Sensitivity of cell lines to mitomycin C

NEK1-Mediated Phosphorylation of YAP1 Is Key to Prostate Cancer Progression

The key to preventing mCRPC progression is understanding how androgen-dependent PCa cells progress to independence and modify their transcriptional repertoire accordingly. We recently identified a novel axis of the Hippo pathway characterized by the sequential kinase cascade induced by androgen deprivation, AR−>TLK1B>NEK1>pYAP1-Y407, leading to CRPC adaptation. Phosphorylation of YAP1-Y407 increases upon ADT or induction of DNA damage, correlated with the known increase in NEK1 expression/activity, and this is suppressed in the Y407F mutant. Dominant expression of YAP1-Y407F in Hek293 cells reprograms the YAP1-mediated transcriptome to reduce TEAD- and p73-regulated gene expression and mediates sensitivity to MMC. NEK1 haploinsufficient TRAMP mice display reduced YAP1 expression and, if castrated, fail to progress to overt prostate carcinomas, even while displaying reduced E-Cadherin (E-Cad) expression in hyperplastic ductules. YAP1 overexpression, but not the Y407F mutant, transforms LNCaP cells to androgen-independent growth with a mesenchymal morphology. Immunohistochemical examination of prostate cancer biopsies revealed that the pYAP1-Y407 nuclear signal is low in samples of low-grade cancer but elevated in high GS specimens. We also found that J54, a pharmacological inhibitor of the TLK1>NEK1>YAP1 nexus leading to degradation of YAP1, can suppress the transcriptional reprogramming of LNCaP cells to androgen-independent growth and EMT progression, even when YAP1-WT is overexpressed.

Intravesical chemotherapy of high-grade bladder cancer with HTI-286, a synthetic analogue of the marine sponge product hemiasterlin

PURPOSE

HTI-286 is a fully synthetic analogue of the natural tripeptide hemiasterlin that inhibits tubulin polymerization and has strong cytotoxic potential. In this study, we evaluate the inhibitory effects of HTI-286 on human bladder cancer growth, both in vitro and as an intravesical agent in an orthotopic murine model.

EXPERIMENTAL DESIGN

Various bladder cancer cell lines were treated with HTI-286 and mitomycin C (MMC) in vitro. Human KU-7 bladder tumor cells that stably express firefly luciferase were inoculated in female nude mice by intravesical instillation and quantified using bioluminescence imaging. Mice with established KU-7-luc tumors were given HTI-286 or MMC intravesically twice a week for 2 h. Pharmacokinetic data was obtained using high-performance liquid chromatography-mass spectrometry analyses.

RESULTS

In vitro, HTI-286 was a potent inhibitor of proliferation in all tested cell lines and induced marked increases in apoptosis of KU-7-luc cells even after brief exposure. In vivo, HTI-286 significantly delayed cancer growth of bladder tumors in a dose-dependent fashion. HTI-286, at a concentration of 0.2 mg/mL, had comparable strong cytotoxicity as 2.0 mg/mL of MMC. The estimated systemic bioavailability of intravesically given HTI-286 was 1.5% to 2.1% of the initial dose.

CONCLUSIONS

Intravesical HTI-286 instillation therapy showed promising antitumor activity and minimal toxicity in an orthotopic mouse model of high-grade bladder cancer. These findings provide preclinical proof-of-principle for HTI-286 as an intravesical therapy for nonmuscle-invasive bladder cancer and warrant further evaluation of efficacy and safety in early-phase clinical trials.

Cytotoxicity against insect cells of entomopathogenic fungi of the genera Hypocrella (anamorph Aschersonia): possible agents for biological control

Extracts from entomopathogenic fungi of the genus Hypocrella (7 species) and its anamorph Aschersonia (11 species) were screened for cytotoxicity to Sf9 and C6/36 insect cells and L929, BHK(21)C13 and HepG2 mammalian cells. Cytotoxic extracts to insect cells (ID50's < or = 10 microg ml(-1)) but not to mammalian cells (ID50's > or = 10 microg ml(-1)) conformed to the criteria of the project and were considered 'lead' extracts for further investigation. 'Leads' were found in two of the Hypocrella species: H. discoidea, and H. tamurai and in three of the Aschersonia species: A. samoensis, A. badia, and A. tamurai. Bioassay-guided fractionation of the cell extract of the fungus A. samoensis BCC 1393 led to the identification of two known anthraquinone dimers, (+)rugulosin (1) and skyrin (2) which showed selective toxicity towards insect cells. (+)Rugulosin (1) and skyrin (2) exhibited strong cytotoxic activity against the insect cell line Sf9 with respective ID50 values of 1.2 and 9.6 microg ml(-1), but showed weak activity toward mammalian cells. This first report of (+)rugulosin (1) and skyrin (2) in A. samoensis is confirmed and demonstrated in another four strains of A. samoensis isolated in Thailand. The preferential cytotoxicity against Sf9 insect cells gives evidence that these insect-pathogenic fungi of the Hypocrella/Aschersonia group might be useful as an agent for pest control.

Combination of adenovirus-mediated thymidine kinase gene therapy with cytotoxic chemotherapy in bladder cancer in vitro

We evaluated efficacy, toxicity and potential synergism of adenoviral-mediated thymidine kinase (tk)- ganciclovir (GCV) gene therapy in combination with 4 cytotoxic chemotherapeutic agents (doxorubicin, cisplatin, mitomycin C, and methotrexate) in 3 human bladder cancer cell lines. Cell lines were exposed to (1) 10 different concentrations of adenovirus expressing tk plus GCV; (2) 8 different concentrations of either doxorubicin, methotrexate, mitomycin C or cisplatin; or (3) combination treatment consisting of either low-, medium- or high-dose tk-GCV gene therapy plus 8 different concentrations of a single chemotherapeutic agent. Cell survival was determined using a MTT-based cell proliferation-assay. For most combinations, adding chemotherapy to tk-GCV gene therapy did not result in any therapeutic benefit. In some scenarios, we observed modest improvement with combinations of high-dose tk-GCV gene therapy and high-dose standard chemotherapy over tk-GCV monotherapy. Low concentrations of methotrexate enhanced the antitumor effects of low- and medium-dose tk-GCV gene therapy. Low level negative interference between tk-GCV gene therapy and chemotherapy occurred in some combinations but was overall negligible. In general, adding chemotherapy to tk-GCV gene therapy did not demonstrate significant therapeutic benefit in vitro. High doses of chemotherapeutic agents should be used in combination with tk-GCV gene therapy in order to take advantage of the occasional instance where modest improvement occurred with combination therapy. Additional studies exploring the role of methotrexate in enhancing the tk-GCV system are required. Investigation of other, potentially more synergistic chemotherapeutic agents in combination with tk-GCV is warranted.