Abstract 5229: Expression and regulation of chondroitin sulfate in prostate cancer

Increased levels of chondroitin sulfate (CS) glycosaminoglycans (GAGs) in prostate cancer (PC) have been observed for more than three decades. In 1984, De Klerk et al. noted that hyperplastic and cancerous prostate contained elevated levels of CS while other GAGs, like heparin sulfate (HS), were decreased. Chondroitin sulfate-modified proteoglycans (CSPGs), such as versican or tomoregulin (TENB2), have been promoted as PC progression markers. They have been associated with cell attachment to the matrix, the metastatic phenotype, disease progression, and androgen independence. Functionally, pericellular enrichment of CSPGs in the PC microenvironment promotes cell motility. Our team has discovered that human tumors display high levels of a specific highly sulfate type of CS normally restricted to placental and fetal tissue compartment. This "oncofetal" CS (ofCS) GAG can be conveniently detected and targeted using recombinant CS-binding VAR2CSA (rVAR2) lectins, derived from the malaria parasite Plasmodium falciparum. Recently, we identified chondroitin sulfate biosynthesis as being controlled by androgens in PC, modulating expression of the CHST11 and CHST13 carbon-4 GalNAc sulfotransferases. We established that these enzymes are under direct control of the androgen receptor (AR), regulating synthesis of the cancer-associated ofCS-modification on CSPGs. Glycosylation has a key role in many important biologic processes in cancer including cell differentiation. We identified CHST11 to be highly increased in high-risk neuroendocrine prostate cancer (NEPC) both in vitro, in vivo, and in situ. Moreover, cells that expressed neuroendocrine markers showed higher level of sulfation and ofCS. Our work reveals that alterations in GAG signatures regulated by AR might be responsible for progression neuroendocrine differentiation in prostate cancer. The prostate is an abundant secretor of PGs, and tumor-specific alterations in GAG signatures such as ofCS therefore constitute an untapped reservoir of potential biomarkers to be exploited as therapeutic targets.

Citation Format: Nader Al Nakouzi, Chris Kedong Wang, Irina Nelepcu, Coralie Crouzit, Noushin Nabavi, Amal Almami, Htoo Zarni Oo, Thomas Mandel Clausen, Tobias Gustavsson, Ali Salanti, Mads Daugaard. Expression and regulation of chondroitin sulfate in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5229.

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.

ING3 is associated with increased cell invasion and lethal outcome in ERG-negative prostate cancer patients

The inhibitor of growth family member 3 (ING3) is a member of the ING tumor suppressor family. Although its expression has been reported in various types of cancers, the role of ING3 and its prognostic value in prostate cancer (PCa) has not been investigated. ING3 expression and prognostic value was assessed in a cohort of PCa patients (n = 312) treated with transurethral resection of prostate using immumoflourescent automated quantitative analysis (AQUA) system. In vitro studies were carried out in conjunction to investigate its expression in various PCa cell lines. ING3 knockdown was also carried out in DU145 cell lines to assess for any changes in invasion and migration. ING3 expression was highest in benign prostate tissues (mean 3.2 ± 0.54) compared to PCa (mean 2.5 ± 0.26) (p = 0.437), advanced prostate cancer (AdvPCa) (mean 1.5 ± 0.32) (p = 0.004), and castration-resistant prostate cancer (CRPC) (mean 2.28 ± 0.32) (p = 0.285). ING3 expression was inversely correlated to Gleason score (p = 0.039) and ETS-related gene (ERG) expression (p = 0.019). Higher ING3 expression was marginally associated with lethal disease (p = 0.052), and this was more pronounced in patients with ERG-negative status (p = 0.018). Inhibition of ING3 in DU145 PCa cells using small interfering RNA (siRNA) was associated with decreased cell invasion (p = 0.0016) and cell migration compared to control cells. ING3 is significantly associated with PCa disease progression and cancer-specific mortality. To our knowledge, this is the first report suggesting an oncogenic function of ING3, previously well known as a tumor suppressor protein. Further studies should investigate potential-related pathways in association to ING3.

ING3 protein expression profiling in normal human tissues suggest its role in cellular growth and self-renewal

Members of the INhibitor of Growth (ING) family of proteins act as readers of the epigenetic code through specific recognition of the trimethylated form of lysine 4 of histone H3 (H3K4Me3) by their plant homeodomains. The founding member of the family, ING1, was initially identified as a tumor suppressor with altered regulation in a variety of cancer types. While alterations in ING1 and ING4 levels have been reported in a variety of cancer types, little is known regarding ING3 protein levels in normal or transformed cells due to a lack of reliable immunological tools. In this study we present the characterization of a new monoclonal antibody we have developed against ING3 that specifically recognizes human and mouse ING3. The antibody works in western blots, immunofluorescence, immunoprecipitation and immunohistochemistry. Using this antibody we show that ING3 is most highly expressed in small intestine, bone marrow and epidermis, tissues in which cells undergo rapid proliferation and renewal. Consistent with this observation, we show that ING3 is expressed at significantly higher levels in proliferating versus quiescent epithelial cells. These data suggest that ING3 levels may serve as a surrogate for growth rate, and suggest possible roles for ING3 in growth and self renewal and related diseases such as cancer.