ESR1 mutations: Pièce de résistance

The crosstalk between ubiquitination and endocrine therapy

Endocrine therapy (ET), also known as hormone therapy, refers to the treatment of tumors by regulating and changing the endocrine environment and hormone levels. Its related mechanism is mainly through reducing hormone levels and blocking the binding of hormones to corresponding receptors, thus blocking the signal transduction pathway to stimulate tumor growth. However, with the application of ET, some patients show resistance to ET, which is attributed to abnormal accumulation of hormone receptors (HRs) and the production of multiple mutants of HRs. The targeted degradation of abnormal accumulation protein mediated by ubiquitination is an important approach that regulates the protein level and function of intracellular proteins in eukaryotes. Here, we provide a brief description of the traditional and novel drugs available for ET in this review. Then, we introduce the link between ubiquitination and ET. In the end, we elaborate the clinical application of ET combined with ubiquitination-related molecules. KEY MESSAGES: • A brief description of the traditional and novel drugs available for endocrine therapy (ET). • The link between ubiquitination and ET. • The clinical application of ET combined with ubiquitination-related molecules.

The association between type of endocrine therapy and development of estrogen receptor-1 mutation(s) in patients with hormone-sensitive advanced breast cancer: A systematic review and meta-analysis of randomized and non-randomized trials

BACKGROUND

Breast cancer has, due to its high incidence, the highest mortality of cancer in women. The most common molecular type of breast cancer is the luminal subtype, which expresses estrogen and progesterone receptors and is typically treated with surgery and adjuvant endocrine therapy (ET). Estrogen receptor alpha (ERα), encoded by the estrogen receptor-1 (ESR1) gene, is expressed in approximately 70% of all breast cancers, and ET represents a major treatment modality in ERα-positive cancers. However, resistance to different ET evolves frequently, leading to disease progression or recurrence in ER+ breast cancer. Acquired mutations in the Ligand Binding Domain (LBD) of the ERα referred as ESR1 mutations; could be selected by ET itself leading to resistance over the course of ET therapy.

OBJECTIVE

The goal of this review is to estimate the effect of Aromatase Inhibitors (AIs), Tamoxifen (TAM) and Fulvestrant (FUL) on the development of ESR1 mutations in hormone-sensitive advanced breast cancer.

METHODS

A systematic review of qualitative studies published between January 1st, 2007 and March 1st, 2019 was conducted using the PubMed and Thomas Reuters Web of Science databases. Search terms included ESR1 mutations, estrogen receptor, breast cancer, recurrent, metastatic disease, aromatase inhibitors, fulvestrant and tamoxifen. Only full-text studies in English concerning the development of ESR1 mutations and their outcomes on disease progression were included. Selection of studies was performed using predefined data fields, taking study quality indicators into consideration. Inclusion criteria of the study populations were: Ghoncheh et al. (2016) [1] female patients above 18 years; Nielsen et al. (2011) [2] Estrogen-receptor positive (ER+) breast cancer in the advanced setting; Reinert et al. (2017) [3] previous exposure to endocrine therapy including SERDs (preferably Fulvestrant), SERMs (preferably Tamoxifen) or Aromatase Inhibitors.

RESULTS

The current review enrolled 16 articles, including 4 multicentre double blinded RCTs and 12 cohorts and comprising a total of 2632 patients. The overall incidence rate of the ESR1 mutation was 24% (95% CI: 18%-31%). We observed that D538G was the most frequent ESR1 mutation. Several studies showed that prior endocrine therapy (AIs, TAM, FUL) could result in an ESR1 mutation and therapy resistance leading to disease progression or recurrence. Different mechanisms had been implied to explain the underlying ET resistance. One of the key findings of this work is the significant difference in ESR1 mutation incidence between patients with and without AI therapy (OR: 9.34, 95% CI: 3.28-26.62, P ≤.001).

CONCLUSION

ESR1 mutations are not uncommon phenomenon in patients with hormone-sensitive advanced breast cancer. There is a significant higher incidence rate of ESR1 mutations in patients with previous AI-containing therapeutic regimens, compared to those who received non-AI containing regimes. These ESR1 mutations could lead to the development of complete endocrine resistance to AI, whereas only partial resistance is seen in case of TAM or FUL.

The comparison of MAMA PCR and SSCP PCR to study chromosomal resistance against Ciprofloxacin and Nalidixic acid in Escherichia coli and Klebsiella pneumoniae

The mutation in gyrA and parC genes alters amino acids. Also, it causes resistance against Fluoroquinolones in E. coli and K. pneumoniae. The purpose of this study was to diagnose the significant mutation of gyrA (ser83-asp87) and parC (ser80-glu84) genes through using MAMA PCR and SSCP PCR methods. In so doing, the isolated samples were collected. Then, utilizing agar disc diffusion method, the researchers performed antibiotic sensitivity test. Moreover, Fluoroquinolones resistance was confirmed by E-test method (MIC experiment). Furthermore, the obtained data from MAMA PCR method were sequenced accidentally. According to the findings, among 103 isolated samples, 65 samples (63/2%) were belonged to E. coli and 38 samples (36/8%) to K. pneumoniae. In all E. coli that resisted to Ciprofloxacin, at least one mutation were observed. Also, at least one mutation was observed in all K. pneumoniae samples that resisted to Ciprofloxacin. However, four mutation points were detected for each of seven samples and, interestingly, there was no mutation in five sensitive samples to Ciprofloxacin. In addition, the results revealed that the mutation in gyrA and parC genes was closely related to Quinolones resistance. Based on the findings, preparing an infection control program in Iran is highly required.