LY294002-geldanamycin heterodimers as selective inhibitors of the PI3K and PI3K-related family

Several LY294002-GM heterodimers were synthesized with the intent of modulating their activity in the presence of hsp90 and thereby creating selective inhibitors of PI3K and PI3K-related family.

Inhibition of heat shock protein 90 function by ansamycins causes the morphological and functional differentiation of breast cancer cells

17-(Allylamino)-17-demethoxygeldanamycin (17-AAG) is an ansamycin antibiotic that binds to a conserved pocket in Hsp90 and induces the degradation of proteins that require this chaperone for conformational maturation. 17-AAG causes a retinoblastoma (RB)-dependent G1 block in cancer cells and is now in clinical trial. In breast cancer cells, G1 block is accompanied by differentiation and followed by apoptosis. The differentiation is characterized by specific changes in morphology and induction of milk fat proteins and lipid droplets. In cells lacking RB, neither G1 arrest nor differentiation occurs; instead, they undergo apoptosis in mitosis. Introduction of RB into these cells restores the differentiation response to 17-AAG. Inhibitors of the ras, mitogen-activated protein kinase, and phosphatidylinositol 3-kinase pathways cause accumulation of milk fat proteins and induction of lipid droplets when associated with G1 arrest but do not cause morphological changes. Thus, regulation of Hsp90 function by 17-AAG in breast cancer cells induces RB-dependent morphological and functional mammary differentiation. G1 arrest is sufficient for some but not all aspects of the phenotype. Induction of differentiation may be responsible for some of the antitumor effects of this drug.

A small molecule designed to bind to the adenine nucleotide pocket of Hsp90 causes Her2 degradation and the growth arrest and differentiation of breast cancer cells

BACKGROUND

The Hsp90s contain a conserved pocket that binds ATP/ADP and plays an important role in the regulation of chaperone function. Occupancy of this pocket by several natural products (geldanamycin (GM) and radicicol) alters Hsp90 function and results in the degradation of a subset of proteins (i.e. steroid receptors, Her2, Raf). We have used the structural features of this pocket to design a small molecule inhibitor of Hsp90.

RESULTS

The designed small molecule PU3 competes with GM for Hsp90 binding with a relative affinity of 15-20 microM. PU3 induces degradation of proteins, including Her2, in a manner similar to GM. Furthermore, PU3 inhibits the growth of breast cancer cells causing retinoblastoma protein hypophosphorylation, G1 arrest and differentiation.

CONCLUSIONS

PU3 is representative of a novel class of synthetic compounds that binds to Hsp90 and inhibits the proliferation of cancer cells. These reagents could provide a new strategy for the treatment of cancers.

A peptidomimetic inhibitor of ras functionality markedly suppresses growth of human prostate tumor xenografts in mice. Prospects for long-term clinical utility

PURPOSE

These studies sought to evaluate the antitumor properties of an inhibitor of ras functionality, L-744,832, which acts at the level of its associated protein farnesyltransferase.

METHODS

Studies were carried out to measure the effects of L-744,832 alone and in combination with paclitaxel (PTXL) against TSU-PR1, DU-145 and PC-3 human prostate tumors xenografted to NCR-nul (AT) mice. Tumor-bearing mice were treated on a schedule of daily for 5 days x2 or 3 with the MTD of L-744,832 and every 3-4 days x4 with the MTD of PTXL starting 3-5 days after tumor implantation. Tumor volume in millimeters (4/3pir3) was measured 3 5 days after cessation of treatment and the increase in tumor volume in treated and control groups compared. Statistical analysis was carried out by the Chi-squared test.

RESULTS

L-744,832 at its MTD markedly inhibited the growth of all three tumors (TIC for increase in tumor mass varied from 11% to 15% and inhibition of growth had a rapid onset (within 1-2 days) and was independent of ras gene status. Estimated tumor doubling times were 8-12-fold greater in treated animals than in control animals. Treatment with L-744,832 for as long as 3 weeks had no untoward effects on the mice as determined by gross examination or necropsy. Administration of L-744,832 with this same dose and schedule potentiated the growth-inhibitory effect of PTXL at its MTD and induced some regression of TSU-PR1 with no obvious deleterious effects on the mice.

CONCLUSIONS

L-744,832 could be safely administered over a protracted period of time to mice at doses which were markedly inhibitory to the growth of three human prostate tumor xenografts and in combination with PTXL was also well tolerated and brought about some regression of the TSU-PR1 tumor. Overall, these results suggest that L-744,832 could be clinically useful for long-term treatment of early-stage prostate cancer in patients and as an adjunct to cytotoxic therapy for late stages of this disease.

Inhibition of Hsp90 function by ansamycins causes retinoblastoma gene product-dependent G1 arrest

The ansamycin antibiotics, herbimycin A (HA) and geldanamycin (GM), bind to a conserved pocket in heat shock protein 90 (Hsp90) and alter the function of this chaperone protein. Occupancy of this pocket results in the degradation of a subset of signaling molecules. These include proteins known to associate with Hsp90, e.g., the steroid receptors and Raf, as well as certain transmembrane tyrosine kinases, such as the ErbB receptor family. In a variety of tumor cell lines, treatment with HA potently inhibited cellular proliferation by inducing G1 arrest. This arrest was accompanied by hypophosphorylation of the retinoblastoma gene product (RB) and rapid down-regulation of cyclin D- and E-associated kinase activities. Inhibition of kinase activity was found to result from loss in expression of cyclins D1, D3, and E, as well as the associated cyclin-dependent kinases, cyclin-dependent kinase 4 and cyclin-dependent kinase 6. In addition, HA treatment also caused a late induction of p27(Kip1) protein. The loss of cyclin D preceded the other effects of HA, suggesting that it might be the primary cause of G1 arrest. To determine whether the effects of HA are mediated by selective inhibition of the cyclin D-RB pathway, HA was added to tumor cell lines lacking functional RB. HA treatment of Rb-negative tumor cell lines failed to elicit a G1 arrest. In addition, after release from synchronization with nocodazole, Rb-negative but not Rb-positive cell lines were able to progress through G1 into S phase in the presence of HA. Together, these findings suggest that induction of G1 arrest by HA results from down-regulation of cyclin D expression and its associated kinase activity. Furthermore, these findings imply that Hsp90 selectively regulates signaling pathways upstream of RB.

Synthesis and evaluation of geldanamycin-testosterone hybrids

Geldanamycin (GDM) binds to the Hsp90 chaperone protein resulting in the degradation of several important signaling proteins. A series of GDM-testosterone linked hybrids has been synthesized and evaluated for activity against prostate cancer cell lines. The hybrid with the greatest activity exhibits potent and selective cytotoxicity against prostate cancer cells containing the androgen receptor.

Identification of a geldanamycin dimer that induces the selective degradation of HER-family tyrosine kinases

Geldanamycin (GM) is a natural antibiotic that binds Hsp90 and induces the degradation of receptor tyrosine kinases, steroid receptors, and Raf. It is a potent inhibitor of cancer cells that overexpress HER-kinases, but its effects on other important proteins may cause significant toxicity and limit its clinical use. We report the synthesis and identification of a GM dimer, GMD-4c, which had selective activity against HER-kinases. Selectivity was a function of linker length and required two intact GM moieties. GMD-4c is a potent inducer of G1 block and apoptosis of breast cancer cell lines that overexpress HER2, but does not appreciably inhibit the growth of 32D cells that lack HER-kinases. GMD-4c could be useful in the treatment of carcinomas dependent on HER-kinases.

Orbital lipogranuloma after sinus surgery

PURPOSE

To report the treatment and histopathological findings in two cases who developed eyelid swelling, proptosis and diplopia due to orbital and lid lipogranuloma after endoscopic surgery of the maxillary and ethmoidal sinuses.

METHODS

To relieve the proptosis and diplopia, debulking surgery was done on the eyelids and orbit. The tissue removed was sent for histopathological examination.

RESULTS

The two patients improved after surgery. The eyelid swelling, proptosis and diplopia subsided and ocular movements became normal. Histopathologic examination disclosed an extensive lipogranuloma.

CONCLUSIONS

Extensive orbital and eyelid lipogranuloma causing proptosis and diplopia is a rare complication of endoscopic sinus surgery, and can be relieved by surgical debulking.

Polysulfated heparinoids selectively inactivate heparin-binding angiogenesis factors

Angiogenesis is a prerequisite for tumor expansion and metastasis. The angiogenic potential of the heparin-binding growth factors acidic fibroblast growth factor (FGF) and basic FGF has been demonstrated in various publications. We studied the inhibitory effects of suramin and the polysulfated heparinoids pentosan polysulfate, dextran sulfate, and fucoidan on the action of FGF. As an experimental model, we used the adrenal cancer cell line SW 13, whose anchorage-independent growth depends on the presence of FGF. The polysulfated heparinoids inhibited FGF-induced growth and binding to the receptor at an IC50 of 0.5-3 micrograms/ml. Suramin inhibited FGF at an IC50 of 100 micrograms/ml. The polysulfated heparinoids exerted no effect on IGF-1 or TGF alpha-related growth. Suramin inhibited the anchorage-independent growth induced by IGF-1 or TGF alpha only at an IC50 of 100 micrograms/ml. Our results indicate that suramin inhibits growth factors in a nonselective way. By contrast, polysulfated heparinoids exert a selective inhibitory effect on heparin binding angiogenesis factors at an IC50, which is 100 times below the IC50 of suramin. Therefore, the administration of polysulfated heparinoids might become a novel approach to tumor therapy based on blocking angiogenesis.

Local control with multimodality therapy for stage 4 neuroblastoma

PURPOSE

To evaluate the efficacy of 21 Gy hyperfractionated radiotherapy for local control in conjunction with surgery and intensive systemic therapy for patients with Stage 4 neuroblastoma.

METHODS AND MATERIALS

After achieving a partial or complete remission, 47 children, ages 1-10 years, with Stage 4 neuroblastoma were treated on four consecutive institutional protocols (N4-N7) with dose-intensive multi-agent chemotherapy, maximal surgical debulking, and hyperfractionated radiotherapy (1.5 Gy twice a day to 21 Gy). Radiotherapy fields encompassed the initial tumor volume and regional lymph nodes plus a 3-cm margin. This was followed by consolidation with either autologous bone marrow transplantation (N4 and N5) or immunotherapy (N6 and N7).

RESULTS

Forty-five of 47 patients had a complete response to surgery and chemotherapy prior to radiotherapy. Five-year actuarial rates of local control, progression-free survival, and overall survival were 84%, 40%, and 45%, respectively. Among 26 patients who relapsed, 1 failed only at the primary site, 22 developed distant metastases exclusively, and 3 had both local and distant failures. There were no acute complications of radiotherapy.

CONCLUSION

Hyperfractionated radiotherapy to 21 Gy, in conjunction with dose-intensive systemic therapy and aggressive surgical resection, is well tolerated and is associated with durable local control for most patients with Stage 4 neuroblastoma.

Inhibition of Src kinases by a selective tyrosine kinase inhibitor causes mitotic arrest

src kinase activity is elevated in some human tumors, including breast and colon cancers. The precise cellular function of the src family kinases is not clearly understood, but they appear to be involved in numerous signaling pathways. We studied the effects of PD173955, a novel src family-selective tyrosine kinase inhibitor, on cancer cell lines and found that it has significant antiproliferative activity due to a potent arrest of mitotic progression. The mitotic block occurs after chromosome condensation in prophase, before spindle assembly and without loss of cyclin A and B kinase activities. This effect is seen in cancer cell lines of all types with low or high activities of src kinases as well as in untransformed cell lines. In MDA-MB-468 breast cancer cells, this drug produces a rapid inhibition of cellular src and yes kinase activities as well as suppression of the mitotic hyperactivity of these kinases. This compound defines a novel class of antimitotic drugs that work through inhibition of src kinases and possibly other protein kinases that are required for progression through the initial phases of mitosis.

Constitutive overexpression of cyclin D1 in human breast epithelial cells does not prevent G1 arrest induced by deprivation of epidermal growth factor

Non-transformed human breast epithelial cell line MCF10A is dependent on exogenous epidermal growth factor (EGF) for continued growth. Complete G1 arrest was rapidly induced following EGF deprivation. The cell cycle arrest was accompanied by increased levels of p27KIP1, a cyclin-dependent kinase inhibitor, and reduced level of cyclin D1. This was associated with strong inhibition of cyclin-dependent kinase 2 and cyclin D1-associated kinase activities. Introduction of exogenous cyclin D1 into MCF10A (MCF10AD1) cells resulted in an accelerated cell growth rate but did not confer colony-forming capacity. Cell cycle arrest was still achieved in MCF10AD1 cells following EGF deprivation. In the great majority of MCF10AD1 clones, accumulation in G1 phase was accompanied by reduced cyclin D1 and increased p27KIP1 protein levels. In two clones where cyclin D remained unchanged during G1 arrest, it was found that more cyclin D1 protein was bound to p27KIP1. The data demonstrate that ectopic expression of cyclin D1 alone could not transform MCF10A cells nor was it sufficient to prevent G1 arrest induced by EGF deprivation.

Heat shock protein 90 mediates macrophage activation by Taxol and bacterial lipopolysaccharide

Taxol, a plant-derived antitumor agent, stabilizes microtubules. Taxol also elicits cell signals in a manner indistinguishable from bacterial lipopolysaccharide (LPS). LPS-like actions of Taxol are controlled by the lps gene and are independent of binding to the known Taxol target, beta-tubulin. Using biotin-labeled Taxol, avidin-agarose affinity chromatography, and peptide mass fingerprinting, we identified two Taxol targets from mouse macrophages and brain as heat shock proteins (Hsps) of the 70- and 90-kDa families. Geldanamycin, a specific inhibitor of the Hsp 90 family, blocked the nuclear translocation of NF-kappaB and expression of tumor necrosis factor in macrophages treated with Taxol or with LPS. Geldanamycin did not block microtubule bundling by Taxol or macrophage activation by tumor necrosis factor. Thus, Taxol binds Hsps, and Hsp 90 helps mediate the activation of macrophages by Taxol and by LPS.

Synthesis and evaluation of geldanamycin-estradiol hybrids

Geldanamycin (GDM) binds to the Hsp90 chaperone protein and causes the degradation of several important signalling proteins. A series of novel estradiol-geldanamycin hybrids has been synthesized and evaluated for their ability to induce the selective degradation of the estrogen receptor (ER). The hybrid compounds are active and more selective than the parent causing degradation of ER and HER2, but not other GDM targets.

The microtubule-stabilizing agents epothilones A and B and their desoxy-derivatives induce mitotic arrest and apoptosis in human prostate cancer cells

Epothilones are a new class of natural products that bind to tubulin and prevent the depolymerization of microtubules, although they have no structural similarity to paclitaxel. Taxanes are only marginally effective in the treatment of disseminated prostate cancer, although they may have useful activity when administered in combination with estramustine. Unlike paclitaxel, epothilones are not substrates for P-glycoprotein and are active in multidrug resistant cells. Epothilones A and B (EA, EB) have recently been synthesized in toto. In this report, we examine the effects of synthetic epothilones and their desoxy derivatives, as well as paclitaxel, on prostate cancer cell lines. EB was the most active of these compounds in tissue culture (IC(50): 50-75 pM), four to ten-fold more potent than paclitaxel. EA and the desoxyderivatives of EA and EB (dEA, dEB) were also active, but less potent than EB. Each of these compounds causes mitotic block followed by apoptotic cell death. The relative potencies for cell cycle arrest and cytotoxicity directly correlate with the ability of the drugs to bind microtubules, stabilize mitotic spindles and induce the formation of interphase microtubule bundles. Therefore, synthetic epothilones are potent inhibitors of prostate cancer cell lines and work in a fashion similar to paclitaxel. Recently, we showed that farnesyl transferase inhibitors sensitize tumor cells to paclitaxel-induced mitotic arrest. We now have extended these observations to show that paclitaxel and the epothilones synergize with FTI to arrest the growth of prostate cancer cells. Moreover, this occurs in DU145, a cell line that is not particularly sensitive to the FTI. The combination of FTI and epothilone represent a new potential clinical strategy for the treatment of advanced prostatic cancer.

Cyclin D expression is controlled post-transcriptionally via a phosphatidylinositol 3-kinase/Akt-dependent pathway

Cyclin D expression is regulated by growth factors and is necessary for the induction of mitogenesis. Herbimycin A, a drug that binds to Hsp90, induces the destruction of tyrosine kinases and causes the down-regulation of cyclin D and an Rb-dependent growth arrest in the G1 phase of the cell cycle. We find that the induction of D-cyclin expression by serum and its repression by herbimycin A are regulated at the level of mRNA translation. Induction of cyclin D by serum occurs prior to the induction of its mRNA and does not require transcription. Herbimycin A repression is characterized by a decrease in the synthetic rate of D-cyclins prior to changes in mRNA expression and in the absence of changes in the half-life of the protein. This effect on D-cyclin translation is mediated via a phosphatidylinositol 3-kinase (PI 3-kinase)-dependent pathway. PI 3-kinase inhibitors such as wortmannin and LY294002, and rapamycin, an inhibitor of FRAP/TOR, cause a decline in the level of D-cyclins, whereas inhibitors of mitogen-activated protein kinase kinase and farnesyltransferase do not. Cells expressing the activated, myristoylated form of Akt kinase, a target of PI 3-kinase, are refractory to the effects of herbimycin A or serum starvation on D-cyclin expression. These data suggest that serum induction of cyclin D expression results from enhanced translation of its mRNA and that this results from activation of a pathway that is dependent upon PI 3-kinase and Akt kinase.

A farnesyl-protein transferase inhibitor induces p21 expression and G1 block in p53 wild type tumor cells

Farnesylation is required for the membrane partition and function of several proteins, including Ras. Farnesyl-protein transferase inhibitors (FTIs) were developed to prevent Ras processing and thus to be effective agents for the treatment of cancers harboring mutated ras. However, FTIs inhibit the growth of most tumor cells and several xenograft models, irrespective of whether they possess mutated ras. Furthermore, the antiproliferative effect is not correlated with inhibition of Ki-Ras processing; tumors with wild type ras are inhibited, and FTIs are not particularly toxic. These data suggest that the mechanism of FTI action is complex and may involve other targets besides Ras. To begin to understand how FTIs work, we investigated the mechanism of growth inhibition. FTI causes G1 arrest in a subset of sensitive lines. This is accomplished by transcriptional induction of p21, which mediates the inhibition of cyclin E-associated protein kinase activity, pRb hypophosphorylation and inhibition of DNA replication. Induction of p21 is p53-dependent; it does not occur in cells with mutant p53 or in cells expressing human papillomavirus E6. However, neither p53 nor p21 are required for inhibition of cell proliferation. FTI still blocks the growth of cells deficient in these proteins. In the absence of p21, G1 block is relaxed, DNA replication is not affected, and cells become polyploid and undergo apoptosis. These results suggest that farnesylated protein(s) may be involved in regulating p53 function and in coordinating entrance into S, and that the consequences of FTI treatment are a function of the other mutations found in the tumor cell.

Bilateral Kimura's disease with devastating visual outcome

Kimura's disease is a chronic inflammatory disease involving connective tissues. We treated a patient with bilateral periocular Kimura's disease causing eyelid deformity and exophthalmos for over 20 years. She has been operated on 23 times and biopsies were taken and studied histologically. The disease continued despite the multiple surgical excisions. The consequent exophthalmos and lid changes caused lagophthalmos that resulted in severe visual impairment due to chronic bilateral corneal exposure. Kimura's disease may have a devastating effect on visual function.

Ulnar nerve palsy following fracture of the shaft of the humerus

We present an unusual case of ulnar nerve palsy associated with humeral shaft fracture. Initial examination showed swelling and tenderness. No mention of neurological deficit was found in the patient's file. Radiography showed a displaced midshaft fracture. Closed reduction and intramedullary nailing were performed. Ulnar nerve palsy was noted by the attending physician afterward, and, after four months of nonoperative treatment without any obvious improvement, the patient was referred to our center. During surgery, the nerve was found to be transected and an end-to-end repair was performed. Five months after surgery, signs of motor recovery were present. This case demonstrates that ulnar nerve injury can occur with a closed fracture of the humeral shaft.

Farnesyl transferase inhibitors cause enhanced mitotic sensitivity to taxol and epothilones

An important class of cellular proteins, which includes members of the p21ras family, undergoes posttranslational farnesylation, a modification required for their partition to membranes. Specific farnesyl transferase inhibitors (FTIs) have been developed that selectively inhibit the processing of these proteins. FTIs have been shown to be potent inhibitors of tumor cell growth in cell culture and in murine models and at doses that cause little toxicity to the animal. These data suggest that these drugs might be useful therapeutic agents. We now report that, when FTI is combined with some cytotoxic antineoplastic drugs, the effects on tumor cells are additive. No interference is noted. Furthermore, FTI and agents that prevent microtubule depolymerization, such as taxol or epothilones, act synergistically to inhibit cell growth. FTI causes increased sensitivity to induction of metaphase block by these agents, suggesting that a farnesylated protein may regulate the mitotic check point. The findings imply that FTI may be a useful agent for the treatment of tumors with wild-type ras that are sensitive to taxanes.