The transcription factor KLF4 as an independent predictive marker for pathologic complete remission in breast cancer neoadjuvant chemotherapy: a case-control study

Post-transcriptional repression of circadian component CLOCK regulates cancer-stemness in murine breast cancer cells

Disruption of the circadian clock machinery in cancer cells is implicated in tumor malignancy. Studies on cancer therapy reveal the presence of heterogeneous cells, including breast cancer stem-like cells (BCSCs), in breast tumors. BCSCs are often characterized by high aldehyde dehydrogenase (ALDH) activity, associated with the malignancy of cancers. In this study, we demonstrated the negative regulation of ALDH activity by the major circadian component CLOCK in murine breast cancer 4T1 cells. The expression of CLOCK was repressed in high-ALDH-activity 4T1, and enhancement of CLOCK expression abrogated their stemness properties, such as tumorigenicity and invasive potential. Furthermore, reduced expression of CLOCK in high-ALDH-activity 4T1 was post-transcriptionally regulated by microRNA: miR-182. Knockout of miR-182 restored the expression of CLOCK, resulted in preventing tumor growth. Our findings suggest that increased expression of CLOCK in BCSCs by targeting post-transcriptional regulation overcame stemness-related malignancy and may be a novel strategy for breast cancer treatments.

BC-TFdb: a database of transcription factor drivers in breast cancer

Transcription factors (TFs) are DNA-binding proteins, which regulate many essential biological functions. In several cancer types, TF function is altered by various direct mechanisms, including gene amplification or deletion, point mutations, chromosomal translocations, expression alterations, as well as indirectly by non-coding DNA mutations influencing the binding of the TF. TFs are also actively involved in breast cancer (BC) initiation and progression. Herein, we have developed an open-access database, BC-TFdb (Breast Cancer Transcription Factors database), of curated, non-redundant TF involved in BC. The database provides BC driver TFs related information including genomic sequences, proteomic sequences, structural data, pathway information, mutations information, DNA binding residues, survival and therapeutic resources. The database will be a useful platform for researchers to obtain BC-related TF-specific information. High-quality datasets are downloadable for users to evaluate and develop computational methods for drug designing against BC. Database URL: https://www.dqweilab-sjtu.com/index.php.

New insight into the significance of KLF4 PARylation in genome stability, carcinogenesis, and therapy

KLF4 plays a critical role in determining cell fate responding to various stresses or oncogenic signaling. Here, we demonstrated that KLF4 is tightly regulated by poly(ADP‐ribosyl)ation (PARylation). We revealed the subcellular compartmentation for KLF4 is orchestrated by PARP1‐mediated PARylation. We identified that PARylation of KLF4 is critical to govern KLF4 transcriptional activity through recruiting KLF4 from soluble nucleus to the chromatin. We mapped molecular motifs on KLF4 and PARP1 that facilitate their interaction and unveiled the pivotal role of the PBZ domain YYR motif (Y430, Y451 and R452) on KLF4 in enabling PARP1‐mediated PARylation of KLF4. Disruption of KLF4 PARylation results in failure in DNA damage response. Depletion of KLF4 by RNA interference or interference with PARP1 function by KLF4^YYR/AAA (a PARylation‐deficient mutant) significantly sensitizes breast cancer cells to PARP inhibitors. We further demonstrated the role of KLF4 in modulating homologous recombination through regulating BRCA1 transcription. Our work points to the synergism between KLF4 and PARP1 in tumorigenesis and cancer therapy, which provides a potential new therapeutic strategy for killing BRCA1‐proficient triple‐negative breast cancer cells.

Recent Discoveries on the Involvement of Krüppel-Like Factor 4 in the Most Common Cancer Types

Krüppel-like factor 4 (KLF4) is a transcription factor highly conserved in evolution. It is particularly well known for its role in inducing pluripotent stem cells. In addition, KLF4 plays many roles in cancer. The results of most studies suggest that KLF4 is a tumor suppressor. However, the functioning of KLF4 is regulated at many levels. These include regulation of transcription, alternative splicing, miRNA, post-translational modifications, subcellular localization, protein stability and interactions with other molecules. Simple experiments aimed at assaying transcript levels or protein levels fail to address this complexity and thus may deliver misleading results. Tumor subtypes are also important; for example, in prostate cancer KLF4 is highly expressed in indolent tumors where it impedes tumor progression, while it is absent from aggressive prostate tumors. KLF4 is important in regulating response to many known drugs, and it also plays a role in tumor microenvironment. More and more information is available about upstream regulators, downstream targets and signaling pathways associated with the involvement of KLF4 in cancer. Furthermore, KLF4 performs critical function in the overall regulation of tissue homeostasis, cellular integrity, and progression towards malignancy. Here we summarize and analyze the latest findings concerning this fascinating transcription factor.

Predictors of Neoadjuvant Chemotherapy Response in Breast Cancer: A Review

Neoadjuvant chemotherapy (NAC) largely increases operative chances and improves prognosis of the local advanced breast cancer patients. However, no specific means have been invented to predict the therapy responses of patients receiving NAC. Therefore, we focus on the alterations of tumor tissue-related microenvironments such as stromal tumor-infiltrating lymphocytes status, cyclin-dependent kinase expression, non-coding RNA transcription or other small molecular changes, in order to detect potentially predicted biomarkers which reflect the therapeutic efficacy of NAC in different subtypes of breast cancer. Further, possible mechanisms are also discussed to discover feasible treatment targets. Thus, these findings will be helpful to promote the prognosis of breast cancer patients who received NAC and summarized in this review.

Transcription Factor Profiling to Predict Recurrence-Free Survival in Breast Cancer: Development and Validation of a Nomogram to Optimize Clinical Management

Breast cancer (BC) is the most frequently diagnosed cancer and the leading cause of cancer-related death in young women. Several prognostic and predictive transcription factor (TF) markers have been reported for BC; however, they are inconsistent due to small datasets, the heterogeneity of BC, and variation in data pre-processing approaches. This study aimed to identify an effective predictive TF signature for the prognosis of patients with BC. We analyzed the TF data of 868 patients with BC in The Cancer Genome Atlas (TCGA) database to investigate TF biomarkers relevant to recurrence-free survival (RFS). These patients were separated into training and internal validation datasets, with GSE2034 and GSE42568 used as external validation sets. A nine-TF signature was identified as crucially related to the RFS of patients with BC by univariate Cox proportional hazard analysis, least absolute shrinkage and selection operator (LASSO) Cox regression analysis, and multivariate Cox proportional hazard analysis in the training dataset. Kaplan–Meier analysis revealed that the nine-TF signature could significantly distinguish high- and low-risk patients in both the internal validation dataset and the two external validation sets. Receiver operating characteristic (ROC) analysis further verified that the nine-TF signature showed a good performance for predicting the RFS of patients with BC. In addition, we developed a nomogram based on risk score and lymph node status, with C-index, ROC, and calibration plot analysis, suggesting that it displays good performance and clinical value. In summary, we used integrated bioinformatics approaches to identify an effective predictive nine-TF signature which may be a potential biomarker for BC prognosis.

Krüppel-like factors in breast cancer: Function, regulation and clinical relevance

Breast cancer has accounted for the leading cause of cancer-related mortality among women worldwide. Although the progress in its diagnosis and treatment has come at a remarkable pace during the past several decades, there are still a wide array of problems regarding its progression, metastasis and treatment resistance that have not yet been fully clarified. Recently, an increasing number of studies have revealed that some members of Krüppel-like factors(KLFs) are significantly associated with cell proliferation, apoptosis, metastasis, cancer stem cell regulation and prognostic and predictive value for patients in breast cancer, indicating their promising prognostic and predictive potential for breast cancer survival and outcome. In this review, we will summarize our current knowledge of the functions, regulations and clinical relevance of KLFs in breast cancer.

Association of multiple genetic variants with breast cancer susceptibility in the Han Chinese population

We selected 13 tag single nucleotide polymorphisms (tSNPs) to investigate whether they were associated with breast cancer risk in the Chinese Han population. Upon statistical analyses of clinical data from 551 patients and 577 controls, we found that six of the 13 SNPs were associated with breast cancer; namely, rs4973768(Odds ratio (OR) = 1.30, 95% confidence interval (CI) =1.01-1.67), rs981782(OR =1.30, 95% CI=1.01-1.66), rs1432679(OR =0.84, 95% CI=0.70-0.99), rs10759243(OR=1.30, 95%CI=1.09-1.55), rs10822013(OR =1.18, 95% CI=1.00-1.39) and rs704010(OR =1.63, 95% CI=1.04-2.56). When stratified based on breast cancer subtype, our analyses revealed that three SNPs (rs981782, rs10759243 and rs704010) correlated with ER+ breast cancer, while another three (rs4973768, rs1432679 and rs10822013) correlated with ER- breast cancer. We obtained similar results while investigating the correlation of SNPs with PR status or clinical stage. Our results suggest that associations identified between SNPs and breast cancer through genome-wide association studies (GWAS) may not always be generalizable across races.

Enrichment of CD44 in basal-type breast cancer correlates with EMT, cancer stem cell gene profile, and prognosis

Cluster of differentiation 44 (CD44) is a transmembrane glycoprotein that serves as the receptor for the extracellular matrix component hyaluronic acid. CD44 has been reported to play key roles in cell proliferation, motility, and survival, but its role in breast cancer remains controversial. In this study, we conducted a meta-analysis. A total of 23 published Gene Expression Omnibus databases were included to evaluate the association between CD44 mRNA expression and clinicopathological characteristics or prognosis of the patients with breast cancer. Our analysis revealed that CD44 expression was associated with clinicopathological features, including the histological grade, estrogen receptor status, progesterone receptor status, and human epidermal growth factor receptor-2 status. Higher levels of CD44 expression were observed in the basal subtype of breast cancer both at the mRNA and protein levels (odds ratio [OR] =2.08, 95% confidence interval [CI]: 1.72–2.52; OR =2.11, 95% CI: 1.67–2.68). Patients with CD44 overexpression exhibited significantly worse overall survival (hazard ratio =1.27; 95% CI: 1.04–1.55). Whole gene profile analysis revealed that CD44 expression was enriched in basal-type breast cancer and correlated with epithelial–mesenchymal transition and cancer stem cell gene profiles. In summary, our analyses indicated that CD44 potentially might be a prognostic marker for breast cancer and thus can serve as a therapeutic target for basal-type breast cancer.

Interplay between arginine methylation and ubiquitylation regulates KLF4-mediated genome stability and carcinogenesis

KLF4 is an important regulator of cell-fate decision, including DNA damage response and apoptosis. We identify a novel interplay between protein modifications in regulating KLF4 function. Here we show that arginine methylation of KLF4 by PRMT5 inhibits KLF4 ubiquitylation by VHL and thereby reduces KLF4 turnover, resulting in the elevation of KLF4 protein levels concomitant with increased transcription of KLF4-dependent p21 and reduced expression of KLF4-repressed Bax. Structure-based modelling and simulations provide insight into the molecular mechanisms of KLF4 recognition and catalysis by PRMT5. Following genotoxic stress, disruption of PRMT5-mediated KLF4 methylation leads to abrogation of KLF4 accumulation, which, in turn, attenuates cell cycle arrest. Mutating KLF4 methylation sites suppresses breast tumour initiation and progression, and immunohistochemical stain shows increased levels of both KLF4 and PRMT5 in breast cancer tissues. Taken together, our results point to a critical role for aberrant KLF4 regulation by PRMT5 in genome stability and breast carcinogenesis.

Krüppel-like factor 4 plays an important role in regulating responses to DNA damage, cell-fate decision and apoptosis. Here the authors show that aberrant regulation by methyltransferase PRMT5 results in failure to arrest the cell cycle and genome instability, pointing to a role in carcinogenesis.

Micheliolide overcomes KLF4-mediated cisplatin resistance in breast cancer cells by downregulating glutathione

Micheliolide (MCL) is a promising novel compound with broad-spectrum anticancer activity. However, little is known regarding its action and mechanism in breast cancer. To explore the potential therapeutic application of MCL as a chemosensitivity modulator, this study investigated the effects of MCL on cisplatin sensitivity in breast cancer and the underlying mechanisms. In the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytotoxicity assay and a xenograft tumor model, MCL enhanced the cisplatin sensitivity of the breast cancer cell line MCF-7 both in vitro and in vivo. Treatment of MCF-7 cells with low-dose cisplatin (10 µM) was sufficient to enrich the proportion of ALDH(+) cells and upregulate Krüppel-like factor 4 (KLF4) expression. The results obtained from knockdown and overexpression experiments demonstrate that KLF4 is both necessary and sufficient to induce a cisplatin resistance phenotype in breast cancer cells. Furthermore, the glutathione (GSH) content was elevated in MCF-7 cells after overexpression of KLF4. KLF4-mediated resistance to cisplatin was found to be abrogated by treatment with buthionine sulfoximine, an inhibitor of GSH synthesis. MCL induced GSH depletion and severe cell death in KLF4-overexpressing MCF-7 cells following exposure to cisplatin. Therefore, these results suggest that MCL-mediated direct depletion of GSH represents a major mechanism in reversing KLF4-induced cisplatin resistance in MCF-7 cells.