Let-7i Reduces Aggressive Phenotype and Induces BRCAness in Ovarian Cancer Cells

High-grade serous carcinoma of the ovary is a deadly gynecological cancer with poor long-term survival. Dysregulation of microRNAs has been shown to contribute to the formation of cancer stem cells (CSCs), an important part of oncogenesis and tumor progression. The let-7 family of microRNAs has previously been shown to regulate stemness and has tumor suppressive actions in a variety of cancers, including ovarian. Here, we demonstrate tumor suppressor actions of let-7i: repression of cancer cell stemness, inhibition of migration and invasion, and promotion of apoptosis, features important for cancer progression, relapse, and metastasis. Let-7i over-expression results in increased sensitivity to the PARP inhibitor olaparib in samples without BRCA mutations, consistent with induction of BRCAness phenotype. We also show that let-7i inhibits the expression of several factors involved in the homologous recombination repair (HRR) pathway, providing potential mechanisms by which the BRCAness phenotype could be induced. These actions of let-7i add to the rationale for use of this miRNA as a treatment for ovarian cancer patients, including those without mutations in the HRR pathway.

Polymorphisms in microRNA let-7 binding sites of the HIF1AN and CLDN12 genes can predict pathologic complete response to taxane- and platinum-based neoadjuvant chemotherapy in breast cancer

Background

Germline genetic polymorphisms in certain genes are associated with response to anthracycline- and taxane-based neoadjuvant chemotherapy in breast cancer (BC). Recent evidence has indicated that microRNA (miRNA) let-7 expression is associated with response to chemotherapeutics. This study aims to evaluate the potential role of let-7 miRNA-related single nucleotide polymorphisms (mirSNPs) in the prediction of pathologic complete response to taxane- and platinum-based neoadjuvant chemotherapy in locally advanced breast cancer (LABC).

Methods

We genotyped the SNPs that reside in and around miRNA let-7 binding sites of two target genes: hypoxia-inducible factor 1 subunit alpha inhibitor (HIF1AN) and claudin 12 (CLDN12). The distribution frequencies of the SNPs were genotyped in LABC patients who received taxane- and platinum-based neoadjuvant chemotherapy. Associations among tumour-relevant biomarkers, genotype and pathological complete response (pCR) were evaluated using Student's t-test for continuous variables and the chi-square or Fisher's exact tests for non-categorical variables. The modified odds ratios (ORs) with their 95% confidence intervals (CIs) were calculated by a multivariate logistic regression analysis to explore the association of genotype with pCR.

Results

For rs11292, which is located in the 3'-untranslated region (UTR) of HIF1AN, significant differences were detected in codominant, dominant and overdominant models between the patients who achieved pCR and those who did not (non-pCR) (P<0.05) in a multivariate analysis. For rs1017105, which is located in the 3'-UTR of CLDN12, significant differences were observed in the recessive model between the pCR and non-pCR patients with luminal-type BC.

Conclusions

Let-7-related mirSNPs could predict pathologic complete response to taxane- and platinum-based neoadjuvant chemotherapy in LABC, which suggests the potential role of variants of miRNA let-7-related gene networks as predictive markers in a clinical setting.

Single nucleotide polymorphisms of let-7-related genes increase susceptibility to breast cancer

BACKGROUND

Let-7 is a microRNA (miRNA) that targets the β2 adrenergic receptor (ADRB2), hypoxia inducible factor 1 subunit alpha inhibitor (HIF1AN), and claudin 12 (CLDN12) genes. Single nucleotide polymorphisms (SNPs) in the structural or regulatory regions of these miRNA let-7-related genes may be associated with breast cancer carcinogenesis and prognosis. Low let-7 expression may increase breast cancer risk. We investigated the effects of let-7-related gene SNP (mirSNPs) on breast cancer risk and clinical outcomes.

METHODS

The distribution frequencies of the three SNPs were genotyped in patients with breast cancer and controls. Multivariate logistic regression analysis was used to evaluate the association between the SNPs and susceptibility to breast cancer. We investigated the effects of these mirSNPs prospectively on disease-free survival (DFS) using the Kaplan-Meier method and the extended multivariate Cox model.

RESULTS

We found that rs1042713 in the ADRB2 gene and rs11292 in the 3'-UTR of the HIF1AN gene were associated with breast cancer susceptibility (P<0.05). The CLDN12 rs1017105 genotype was associated with estrogen receptor (P=0.031) and progesterone receptor status (P=0.007). The number of risk alleles was associated with estrogen receptor (P=0.034) status in breast cancer patients. In the survival analysis, the extended Cox model demonstrated that rs1042713 (P=0.000) and rs1017105 (P=0.004) were independent predictors of DFS. The number of risk alleles of the ADRB2, HIF1AN, and CLDN12 genes was an independent predictor of DFS (P<0.001).

CONCLUSION

Let-7-related mirSNPs might be associated with carcinogenesis and clinical outcome in breast cancer, suggesting that variants of miRNA let-7-related gene networks coregulate breast cancer characteristics.

Toll-like receptor signaling and stages of addiction

BACKGROUND

Athina Markou and her colleagues discovered persistent changes in adult behavior following adolescent exposure to ethanol or nicotine consistent with increased risk for developing addiction. Building on Dr. Markou's important work and that of others in the field, researchers at the Bowles Center for Alcohol Studies have found that persistent changes in behavior following adolescent stress or alcohol exposure may be linked to induction of immune signaling in brain.

AIM

This study aims to illuminate the critical interrelationship of the innate immune system (e.g., toll-like receptors [TLRs], high-mobility group box 1 [HMGB1]) in the neurobiology of addiction.

METHOD

This study reviews the relevant research regarding the relationship between the innate immune system and addiction.

CONCLUSION

Emerging evidence indicates that TLRs in brain, particularly those on microglia, respond to endogenous innate immune agonists such as HMGB1 and microRNAs (miRNAs). Multiple TLRs, HMGB1, and miRNAs are induced in the brain by stress, alcohol, and other drugs of abuse and are increased in the postmortem human alcoholic brain. Enhanced TLR-innate immune signaling in brain leads to epigenetic modifications, alterations in synaptic plasticity, and loss of neuronal cell populations, which contribute to cognitive and emotive dysfunctions. Addiction involves progressive stages of drug binges and intoxication, withdrawal-negative affect, and ultimately compulsive drug use and abuse. Toll-like receptor signaling within cortical-limbic circuits is modified by alcohol and stress in a manner consistent with promoting progression through the stages of addiction.

Soma influences GSC progeny differentiation via the cell adhesion-mediated steroid-let-7-Wingless signaling cascade that regulates chromatin dynamics

It is known that signaling from the germline stem cell niche is required to maintain germline stem cell identity in Drosophila. However, it is not clear whether the germline stem-cell daughters differentiate by default (because they are physically distant from the niche) or whether additional signaling is necessary to initiate the differentiation program. Previously, we showed that ecdysteroid signaling cell non-autonomously regulates early germline differentiation via its soma-specific co-activator and co-repressor, Taiman and Abrupt. Now, we demonstrate that this regulation is modulated by the miRNA let-7, which acts in a positive feedback loop to confer ecdysone signaling robustness via targeting its repressor, the transcription factor Abrupt. This feedback loop adjusts ecdysteroid signaling in response to some stressful alterations in the external and internal conditions, which include temperature stress and aging, but not nutritional deprivation. Upon let-7 deficit, escort cells fail to properly differentiate: their shape, division, and cell adhesive characteristics are perturbed. These cells have confused cellular identity and form columnar-like rather than squamous epithelium and fail to send protrusions in between differentiating germline cysts, affecting soma-germline communication. Particularly, levels of the homophilic cell adhesion protein Cadherin, which recruits Wg signaling transducer β-catenin, are increased in mutant escort cells and, correspondingly, in the adjacent germline cells. Readjustment of heterotypic (soma-germline) cell adhesion modulates Wg signaling intensity in the germline, which in turn regulates histone modifications that promote expression of the genes necessary to trigger early germline differentiation. Thus, our data first show the intrinsic role for Wg signaling in the germline and support a model where the soma influences the tempo of germline differentiation in response to external conditions.