Transcription Factor HBP1 Enhances Radiosensitivity by Inducing Apoptosis in Prostate Cancer Cell Lines

Kinase inhibitors increase individual radiation sensitivity in normal cells of cancer patients

Purpose

Kinase inhibitors (KI) are known to increase radiosensitivity, which can lead to increased risk of side effects. Data about interactions of commonly used KI with ionizing radiation on healthy tissue are rare.

Patients and methods

Freshly drawn blood samples were analyzed using three-color FISH (fluorescence in situ hybridization) to measure individual radiosensitivity via chromosomal aberrations after irradiation (2 Gy). Thresholds of 0.5 and 0.6 breaks/metaphase (B/M) indicate moderate or clearly increased radiosensitivity.

Results

The cohorts consisted of healthy individuals (NEG, n = 219), radiosensitive patients (POS, n = 24), cancer patients (n = 452) and cancer patients during KI therapy (n = 49). In healthy individuals radiosensitivity (≥ 0.6 B/M) was clearly increased in 5% of all cases, while in the radiosensitive cohort 79% were elevated. KI therapy increased the rate of sensitive patients (≥ 0.6 B/M) to 35% significantly compared to 19% in cancer patients without KI (p = 0.014). Increased radiosensitivity of peripheral blood mononuclear cells (PBMCs) among patients occurred in six of seven KI subgroups. The mean B/M values significantly increased during KI therapy (0.47 ± 0.20 B/M without compared to 0.50 ± 0.19 B/M with KI, p = 0.047).

Conclusions

Kinase inhibitors can intensify individual radiosensitivity of PBMCs distinctly in 85% of tested drugs.

Epigenetic mechanisms underlying prostate cancer radioresistance

Radiotherapy (RT) is one of the mainstay treatments for prostate cancer (PCa), a highly prevalent neoplasm among males worldwide. About 30% of newly diagnosed PCa patients receive RT with a curative intent. However, biochemical relapse occurs in 20–40% of advanced PCa treated with RT either alone or in combination with adjuvant-hormonal therapy. Epigenetic alterations, frequently associated with molecular variations in PCa, contribute to the acquisition of a radioresistant phenotype. Increased DNA damage repair and cell cycle deregulation decreases radio-response in PCa patients. Moreover, the interplay between epigenome and cell growth pathways is extensively described in published literature. Importantly, as the clinical pattern of PCa ranges from an indolent tumor to an aggressive disease, discovering specific targetable epigenetic molecules able to overcome and predict PCa radioresistance is urgently needed. Currently, histone-deacetylase and DNA-methyltransferase inhibitors are the most studied classes of chromatin-modifying drugs (so-called ‘epidrugs’) within cancer radiosensitization context. Nonetheless, the lack of reliable validation trials is a foremost drawback. This review summarizes the major epigenetically induced changes in radioresistant-like PCa cells and describes recently reported targeted epigenetic therapies in pre-clinical and clinical settings.

Prediction of Radioresistant Prostate Cancer Based on Differentially Expressed Proteins

INTRODUCTION

Although relapses after radiotherapy are common in prostate cancer (PCA) patients, those with a high risk for radioresistance cannot be identified prior to treatment yet. Therefore, this proof-of-concept study was performed to compare protein expression profiles of patients with radio-recurrent PCA to patients treated with primary radical prostatectomy separated by Gleason risk groups. We hypothesized that radio-recurrent PCA have a similar protein expression as high-risk Gleason PCA.

METHODS

Patient cohorts consisted of (i) 31 patients treated with salvage prostatectomy for locally recurrent PCA after primary radiotherapy and (ii) 94 patients treated with primary prostatectomy split into a Gleason high-risk (≥4 + 3; n = 42 [44.7%]) versus a low-risk group (≤3 + 4; n = 52 [55.3%]). Immunohistochemistry was performed using 15 antibodies with known association to radioresistance in PCA in vitro. ELISA was used for validation of selected markers in serum.

RESULTS

Androgen receptor (AR) was overexpressed in most radio-recurrent PCA (89.7%) and in most primary high-risk Gleason PCA (87.8%; p = 0.851), while only 67.3% of the low-risk group showed an expression (p = 0.017). Considering the highest Gleason pattern in primary PCA, aldo-keto reductase family 1 member C3 (AKR1C3) was most similarly expressed by patients with radio-recurrent PCA and patients with Gleason patterns 4 and 5 (p = 0.827 and p = 0.893) compared to Gleason pattern 3 (p = 0.20). These findings were supported by ELISA.

CONCLUSION

This is the first study to evaluate protein markers in order to predict radioresistance in PCA. Our results point to AR and AKR1C3 as the most promising markers that might help stratify patients for radiotherapy.

Long noncoding RNA actin filament-associated protein 1 antisense RNA 1 promotes malignant phenotype through binding with lysine-specific demethylase 1 and repressing HMG box-containing protein 1 in non-small-cell lung cancer

The number of documented long noncoding RNAs (lncRNAs) has dramatically increased, and their biological functions and underlying mechanisms in pathological processes, especially cancer, remain to be elucidated. Actin filament‐associated protein 1 antisense RNA 1 (AFAP1‐AS1) is a 6810‐nt lncRNA located on chromosome 4p16.1 that was first reported to be upregulated in esophageal adenocarcinoma tissues and cell lines. Here we reported that AFAP1‐AS1, recruiting and binding to lysine‐specific demethylase 1 (LSD1), was generally overexpressed in human non‐small‐cell lung cancer (NSCLC) tissues using quantitative real‐time PCR. Higher AFAP1‐AS1 expression was significantly correlated with larger tumor size (P = .008), lymph node metastasis (P = .025), higher TNM stage (P = .024), and worse overall survival in NSCLC patients. In vitro experiments revealed that AFAP1‐AS1 downregulation inhibited cell migration and induced apoptosis; AFAP1‐AS1 knockdown also hindered tumorigenesis in vivo. Moreover, mechanistic investigations including RNA immunoprecipitation and ChIP assays validated that AFAP1‐AS1 repressed HMG box‐containing protein 1 (HBP1) expression by recruiting LSD1 to the HBP1 promoter regions in PC‐9 and H1975 cells. Furthermore, HBP1 functions as a tumor suppressor, and its ectopic expression hindered cell proliferation. Rescue assays determined that the oncogenic effect of AFAP1‐AS1 is partially dependent on the epigenetic silencing of HBP1. In conclusion, our results indicate that AFAP1‐AS1 is carcinogenic and that the AFAP1‐AS1/LSD1/HBP1 axis could constitute a new therapeutic direction for NSCLC.

The HMG box transcription factor HBP1: a cell cycle inhibitor at the crossroads of cancer signaling pathways

HMG box protein 1 (HBP1) is a transcription factor and a potent cell cycle inhibitor in normal and cancer cells. HBP1 activates or represses the expression of different cell cycle genes (such as CDKN2A, CDKN1A, and CCND1) through direct DNA binding, cofactor recruitment, chromatin remodeling, or neutralization of other transcription factors. Among these are LEF1, TCF4, and MYC in the WNT/beta-catenin pathway. HBP1 also contributes to oncogenic RAS-induced senescence and terminal cell differentiation. Collectively, these activities suggest a tumor suppressor function. However, HBP1 is not listed among frequently mutated cancer driver genes. Nevertheless, HBP1 expression is lower in several tumor types relative to matched normal tissues. Several micro-RNAs, such as miR-155, miR-17-92, and miR-29a, dampen HBP1 expression in cancer cells of various origins. The phosphatidylinositol-3 kinase (PI3K)/AKT pathway also inhibits HBP1 transcription by preventing FOXO binding to the HBP1 promoter. In addition, AKT directly phosphorylates HBP1, thereby inhibiting its transcriptional activity. Taken together, these findings place HBP1 at the center of a network of micro-RNAs and oncoproteins that control cell proliferation. In this review, we discuss our current understanding of HBP1 function in human physiology and diseases.

MiR-21 improves invasion and migration of drug-resistant lung adenocarcinoma cancer cell and transformation of EMT through targeting HBP1

This study was aimed at the investigation of the effects of miR-21 on drug resistance, invasion, migration, and epithelial-mesenchymal transition (EMT) of lung adenocarcinoma cells and the related molecular mechanisms. Cell viability of A549 cell line was measured by MTT assay. Wound healing assay and transwell assay were, respectively, employed to examine cell migration and invasion abilities. The cells were transfected with miR-21 mimic or inhibitor using Lipofectamine 3000. The target relationship between miR-21 and HBP1 was confirmed by luciferase reporter gene assay. Western blot and qRT-PCR were used to examine the expression of HBP1 and EMT-related molecules. Compared with A549 cells, drug resistance of A549/PTX cells and A549/DDP cells were obviously stronger. A549/PTX cells and A549/DDP cells had stronger ability of migration and invasion compared with parental A549 cells. Meanwhile, EMT of A549/PTX and A549/DDP was significantly higher than that of A549 cells. MiR-21 promoted migration, invasion, and EMT of human lung adenocarcinoma cancer cells. Our experiment also verified the target relationship between miR-21 and HBP1. MiR-21 may affect migration and invasion ability of drug-resistant lung adenocarcinoma cells by targeting HBP1, therefore modulating EMT.

HMG-box transcription factor 1: a positive regulator of the G1/S transition through the Cyclin-CDK-CDKI molecular network in nasopharyngeal carcinoma

HMG-box transcription factor 1 (HBP1) has been reported to be a tumor suppressor in diverse malignant carcinomas. However, our findings provide a conclusion that HBP1 plays a novel role in facilitating nasopharyngeal carcinoma (NPC) growth. The Kaplan-Meier analysis indicates that high expression HBP1 and low miR-29c expression both are negatively correlated with the overall survival rates of NPC patients. HBP1 knockdown inhibits cellular proliferation and growth, and arrested cells in G1 phase rather than affected cell apoptosis via flow cytometry (FCM) analysis. Mechanistically, HBP1 induces the expression of CCND1 and CCND3 levels by binding to their promoters, and binds to CDK4, CDK6 and p16^INK4A promoters while not affects their expression levels. CCND1 and CCND3 promote CCND1-CDK4, CCND3-CDK6, and CDK2-CCNE1 complex formation, thus, E2F-1 and DP-1 are activated to accelerate the G1/S transition in the cell cycle. MiR-29c is down-regulated and correlated with NPC tumorigenesis and progression. Luciferase assays confirms that miR-29c binds to the 3' untranslated region (3'-UTR) of HBP1. Introduction of pre-miR-29c decreased HBP1 mRNA and protein levels. Therefore, the high endogenous HBP1 expression might be attributed to the low levels of endogenous miR-29c in NPC. In addition, HBP1 knockdown and miR-29c agomir administration both decrease xenograft growth in nude mice in vivo. It is firstly reported that HBP1 knockdown inhibited the proliferation and metastasis of NPC, which indicates that HBP1 functions as a non-tumor suppressor gene in NPC. This study provides a novel potential target for the prevention of and therapies for NPC.

Biological function and mechanism of miR-33a in prostate cancer survival and metastasis: via downregulating Engrailed-2

OBJECTIVE

Recent studies have identified Engrailed-2 (EN-2), a homeobox-containing transcription factor, as a candidate oncogene in prostate cancer (PC). Therapeutic targeting on EN-2, however, is limited because the mechanism underlying EN-2 overexpression in prostatic cancer cells is unknown. This study was to investigate the potential regulatory role of miR-33a on EN-2 expression and explore this signaling axis in ability of prostate cancer survival and metastasis.

METHODS

The relative expression of miR-33a and EN-2 in paired prostate cancer tissue and adjacent normal tissue as well as in prostate cancer cell lines, PC3 and DU145, was determined using quantitative real-time PCR or western blot, respectively. Cells survival, migration and invasion were evaluated by assays of MTT, TUNEL and Boyden chamber assays, respectively. Direct regulation of EN-2 by miR-33a was examined by luciferase reporter assay.

RESULTS

The data showed that miR-33a was upregulated and EN-2 was downregulated in both prostate cancer tissue and prostate cancer cells. miR-33a overexpression suppresses prostate cancer cell survival and metastasis. miR-33a can directly act on EN-2 expression by binding to 3'UTR of its mRNA. Also, miR-33a negatively regulated EN-2 mRNA and protein expression. In pcDNA-EN-2 and miR-33a mimic co-transfected PC3 and DU145 cells, EN-2 overexpression reverses the anti-cell survival and metastasis actions of miR-33a overexpression. The pivotal role of miR-33a in inhibiting prostate tumor growth was confirmed in xenograft models of prostate cancer.

CONCLUSION

Our data suggest that the functional interaction of miR-33a and EN-2 is involved in tumorigenesis of prostate cancer. Also in this process EN-2 serves as a negative responder for miR-33a.