Antitumor drug cross-resistance in vivo in a murine P388 leukemia resistant to ethyl 5-amino-1,2-dihydro-2-methyl-3-phenylpyrido[3,4-b]pyrazin-7 - ylcarbamate 2-hydroxyethanesulfonate hydrate (NSC 370,147) 370147

Crocodylus porosus: a potential source of anticancer molecules

Background

Cancer remains a global threat resulting in significant morbidity and mortality despite advances in therapeutic interventions, suggesting urgency for identification of anticancer agents. Crocodiles thrive in polluted habitat, feed on germ-infested meat, are exposed to carcinogenic heavy metals, are the very few species to survive the catastrophic Cretaceous–Paleogene extinction event, yet have a prolonged lifespan and rarely been reported to develop cancer. Therefore, we hypothesised that animals living in polluted environments such as crocodiles possess anticancer molecules/mechanisms.

Methods

Crocodylus porosus was procured, blood collected, dissected and lysates prepared from internal organs. Organ lysates and sera were tested for growth inhibition, cytotoxic effects and cell survival against HeLa, PC3 and MCF7 cells and subjected to liquid chromatography mass spectrometry. RNA transcriptome analysis and differential gene analysis were performed using Galaxy Bioinformatics.

Results

Sera exhibited potent growth inhibition and cytotoxic effects against cancer cells. 80 molecules were detected from C. porosus and 19 molecules were putatively identified. Additionally, more than 100 potential anticancer peptides were identified from sera using bioinformatics based on peptide amino acid composition, binary profile, dipeptide composition and pseudo-amino acid composition. Following transcriptome analysis, 14 genes in treated HeLa cells, 51 genes in treated MCF7 cells and 2 genes in treated PC3 cells, were found to be expressed, compared with untreated controls.

Conclusion

Animals residing in polluted milieus are an unexploited source for prospective pharmaceutical drugs, and could lead to identification of novel antitumour compound(s) and/or further understanding of the mechanisms of cancer resistance.

Intracellular delivery of the reactive oxygen species generating agent D-penicillamine upon conjugation to poly-L-glutamic acid

D-penicillamine is an aminothiol that is cytotoxic to cancer cells and generates dose dependent reactive oxygen species (ROS) via copper catalyzed oxidation. However, the delivery of D-pen to cancer cells remains a challenge due to its high hydrophilicity, highly reactive thiol group and impermeability to the cell membrane. To overcome this challenge, we investigated a novel poly-L-glutamic acid (PGA) conjugate of D-pen (PGA-D-pen) where D-pen was conjugated to PGA modified with 2-(2-pyridyldithio)-ethylamine (PDE) via disulfide bonds. Confocal microscopy and cell uptake studies showed that the fluorescently labeled PGA-D-pen was taken up by human leukemia cells (HL-60) in a time dependent manner. Treatment of HL-60, murine leukemia cells (P388) and human breast cancer cells (MDA-MB-468) with PGA-D-pen resulted in dose dependent cytotoxicity and elevation of intracellular ROS levels. PGA-D-pen induced apoptosis in HL-60 cells which was verified by Annexin V binding. The in vivo evaluation of the conjugate in the P388 murine leukemia model (intraperitoneal) resulted in significant enhancement in the survival of CD2F1 mice over vehicle control.

A phase II study of CI-980 in previously untreated extensive small cell lung cancer: an Ohio State University phase II research consortium study

CI-980, (ethyl (S)-(5-amino-1,2-dihydro-2-methyl-3-phenylpyrido[3,4-b] pyrazine-7-yl) carbamate 2-hydroxyethansulfonate (1:1)), is a water-soluble mitotic inhibitor. It acts by binding to the colchicine-binding site on tubulin, a site different from that of the vinca alkaloids, inhibiting tubulin polymerization. Cells exposed to CI-980 accumulate in M phase and die. In preclinical tumor models, CI-980 showed a broad spectrum of activity, including in multi-drug resistant tumor cell lines, with activity at least equal to that of vincristine. Extensive small cell lung cancer, despite its responsiveness to chemotherapy, is usually an incurable disease with survival in patients of less than one year. Due to the preclinical activity of CI-980 and its similar mechanism of action to drugs effective in small cell lung cancer, a phase II trial in extensive small cell lung cancer was initiated by The Ohio State University Phase II Research Consortium. A "window of opportunity" design was chosen where a short six-week trial of the drug was given unless there was significant objective response. Twelve patients were entered in the study and underwent a total of 16 cycles of chemotherapy. The median age of the patients was 54 years old (range 34-71) and performance status was ECOG 0 (four patients), ECOG 1 (seven patients), and ECOG 2 (one patient). The patients were treated with a 72-hr infusion at a dose of 4.5 mg/m2/day. Toxicity was predominantly myelosuppression with granulocytopenia (nine episodes), and anemia (seven episodes). There were no objective responses with 11 patients being removed from study due to progressive disease. Evaluation of leukocyte microtubule structure in peripheral blood revealed microtubule depolymerization, which was seen after treatment (t = 72 hr) and was reversible within 24 hr of stopping the drug. We conclude that despite antitumor activity demonstrated in preclinical studies, CI-980 does not have biological activity in previously untreated small cell lung cancer at this dose and infusion protocol.