KU675, a Concomitant Heat-Shock Protein Inhibitor of Hsp90 and Hsc70 that Manifests Isoform Selectivity for Hsp90α in Prostate Cancer Cells.

The 90-kDa heat-shock protein (Hsp90) assists in the proper folding of numerous mutated or overexpressed signal transduction proteins that are involved in cancer. Inhibiting Hsp90 consequently is an attractive strategy for cancer therapy as the concomitant degradation of multiple oncoproteins may lead to effective antineoplastic agents. Here we report a novel C-terminal Hsp90 inhibitor, designated KU675, that exhibits potent antiproliferative and cytotoxic activity along with client protein degradation without induction of the heat-shock response in both androgen-dependent and -independent prostate cancer cell lines.

Hsp90 C-terminal inhibitors exhibit antimigratory activity by disrupting the Hsp90α/Aha1 complex in PC3-MM2 cells.

Human Hsp90 isoforms are molecular chaperones that are often up-regulated in malignances and represent a primary target for Hsp90 inhibitors undergoing clinical evaluation. Hsp90α is a stress-inducible isoform of Hsp90 that plays a significant role in apoptosis and metastasis. Though Hsp90α is secreted into the extracellular space under metastatic conditions, its role in cancer biology is poorly understood.

Human cancer xenografts in outbred nude mice can be confounded by polymorphisms in a modifier of tumorigenesis.

Tumorigenicity studies often employ outbred nude mice, in the absence of direct evidence that this mixed genetic background will negatively affect experimental outcome. Here we show that outbred nude mice carry two different alleles of Pla2g2a, a genetic modifier of intestinal tumorigenesis in mice. Here, we identify previous unreported linked polymorphisms in the promoter, noncoding and coding sequences of Pla2g2a and show that outbred nude mice from different commercial providers are heterogeneous for this polymorphic Pla2g2a allele.

Development of a high-throughput screening cancer cell-based luciferase refolding assay for identifying Hsp90 inhibitors.

The 90 kDa heat-shock protein (Hsp90) and other cochaperones allow for proper folding of nascent or misfolded polypeptides. Cancer cells exploit these chaperones by maintaining the stability of mutated and misfolded oncoproteins and allowing them to evade proteosomal degradation. Inhibiting Hsp90 is an attractive strategy for cancer therapy, as the concomitant degradation of multiple oncoproteins may lead to effective anti-neoplastic agents.

Evaluation of a reductively activated duocarmycin prodrug against murine and human solid cancers.

In treating cancer with clinically approved chemotherapies, the high systemic toxicity and lack of selectivity for malignant cells often result in an overall poor response rate. One pharmacological approach to improve patient response is to design targeted therapies that exploit the cancer milieu by reductively activating prodrugs, which results in the selective release of the free drug in the tumor tissue. Previously, we characterized prodrugs of seco-CBI-indole 2 (CBI-indole 2) designed to be activated in hypoxic tumor microenvironments, wherein the tumor maintains higher concentrations of "reducing" nucleophiles capable of preferentially releasing the free drug by nucleophilic attack on a weak N-O bond.

Efficacious cyclic N-acyl O-amino phenol duocarmycin prodrugs.

Two novel cyclic N-acyl O-amino phenol prodrugs are reported as new members of a unique class of reductively cleaved prodrugs of the duocarmycin family of natural products. These prodrugs were explored with the expectation that they may be cleaved selectively within hypoxic tumor environments that have intrinsically higher concentrations of reducing nucleophiles and were designed to liberate the free drug without the release of an extraneous group. In vivo evaluation of the prodrug 6 showed that it exhibits extraordinary efficacy (T/C > 1500, L1210; 6/10 one year survivors), substantially exceeding that of the free drug, that its therapeutic window of activity is much larger, permitting a dosing ≥ 40-fold higher than the free drug, and yet that it displays a potency in vivo that approaches the free drug (within 3-fold).

A novel, unusually efficacious duocarmycin carbamate prodrug that releases no residual byproduct.

A unique heterocyclic carbamate prodrug of seco-CBI-indole(2) that releases no residual byproduct is reported as a new member of a class of hydrolyzable prodrugs of the duocarmycin and CC-1065 family of natural products. The prodrug was designed to be activated by hydrolysis of a carbamate releasing the free drug without the cleavage release of a traceable extraneous group. Unlike prior carbamate prodrugs examined that are rapidly cleaved in vivo, the cyclic carbamate was found to be exceptionally stable to hydrolysis under both chemical and biological conditions providing a slow, sustained release of the exceptionally potent free drug.

The hERG channel is dependent upon the Hsp90α isoform for maturation and trafficking.

Heat shock protein 90 (Hsp90) has emerged as a promising therapeutic target for the treatment of cancer. Several Hsp90 inhibitors have entered clinical trials. However, some toxicological detriments have arisen, such as cardiotoxicity resulting from hERG inhibition following the administration of Hsp90 inhibitors.

Development and characterization of a novel C-terminal inhibitor of Hsp90 in androgen dependent and independent prostate cancer cells.

Background: The molecular chaperone, heat shock protein 90 (Hsp90) has been shown to be overexpressed in a number of cancers, including prostate cancer, making it an important target for drug discovery. Unfortunately, results with N-terminal inhibitors from initial clinical trials have been disappointing, as toxicity and resistance resulting from induction of the heat shock response (HSR) has led to both scheduling and administration concerns. Therefore, Hsp90 inhibitors that do not induce the heat shock response represent a promising new direction for the treatment of prostate cancer.

Design, synthesis, and evaluation of duocarmycin O-amino phenol prodrugs subject to tunable reductive activation.

A series of N-acyl O-amino derivatives of seco-CBI-indole(2) are reported and examined as prototypical members of a unique class of reductively activated (cleaved) prodrugs of the duocarmycin and CC-1065 family of antitumor agents. These prodrugs were designed to be potentially preferentially activated in hypoxic tumor environments which carry an intrinsically higher concentration of "reducing" nucleophiles (e.g.

KU135, a novel novobiocin-derived C-terminal inhibitor of the 90-kDa heat shock protein, exerts potent antiproliferative effects in human leukemic cells.

The 90-kDa heat shock protein (Hsp90) assists in the proper folding of numerous mutated or overexpressed signal transduction proteins that are involved in cancer. Consequently, there is considerable interest in developing chemotherapeutic drugs that specifically disrupt the function of Hsp90. Here, we investigated the extent to which a novel novobiocin-derived C-terminal Hsp90 inhibitor, designated KU135, induced antiproliferative effects in Jurkat T-lymphocytes.

Characterization of a novel novobiocin analogue as a putative C-terminal inhibitor of heat shock protein 90 in prostate cancer cells.

Purpose: Hsp90 is important in the folding, maturation and stabilization of pro-tumorigenic client proteins and represents a viable drug target for the design of chemotherapies. Previously, we reported the development of novobiocin analogues designed to inhibit the C-terminal portion of Hsp90, which demonstrated the ability to decrease client protein expression. We now report the characterization of the novel novobiocin analogue, F-4, which demonstrates improved cytotoxicity in prostate cancer cell lines compared to the N-terminal inhibitor, 17-AAG.

A unique class of duocarmycin and CC-1065 analogues subject to reductive activation.

N-Acyl O-amino phenol derivatives of CBI-TMI and CBI-indole2 are reported as prototypical members of a new class of reductively activated prodrugs of the duocarmycin and CC-1065 class of antitumor agents. The expectation being that hypoxic tumor environments, with their higher reducing capacity, carry an intrinsic higher concentration of "reducing" nucleophiles (e.g.

Prostaglandin E2 selectively antagonizes prostaglandin F2alpha-stimulated T-cell factor/beta-catenin signaling pathway by the FPB prostanoid receptor.

FP prostanoid receptors are G-protein-coupled receptors that consist of two isoforms named FPA and FPB. Both isoforms activate inositol phosphate second messenger signaling pathways by their endogenous ligand prostaglandin F2alpha (PGF2alpha). Previously we have shown that both isoforms undergo Rho-mediated cell rounding following treatment with PGF2alpha.

Cloning and localization of hFP(S): a six-transmembrane mRNA splice variant of the human FP prostanoid receptor.

FP prostanoid receptors are G-protein coupled receptors that mediate the actions of prostaglandin F2alpha. Two isoforms, designated FP(A) and FP(B), have been previously described. We now report the cloning of a FP receptor mRNA alternative splice variant from human heart and placenta cDNA, named hFP(S).

Modulation of JB6 mouse epidermal cell transformation response by the prostaglandin F2alpha receptor.

Prostaglandin F(2alpha) (PGF(2alpha)) modulates clonal selection processes in the mouse skin model of carcinogenesis. In this study we investigated whether JB6 mouse epidermal cells expressed a functional PGF(2alpha) receptor (FP) coupled with a cell-transformation response. Treatment of JB6 cells with an FP agonist (fluprostenol) potently (pM-nM) increased anchorage-dependent and anchorage-independent growth.