Evaluation of a short RNA within Prostate Cancer Gene 3 in the predictive role for future cancer using non-malignant prostate biopsies.

BACKGROUND: Prostate Cancer 3 (PCA3) is a long non-coding RNA (ncRNA) upregulated in prostate cancer (PCa). We recently identified a short ncRNA expressed from intron 1 of PCA3. Here we test the ability of this ncRNA to predict the presence of cancer in men with a biopsy without PCa. METHODS: We selected men whose initial biopsy did not identify PCa and selected matched cohorts whose subsequent biopsies revealed PCa or benign tissue. We extracted RNA from the initial biopsy and measured PCA3-shRNA2, PCA3 and PSA (qRT-PCR). RESULTS: We identified 116 men with and 94 men without an eventual diagnosis of PCa in 2-5 biopsies (mean 26 months), collected from 2002-2008. The cohorts were similar for age, PSA and surveillance period. We detected PSA and PCA3-shRNA2 RNA in all samples, and PCA3 RNA in 90% of biopsies. The expression of PCA3 and PCA3-shRNA2 were correlated (Pearson's r = 0.37, p<0.01). There was upregulation of PCA3 (2.1-fold, t-test p = 0.02) and PCA3-shRNA2 (1.5-fold) in men with PCa on subsequent biopsy, although this was not significant for the latter RNA (p = 0.2). PCA3 was associated with the future detection of PCa (C-index 0.61, p = 0.01). This was not the case for PCA3-shRNA2 (C-index 0.55, p = 0.2). CONCLUSIONS: PCA3 and PCA3-shRNA2 expression are detectable in historic biopsies and their expression is correlated suggesting co-expression. PCA3 expression was upregulated in men with PCa diagnosed at a future date, the same did not hold for PCA3-shRNA2. Futures studies should explore expression in urine and look at a time course between biopsy and PCa detection

Phosphoproteome and drug-response effects mediated by the three protein phosphatase 2A inhibitor proteins CIP2A, SET, and PME-1

Protein phosphatase 2A (PP2A) critically regulates cell signaling and is a human tumor suppressor. PP2A complexes are modulated by proteins such as cancerous inhibitor of protein phosphatase 2A (CIP2A), protein phosphatase methylesterase 1 (PME-1), and SET nuclear proto-oncogene (SET) that often are deregulated in cancers. However, how they impact cellular phosphorylation and how redundant they are in cellular regulation is poorly understood. Here, we conducted a systematic phosphoproteomics screen for phosphotargets modulated by siRNA-mediated depletion of CIP2A, PME-1, and SET (to reactivate PP2A) or the scaffolding A-subunit of PP2A (PPP2R1A) (to inhibit PP2A) in HeLa cells. We identified PP2A-modulated targets in diverse cellular pathways, including kinase signaling, cytoskeleton, RNA splicing, DNA repair, and nuclear lamina. The results indicate nonredundancy among CIP2A, PME-1, and SET in phosphotarget regulation. Notably, PP2A inhibition or reactivation affected largely distinct phosphopeptides, introducing a concept of nonoverlapping phosphatase inhibition- and activation-responsive sites (PIRS and PARS, respectively). This phenomenon is explained by the PPP2R1A inhibition impacting primarily dephosphorylated threonines, whereas PP2A reactivation results in dephosphorylation of clustered and acidophilic sites. Using comprehensive drug-sensitivity screening in PP2A-modulated cells to evaluate the functional impact of PP2A across diverse cellular pathways targeted by these drugs, we found that consistent with global phosphoproteome effects, PP2A modulations broadly affect responses to more than 200 drugs inhibiting a broad spectrum of cancer-relevant targets. These findings advance our understanding of the phosphoproteins, pharmacological responses, and cellular processes regulated by PP2A modulation and may enable the development of combination therapies

Structural mechanism for inhibition of PP2A-B56α and oncogenicity by CIP2A.

The protein phosphatase 2A (PP2A) heterotrimer PP2A-B56α is a human tumour suppressor. However, the molecular mechanisms inhibiting PP2A-B56α in cancer are poorly understood. Here, we report molecular level details and structural mechanisms of PP2A-B56α inhibition by an oncoprotein CIP2A. Upon direct binding to PP2A-B56α trimer, CIP2A displaces the PP2A-A subunit and thereby hijacks both the B56α, and the catalytic PP2Ac subunit to form a CIP2A-B56α-PP2Ac pseudotrimer. Further, CIP2A competes with B56α substrate binding by blocking the LxxIxE-motif substrate binding pocket on B56α. Relevant to oncogenic activity of CIP2A across human cancers, the N-terminal head domain-mediated interaction with B56α stabilizes CIP2A protein. Functionally, CRISPR/Cas9-mediated single amino acid mutagenesis of the head domain blunted MYC expression and MEK phosphorylation, and abrogated triple-negative breast cancer in vivo tumour growth. Collectively, we discover a unique multi-step hijack and mute protein complex regulation mechanism resulting in tumour suppressor PP2A-B56α inhibition. Further, the results unfold a structural determinant for the oncogenic activity of CIP2A, potentially facilitating therapeutic modulation of CIP2A in cancer and other diseases

N-substituted valiolamine derivatives as potent inhibitors of endoplasmic reticulum α-glucosidases I and II with antiviral activity

Most enveloped viruses rely on the host cell endoplasmic reticulum (ER) quality control (QC) machinery for proper folding of glycoproteins. The key ER α-glucosidases (α-Glu) I and II of the ERQC machinery are attractive targets for developing broad-spectrum antivirals. Iminosugars based on deoxynojirimycin have been extensively studied as ER α-glucosidase inhibitors; however, other glycomimetic compounds are less established. Accordingly, we synthesized a series of N-substituted derivatives of valiolamine, the iminosugar scaffold of type 2 diabetes drug voglibose. To understand the basis for up to 100,000-fold improved inhibitory potency, we determined high-resolution crystal structures of mouse ER α-GluII in complex with valiolamine and 10 derivatives. The structures revealed extensive interactions with all four α-GluII subsites. We further showed that N-substituted valiolamines were active against dengue virus and SARS-CoV-2 in vitro. This study introduces valiolamine-based inhibitors of the ERQC machinery as candidates for developing potential broad-spectrum therapeutics against the existing and emerging viruses

Combined inhibition of tumor suppressors PTEN and PP2A drives anoikis resistance and is associated with therapy relapse in prostate cancer

Reactivation of tumor suppressor phosphatases may provide entirely novel opportunities for cancer therapy. Here, we discover clinically relevant functional co-operation between loss of activities of two human tumor suppressor phosphatases, PTEN, and PP2A. Analysis of prostate cancer tissue microarray material consisting of 358 patients treated primarily with radical prostatectomy revealed that overexpression of PP2A inhibitor protein PME-1 associates with significantly shorter time to therapy relapse in patients with PTEN-deficient PrCa. Further, PP2A inhibition by PME-1 overexpression in PTEN-deficient cell models inhibits apoptosis induction in anchorage-independent conditions (anoikis). PP2A reactivation by small molecules (SMAPs) was also found to inhibit viability of PTEN-deficient PrCa cells. Importantly, rather than regulating the well-known PP2A target pathways, PME-1 was found to physically associate with, and to regulate deformability of the nuclear lamina in PrCa cells. Mass spectrometry phosphoproteomics analysis identified several PME-1-regulated nuclear lamina constituents, and PME-1 deficient cells with compromised nuclear lamina were particularly vulnerable to apoptosis induction by mechanical stress. As a direct molecular target, Lamin A/C phosphorylation was found to be protected by PME-1-mediated PP2A inhibition under anoikis-inducing conditions. PME-1 inhibition in PrCa cells resulted in increased apoptosis in an in ovo tumor model, and PME-1-depleted cells had compromised long-term survival in zebrafish circulation. In summary we discover that PP2A reactivation by PME-1 targeting sensitizes PTEN-deficient PrCa cells to anoikis. Clinically, the results identify PME-1 as a novel candidate biomarker for increased relapse risk in PTEN-deficient PrCa, and indicate pharmacological PP2A activation as a novel potential therapeutic approach against circulating prostate cancer cells. At the general level, the results clearly emphasize the need for better understanding of phosphatases as key modulators of cancer progression. Citation Format: Christian Rupp, Aleksi Isomursu, Anna Aakula, Andrew Erickson, Song-Ping Li, Amanpreet Kaur, Pragya Shah, Yuba R. Pokharel, Lloyd Trottman, Jan Lammerding, Antti Rannikko, Pekka Taimen, Tuomas Mirtti, Ilkka Paatero, Johanna Ivaska, Jukka K. Westermarck. Combined inhibition of tumor suppressors PTEN and PP2A drives anoikis resistance and is associated with therapy relapse in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 348

Structural mechanism for inhibition of PP2A-B56α and oncogenicity by CIP2A

The protein phosphatase 2A (PP2A) heterotrimer PP2A-B56α is a human tumour suppressor. However, the molecular mechanisms inhibiting PP2A-B56α in cancer are poorly understood. Here, we report molecular level details and structural mechanisms of PP2A-B56α inhibition by an oncoprotein CIP2A. Upon direct binding to PP2A-B56α trimer, CIP2A displaces the PP2A-A subunit and thereby hijacks both the B56α, and the catalytic PP2Ac subunit to form a CIP2A-B56α-PP2Ac pseudotrimer. Further, CIP2A competes with B56α substrate binding by blocking the LxxIxE-motif substrate binding pocket on B56α. Relevant to oncogenic activity of CIP2A across human cancers, the N-terminal head domain-mediated interaction with B56α stabilizes CIP2A protein. Functionally, CRISPR/Cas9-mediated single amino acid mutagenesis of the head domain blunted MYC expression and MEK phosphorylation, and abrogated triple-negative breast cancer in vivo tumour growth. Collectively, we discover a unique multi-step hijack and mute protein complex regulation mechanism resulting in tumour suppressor PP2A-B56α inhibition. Further, the results unfold a structural determinant for the oncogenic activity of CIP2A, potentially facilitating therapeutic modulation of CIP2A in cancer and other diseases.ISSN:2041-172