ING3 promotes prostate cancer growth by activating the androgen receptor

Background The androgen receptor (AR) is a major driver of prostate cancer, and increased AR levels and co-activators of the receptor promote the development of prostate cancer. INhibitor of Growth (ING) proteins target lysine acetyltransferase or lysine deacetylase complexes to the histone H3K4Me3 mark of active transcription, to affect chromatin structure and gene expression. ING3 is a stoichiometric member of the TIP60 lysine acetyltransferase complex implicated in prostate cancer development. Methods Biopsies of 265 patients with prostate cancer were stained for ING3, pan-cytokeratin, and DNA. LNCaP and C4-2 androgen-responsive cells were used for in vitro assays including immunoprecipitation, western blotting, Luciferase reporter assay and quantitative polymerase chain reaction. Cell viability and migration assays were performed in prostate cancer cell lines using scrambled siRNA or siRNA targeting ING3. Results We find that ING3 levels and AR activity positively correlate in prostate cancer. ING3 potentiates androgen effects, increasing expression of androgen-regulated genes and androgen response element-driven reporters to promote growth and anchorage-independent growth. Conversely, ING3 knockdown inhibits prostate cancer cell growth and invasion. ING3 activates the AR by serving as a scaffold to increase interaction between TIP60 and the AR in the cytoplasm, enhancing receptor acetylation and translocation to the nucleus. Activation is independent of ING3's ability to target the TIP60 complex to H3K4Me3, identifying a previously unknown chromatin-independent cytoplasmic activity for ING3. In agreement with in vitro observations, analysis of The Cancer Genome Atlas (TCGA) data (n = 498) and a prostate cancer tissue microarray (n = 256) show that ING3 levels are higher in aggressive prostate cancers, with high levels of ING3 predicting shorter patient survival in a low AR subgroup. Including ING3 levels with currently used indicators such as the Gleason score provides more accurate prognosis in primary prostate cancer. Conclusions In contrast to the majority of previous reports suggesting tumor suppressive functions in other cancers, our observations identify a clear oncogenic role for ING3, which acts as a co-activator of AR in prostate cancer. Data from TCGA and our previous and current tissue microarrays suggest that ING3 levels correlate with AR levels and that in patients with low levels of the receptor, ING3 level could serve as a useful prognostic biomarker

Regulation of Cell Death by The Drosophila ING Proteins

The inhibitor of growth (ING) family of type II tumor suppressors (ING1-ING5) are involved in various cellular processes including apoptosis, DNA repair and tumor growth. INGs are subunits of histone deacetylase (HDAC) and histone acetyltransferase (HAT) complexes. The Drosophila genome encodes 3 ING homologues, dING 2, 3 and 4. In this research, I showed that overexpression of dING2 leads to smaller tissue and clone size in Drosophila. dING2 was sufficient to induce caspase-dependent but p53-independent cell death, which promoted expression of the pro-apoptotic gene, reaper. Experiments conducted on polyploid tissues revealed that clonal overexpression of dING2 had little effect in cells in the larval fat body, but resulted in smaller salivary glands. My experiments established that overexpression of dING3 induces caspase-dependent cell death. However, neither dING2 nor dING3 is required for IR-induced apoptosis. This work should provide valuable insights into the role of INGs in apoptosis

Additional file 1: Figure S1. of ING3 promotes prostate cancer growth by activating the androgen receptor

The four panels show representative images of a line of C4-2 cells stably infected with inducible lentiviral shCtrl or shING3, with or without Dox. The western blots show the efficiency of ING3 knockdown in the presence or absence of Dox. Figure S2. (A) Lysates from three AR-positive prostate cancer cell lines were subject to western blotting with antibodies against ING3, GAPDH, and actin. (B) mRNA levels of ING3 were normalized to actin in three prostate cancer cell lines. (C) LNCaP, C4-2, and VCaP cells were grown in media with charcoal stripped serum (CSS) for 48 h and treated with mibolerone (MB) or bicalutamide (Bic). Protein levels of ING3 and AR were visualized by western blotting with actin used as a loading control. (D) qRT-PCR study of ING3 in LNCaP cells after treatment with increasing concentrations of MB. The left graph shows mRNA levels of ING3 in response to MB. The right graph shows mRNA levels of seven androgen-regulated genes in response to MB. (E) A cycloheximide experiment using LNCaP cells grown in the presence or absence of MB to estimate ING3 half-life. Figure S3. (A) HEK293T cells were co-transfected with 1 μg of Myc-tagged AR and 1 μg of either empty vector or HA-tagged ING3 +/– 10 nM MB. ING3 was pulled down with HA-affinity beads, and precipitates were blotted with α-AR and α-HA. (B) To determine the effects of DNA on the interaction, co-immunoprecipitations were repeated with addition of ethidium bromide (EtBr). ING3 was precipitated using HA-affinity beads. Figure S4. LNCaP cells were infected with shCtrl or shING3 lentiviral particles for 72h under androgen deprived conditions and stained with anti-Ki67. Arrows indicate infected (RFP-positive) cells with associated Ki67 staining. RFP-positive and Ki67-positive cells were counted and percentages are shown in the table. Figure S5. ING3 affects PC migration. (A) LNCaP, PC3, and DU145 cells were transfected with either siCtrl or siING3 and, in case of LNCaP, treated with 1 nM MB for the times indicated. Transwell migration assays were performed at the indicated time points. Representative images are shown. (B) Images were taken from six random fields for each condition and counted manually on a computer using a blind experimental protocol (t test * < 0.05, ** < 0.01). (C) Wounds were made in monolayers of C4-2 cells stably expressing either shCtrl or shING3 in the presence of 10 nM MB and Dox to induce shRNA expression. Wounds were then allowed to heal during a course of 4 days. Images were taken from the same fields for each condition. Percentage of healed wound was then calculated based on pixels observed in each condition. (D) LNCaP cells were transfected with siCtrl or siING3 and treated with 1 nM MB for 72 h, then fixed and stained with Texas Red-conjugated phalloidin. Arrows highlight actin projections along cell axes consistent with filopodia formation. (E) The numbers of actin projections per cell were counted in a blind experimental protocol from a total of 50 cells, and the mean number of filopodia/cell was plotted (t test *** < 0.001). Figure S6. Representative images of prostate cancer samples showing low and high expression of AR as determined by immunohistochemistry. Samples are from the prostate cancer patient cohort used in this study. Figure S7. Kaplan-Meier survival curves using Gleason score as a known prognostic marker in the derivation and validation datasets. Figure S8. Kaplan-Meier survival curves in our prostate cancer patient cohort with low levels of AR, in the derivation and validation datasets. (PPT 4506 kb

Survivin as a Preferential Target for Cancer Therapy

Cancer is typically a consequence of imbalance between cell death and proliferation in a way favorable to cell proliferation and survival. Most conventional cancer therapies are based on targeting rapidly growing cancerous cells to block growth or enhance cell death, thereby, restoring the balance between these processes. In many instances, malignancies that develop resistance to current treatment modalities, such as chemotherapy, immunotherapy, and radiotherapy often present the greatest challenge in subsequent management of the patient. Studies have shown that under normal circumstances, cells utilize different death mechanisms, such as apoptosis (programmed cell death), autophagy, mitotic catastrophe, and necrosis to maintain homeostasis and physiological integrity of the organism, but these processes often appear to be altered in cancer. Thus, in recent years developing various strategies for administration of cytotoxic chemotherapeutics in combination with apoptosis-sensitizing reagents is receiving more emphasis. Here, we review the properties of the anti-apoptotic protein, survivin, a member of the inhibitor of apoptosis protein (IAP) family and the clinical feasibility and anti-cancer potential of drugs targeting this protein. We also discuss some key points and concerns that should be taken into consideration while developing drugs that target apoptotic proteins, such as survivin