Ro 3306

RO-3306 is an ATP-competitive, potent cyclin-dependent kinase (CDK) 1 inhibitor with Ki values of 35 and 110 nM for cdk1/cyclin B1 and cdk1/cyclin A, respectively.
Cell cycle progression is regulated by a series of CDKs. Cdk1 controls the cell cycle entry into mitosis. It forms a bipartite complex with cyclin B and phosphorylates a spectrum of substrates that coordinate nuclear envelope breakdown, chromosome condensation, assembly of the mitotic spindle and activation of the spindle assembly checkpoint.  
CDK1 inhibitor RO-3306 was reported to impair BRCA1 localization to DSBs, and consistent with this, suppressed RAD51 focus formation in DU145 cells when applied at the GI50 (1μM).  Co-treatment of 100 nM AZ12253801 and 1 μM RO-3306 manifested a marked increase in pre-G1
DNA, indicating apoptosis induction. In viability assays, RO-3306 induced a significant shift to the left of the AZ12253801 dose-response curve, with 2.4-fold reduction in GI50, comparable to RAD51 depletion or inhibition. At sub-50nM AZ12253801 concentrations there was more striking sensitization, with 13-fold reduction in GI80. Paralleling effects of RAD51 knockdown, RO-3306 did not affect AZ12253801 sensitivity of PC3 or LNCaP cells, but did sensitize 22Rv1 cells.
References:
[1]. Lodhia KA, Gao S, Aleksic T, et al. Suppression of homologous recombination sensitizes human tumor cells to IGF-1R inhibition. Int J Cancer. 2014 Nov 12.

A specific inhibitor of CDK1, RO-3306, reversibly arrests meiosis during in vitro maturation of porcine oocytes.[Pubmed:24374180]

Anim Reprod Sci. 2014 Jan 30;144(3-4):102-8.

CDK1 plays pivotal role in meiotic progression of oocytes from G2 to metaphase II (MII) stage. In this study, we investigated the possibility of utilizing a selective inhibitor of CDK1, RO-3306, as a novel agent for the synchronization of oocyte maturation. Two groups of cumulus-oocyte complexes (COCs) were treated with 10 muM RO-3306. The first group was treated for 44 h, whereas the second group was transferred to drug-free medium after a 20 h treatment. MII-stage oocytes from each group were confirmed by cytoplasmic maturation and embryonic development assays. Treatment of immature porcine oocytes with RO-3306 for 20 h arrested them at the germinal vesicle (GV) stage. The GV-arrest effect of RO-3306 was reversible: when RO-3306-arrested COCs were subsequently cultured for 24h in the absence of RO-3306, 76.19 +/- 2.68% of these oocytes reached the MII stage after 44 h of in vitro maturation, a rate similar to that of non-treated control oocytes (79.08 +/- 3.23%). Furthermore, RO-3306-treated oocytes transferred to drug-free media did not differ significantly from controls (P>0.05) with respect to cleavage and blastocyst formation upon parthenogenetic activation. To explore the underlying molecular mechanisms, we examined the expression patterns of four representative maternal transcripts, CDK1, Cyclin B1, GDF9, and BMP15, by real-time polymerase chain reaction (PCR) and poly(A)-test PCR (PAT assay). RO-3306 treatment increased expression of CDK1 but had no effect on the expression of the other genes. These data suggest that RO-3306 efficiently blocks and synchronizes the meiotic progression of porcine oocytes at the GV stage without affecting their meiotic and cytoplasmic maturation.

Jumping the nuclear envelop barrier: Improving polyplex-mediated gene transfection efficiency by a selective CDK1 inhibitor RO-3306.[Pubmed:27212103]

J Control Release. 2016 Jul 28;234:90-7.

Successful transfection of plasmid DNA (pDNA) requires intranuclear internalization of pDNA effectively and the nuclear envelope appears to be one of the critical intracellular barriers for polymer mediated pDNA delivery. Polyethylenimine (PEI), as the classic cationic polymer, compact the negatively charged pDNA tightly and make up stable polyplexes. The polyplexes are too large to enter the nuclear through nuclear pores and it is believed that the nuclear envelope breakdown in mitosis could facilitate the nuclear entry of polyplexes. To jump the nuclear envelope barrier, we used a selective and reversible CDK1 inhibitor RO-3306 to control the G2/M transition of the cell cycle and increased the proportion of mitotic cells which have disappeared nuclear envelope during transfection. Herein, we show that RO-3306 remarkably increases the transfection efficiency of PEI polyplexes through enhanced nuclear localization of PEI and pDNA. However, RO-3306 is less effective to the charge-reversal polymer poly[(2-acryloyl)ethyl(p-boronic acid benzyl)diethylammonium bromide] (B-PDEAEA) which responses to cellular stimuli and releases free pDNA in cytoplasm. Our findings not only offer new opportunities for improving non-viral based gene delivery but also provide theoretical support for the rational design of novel functional polymers for gene delivery. We also report current data showing that RO-3306 synergizes TRAIL gene induced apoptosis in cancer cells.

Cyclin-dependent kinase 1 inhibitor RO-3306 enhances p53-mediated Bax activation and mitochondrial apoptosis in AML.[Pubmed:19385969]

Cancer Sci. 2009 Jun;100(6):1128-36.

Cyclin-dependent kinase (CDK) 1 and the murine double minute 2 homolog (MDM2)-p53 interaction are potential therapeutic targets in cancer, and their inhibition has been reported to be more proapoptotic in malignant cells compared to normal cells. We investigated the effect of CDK1 inhibition on p53 signaling after simultaneous dual blockade using the CDK1 inhibitor RO-3306 and the MDM2 inhibitor Nutlin-3 in AML. Treatment of growing AML cells with RO-3306 induced G2/M-phase cell cycle arrest and apoptosis in a dose- and time-dependent manner. We found that RO-3306 acts cooperatively with Nutlin-3 to induce mitochondrial apoptosis in a cell cycle-independent fashion. RO-3306 downregulated expression of the antiapoptotic proteins Bcl-2 and survivin and blocked p53-mediated induction of p21 and MDM2. CDK1 siRNA experiments showed that reduced CDK1 expression affects p53-induced p21 transactivation. We suggest that RO-3306 actively enhances downstream p53 signaling to promote apoptosis and that a combination strategy aimed at both inhibiting CDK1 and activating p53 signaling is potentially effective in AML, where TP53 mutations are rare and downstream p53 signaling is intact.

RO-3306 prevents postovulatory aging-mediated spontaneous exit from M-II arrest in rat eggs cultured in vitro.[Pubmed:26898445]

Biomed Pharmacother. 2016 Mar;78:216-225.

BACKGROUND: Postovulatory aging-mediated spontaneous exit from metaphase-II (M-II) arrest deteriorates egg quality and limits assisted reproductive technologies outcome (ART) outcome. Present study was aimed to find out whether RO-3306, specific cyclin dependent kinase 1 (Cdk1) inhibitor could protect against postovulatory aging-mediated spontaneous exit from M-II arrest in rat eggs cultured in vitro. METHODS: Freshly ovulated M-II arrested eggs were exposed to various concentrations of RO-3306 for 3h in vitro. The morphological changes, percentage of spontaneous exit from M-II arrest, total and specific phosphorylation status of Cdk1, cyclin B1 level and Cdk1 activity were analyzed. RESULTS: Data suggest that RO-3306 protected postovulatory aging-mediated spontaneous exit from M-II arrest in a concentration-dependent manner. Postovulatory aging increased Thr14/Tyr15 phosphorylated Cdk1 level, decreased Thr161 phosphorylated Cdk1 as well as cyclin B1 levels and increased Cdk1 activity in aged eggs cultured in vitro. On the other hand, RO-3306 protected postovulatory aging-induced changes in specific phosphorylation of Cdk1, cyclin B1 level, inhibited the kinase activity and prevented spontaneous exit from M-II arrest. CONCLUSIONS: Our results suggest that postovulatory aging destabilizes MPF by modulating specific phosphorylation of Cdk1 and cyclin B1 level. RO-3306 prevented these changes and maintained M-II arrest in rat eggs cultured in vitro. Hence, maintenance of M-II arrest in ovulated eggs using RO-3306 could be beneficial to increase the number of eggs available for various ART programs.

CDK1 regulates mediator of DNA damage checkpoint 1 during mitotic DNA damage.[Pubmed:22962268]

Cancer Res. 2012 Nov 1;72(21):5448-53.

Cells engage sophisticated programs of DNA damage response (DDR) and repair to guard against genetic mutations. Although there is significant knowledge concerning DDR in interphase cells, much less is known about these processes in mitosis. Direct interaction between MDC1, a master DDR organizer, and a marker of DNA damage, histone gammaH2AX, is required to trigger robust repair. Here we show that the DNA damage-induced interaction between MDC1 and gammaH2AX is attenuated in mitosis. Furthermore, inhibition in the activity of the core mitotic regulator CDK1, either by pharmacologic inhibition or siRNA attenuation, enhances MDC1-gammaH2AX colocalization in mitosis. Our findings offer key new insights into how DDR is controlled during mitosis.

Ro-3306 is a potent and selective inhibitor of CDK1, with Kis of 20 nM, 35 nM and 340 nM for CDK1, CDK1/cyclin B1 and CDK2/cyclin E, respectively.

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