive tumors, but not for HER2-negative tumors compared with results of non-anthracycline regimens. Currently it is believed that the positive association between HER2 status and anthracycline sensitivity is indirect, that is, their association may be mediated through topoisomerase II alpha (TOP2A), a target molecule of anthracyclines, since TOP2A is near HER-2 and co-amplification of the TOP2A gene frequently occurs in HER2-amplified tumors. This strongly suggests that TOP2A gene amplification is a predictive factor for anthracyline-based regimens. The Collaborative Study Group of Scientific Research of the Japanese Breast Cancer Society has demonstrated that TOP2A-positive and BRCA1-negative subsets evaluated by immunohistochemical staining show a significantly higher pathological complete response when treated with preoperative epirubicin-containing regimens. Combining these findings with the observation that triple-negative tumors and basal-like tumors respond to anthracycline treatment suggests that not only HER2-positive tumors but also a distinct subset of HER2-negative tumors may be sensitive to anthracycline-based regimens.

Stem cell marker aldehyde dehydrogenase 1-positive breast cancers are characterized by negative estrogen receptor, positive human epidermal growth factor receptor type 2, and high Ki67 expression

Recently, aldehyde dehydrogenase (ALDH) 1 has been identified as a reliable marker for breast cancer stem cells. The aim of our study was to investigate the clinicopathological characteristics of breast cancers with ALDH1+ cancer stem cells. In addition, the distribution of ALDH1+ tumor cells was compared on a cell-by-cell basis with that of estrogen receptor (ER)+, Ki67+, or human epidermal growth factor receptor type 2 (HER2)+ tumor cells by means of double immunohistochemical staining. Immunohistochemical staining of ALDH1 was applied to 203 primary breast cancers, and the results were compared with various clinicopathological characteristics of breast cancers including tumor size, histological grade, lymph node metastases, lymphovascular invasion, ER, progesterone receptor, HER2, Ki67, and topoisomerase 2A as well as prognosis. Immunohistochemical double staining of ALDH1 and ER, Ki67, or HER2 was also carried out to investigate their distribution. Of the 203 breast cancers, 21 (10%) were found to be ALDH1+, and these cancers were significantly more likely to be ER- (P = 0.004), progesterone receptor- (P = 0.025), HER2+ (P = 0.001), Ki67+ (P < 0.001), and topoisomerase 2A+ tumors (P = 0.012). Immunohistochemical double staining studies showed that ALDH1+ tumor cells were more likely to be ER-, Ki67-, and HER2+ tumor cells. Patients with ALDH1 (score 3+) tumors showed a tendency (P = 0.056) toward a worse prognosis than did those with ALDH1- tumors. Breast cancers with ALDH1+ cancer stem cells posses biologically aggressive phenotypes that tend to have a poor prognosis, and ALDH1+ cancer stem cells are characterized by ER-, Ki67-, and HER2+.

Basal-like subtype and BRCA1 dysfunction in breast cancers

Basal-like breast cancers are characterized by their unique expression profile, with the frequent loss of BRCA1, caused by such mechanisms as promoter methylation and the overexpression of high-mobility group proteins of the A type 1 or inhibitor of differentiation 4. Clinicopathologically, basal-like cancers are estrogen receptor-, progesterone receptor-, and human epidermal growth factor receptor type 2 (HER2)-negative; they are of high grade and have a poor prognosis. The fundamental similarity between BRCA1-mutated and basal-like cancers indicates that disruption of BRCA1 may be an essential common initial pathogenic event. Furthermore, p53 mutation and EGFR overexpression occur similarly in BRCA1-mutated and basal-like cancers; these shared alterations provide very important information for understanding not only the genetic and epigenetic carcinogenic pathways in these tumors but also therapeutic strategies. Despite the limited available clinical data about response to chemotherapy, anthracycline-based chemotherapy seems to be effective in a distinct subset of basal-like cancers. Both disrupted BRCA1 and overexpressed topoisomerase II-alpha possibly found in basal-like cancers are speculated to be associated with their increased sensitivity to anthracyclines. If these tumors respond to this chemotherapy, a favorable prognosis might be expected; however, in patients who do not respond, the prognosis is poor. Currently, the sensitivity of basal-like cancers to taxanes is not clear, but considering that these tumors have disrupted mitotic checkpoint function, a poor response may be suggested. On the basis of in vitro studies, BRCA1-disrupted basal-like cancers may be sensitive to DNA-damaging agents including platinum-based compounds, topoisomerase I and II inhibitors, and alkylating agents. In future, new therapeutic approaches for patients with basal-like cancers that are unlikely to respond to chemotherapy should focus on molecules that are involved in the pathogenic pathways of this disease.