Doxazolidine induction of apoptosis by a topoisomerase II independent mechanism

Photoactivatable Prodrug of Doxazolidine Targeting Exosomes

Natural lipid nanocarriers, exosomes, carry cell-signaling materials such as DNA and RNA for intercellular communications. Exosomes derived from cancer cells contribute to the progression and metastasis of cancer cells by transferring oncogenic signaling molecules to neighboring and remote premetastatic sites. Therefore, applying the unique properties of exosomes for cancer therapy has been expected in science, medicine, and drug discovery fields. Herein, we report that an exosome-targeting prodrug system, designated MARCKS-ED-photodoxaz, could spatiotemporally control the activation of an exquisitely cytotoxic agent, doxazolidine (doxaz), with UV light. The MARCKS-ED peptide enters a cell by forming a complex with the exosomes in situ at its plasma membrane and in the media. MARCKS-ED-photodoxaz releases doxaz under near-UV irradiation to inhibit cell growth with low nanomolar IC₅₀ values. The MARCKS-ED-photodoxaz system targeting exosomes and utilizing photochemistry will potentially provide a new approach for the treatment of cancer, especially for highly progressive and invasive metastatic cancers.

GSH-targeted nanosponges increase doxorubicin-induced toxicity "in vitro" and "in vivo" in cancer cells with high antioxidant defenses

Several reports indicate that chemo-resistant cancer cells become highly adapted to intrinsic oxidative stress by up-regulating their antioxidant systems, which causes an increase of intracellular GSH content. Doxorubicin is one of the most widely used drugs for tumor treatment, able to kill cancer cells through several mechanisms. However, doxorubicin use is limited by its toxicity and cancer resistance. Therefore, new therapeutic strategies able to reduce doses and to overcome chemo-resistance are needed. A new class of glutathione-responsive cyclodextrin nanosponges (GSH-NS), is able to release anticancer drugs preferentially in cells having high GSH content. Doxorubicin-loaded GSH-NS, in the cancer cells with high GSH content, inhibited clonogenic growth, cell viability, topoisomerase II activity and induced DNA damage with higher effectiveness than free drug. Moreover, GSH-NS reduced the development of human tumor in xenograft models more than free drug. These characteristics indicate that GSH-NS can be a suitable drug delivery carrier for future applications in cancer therapy.

Transcription factor Ets1 cooperates with estrogen receptor α to stimulate estradiol-dependent growth in breast cancer cells and tumors

The purpose of this study was to explore the role of transcription factor Ets1 in estrogen receptor α (ERα)-positive breast cancer progression. We expressed human Ets1 or empty vector in four human ERα-positive breast cancer cell lines and observed increased colony formation. Further examination of cellular responses in stable Ets1-expressing MCF7 clones displayed increased proliferation, migration, and invasion. Ets1-expressing MCF7 tumors grown in the mammary fat pads of nude mice exhibited increased rates of tumor growth (7.36±2.47 mm(3)/day) compared to control MCF7 tumors (2.52±1.70 mm(3)/day), but maintained their dependence on estradiol for tumor growth. Proliferation marker Ki-67 staining was not different between control and Ets1-expressing tumors, but Ets1-expressing tumors exhibited large necrotic centers and elevated apoptotic staining. Ets1 was shown to cooperate with ERα and the p160 nuclear receptor coactivator (NCOA/SRC) family to increase activation of a consensus estrogen response element luciferase reporter construct. Ets1-expressing MCF7 cells also exhibited elevated expression of the ERα target genes, progesterone receptor and trefoil factor 1. Using GST-pulldown assays, Ets1 formed stable complexes containing both ERα and p160 nuclear receptor coactivators. Taken together, these data suggest that the Ets1-dependent estradiol sensitization of breast cancer cells and tumors may be partially due to the ability of Ets1 to cooperate with ERα and nuclear receptor coactivators to stimulate transcriptional activity of estrogen-dependent genes.

Differential in vitro activity of the DNA topoisomerase inhibitor idarubicin against Trypanosoma rangeli and Trypanosoma cruzi

In this study the effect of eight DNA topoisomerase inhibitors on the growth Trypanosoma rangeli epimastigotes in cell culture was investigated. Among the eight compounds tested, idarubicin was the only compound that displayed promising trypanocidal activity with a half-maximal growth inhibition (GI(50)) value in the sub-micromolar range. Fluorescence-activated cell sorting analysis showed a reduction in DNA content in T. rangeli epimastigotes when treated with idarubicin. In contrast to T. rangeli, against Trypanosoma cruzi epimastigotes idarubicin was much less effective exhibiting a GI(50) value in the mid-micromolar range. This result indicates that idarubicin displays differential toxic effects in T. rangeli and T. cruzi. Compared with African trypanosomes, it seems that American trypanosomes are generally less susceptible to DNA topoisomerase inhibitors.

Synthesis and biological characterization of protease-activated prodrugs of doxazolidine

Doxazolidine (doxaz) is a new anthracycline anticancer agent. While structurally similar to doxorubicin (dox), doxaz acts via a distinct mechanism to selectively enhance anticancer activity over cardiotoxicity, the most significant clinical impediment to successful anthracycline treatment. Here, we describe the synthesis and characterization of a prodrug platform designed for doxaz release mediated by secreted proteolytic activity, a common association with invasiveness and poor prognosis in cancer patients. GaFK-Doxaz is hydrolyzable by the proteases plasmin and cathepsin B, both strongly linked with cancer progression, as well as trypsin. We demonstrate that activation of GaFK-Doxaz releases highly potent doxaz that powerfully inhibits the growth of a wide variety of cancer cells (average IC(50) of 8 nM). GaFK-Doxaz is stable in human plasma and is poorly membrane permeable, thereby limiting activation to locally secreted proteolytic activity and reducing the likelihood of severe side effects.

Chemo brain (chemo fog) as a potential side effect of doxorubicin administration: role of cytokine-induced, oxidative/nitrosative stress in cognitive dysfunction

Doxorubicin (ADRIAMYCIN, RUBEX) is a chemotherapeutic agent that is commonly administered to breast cancer patients in standard chemotherapy regimens. As true of all such therapeutic cytotoxic agents, it can damage normal, noncancerous cells and might affect biochemical processes in a manner that might lead to, or contribute to, chemotherapy-induced cognitive deficits when administered either alone or in combination with other agents.

Preclinical efficacy of a carboxylesterase 2-activated prodrug of doxazolidine

Doxazolidine (Doxaz) is a functionally distinct formaldehyde conjugate of doxorubicin (Dox) that induces cancer cell death in Dox-sensitive and resistant cells. Pentyl PABC-Doxaz (PPD) is a prodrug of Doxaz that is activated by carboxylesterase 2 (CES2), which is expressed by liver, non-small-cell lung, colon, pancreatic, renal, and thyroid cancer cells. Here, we demonstrate that in two murine models, PPD was effective at slowing tumor growth and demonstrated markedly reduced cardiotoxic and nephrotoxic effects, as well as better tolerance, relative to Dox. Hepatotoxicity, consistent with liver expression of the murine CES2 homologue, was induced by PPD. Unlike irinotecan, a clinical CES2-activated prodrug, PPD produced no visible gastrointestinal damage. Finally, we demonstrate that cellular response to PPD may be predicted with good accuracy using CES2 expression and Doxaz sensitivity, suggesting that these metrics may be useful as clinical biomarkers for sensitivity of a specific tumor to PPD treatment.