LSD1 inhibition suppresses ASCL1 and de-represses YAP1 to drive potent activity against neuroendocrine prostate cancer

Lysine-specific demethylase 1 (LSD1 or KDM1A ) has emerged as a critical mediator of tumor progression in metastatic castration-resistant prostate cancer (mCRPC). Among mCRPC subtypes, neuroendocrine prostate cancer (NEPC) is an exceptionally aggressive variant driven by lineage plasticity, an adaptive resistance mechanism to androgen receptor axis-targeted therapies. Our study shows that LSD1 expression is elevated in NEPC and associated with unfavorable clinical outcomes. Using genetic approaches, we validated the on-target effects of LSD1 inhibition across various models. We investigated the therapeutic potential of bomedemstat, an orally bioavailable, irreversible LSD1 inhibitor with low nanomolar potency. Our findings demonstrate potent antitumor activity against CRPC models, including tumor regressions in NEPC patient-derived xenografts. Mechanistically, our study uncovers that LSD1 inhibition suppresses the neuronal transcriptional program by downregulating ASCL1 through disrupting LSD1:INSM1 interactions and de-repressing YAP1 silencing. Our data support the clinical development of LSD1 inhibitors for treating CRPC - especially the aggressive NE phenotype.

Statement of Significance

Neuroendocrine prostate cancer presents a clinical challenge due to the lack of effective treatments. Our research demonstrates that bomedemstat, a potent and selective LSD1 inhibitor, effectively combats neuroendocrine prostate cancer by downregulating the ASCL1- dependent NE transcriptional program and re-expressing YAP1.

Third generation quinoline-3-carboxamide transcriptional disrupter of HDAC4, HIF-1α, and MEF-2 signaling for metastatic castration-resistant prostate cancer

BACKGROUND

The quinoline-3-carboxamide, Tasquinimod (TasQ), is orally active as a maintenance therapy with an on-target mechanism-of-action via allosteric binding to HDAC4. This prevents formation of the HDAC4/NCoR1/HDAC3 complex, disrupting HIF-1α transcriptional activation and repressing MEF-2 target genes needed for adaptive survival signaling in the compromised tumor micro environment. In phase 3 clinical testing against metastatic castration-resistant prostate cancer(mCRPC), TasQ (1 mg/day) increased time-to-progression, but not overall survival.

METHODS

TasQ analogs were chemically synthesized and tested for activity compared to the parental compound. These included HDAC4 enzymatic assays, qRT-PCR and western blot analyses of gene and protein expression following treatment, in vitro and in vivo efficacy against multiple prostate cancer models including PDXs, pharmacokinetic analyses,AHR binding and agonist assays, SPR analyses of binding to HDAC4 and NCoR1, RNAseq analysis of in vivo tumors, 3D endothelial sprouting assays, and a targeted kinase screen. Genetic knockout or knockdown controls were used when appropriate.

RESULTS

Here, we document that, on this regimen (1 mg/day), TasQ blood levels are 10-fold lower than the optimal concentration (≥2 μM) needed for anticancer activity, suggesting higher daily doses are needed. Unfortunately, we also demonstrate that TasQ is an arylhydrocarbon receptor (AHR) agonist, which binds with an EC50 of 1 μM to produce unwanted off-target side effects. Therefore, we screened a library of TasQ analogsto maximize on-target versus off-target activity. Using this approach, we identified ESATA-20, which has ~10-fold lower AHR agonism and 5-fold greater potency against prostate cancer patient-derived xenografts.

CONCLUSION

This increased therapeuticindex nominates ESATA-20 as a lead candidate forclinical development as an orally active third generation quinoline-3-carboxamide analog thatretains its on-target ability to disrupt HDAC4/HIF-1α/MEF-2-dependent adaptive survival signaling in the compromisedtumor microenvironment found in mCRPC.

Androgen receptor activity in prostate cancer dictates efficacy of bipolar androgen therapy through MYC

Testosterone is the canonical growth factor of prostate cancer but can paradoxically suppress its growth when present at supraphysiological levels. We have previously demonstrated that the cyclical administration of supraphysiological androgen (SPA), termed bipolar androgen therapy (BAT), can result in tumor regression and clinical benefit for patients with castration-resistant prostate cancer. However, predictors and mechanisms of response and resistance have been ill defined. Here, we show that growth inhibition of prostate cancer models by SPA required high androgen receptor (AR) activity and were driven in part by downregulation of MYC. Using matched sequential patient biopsies, we show that high pretreatment AR activity predicted downregulation of MYC, improved clinical response, and prolonged progression-free and overall survival for patients on BAT. BAT induced strong downregulation of AR in all patients, which is shown to be a primary mechanism of acquired resistance to SPA. Acquired resistance was overcome by alternating SPA with the AR inhibitor enzalutamide, which induced adaptive upregulation of AR and resensitized prostate cancer to SPA. This work identifies high AR activity as a predictive biomarker of response to BAT and supports a treatment paradigm for prostate cancer involving alternating between AR inhibition and activation.

NOTCH1 PEST domain variants are responsive to standard of care treatments despite distinct transformative properties in a breast cancer model

Activating variants in the PEST region of NOTCH1 have been associated with aggressive phenotypes in human cancers, including triple-negative breast cancer (TNBC). Previous studies suggested that PEST domain variants in TNBC patients resulted in increased cell proliferation, invasiveness, and decreased overall survival. In this study, we assess the phenotypic transformation of activating NOTCH1 variants and their response to standard of care therapies. AAV-mediated gene targeting was used to isogenically incorporate 3 NOTCH1 variants, including a novel TNBC frameshift variant, in two non-tumorigenic breast epithelial cell lines, MCF10A and hTERT-IMEC. Two different variants at the NOTCH1 A2241 site (A2441fs and A2441T) both demonstrated increased transformative properties when compared to a non-transformative PEST domain variant (S2523L). These phenotypic changes include proliferation, migration, anchorage-independent growth, and MAPK pathway activation. In contrast to previous studies, activating NOTCH1 variants did not display sensitivity to a gamma secretase inhibitor (GSI) or resistance to chemotherapies. This study demonstrates distinct transformative phenotypes are specific to a given variant within NOTCH1 and these phenotypes do not correlate with sensitivities or resistance to chemotherapies or GSIs. Although previous studies have suggested NOTCH1 variants may be prognostic for TNBC, our study does not demonstrate prognostic ability of these variants and suggests further characterization would be required for clinical applications.

Post-Hypoxic Cells Promote Metastatic Recurrence after Chemotherapy Treatment in TNBC

Simple Summary

Intratumoral hypoxia is a negative prognostic factor in breast cancer progression and recurrence. By implementing a hypoxia fate-mapping system, we followed cells that experience intratumoral hypoxia in vivo and determined that these cells have an increased ability to metastasize compared to cells that were never exposed to hypoxia. In this work, we investigate whether cells that experienced intratumoral hypoxia are also resistant to chemotherapy. By utilizing both in vivo and ex vivo models, we conclude that metastatic cells found in the lung and liver, that were exposed to hypoxia in the primary tumor, are less sensitive to doxorubicin and paclitaxel and drive recurrence after treatment. Our studies also suggest that chemoresistance is associated with a cancer stem cell-like phenotype that is maintained in post-hypoxic cells.

Abstract

Hypoxia occurs in 90% of solid tumors and is associated with treatment failure, relapse, and mortality. HIF-1α signaling promotes resistance to chemotherapy in cancer cell lines and murine models via multiple mechanisms including the enrichment of breast cancer stem cells (BCSCs). In this work, we utilize a hypoxia fate-mapping system to determine whether triple-negative breast cancer (TNBC) cells that experience hypoxia in the primary tumor are resistant to chemotherapy at sites of metastasis. Using two orthotopic mouse models of TNBC, we demonstrate that cells that experience intratumoral hypoxia and metastasize to the lung and liver have decreased sensitivity to doxorubicin and paclitaxel but not cisplatin or 5-FU. Resistance to therapy leads to metastatic recurrence caused by post-hypoxic cells. We further determined that the post-hypoxic cells that metastasize are enriched in pathways related to cancer stem cell gene expression. Overall, our results show that even when hypoxic cancer cells are reoxygenated in the bloodstream they retain a hypoxia-induced cancer stem cell-like phenotype that persists and promotes resistance and eventually recurrence.

Targeted delivery of cytotoxic proteins to prostate cancer via conjugation to small molecule urea-based PSMA inhibitors

Prostate cancer cells are characterized by a remarkably low proliferative rate and the production of high levels of prostate-specific proteases. Protein-based toxins are attractive candidates for prostate cancer therapy because they kill cells via proliferation-independent mechanisms. However, the non-specific cytotoxicity of these potent cytotoxins must be redirected to avoid toxicity to normal tissues. Prostate-Specific Membrane Antigen (PSMA) is membrane-bound carboxypeptidase that is highly expressed by prostate cancer cells. Potent dipeptide PSMA inhibitors have been developed that can selectively deliver and concentrate imaging agents within prostate cancer cells based on continuous PSMA internalization and endosomal cycling. On this basis, we conjugated a PSMA inhibitor to the apoptosis-inducing human protease Granzyme B and the potent Pseudomonas exotoxin protein toxin fragment, PE35. We assessed selective PSMA binding and entrance into tumor cell to induce cell death. We demonstrated these agents selectively bound to PSMA and became internalized. PSMA-targeted PE35 toxin was selectively toxic to PSMA producing cells in vitro. Intratumoral and intravenous administration of this toxin produced marked tumor killing of PSMA-producing xenografts with minimal host toxicity. These studies demonstrate that urea-based PSMA inhibitors represent a simpler, less expensive alternative to antibodies as a means to deliver cytotoxic proteins to prostate cancer cells.

Hierarchical tumor heterogeneity mediated by cell contact between distinct genetic subclones

Intratumor heterogeneity is an important mediator of poor outcomes in many cancers, including breast cancer. Genetic subclones frequently contribute to this heterogeneity; however, their growth dynamics and interactions remain poorly understood. PIK3CA and HER2 alterations are known to coexist in breast and other cancers. Herein, we present data that describe the ability of oncogenic PIK3CA mutant cells to induce the proliferation of quiescent HER2 mutant cells through a cell contact-mediated mechanism. Interestingly, the HER2 cells proliferated to become the major subclone over PIK3CA counterparts both in vitro and in vivo. Furthermore, this phenotype was observed in both hormone receptor-positive and -negative cell lines, and was dependent on the expression of fibronectin from mutant PIK3CA cells. Analysis of human tumors demonstrated similar HER2:PIK3CA clonal dynamics and fibronectin expression. Our study provides insight into nonrandom subclonal architecture of heterogenous tumors, which may aid the understanding of tumor evolution and inform future strategies for personalized medicine.

Microparticle Encapsulation of a Prostate-targeted Biologic for the Treatment of Liver Metastases in a Preclinical Model of Castration-resistant Prostate Cancer

PRX302 is a highly potent, mutant bacterial pore-forming biologic protoxin engineered for selective activation by PSA, a serine protease expressed by benign and malignant prostate epithelial cells. Although being developed as a local therapy for benign prostatic hyperplasia and localized prostate cancer, PRX302 cannot be administered systemically as a treatment for metastatic disease due to binding to ubiquitously expressed glycosylphosphatidylinositol (GPI)-anchored proteins, which leads to poor accumulation within the tumor microenvironment. To overcome this limitation, poly-lactic-co-glycolic acid (PLGA) microparticles encapsulating the protoxin were developed, which are known to accumulate in the liver, a major site of metastasis for prostate cancer and other solid tumors. A highly sensitive and reproducible sandwich ELISA to quantify PRX302 released from microparticles was developed. Utilizing this assay, PRX302 release from different microparticle formulations was assessed over multiple days. Hemolysis assays documented PSA-dependent pore formation and lytic potential (i.e., function) of the released protoxin. MTT assays demonstrated that conditioned supernatant from PRX302-loaded, but not blank (i.e., unloaded), PLGA microparticles was highly cytotoxic to PC3 and DU145 human prostate cancer cells in the presence of exogenous PSA. Microparticle encapsulation prevented PRX302 from immediately interacting with GPI-anchored proteins as demonstrated in a competition assay, which resulted in an increased therapeutic index and significant antitumor efficacy following a single dose of PRX302-loaded microparticles in a preclinical model of prostate cancer liver metastasis with no obvious toxicity. These results document that PRX302 released from PLGA microparticles demonstrate in vivo antitumor efficacy in a clinically relevant preclinical model of metastatic prostate cancer.

The estrogen receptor-alpha S118P variant does not affect breast cancer incidence or response to endocrine therapies

PURPOSE

Estrogen receptor-alpha (ER) is a therapeutic target of ER-positive (ER+) breast cancers. Although ER signaling is complex, many mediators of this pathway have been identified. Specifically, phosphorylation of ER at serine 118 affects responses to estrogen and therapeutic ligands and has been correlated with clinical outcomes in ER+ breast cancer patients. We hypothesized that a newly described germline variant (S118P) at this residue would drive cellular changes consistent with breast cancer development and/or hormone resistance.

METHODS

Isogenic human breast epithelial cell line models harboring ER S118P were developed via genome editing and characterized to determine the functional effects of this variant. We also examined the frequency of ER S118P in a case-control study (N = 536) of women with and without breast cancer with a familial risk.

RESULTS

In heterozygous knock-in models, the S118P variant demonstrated no significant change in proliferation, migration, MAP Kinase pathway signaling, or response to the endocrine therapies tamoxifen and fulvestrant. Further, there was no difference in the prevalence of S118P between women with and without cancer relative to population registry databases.

CONCLUSIONS

This study suggests that the ER S118P variant does not affect risk for breast cancer or hormone therapy resistance. Germline screening and modification of treatments for patients harboring this variant are likely not warranted.

PSA-selective activation of cytotoxic human serine proteases within the tumor microenvironment as a therapeutic strategy to target prostate cancer

Prostate cancer is the most diagnosed malignancy and the second leading cause of cancer-related death in American men. While localized therapy is highly curative, treatments for metastatic prostate cancer are largely palliative. Thus, new innovative therapies are needed to target metastatic tumors. Prostate-Specific Antigen (PSA) is a chymotrypsin-like protease with a unique substrate specificity that is secreted by both normal and malignant prostate epithelial cells. Previous studies demonstrated the presence of high levels (μM-mM) of enzymatically active PSA is present in the extracellular fluid of the prostate cancer microenvironment. Because of this, PSA is an attractive target for a protease activated pro-toxin therapeutic strategy. Because prostate cancers typically grow very slowly, a strategy employing a proliferation-independent cytotoxic payload is preferred. Recently, it was shown that the human protease Granzyme B (GZMB), at low micromolar concentrations in the extracellular space, can cleave an array of extracellular matrix (ECM) proteins thus perturbing cell growth, signaling, motility, and integrity. It is also well established that other human proteases such as trypsin can induce similar effects. Because both enzymes require N-terminal proteolytic activation, we propose to convert these proteins into PSA-activated cytotoxins. In this study, we examine the enzymatic and cell targeting parameters of these PSA-activated cytotoxic serine proteases. These pro-enzymes were activated robustly by PSA and induced ECM damage that led to the death of prostate cancer cells in vitro thus supporting the potential use of this strategy as means to target metastatic prostate cancers.

GATA3 frameshift mutation promotes tumor growth in human luminal breast cancer cells and induces transcriptional changes seen in primary GATA3 mutant breast cancers

The GATA3 transcription factor is one of the most frequently mutated genes in breast cancer. Heterozygous mutations, mostly frameshifts, are seen in 15% of estrogen receptor positive breast cancers, the subtype in which these mutations are almost exclusively found. Mouse studies have shown that Gata3 is critical for breast development and that GATA3 gene dosage affects breast tumor progression. Human patient data have shown that high Gata3 expression, a feature of luminal subtype breast cancers, is associated with a better prognosis. Although the frequency of GATA3 mutation suggests an important role in breast cancer development or progression, there is little understanding of how mutations in GATA3 affect its function in luminal breast epithelial cells and what gene expression changes result as a consequence of the mutations. Here, using gene editing, we have created two sets of isogenic human luminal breast cancer cell lines with and without a hotspot truncating GATA3 mutation. GATA3 mutation enhanced tumor growth in vivo but did not affect sensitivity to clinically used hormonal therapies or chemotherapeutic agents. We identified genes with upregulated and downregulated expression in GATA3 mutant cells, a subset of which was concordantly differentially expressed in GATA3 mutant primary luminal breast cancers. Addback of mutant GATA3 recapitulated mutation-specific gene expression changes and enhanced soft agar colony formation, suggesting a gain of function for the mutant protein.

PIK3CA mutations and TP53 alterations cooperate to increase cancerous phenotypes and tumor heterogeneity

BACKGROUND/PURPOSE

The combined contributions of oncogenes and tumor suppressor genes toward carcinogenesis remain poorly understood. Elucidation of cancer gene cooperativity can provide new insights leading to more effective use of therapies.

EXPERIMENTAL DESIGN/METHODS

We used somatic cell genome editing to introduce singly and in combination PIK3CA mutations (E545K or H1047R) with TP53 alterations (R248W or knockout), to assess any enhanced cancerous phenotypes. The non-tumorigenic human breast epithelial cell line, MCF10A, was used as the parental cell line, and resultant cells were assessed via various in vitro assays, growth as xenografts, and drug sensitivity assays using targeted agents and chemotherapies.

RESULTS

Compared to single-gene-targeted cells and parental controls, cells with both a PIK3CA mutation and TP53 alteration had increased cancerous phenotypes including cell proliferation, soft agar colony formation, aberrant morphology in acinar formation assays, and genomic heterogeneity. Cells also displayed varying sensitivities to anti-neoplastic drugs, although all cells with PIK3CA mutations showed a relative increased sensitivity to paclitaxel. All cell lines remained non-tumorigenic.

CONCLUSIONS

This cell line panel provides a resource for further elucidating cooperative genetic mediators of carcinogenesis and response to therapies.

Ki-67 is required for maintenance of cancer stem cells but not cell proliferation

Ki-67 expression is correlated with cell proliferation and is a prognostic marker for various cancers; however, its function is unknown. Here we demonstrate that genetic disruption of Ki-67 in human epithelial breast and colon cancer cells depletes the cancer stem cell niche. Ki-67 null cells had a proliferative disadvantage compared to wildtype controls in colony formation assays and displayed increased sensitivity to various chemotherapies. Ki-67 null cancer cells showed decreased and delayed tumor formation in xenograft assays, which was associated with a reduction in cancer stem cell markers. Immunohistochemical analyses of human breast cancers revealed that Ki-67 expression is maintained at equivalent or greater levels in metastatic sites of disease compared to matched primary tumors, suggesting that maintenance of Ki-67 expression is associated with metastatic/clonogenic potential. These results elucidate Ki-67's role in maintaining the cancer stem cell niche, which has potential diagnostic and therapeutic implications for human malignancies.

Bipolar Androgen Therapy for Men With Androgen Ablation Naïve Prostate Cancer: Results From the Phase II BATMAN Study

BACKGROUND

We have previously documented a paradoxical anti-tumor effect when castration-resistant prostate cancer patients were treated with intermittent, high-dose testosterone (i.e., Bipolar Androgen Therapy; BAT). Because, an adaptive increase in androgen receptor expression following chronic androgen deprivation therapy (ADT) may underlie this effect, we tested whether men with hormone-sensitive (HS) prostate cancer (PC) would also respond to BAT if given following a 6-month ADT lead-in.

METHODS

Asymptomatic HS PC patients with low metastatic burden or non-metastatic biochemically recurrent disease were enrolled. Following 6-month of ADT, those with a PSA <4 ng/ml went on to receive alternating 3-month cycles of BAT and ADT. BAT was administered as intramuscular testosterone (T) cypionate or enanthate 400 mg on Days (D) 1, 29, and 57. ADT was continued throughout the study to allow rapid cycling from near castrate to supraphysiologic range T following T injections. The primary endpoint was the percent of patients with a PSA <4 ng/ml after 18 months. Secondary endpoints included radiographic response and quality of life (QoL).

RESULTS

Twenty-nine of 33 patients received BAT following the ADT lead-in. The primary endpoint was met, with 17/29 men (59%, 90% confidence interval: 42-74%) having a PSA <4 ng/ml at 18 months. Ten patients receiving BAT had RECIST evaluable disease, and eight (80%) objective responses were observed (four complete; four partial). Three patients progressed per RECIST criteria and three had unconfirmed progression on bone scan. Men treated with 6-month of ADT had improved QoL following the first cycle of BAT as measured by the SF-36, FACT-P, and IIEF surveys.

CONCLUSIONS

BAT demonstrated preliminary efficacy in men with HS PC following 6-month of ADT. BAT may improve QoL in men treated with ADT. Prostate 76:1218-1226, 2016. © 2016 Wiley Periodicals, Inc.

Iterative design of emetine-based prodrug targeting fibroblast activation protein (FAP) and dipeptidyl peptidase IV DPPIV using a tandem enzymatic activation strategy

BACKGROUND

There is an urgent need to develop new agents for treating metastatic prostate cancer to overcome multiple drug resistance to the current standard targeted cancer therapy. Emetine is a highly cytotoxic natural product protein synthesis inhibitor, which is toxic to all cell types. Its cytotoxicity can be blocked by derivatizing its N-2' position. Thus emetine can be selectively delivered to cancer cells in the region of metastatic cancer as a prodrug that will be activated by an enzyme selectively overexpressed within the metastatic tumor microenvironment. In this work, we convert emetine to a prodrug activatable by the fibroblast activation protein (FAP), a serine protease overexpressed by the carcinoma associated fibroblasts.

METHOD

By using an iterative structure-activity relationship strategy, several peptidyl emetine prodrug analogs (1-11) were synthesized by chemical derivatization of emetine at its N-2' position and tested for in-vitro activation by FAP. The lead prodrug 11 is made up of a DPPIV activatable prodrug precursor 10 (Ala-Pro-PABC-Emetine) coupled to FAP substrate (Ala-Ser-Gly-Pro-Ala-Gly-Pro). Activation assays of the prodrugs were performed in purified FAP, DPPIV, FBS, and human serum and were analyzed by LCMS. In vitro cytotoxicity assays of these prodrugs are carried out in prostate (LNCaP, PC3) and breast (MCF7 and MDA-MB-231) cancer cell lines. The prodrugs are also tested in normal immortalized human prostatic epithelial cell line (PrEC).

RESULTS

The lead FAP activated emetine prodrug 11 is activated to emetine in tandem by FAP and DPPIV in about 70% conversion within 24 hr. In prostate and breast cancer cell lines treated with prodrug 11, it is found to be equipotent with emetine in the presence of FAP and DPPIV. However, in the PrEC cell line grown in serum free media, prodrug 11 is more than 200-fold less cytotoxic than emetine in the absence of FAP and DPPIV.

CONCLUSION

This FAP activated prodrug of cytotoxic agent emetine further shows the crucial role of the N-2' position of emetine in controlling its cytotoxicity. Significantly reduced toxicity observed in the PrEC cell line in the absence of FAP and DPPIV shows that prodrug 11 could be systemically delivered to regions of metastatic prostate cancer or other solid tumor for activation by cancer selective enzymes within the cancer microenvironment, such as FAP that is overexpressed by the carcinoma-associated fibroblasts. The two-step tandem enzymatic activation of prodrug 11 by FAP and DPPIV is a strategy for overcoming steric hindrance.

Trametinib with and without pazopanib has potent preclinical activity in thyroid cancer

Multikinase inhibitors (MKIs) targeting VEGF receptors and other receptor tyrosine kinases have shown considerable activity in clinical trials of thyroid cancer. Thyroid cancer frequently exhibits activation of the RAS/RAF/MEK/ERK pathway. In other types of cancer, paradoxical ERK activation has emerged as a potential resistance mechanism to RAF-inhibiting drugs including MKIs such as sorafenib and pazopanib. We therefore queried whether the MEK inhibitor trametinib, could augment the activity of pazopanib in thyroid cancer cell lines. Trametinib potently inhibited growth in vitro (GI₅₀ 1.1–4.8 nM), whereas pazopanib had more limited in vitro activity, as anticipated (GI₅₀ 1.4–7.1 µM). We observed progressive upregulation of ERK activity with pazopanib treatment, an effect abrogated by trametinib. For xenografts (bearing either KRAS^G12R or BRAF^V600E mutations), the combination of trametinib and pazopanib led to sustained shrinkage in tumor volume by 50% or more, compared to pre-treatment baseline. Trametinib also was highly effective as a single agent, compared to pazopanib alone. These preclinical findings support the evaluation of trametinib, alone or in combination with pazopanib or other kinase inhibitors, in thyroid cancer clinical trials. We highlight the importance of pharmacodynamic assessment of the ERK pathway for patients enrolled in trials involving MKIs.

Anti-cancer potency of tasquinimod is enhanced via albumin-binding facilitating increased uptake in the tumor microenvironment

Tasquinimod, an orally active quinoline-3-carboxamide, binds with high affinity to HDAC4 and S100A9 in cancer and infiltrating host cells within compromised tumor microenvironment inhibiting adaptive survival pathways needed for an angiogenic response. Clinical trials document that as low as 0.5-1mg tasquinimod/day is therapeutic against castrate resistant metastatic prostate cancer. Tasquinimod is metabolized via cytochrome P4503A4, but ketoconazole at a dose which completely inhibits CYP3A metabolism does not affect tasquinimod's ability to inhibit endothelial “sprouting” in vitro or anti-cancer efficacy against human prostate cancer xenografts in vivo.

Tasquinimod's potency is facilitated by its reversible binding (K_d < 35 μM) to the IIA subdomain of albumin (Sudlow's site I). As blood vessels within the compromised cancer microenvironment are characterized by a higher degree of leakiness than those in normal tissues, this results in an enhanced uptake of tasquinimod bound to albumin in cancer tissue via a tumor specific process known as the “enhanced permeability and retention” (i.e., EPR) effect. Thus, despite plasma levels of < 1 μM, the EPR effect results in intracellular drug concentrations of 2-3 μM, levels several-fold higher than needed for inhibition of endothelial sprouting (IC₅₀ ~ 0.5 μM) or for inhibition of HDAC4 and S100A9 mediated tumor growth.

Pharmacokinetics and toxicology of a fibroblast activation protein (FAP)-activated prodrug in murine xenograft models of human cancer

BACKGROUND

As carcinoma progresses, the stroma undergoes a variety of phenotypic changes, including the presence of carcinoma-associated fibroblasts (CAFs) that express fibroblast activation protein (FAP). FAP is a post-prolyl endopeptidase whose expression in a healthy adult is largely restricted to the cancer-associated stroma. FAP-targeted prodrugs with a 100-fold greater therapeutic window over the parent compound were previously generated.

METHODS

Prodrugs and non-cleavable controls were incubated in the presence of FAP. Plasma and tumor half-lives (t1/2) of the full-length and active forms of the prodrugs were determined using LCMS. Biodistribution studies of prodrug activation were performed. Histopathological analysis of tissues from treated animals were compared to vehicle-treated controls. Toxicity and efficacy studies were performed in human breast (MDA-MB-231 and MCF-7) and prostate (LNCaP) cancer xenografts models.

RESULTS

These FAP-activated prodrugs have a significantly slower clearance from tumor tissue than the circulation (∼12 vs. ∼4.5 hr). Micromolar concentrations of active drug persist in the tumor. Active drug is detected in non-target tissues; however, histopathologic evaluation reveals no evidence of drug-induced toxicity. A FAP-activated prodrug (ERGETGP-S12ADT) inhibits tumor growth in multiple human breast and prostate cancer xenograft models. The anti-tumor effect is comparable to that observed with docetaxel, but results in significantly less toxicity.

CONCLUSION

FAP-activated prodrugs are a viable strategy for the management of prostate and other cancers. These prodrugs exhibit less toxicity than a commonly used chemotherapeutic agent. Further refinement of the FAP cleavage site for greater specificity may reduce prodrug activation in non-target tissues and enhance clinical benefit.

PIK3CA and AKT1 mutations have distinct effects on sensitivity to targeted pathway inhibitors in an isogenic luminal breast cancer model system

PURPOSE

Activating mutations in the phosphoinositide-3-kinase (PI3K)/AKT/mTOR pathway are present in the majority of breast cancers and therefore are a major focus of drug development and clinical trials. Pathway mutations have been proposed as predictive biomarkers for efficacy of PI3K-targeted therapies. However, the precise contribution of distinct PI3K pathway mutations to drug sensitivity is unknown.

EXPERIMENTAL DESIGN

We describe the creation of a physiologic human luminal breast cancer cell line model to study the phenotype of these mutations using the MCF-7 cell line. We used somatic cell gene targeting to "correct" PIK3CA E545K-mutant alleles in MCF-7 cells to wild-type sequence. The AKT1 E17K hotspot mutation was knocked in on this wild-type background.

RESULTS

Loss of mutant PIK3CA dramatically reduced phosphorylation of AKT proteins and several known AKT targets, but other AKT target proteins and downstream effectors of mTOR were not affected. PIK3CA wild-type cells exhibited reduced proliferation in vitro and in vivo. Knockin of the AKT1 E17K hotspot mutation on this PIK3CA wild-type background restored pathway signaling, proliferation, and tumor growth in vivo. PIK3CA, but not AKT1 mutation, increased sensitivity to the PI3K inhibitor GDC-0941 and the allosteric AKT inhibitor MK-2206.

CONCLUSIONS

AKT1 E17K is a bona fide oncogene in a human luminal breast cancer context. Distinct PI3K pathway mutations confer differential sensitivity to drugs targeting the pathway at different points and by distinct mechanisms. These findings have implications for the use of tumor genome sequencing to assign patients to targeted therapies.

Structural optimization, biological evaluation, and application of peptidomimetic prostate specific antigen inhibitors

Prostate-specific antigen (PSA) is a serine protease produced at high levels by normal and malignant prostate epithelial cells that is used extensively as a biomarker in the clinical management of prostate cancer. To better understand PSA's role in prostate cancer progression, we prepared a library of peptidyl boronic acid-based inhibitors. To enhance selectivity for PSA vs other serine proteases, we modified the P1 site of the inhibitors to incorporate a bromopropylglycine group. This allowed the inhibitors to participate in halogen bond formation with the serine found at the bottom of the specificity pocket. The best of these Ahx-FSQn(boro)Bpg had PSA Ki of 72 nM and chymotrypsin Ki of 580 nM. In vivo studies using PSA-producing xenografts demonstrated that candidate inhibitors had minimal effect on growth but significantly altered serum levels of PSA. Biodistribution of (125)I labeled peptides showed low levels of uptake into tumors compared to other normal tissues.

Single copies of mutant KRAS and mutant PIK3CA cooperate in immortalized human epithelial cells to induce tumor formation

The selective pressures leading to cancers with mutations in both KRAS and PIK3CA are unclear. Here, we show that somatic cell knockin of both KRAS G12V and oncogenic PIK3CA mutations in human breast epithelial cells results in cooperative activation of the phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways in vitro, and leads to tumor formation in immunocompromised mice. Xenografts from double-knockin cells retain single copies of mutant KRAS and PIK3CA, suggesting that tumor formation does not require increased copy number of either oncogene, and these results were also observed in human colorectal cancer specimens. Mechanistically, the cooperativity between mutant KRAS and PIK3CA is mediated in part by Ras/p110α binding, as inactivating point mutations within the Ras-binding domain of PIK3CA significantly abates pathway signaling. In addition, Pdk1 activation of the downstream effector p90RSK is also increased by the combined presence of mutant KRAS and PIK3CA. These results provide new insights into mutant KRAS function and its role in carcinogenesis.

Targeting carcinoma-associated fibroblasts within the tumor stroma with a fibroblast activation protein-activated prodrug

BACKGROUND

Fibroblasts undergo a morphological transformation to a reactive phenotype in the tumor microenvironment characterized by the expression of proteins such as fibroblast activation protein (FAP), a post-prolyl endopeptidase with expression largely restricted to carcinoma-associated fibroblasts. Thapsigargin (TG) is a highly toxic natural plant product that triggers a rise in intracellular calcium levels and apoptosis. FAP is therefore a provocative target for the activation of prodrugs consisting of a FAP-specific peptide coupled to a potent cytotoxic analog of TG.

METHODS

The efficacy of FAP-activated peptidyl-TG prodrugs was tested in vitro in cell proliferation assays and effects on intracellular calcium in human cancer cell lines. The effects of FAP-activated prodrugs on tumor growth and host toxicity were tested in Balb-C nude MCF-7 and LNCaP xenograft mice (n = 9-11 per group). P values were calculated using permutation tests based on 50 000 permutations. Mixed effects models were used to account for correlations among replicate measures. All statistical tests were two-sided.

RESULTS

FAP-activated prodrugs killed human cancer cells at low nanomolar concentrations (MCF-7 cells: IC(50) = 3.5 nM). Amino acid-12ADT analogs from FAP-cleaved prodrugs, but not uncleaved prodrugs, produced a rapid rise in intracellular calcium within minutes of exposure. Immunohistochemical analysis of xenografts exposed to FAP-prodrugs documented stromal-selective cell death of fibroblasts, pericytes, and endothelial cells of sufficient magnitude to inhibit growth of MCF-7 and LNCaP xenografts with minimal systemic toxicity, whereas non-FAP cleavable prodrugs were inactive. MCF-7 and LNCaP xenografts treated with a FAP-activated prodrug had maximal treated-to-control tumor volume ratios of 0.36 (treated: mean = 0.206 mm(3), 95% CI = 0.068 to 0.344 mm(3); control: mean = 0.580 mm(3), 95% CI = 0.267 to 0.893 mm(3)) and 0.24 (treated: mean = 0.131 mm(3), 95% CI = 0.09 to 0.180 mm(3); control: mean = 0.543 mm(3), 95% CI = 0.173 to 0.913 mm(3)), respectively, on day 21 after therapy.

CONCLUSIONS

This study validates the proteolytic activity of FAP as a target for the activation of a systemically delivered cytotoxic prodrug and demonstrates that targeted killing of cells within the stromal compartment of the tumor microenvironment can produce a therapeutic response.

Engineering a prostate-specific membrane antigen-activated tumor endothelial cell prodrug for cancer therapy

Heterogeneous expression of drug target proteins within tumor sites is a major mechanism of resistance to anticancer therapies. We describe a strategy to selectively inhibit, within tumor sites, the function of a critical intracellular protein, the sarcoplasmic/endoplasmic reticulum calcium adenosine triphosphatase (SERCA) pump, whose proper function is required by all cell types for viability. To achieve targeted inhibition, we took advantage of the unique expression of the carboxypeptidase prostate-specific membrane antigen (PSMA) by tumor endothelial cells within the microenvironment of solid tumors. We generated a prodrug, G202, consisting of a PSMA-specific peptide coupled to an analog of the potent SERCA pump inhibitor thapsigargin. G202 produced substantial tumor regression against a panel of human cancer xenografts in vivo at doses that were minimally toxic to the host. On the basis of these data, a phase 1 dose-escalation clinical trial has been initiated with G202 in patients with advanced cancer.

Deletion of p53 in human mammary epithelial cells causes chromosomal instability and altered therapeutic response

The TP53 tumor suppressor gene is the most commonly mutated gene in human cancers. To evaluate the biological and clinical relevance of p53 loss, human somatic cell gene targeting was used to delete the TP53 gene in the non-tumorigenic epithelial cell line, MCF-10A. In all four p53-/- clones generated, cells acquired the capability for epidermal growth factor-independent growth and were defective in appropriate downstream signaling and cell cycle checkpoints in response to DNA damage. Interestingly, p53 loss induced chromosomal instability leading to features of transformation and the selection of clones with varying phenotypes. For example, p53-deficient clones were heterogeneous in their capacity for anchorage-independent growth and invasion. In addition, and of clinical importance, the cohort of p53-null clones showed sensitivity to chemotherapeutic interventions that varied depending not only on the type of chemotherapeutic agent, but also on the treatment schedule. In conclusion, deletion of the TP53 gene from MCF-10A cells eliminated p53 functions, as well as produced p53-/- clones with varying phenotypes possibly stemming from the distinct chromosomal changes observed. Such a model system will be useful to further understand the cancer-specific phenotypic changes that accompany p53 loss, as well as help to provide future treatment strategies for human malignancies that harbor aberrant p53.

Dual Inhibition of Mitogen-Activated Protein Kinase Kinase and Mammalian Target of Rapamycin in Differentiated and Anaplastic Thyroid Cancer

Context

Differentiated thyroid cancer and anaplastic thyroid cancer tumors frequently have activation of the ras/raf /MAPK kinase (MEK)/ERK and phosphatidylinositol 3-kinase (PI-3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathways.

Objective

The objective of the study was to investigate the efficacy of MEK and mTOR inhibitors in preclinical thyroid cancer treatment models with defined mutation status.

Experimental Design

The MEK inhibitor AZD6244 (ARRY-142886) and mTOR inhibitor rapamycin were tested separately and in combination in 10 differentiated thyroid cancer and anaplastic thyroid cancer cell lines and in a xenograft model for evidence of pathway inhibition, growth inhibition, apoptosis, and long-range adaptation and resistance.

Results

Seven of 10 tested lines had evidence of significant basal activity of the PI-3K/AKT/mTOR pathway, with elevated phosphorylated AKT and phosphorylated p70 S6 kinase. Activation of ras/RAF/MEK/ERK was equally common in this panel. All 10 lines exhibited better than 60% growth inhibition with combined MEK and mTOR inhibition, including lines with BRAF, Ret-PTC, ras, and PTEN mutations. Rapamycin or AZD6244 alone achieved this threshold in six and two lines, respectively. Dual-pathway inhibition in the Ret-PTC mutant cell line TPC1 caused an intense G1 arrest in cell culture and reversible cytostatic inhibition in a xenograft model. We did not observe significant feedback up-regulation of AKT activation in either acute or prolonged exposures.

Conclusion

These preclinical results support the inclusion of thyroid cancer patients in early-phase clinical trials combining ras/RAF/MEK/ERK and PI-3K/AKT/mTOR pathway inhibition.

Dual inhibition of mitogen-activated protein kinase kinase and mammalian target of rapamycin in differentiated and anaplastic thyroid cancer

CONTEXT

Differentiated thyroid cancer and anaplastic thyroid cancer tumors frequently have activation of the ras/raf /MAPK kinase (MEK)/ERK and phosphatidylinositol 3-kinase (PI-3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathways.

OBJECTIVE

The objective of the study was to investigate the efficacy of MEK and mTOR inhibitors in preclinical thyroid cancer treatment models with defined mutation status.

EXPERIMENTAL DESIGN

The MEK inhibitor AZD6244 (ARRY-142886) and mTOR inhibitor rapamycin were tested separately and in combination in 10 differentiated thyroid cancer and anaplastic thyroid cancer cell lines and in a xenograft model for evidence of pathway inhibition, growth inhibition, apoptosis, and long-range adaptation and resistance.

RESULTS

Seven of 10 tested lines had evidence of significant basal activity of the PI-3K/AKT/mTOR pathway, with elevated phosphorylated AKT and phosphorylated p70 S6 kinase. Activation of ras/RAF/MEK/ERK was equally common in this panel. All 10 lines exhibited better than 60% growth inhibition with combined MEK and mTOR inhibition, including lines with BRAF, Ret-PTC, ras, and PTEN mutations. Rapamycin or AZD6244 alone achieved this threshold in six and two lines, respectively. Dual-pathway inhibition in the Ret-PTC mutant cell line TPC1 caused an intense G(1) arrest in cell culture and reversible cytostatic inhibition in a xenograft model. We did not observe significant feedback up-regulation of AKT activation in either acute or prolonged exposures.

CONCLUSION

These preclinical results support the inclusion of thyroid cancer patients in early-phase clinical trials combining RAS/RAF/MEK/ERK and PI-3K/AKT/mTOR pathway inhibition.

A prostate-specific antigen activated N-(2-hydroxypropyl) methacrylamide copolymer prodrug as dual-targeted therapy for prostate cancer

Prostate cancer targeted peptide prodrugs that are activated by the serine protease activity of prostate-specific antigen (PSA) are under development in our laboratory. To enhance delivery and solubility of these prodrugs, macromolecular carriers consisting of N-(2-hydroxypropyl) methacrylamide (HPMA)-based copolymers were covalently coupled to a PSA-activated peptide prodrug. HPMA copolymers are water-soluble, nonimmunogenic synthetic carriers that exhibit promise for drug delivery applications. These macromolecular copolymers enter the interstitium of solid tumors by the enhanced permeability and retention effect. The PSA-activated peptide substrate imparts selectivity because it is specifically hydrolyzed to release a cytotoxin at the site of prostate tumor. Enzymatically active PSA is present in high amounts in the extracellular fluid of a tumor, but PSA is inactivated in blood by binding to serum protease inhibitors. As an initial proof of concept, the HPMA copolymer was synthesized with a peptide substrate (HSSKLQ) bound to a fluorophore, 7-amino-4-methylcoumarin (AMC). PSA cleavage of the HPMA-HSSKLQ-AMC copolymer was observed, which led to the synthesis of an HPMA-based copolymer with the prodrug SSKYQ-L12ADT [HPMA-morpholinocarbonyl-Ser-Ser-Lys-Tyr-Gln-Leu-12-aminododecanoyl thapsigargin (JHPD)]. L12ADT is a potent analogue of the highly cytotoxic natural product thapsigargin. HPMA-JHPD was hydrolyzed by PSA in vitro and was toxic to prostate cancer cells in the presence of active PSA. The HPMA-JHPD produced no systemic toxicity when given at a 500 micromol/L L12ADT equivalent dose. Analysis of tumor tissue from mice treated with a single or multiple dose of the HPMA-JHPD copolymer showed release and accumulation of the L12ADT toxin within the tumor tissue.

Selective growth inhibition in BRAF mutant thyroid cancer by the mitogen-activated protein kinase kinase 1/2 inhibitor AZD6244

CONTEXT

Activating mutations in the BRAF gene, primarily at V600E, are associated with poorer outcomes in patients with papillary thyroid cancer. MAPK kinase (MEK), immediately downstream of BRAF, is a promising target for ras-raf-MEK-ERK pathway inhibition.

OBJECTIVE

The objective of the investigation was to study the efficacy of a MEK1/2 inhibitor in thyroid cancer preclinical models with defined BRAF mutation status.

EXPERIMENTAL DESIGN

After treatment with the potent MEK 1/2 inhibitor AZD6244, MEK inhibition and cell growth were examined in four BRAF mutant (V600E) and two BRAF wild-type thyroid cancer cell lines and in xenografts from a BRAF mutant cell line.

RESULTS

AZD6244 potently inhibited MEK 1/2 activity in thyroid cancer cell lines regardless of BRAF mutation status, as evidenced by reduced ERK phosphorylation. Four BRAF mutant lines exhibited growth inhibition at low doses of the drug, with GI50 concentrations ranging from 14 to 50 nm, predominantly via a G0/G1 arrest, comparable with findings in a sensitive BRAF mutant melanoma cell line. In contrast, two BRAF wild-type lines were significantly less sensitive, with GI50 values greater than 200 nm. Nude mouse xenograft tumors derived from the BRAF mutant line ARO exhibited dose-dependent growth inhibition by AZD6244, with effective treatment at 10 mg/kg by oral gavage. This effect was primarily cytostatic and associated with marked inhibition of ERK phosphorylation.

CONCLUSION

AZD6244 inhibits the MEK-ERK pathway across a spectrum of thyroid cancer cells. MEK inhibition is cytostatic in papillary thyroid cancer and anaplastic thyroid cancer cells bearing a BRAF mutation and may have less impact on thyroid cancer cells lacking this mutation.

Prospective Evaluation of the Relationship of Patient Age and Paclitaxel Clinical Pharmacology: Cancer and Leukemia Group B (CALGB 9762)

Purpose

To prospectively evaluate the pharmacokinetics and toxicity profile of paclitaxel in relation to patient age in adults ≥ 55 years old.

Patients and Methods

Paclitaxel was administered at 175 mg/m2 for 3 hours to 153 patients, 46 of whom were ≥ 75 years of age. Pharmacokinetic and toxicity assessments were performed. Data were analyzed by cohort (cohort 1, age 55 to 64 years; cohort 2, age 65 to 74 years; cohort 3, age ≥ 75 years).

Results

Paclitaxel concentration versus time (AUC) and total-body clearance (CLtb) data were available for 122 patients (cohort 1, 46 patients; cohort 2, 44 patients; cohort 3, 32 patients). Mean paclitaxel AUC increased across cohorts (P = .01). Mean (SE) AUCs were 22.4 (2.5) μmol/L × hour, 26.2 (2.8) μmol/L × hour, and 31.7 (5.6) μmol/L × hour for cohorts 1, 2, and 3, respectively. There was a corresponding significant (P = .007) age-related decrease in mean (SE) paclitaxel CLtb (cohort 1, 11.0 [0.7] L/h/m2; cohort 2, 9.3 [0.6] L/h/m2; cohort 3, 8.2 [0.6] L/h/m2). Patients in cohort 3 experienced significantly lower absolute neutrophil count nadirs than did younger groups (P = .02). There was also a significant increase in percentage of patients with ≥ grade 3 neutropenia across age cohorts (cohort 1, 22%; cohort 2, 35%; cohort 3, 49%; P = .006). However, the increased exposure of patients to paclitaxel and increased neutropenia were not reflected in adverse clinical sequelae such as hospitalization for toxicity (P = .82), receiving intravenous antibiotics (P = .21), or experiencing a temperature more than 38°C (P = .45).

Conclusion

Although paclitaxel CLtb decreases with increasing patient age, there is great interpatient variability. Cooperative group studies to evaluate the effect of aging on pharmacokinetics are feasible.

Pharmacokinetics, biodistribution, and antitumor efficacy of a human glandular kallikrein 2 (hK2)-activated thapsigargin prodrug

BACKGROUND

Prostate cancer cells secrete unique proteases such as prostate-specific antigen (PSA) and human glandular kallikrein 2 (hK2) that represent targets for the activation of prodrugs as systemic treatment of metastatic prostate cancer. Previously, a combinatorial peptide library was screened to identify a highly active peptide substrate for hK2. The peptide was coupled to an analog of the potent cytotoxin thapsigargin, L12ADT, to generate an hK2-activated prodrug that was efficiently hydrolyzed by purified hK2, stable to hydrolysis in human and mouse plasma in vitro and selectively toxic to hK2 producing prostate cancer cells in vitro.

METHODS

In the current study, toxicology, pharmacokinetics, prodrug biodistribution, and antitumor efficacy studies were performed to evaluate the hK2-activated prodrug in vivo.

RESULTS

The single intravenous maximally tolerated dose of prodrug was 6 mg/kg (i.e., 3.67 micromole/kg) which produced peak serum concentration of approximately 36 microM and had a half-life of approximately 40 min. In addition, over a 24 hr period <0.5% of free L12ADT analog was observed in plasma. The prodrug demonstrated significant antitumor effect in vivo while it was being administered, but prolonged intravenous administration was not possible due to local toxicity to tail veins. Subcutaneous administration of equimolar doses produced lower plasma AUC compared to intravenous dosing but equivalent intratumoral levels of prodrug following multiple doses.

CONCLUSIONS

The hK2-activated prodrug was stable in vivo. The prodrug, however, was rapidly cleared and difficult to administer over prolonged dosing interval. Additional studies are underway to assess antitumor efficacy with prolonged administration of higher subcutaneous doses of prodrug. Second-generation hK2-activated thapsigargin prodrugs with increased half-lives and improved formulations are also under development.

Activity of irinotecan and the tyrosine kinase inhibitor CEP-751 in medullary thyroid cancer

CONTEXT

Medullary thyroid cancer (MTC) is a cancer of the parafollicular C cells that commonly presents with an inherited or acquired RET gene mutation. There is currently no effective systemic treatment for MTC.

OBJECTIVE

The objective of this study was to investigate a systemic therapeutic approach to treat MTC. We studied the sensitivity of an MTC cell line and xenograft to irinotecan, alone and in combination with the tyrosine kinase inhibitor, CEP-751.

RESULTS

In TT cell culture and xenografts, irinotecan treatment was highly effective. This effect was augmented by treatment with CEP-751. Treatment of TT cell xenografts resulted in durable complete remission in 100% of the mice, with median time to recurrence of 70 d for irinotecan alone and more than 130 d for irinotecan plus CEP-751. Although irinotecan induced an S phase checkpoint arrest in TT cells, CEP-751 in combination with irinotecan resulted in a loss of this arrest. CEP-751 induced a loss in the induction of the DNA repair program marked by phospho-H2AX and the checkpoint pathway marked by the activated Chk1 pathway.

CONCLUSIONS

Irinotecan treatment was highly effective in a preclinical model of human MTC, resulting in complete remission in 100% of the xenografts treated. The duration of remission was further enhanced by combination with the kinase inhibitor, CEP-751. These results suggest that irinotecan, alone or in combination, may be useful for the treatment of MTC.

A fragment of the hypophosphatemic factor, MEPE, requires inducible cyclooxygenase-2 to exert potent anabolic effects on normal human marrow osteoblast precursors

MEPE, 56.6 kDa protein isolated from tumors associated with hypophosphatemic osteomalacia, increases renal phosphate excretion and is expressed in normal human bone cells. AC-100, a central 23-amino acid fragment of MEPE, contains motifs that are important in regulating cellular activities in the bone microenvironment. Thus, we assessed in vitro effects of AC-100 on multipotential normal human marrow stromal (hMS) cells that have the capacity to differentiate into mature osteoblasts. Proliferation was quantified by [H3]thymidine uptake and cell counting and differentiation by the levels of mRNA for the alpha2-chain of type I procollagen (COL1A2), alkaline phosphatase (AP), and osteocalcin (OC) measured using real time reverse transcriptase PCR (RT-PCR) and by the formation of mineralized nodules. AC-100 increased proliferation by 257 +/- 89% (P < 0.005), increased gene expression of COL1A2 by 339 +/- 85% (P < 0.005), AP by 1,437 +/- 40% (P < 0.001), and OC by 1,962 +/- 337% (P < 0.001). In addition, it increased mineralized nodule formation by 81 +/- 14% (P < 0.001) in a dose- and time-dependent fashion. In equimolar dosages, the parent compound, MEPE, had the full activity of the AC-100 fragment. AC-100 elicited a comparable response to both IGF-I and BMP-2 with respect to proliferation and differentiation of hMS cells. Using gene expression microarray analysis, we demonstrated that AC-100 increased (by approximately 3-fold) the mRNA for cyclooxgenase-2 (COX-2), an inducible enzyme required for prostaglandin synthesis. Moreover, NS-398, a specific inhibitor of COX-2 action completely blocked AC-100-induced increases in proliferation and differentiation. Thus, AC-100 has potent anabolic activity on osteoblast precursor cells in vitro and these effects require the induction of COX-2.

Screening a combinatorial peptide library to develop a human glandular kallikrein 2–activated prodrug as targeted therapy for prostate cancer

Objective: Prostate cancer cells secrete the unique protease human glandular kallikrein 2 (hK2) that represents a target for proteolytic activation of cytotoxic prodrugs. The objective of this study was to identify hK2-selective peptide substrates that could be coupled to a cytotoxic analogue of thapsigargin, a potent inhibitor of the sarcoplasmic/endoplasmic reticulum calcium ATPase pump that induces cell proliferation–independent apoptosis through dysregulation of intracellular calcium levels. Methods: To identify peptide sequence requirements for hK2, a combination of membrane-bound peptides (SPOT analysis) and combinatorial chemistry using fluorescence-quenched peptide substrates was used. Peptide substrates were then coupled to 8-O-(12[l-leucinoylamino]dodecanoyl)-8-O-debutanoylthapsigargin (L12ADT), a potent analogue of thapsigargin, to produce a prodrug that was then characterized for hK2 hydrolysis, plasma stability, and in vitro cytotoxicity. Results: Both techniques indicated that a peptide with two arginines NH2-terminal of the scissile bond produced the highest rates of hydrolysis. A lead peptide substrate with the sequence Gly-Lys-Ala-Phe-Arg-Arg (GKAFRR) was hydrolyzed by hK2 with a Km of 26.5 μmol/L, kcat of 1.09 s−1, and a kcat/Km ratio of 41,132 s−1 mol/L−1. The GKAFRR-L12ADT prodrug was rapidly hydrolyzed by hK2 and was stable in plasma, whereas the GKAFRR-L peptide substrate was unstable in human plasma. The hK2-activated thapsigargin prodrug was not activated by cathepsin B, cathepsin D, and urokinase but was an excellent substrate for plasmin. The GKAFRR-L12ADT was selectively cytotoxic in vitro to cancer cells in the presence of enzymatically active hK2. Conclusion: The hK2-activated thapsigargin prodrug represents potential novel targeted therapy for prostate cancer.

Screening a combinatorial peptide library to develop a human glandular kallikrein 2-activated prodrug as targeted therapy for prostate cancer

OBJECTIVE

Prostate cancer cells secrete the unique protease human glandular kallikrein 2 (hK2) that represents a target for proteolytic activation of cytotoxic prodrugs. The objective of this study was to identify hK2-selective peptide substrates that could be coupled to a cytotoxic analogue of thapsigargin, a potent inhibitor of the sarcoplasmic/endoplasmic reticulum calcium ATPase pump that induces cell proliferation-independent apoptosis through dysregulation of intracellular calcium levels.

METHODS

To identify peptide sequence requirements for hK2, a combination of membrane-bound peptides (SPOT analysis) and combinatorial chemistry using fluorescence-quenched peptide substrates was used. Peptide substrates were then coupled to 8-O-(12[L-leucinoylamino]dodecanoyl)-8-O-debutanoylthapsigargin (L12ADT), a potent analogue of thapsigargin, to produce a prodrug that was then characterized for hK2 hydrolysis, plasma stability, and in vitro cytotoxicity.

RESULTS

Both techniques indicated that a peptide with two arginines NH2-terminal of the scissile bond produced the highest rates of hydrolysis. A lead peptide substrate with the sequence Gly-Lys-Ala-Phe-Arg-Arg (GKAFRR) was hydrolyzed by hK2 with a Km of 26.5 micromol/L, kcat of 1.09 s(-1), and a kcat/Km ratio of 41,132 s(-1) mol/L(-1). The GKAFRR-L12ADT prodrug was rapidly hydrolyzed by hK2 and was stable in plasma, whereas the GKAFRR-L peptide substrate was unstable in human plasma. The hK2-activated thapsigargin prodrug was not activated by cathepsin B, cathepsin D, and urokinase but was an excellent substrate for plasmin. The GKAFRR-L12ADT was selectively cytotoxic in vitro to cancer cells in the presence of enzymatically active hK2.

CONCLUSION

The hK2-activated thapsigargin prodrug represents potential novel targeted therapy for prostate cancer.

Use of methotrexate-based peptide substrates to characterize the substrate specificity of prostate-specific membrane antigen (PSMA)

Prostate-Specific Membrane Antigen (PSMA) is a glutamate carboxypeptidase II that is highly expressed by both normal and malignant prostate epithelial cells and by the neovasculature of many tumor types but is not expressed by endothelial cells in normal tissue. PSMA possesses the hydrolytic properties of an N-acetylated alpha-linked acidic dipeptidase (NAALADase) and also functions as a pteroyl poly-gamma-glutamyl carboxypeptidase (i.e., folate hydrolase). Therefore, PSMA can be targeted for activation of peptide-based prodrugs within the extracellular fluid of prostate cancers. In this study, methotrexate-based peptide analogs were evaluated to identify PSMA selective substrates that are also stable to nonspecific hydrolysis in human and mouse plasma. These methotrexate analogs were also characterized for in vitro toxicity against PSMA and nonPSMA producing human cancer cell lines. Analogs containing gamma-linked glutamate residues were most efficiently hydrolyzed by PSMA, but were unstable in plasma. Analogs containing both alpha- and gamma-linked acidic amino acids were less efficiently hydrolyzed by PSMA but were most stable in plasma. Analogs were 5-10 fold more selectively toxic in vitro in the presence of active PSMA. These studies have identified PSMA selective, plasma stable peptide substrates that can be incorporated into prodrugs targeted for activation by PSMA within prostate cancer sites.

Weekly, high-dose paclitaxel in advanced lung carcinoma: a phase II study with pharmacokinetics by the Cancer and Leukemia Group B

BACKGROUND

The Cancer and Leukemia Group B conducted a Phase II trial to evaluate the efficacy, toxicity, and pharmacokinetics of paclitaxel administered at a maximum dose density for patients with chemotherapy-naïve, advanced-stage non-small cell lung carcinoma (NSCLC).

METHODS

Patients with Stage IIIB/IV or recurrent NSCLC, a performance status (PS) score of 0-1, and no history of chemotherapy exposure were eligible. Paclitaxel, 150 mg/m(2), was administered over 3 hours during Weeks 1-6 of an 8-week cycle. Doses were modified for ANC < 1500/microL or for >or= Grade 2 neuropathy on the day of therapy. Treatment continued until toxicity or disease progression. Pharmacokinetics were assessed at Weeks 1, 3, and 5 of Cycle 1.

RESULTS

Thirty-eight patients (median age, 64 years; range, 31-81 years) were treated. There were 21 males (PS = 0 for 17). Eleven patients had received previous radiation, 2 had brain metastases, 25 had adenocarcinoma, 23 had Stage IV disease, 6 had StageIIIB disease, and 9 had recurrent disease. Grade 3-4 granulocytopenia occurred in 39% of patients. There were no deaths due to toxicity. Grade 2 or 3 neuropathy occurred in 29% and 24% of patients, respectively. Ten (27%) patients had Grade 3 hyperglycemia (glucose concentration > 250 mg/dL). There were 16 partial responses (42%; 95% confidence interval [CI], 26-59%). The median survival period was 12.3 months (95% CI, 7.9-19.6%), and the 1-year and 2-year survival rates were 52% (95% CI, 39-71%) and 26% (95% CI, 15-45%), respectively. Paclitaxel pharmacokinetics were consistent with published values and clearance was not induced. Older age and hyperglycemia were associated with greater neurotoxicity.

CONCLUSIONS

Paclitaxel at 150 mg/m(2) per week x 6 every 8 weeks can be administered safely in the cooperative group setting. These Phase II data are comparable to those associated with combination therapy. The weekly dose-dense schedule may be more active than conventional schedules.

Dissociation between androgen responsiveness for malignant growth vs. expression of prostate specific differentiation markers PSA, hK2, and PSMA in human prostate cancer models

BACKGROUND

A detailed understanding is evolving as to how androgen receptor (AR) functions as a transcriptional regulator via its binding to androgen response elements (ARE) within promoter and enhancer regions of prostate-specific differentiation markers such as PSA, hK2, and PSMA. It has been assumed that an understanding of regulation of expression of these marker proteins would also provide an understanding of the mechanisms whereby AR interactions regulate proliferation and survival of malignant prostate cells. In order to validate this hypothesis, we used a series of human prostate cancer models [i.e., LAPC-4, CWR22Rv1, MDA PCA-2b, LNCaP, and C4-2B (derived from LNCaP)] to test whether there is a consistent concordance between androgen responsive regulation for malignant growth vs. regulation of expression of prostate differentiation specific markers PSA, hK2, and PSMA.

METHODS

In order to define androgen growth responsiveness in vivo, human prostate cancer cell lines were inoculated as xenografts into intact vs. surgically castrated adult male nude mice and the subsequent tumor growth response monitored. To assess androgen regulation of PSA and hK2 expression in these cell lines, the concentration of PSA and hK2 in the conditioned standard media and charcoal stripped media +/- androgen from each cell line was determined using an immunoassay system. PSMA enzymatic activity was determined using the PSMA substrate (3)H N-acetylaspartylglutamate ((3)H NAAG).

RESULTS

Wild-type AR expressing LAPC-4 cells are androgen responsive for their in vivo growth. This cell line is also androgen sensitive for the expression of both PSA and hK2 in vitro and express PSMA. CWR22Rv1 cells have a mutated AR and are androgen responsive for growth in vivo and androgen sensitive for hk2 but not PSA expression. CWR22Rv1 produce approximately 1.4-fold more PSA, approximately 18-fold more hK2, and have 21-fold higher PSMA activity than LAPC-4 cells. MDA PCA-2b cells are androgen responsive for growth in vivo and androgen sensitive for PSA expression. MDA PCA-2b cells produce approximately 250-fold more PSA but almost equivalent amounts of hK2 compared to LAPC-4 and have approximately 19-fold higher PSMA activity. Both late passage LNCaP and C4-2B are androgen independent for growth in vivo but remain androgen sensitive for both PSA and hK2 expression. LNCaP cells produce approximately 50-fold more PSA, approximately 35-fold more hK2, and have 28-fold higher PSMA activity compared to LAPC-4. C4-2B cells produce approximately 80-fold higher levels of PSA, approximately 250-fold higher levels of hK2. C4-2B also the highest PSMA activity of the cell lines with 105-fold higher PSMA activity than LAPC-4 and approximately 4-fold higher activity than late passage LNCaP cells.

CONCLUSIONS

Androgen can coordinately regulate both the tumor growth and expression of prostate specific marker genes as observed for the LAPC-4 human prostate cancer cells. Such coordinated regulation, however, is not universal. In all of the other cell lines, there is a dissociation between androgen responsive regulation of malignant growth vs. regulation of expression of prostate specific markers PSA and hK2. In addition, PSMA activity in these cell lines increases as cells become more androgen independent for growth in vivo. These results emphasize that tumor growth and the expression of the specific secretory genes are independently regulated molecular events even if they share a requirement for androgen and/or AR function. Additional independent mechanisms occur in prostate cancer cells for regulation of expression for even the highly related PSA and hK2 genes. Further studies are needed to clarify the mechanisms for androgen ligand-independent, AR-dependent regulation of the genes that directly effect the growth of androgen (i.e., ligand) independent prostate cancer cells. Unfortunately, the data in this present report do not validate the use of the PSA or hK2 gene as surrogates for a model system for such critically important mechanistic studies. Prostate prostate cancer cells. Unfortunately, the data in this present report do not validate the use of the PSA or hK2 gene as surrogates for a model system for such critically important mechanistic studies.

Plasma pharmacokinetics and tissue distribution of 17-(allylamino)-17-demethoxygeldanamycin (NSC 330507) in CD2F1 mice1

PURPOSE

17-(Allylamino)-17-demethoxygeldanamycin (17AAG) is a benzoquinone ansamycin compound agent that has entered clinical trials. Studies were performed in mice to: (1) define the plasma pharmacokinetics, tissue distribution, and urinary excretion of 17AAG after i.v. delivery; (2) to define the bioavailability of 17AAG after i.p. and oral delivery; and (3) to characterize the concentrations of 17AAG metabolites in plasma and tissue.

MATERIALS AND METHODS

All studies were performed in female CD2F1 mice. Preliminary toxicity studies used 17AAG i.v. bolus doses of 20, 40 and 60 mg/kg. Pharmacokinetic studies used i.v. 17AAG doses of 60, 40, and 26.67 mg/kg and i.p. and oral doses of 40 mg/kg. The plasma concentration versus time data were analyzed by compartmental and noncompartmental methods. The concentrations of 17AAG were also determined in brain, heart, lung, liver, kidney, spleen, skeletal muscle, and fat. Urinary drug excretion was calculated until 24 h after treatment.

RESULTS

A 60 mg/kg dose of 17AAG, in its initial, microdispersed formulation, caused no changes in appearance, appetite, waste elimination, or survival of treated animals as compared to vehicle-treated controls. Bolus i.v. delivery of 60 mg/kg microdispersed 17AAG produced "peak" plasma 17AAG concentrations between 5.8 and 19.3 micrograms/ml in mice killed 5 min after injection. Sequential reduction of the 17AAG dose to 40 and 26.67 mg/kg resulted in "peak" plasma 17AAG concentrations between 8.9 and 19.0 micrograms/ml, and 4.8 and 6.1 micrograms/ml, respectively. Noncompartmental analysis of the plasma 17AAG concentration versus time data showed an increase in AUC from 402 to 625 and 1738 micrograms/ml.min when the 17AAG dose increased from 26.67 to 40 and 60 mg/kg, respectively. Across the range of doses studied, 17AAG total body clearance varied from 34 to 66 ml/min per kg. Compartmental modeling of the plasma 17AAG concentration versus time data showed that the data were fitted best by a two-compartment, open, linear model. In each study, substantial concentrations of a material, subsequently identified as 17-(amino)-17-demethoxygeldanamycin (17AG), were measured in plasma. A subsequent, lyophilized formulation of 17AAG proved excessively toxic when delivered i.v. at 60 mg/kg. A repeat i.v. study using a 40 mg/kg dose of this new formulation produced peak plasma 17AAG concentrations of 20.2-38.4 micrograms/ml, and a 17AAG AUC of 912 micrograms/ml.min, which was approximately 50% greater than the AUC produced by a 40 mg/kg dose of microdispersed 17AAG. The bioavailabilities of 17AAG after i.p. and oral delivery were 99% and 24%, respectively. Minimal amounts of 17AAG and 17AG were detected in the urine. After i.v. bolus delivery to mice, 17AAG distributed rapidly to all tissues, except the brain. Substantial concentrations of 17AG were measured in each tissue.

CONCLUSIONS

17AAG has excellent bioavailability when given i.p. but only modest bioavailability when given orally and is metabolized to 17AG and other metabolites when given i.v., i.p., or orally. 17AAG is widely distributed to tissues. These pharmacokinetic data generated have proven relevant to the design of recently initiated clinical trials of 17AAG and could be useful in their interpretation.

Phase I study of paclitaxel given by seven-week continuous infusion concurrent with radiation therapy for locally advanced squamous cell carcinoma of the head and neck

PURPOSE

Paclitaxel is one of the most active agents for squamous cell carcinoma of the head and neck (SCCHN) and an in vitro radiosensitizer. The dose-response relationship for paclitaxel may depend more on exposure duration than on peak concentration. This National Cancer Institute-sponsored phase I trial was designed to determine the feasibility of combining continuous-infusion (CI) paclitaxel with concurrent radiation therapy (RT).

PATIENTS AND METHODS

Patients with previously untreated stage IVA/B SCCHN were eligible. Primary end points were determination of the maximum-tolerated dose, dose-limiting toxicity, and pharmacokinetics for paclitaxel given by CI (24 hours a day, 7 days a week for 7 weeks) during RT (70 Gy/7 weeks).

RESULTS

Twenty-seven patients were enrolled and assessable for toxicity. Nineteen of the patients who completed > or = 70 Gy were assessable for response. Grade 3 skin and mucosal acute reactions occurred at 10.5 mg/m(2)/d, but uninterrupted treatment was possible in five of six patients. At 17 mg/m(2)/d, skin toxicity required a 2-week treatment break for all three patients. The mean paclitaxel serum concentration at dose levels > or = 6.5 mg/m(2)/d exceeded that reported to achieve in vitro radiosensitization. Initial locoregional control was achieved in 14 (58%) of 24 of patients treated to 70 Gy, and control persisted in nine (38%).

CONCLUSION

CI paclitaxel with concurrent RT is a feasible and tolerable regimen for patients with advanced SCCHN and good performance status. Preliminary response and survival data are encouraging and suggest that further study is indicated. The recommended phase II dose of paclitaxel by CI is 10.5 mg/m(2)/d with RT for SCCHN.

Femoral venous flow during laparoscopic gynecologic surgery

The lower-limb venous return, assessed by the peak systolic venous velocities (PSVV) of the left common femoral vein, was recorded at different stages of operation for five patients undergoing major gynecologic operative laparoscopy. The average baseline PSVV was 23.1 cm/s. After positioning the patient in the Trendelenburg position, the PSVV increased to an average of 31.5 cm/s; this was a statistically significant increase. Creation of the pneumoperitoneum changed the waveform from a normal phasic pattern to a dampened, continuous, monophasic waveform. The average PSVV was reduced to 15.9 cm/s; this dampening was statistically significant. Further dampening was evident 1 hour intraoperatively, and the flow became intermittent, with cycles of dampened flow followed by periods of absent flow; these changes in PSVV were not statistically significant. Calf compressors did not increase the femoral PSVV at the beginning of operation, nor at I hour intraoperatively; the decrease was not statistically significant. After release of the pneumoperitoneum, the baseline waveform pattern and velocity returned. The Trendelenburg position used for gynecologic operative laparoscopy was associated with a statistically significant increase in the lower-limb PSVV. This increase did not fully counteract the dampening effect of a pneumoperitoneum on lower-limb PSVV. The authors' study did not support the benefit previously reported on the use of pneumatic calf compressors. The authors therefore recommend continuing the practice of antithrombotic measures for patients undergoing gynecologic operative laparoscopy.

The combination of insulin-like growth factor I and insulin-like growth factor-binding protein-3 reduces insulin requirements in insulin-dependent type 1 diabetes: evidence for in vivo biological activity

Insulin-like growth factor-I (IGF-I) enhances insulin action in normal subjects and in patients with both type 1 and 2 diabetes; however, its administration is associated with significant side effects in a high percentage of patients. The coadministration of IGF binding protein-3 (IGFBP-3, the predominant IGF binding protein in serum) with IGF-I limits IGF-I inducible side effects, but it does not attenuate the ability of IGF-I to enhance protein synthesis and bone accretion; therefore, we determined whether IGF-I/IGFBP-3 would retain biological activity in type 1 DM and limit side effects associated with free IGF-I administration. Twelve patients received recombinant human IGF-I plus IGFBP-3 (2 mg/kg-day) by continuous sc infusion for 2 weeks. Each subject served as his own control; and, during a paired 2-week period, each received a placebo infusion. The order of the treatments was randomized. Subjects were placed on a constant caloric intake but were allowed to adjust insulin doses to maintain appropriate levels of glycemic control. Subjects measured blood glucose four times per day at home and kept a log of their insulin use. Frequent sampling for glucose, insulin, and GH was conducted during four inpatient study periods, one at the beginning and one at the end of each 2-week study interval. During IGF-I/IGFBP-3, insulin doses were reduced by 49%, and mean serum glucose was reduced by 23%. Free insulin levels obtained during frequent sampling in hospital fell 47% on IGF-I/IGFBP-3, compared with control, but showed no change with placebo. Concomitant glucose measurements did not differ in the two treatment groups. There was no change in body weight. Fructosamine levels decreased by 12%, but this was not significant (P < 0.1). Fasting triglyceride was unchanged, but cholesterol declined from 170 +/- 24 to 149 +/- 31 mg/dL (P < 0.05). IGFBP-2 (an IGF-I-dependent responsive variable) rose from 141 +/- 56 to 251 +/- 98 ng/mL (P < 0.01) on IGF-I/IGFBP-3. To analyze the mechanism by which IGF-I/IGFBP-3 might reduce insulin requirements, the change in serum GH was quantified. Mean GH levels were reduced by 72%, from 2.48 to 0.55 ng/mL (P < 0.001). An equal number (40%) of drug- and placebo-treated subjects had minor hypoglycemic episodes at home that required adjustment of insulin doses. No episode was classified as severe. In contrast to previous studies with free IGF-I, there were no cases of edema, headache, jaw pain, retinal edema, or Bell's palsy. No subject withdrew because of drug complications. These findings indicate that IGF-I/IGFBP-3 is biologically active on carbohydrate metabolism, as measured by a decrease in insulin requirements in patients with type 1 diabetes. Further studies will be required to determine the long-term safety and efficacy of this combination in patients with insulin resistance and diabetes.

Phase I study of paclitaxel in combination with a multidrug resistance modulator, PSC 833 (Valspodar), in refractory malignancies

PURPOSE

To determine the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetics of paclitaxel when given with PSC 833 (valspodar) to patients with refractory solid tumors.

PATIENTS AND METHODS

Patients were initially treated with paclitaxel 175 mg/m(2) continuous intravenous infusion (CIVI) over 3 hours. Subsequently, 29 hours of treatment with CIVI PSC 833 was started 2 hours before paclitaxel treatment was initiated. In this combination, the starting dose of paclitaxel was 52.5 mg/m(2). Paclitaxel doses were escalated by 17.5 mg/m(2) increments for four subsequent cohorts. Each cohort consisted of three patients with the exception of the last cohort, which consisted of six patients. Data for the pharmacokinetics of paclitaxel with and without concurrent PSC 833 administration were obtained.

RESULTS

All 18 patients completed at least one course of concurrent treatment (median, two courses; range, one to six) and were evaluable for toxicity. The MTD for paclitaxel with PSC 833 was 122.5 mg/m(2). Neutropenia was the DLT. All patients had PSC 833 blood concentrations greater than 1, 000 ng/mL before, during, and 24 hours after the paclitaxel infusion. PSC 833 produced small increases in the paclitaxel peak plasma concentrations and areas under the concentration-time curve. However, PSC 833 greatly prolonged the terminal phase of paclitaxel, resulting in plasma paclitaxel concentrations of more than 0.05 micromol/L for much longer than expected. As a result, myelosuppression was comparable to that produced by full-dose paclitaxel given without PSC 833. Of the 16 patients who were assessable for response, one patient experienced a partial response and an additional nine patients experienced disease stabilization after paclitaxel treatment alone.

CONCLUSION

Treatment with paclitaxel 122.5 mg/m(2) as a 3-hour CIVI concurrent with a 29-hour CIVI of PSC 833 results in acceptable toxicity. The addition of PSC 833 alters the pharmacokinetics of paclitaxel, which explains the enhanced neutropenia experienced by patients treated with this drug combination.

Home within 24 hours of laparoscopic hysterectomy

We assessed the feasibility of safe discharge home within 24 hours following laparoscopic hysterectomy in 30 patients who met the inclusion criteria and consented to be enrolled in the study group. Patients were admitted on the day of their surgery with the expectation of discharge within 24 hours. Appropriate home nursing follow-up and phone contact by the surgical team were organized preoperatively. Inclusion criteria were: age 30-65 years, absence of any major medical history that would require prolonged hospitalization, availability of home support for the first 48 hours after discharge and presence of a working telephone line and an address within the area of the Community Home Nursing service. All 30 operative procedures were completed without incident. Six patients underwent total laparoscopic hysterectomy (TLH) (all the procedures of hysterectomy being performed laparoscopically including the suturing of uterine arteries, colpotomy and closure of the vaginal vault. The uterus was removed vaginally) and 24 patients underwent laparoscopic hysterectomy (LH) (this techniques differs from TLH in that the colpotomy was performed laparoscopically but the uterosacral ligaments were divided vaginally and the vault also was closed vaginally after the uterus was removed vaginally). The average operating time was 115 minutes (range 85-150 minutes) and the average blood loss was 97 mL (20-250 mL). There were no intraoperative complications, no requirement for transfusion and no readmission to hospital for any of the patients in the study. Postoperative complications were minor (umbilical cellulitis (1), intestinal colic (1)) and both were treated with resolution of the symptoms. Ninety per cent of patients in the study were discharged within 24 hours of their surgery, the average duration of stay being 22.9 hours (20-24 hours). Three patients were not fit for discharge at 24 hours postoperatively due to general lethargy, migraine and nausea; their average discharge time was 53.5 hours. The study showed that laparoscopic hysterectomy can be associated with a reduction in length of in-patient stay compared to traditional laparotomy. Furthermore this reduction could be safely reduced to 24 hours following laparoscopic hysterectomy. There was also an associated cost saving in terms of inpatient bed days. Patient satisfaction with this protocol was high in this selected and motivated group.

Antitumor activity, distribution, and metabolism of 13-cis-retinoic acid as a single agent or in combination with tamoxifen in established human MCF-7 xenografts in mice

PURPOSE

The efficacy of 13-cis-retinoic acid (13-CRA) given as a single agent or in combination with tamoxifen (TAM) was determined in athymic nude mice bearing advanced s.c. MCF-7 human breast cancers.

METHODS

13-CRA alone was given by gavage at doses ranging from 26.4 to 200 mg/kg. TAM alone was given by gavage at doses of 7.5, 15, 30, or 60 mg/kg. For combination studies, each dose of TAM was followed 4 h later by 13-CRA at doses of 25, 50, 100, or 200 mg/kg. All treatments began on day 12 and were continued for 3 weeks.

RESULTS

The median time to two doublings recorded for the control and for 13-CRA and TAM given as single agents at the highest dose were 22.2, 29.2, and 54.7 days, respectively. In combination, 100 and 200 mg/kg 13-CRA with 7.5 mg/kg TAM resulted in a delay in tumor growth at least as high as that achieved with highest-dose TAM alone, but the effect was not synergistic. Pharmacokinetic analysis of 13-CRA was performed in plasma, liver, and tumor from mice bearing 0.5- to 2.0 g carcinomas following a single dose of 100 mg/kg 13-CRA. Results showed that 13-CRA was metabolized differently in various tissues, but concentrations of 13-CRA detected in tumor were in the range reported to be active in vitro. all-trans-Retinoic acid (ATRA) concentrations were about 5% of the 13-CRA concentrations detected in plasma, 68% of those found in liver, and 20% of those found in tumor. 4-oxo-CRA represented between 2% and 10% of 13-CRA concentrations detected in plasma and liver but was not detected in tumor. Furthermore there was no difference in peak plasma 13-CRA concentrations found in the same tissues at 30 min after a single dose or after the eighth dose of 100 mg/kg 13-CRA or 13-CRA and TAM. Mean 13-CRA concentrations detected in liver and tumor were 50-90% and 16-30% of plasma peak concentrations, respectively. No difference in 4-oxo-CRA concentration was observed between the treatment groups.

CONCLUSIONS

These data suggest that 13-CRA is not effective against established human breast tumor xenografts despite the stability of the pharmacokinetics of 13-CRA and the generation of ATRA as a metabolite. The addition of 13-CRA to TAM did not improve the efficacy of TAM against these estrogen-receptor-positive xenografts.

Metabolism of 17-(allylamino)-17-demethoxygeldanamycin (NSC 330507) by murine and human hepatic preparations

17-(Allylamino)-17-demethoxygeldanamycin (17AAG), a compound that is proposed for clinical development, shares the ability of geldanamycin to bind to heat shock protein 90 and GRP94, thereby depleting cells of p185erbB2, mutant p53, and Raf-1. Urine and plasma from mice treated i.v. with 17AAG contained six materials with absorption spectra similar to that of 17AAG. Therefore, in vitro metabolism of 17AAG by mouse and human hepatic preparations was studied to characterize: (a) the enzymes responsible for 17AAG metabolism; and (b) the structures of the metabolites produced. These materials had retention times on high-performance liquid chromatography of approximately 2, 4, 5, 6, 7, and 9 min. When incubated in an aerobic environment with 17AAG, murine hepatic supernatant (9000 x g) produced each of these compounds; the 4-min metabolite was the major product. This metabolism required an electron donor, and NADPH was favored over NADH. Metabolic activity resided predominantly in the microsomal fraction. Metabolism was decreased by approximately 80% in anaerobic conditions and was essentially ablated by CO. Microsomes prepared from human livers produced essentially the same metabolites as produced by murine hepatic microsomes, but the 2-min metabolite was the major product, and the 4-min metabolite was next largest. There was no metabolism of 17AAG by human liver cytosol. Metabolism of 17AAG by human liver microsomes also required an electron donor, with NADPH being preferred over NADH, was inhibited by approximately 80% under anaerobic conditions, and was essentially ablated by CO. Liquid chromatography/mass spectrometry analysis of human and mouse in vitro reaction mixtures indicated the presence of materials with molecular weights of 545, 601, and 619, compatible with 17-(amino)-17-demethoxygeldanamycin (17AG), an epoxide, and a diol, respectively. The metabolite with retention time of 4 min was identified as 17AG by cochromatography and mass spectral concordance with authentic standard. Human microsomal metabolism of 17AAG was inhibited by ketoconazole, implying 3A4 as the responsible cytochrome P450 isoform. Incubation of 17AAG with cloned CYP3A4 produced metabolites 4 and 6. Incubation of 17AAG with cloned CYP3A4 and cloned microsomal epoxide hydrolase produced metabolites 2 and 4, with greatly decreased amounts of metabolite 6. Incubation of 17AAG with human hepatic microsomes and cyclohexene oxide, a known inhibitor of microsomal epoxide hydrolase, did not affect the production of metabolite 4 but decreased the production of metabolite 2 while increasing the production of metabolite 6. These data imply that metabolite 2 is a diol and metabolite 6 is an epoxide. Mass spectral fragmentation patterns and the fact that 17AG is not metabolized argue for the epoxide and diol being formed on the 17-allylamino portion of 17AAG and not on its ansamycin ring. These data have implications with regard to preclinical toxicology and activity testing of 17AAG as well as its proposed clinical development because: (a) production of 17AG requires concomitant production of acrolein from the cleaved allyl moiety; and (b) 17AG, which was not metabolized by microsomes, has been described as being as active as 17AAG in decreasing cellular p185erbB2.

Phase I study of the orally administered butyrate prodrug, tributyrin, in patients with solid tumors

Butyrates have been studied as cancer differentiation agents in vitro and as a treatment for hemoglobinopathies. Tributyrin, a triglyceride with butyrate molecules esterified at the 1, 2, and 3 positions, induces differentiation and/or growth inhibition of a number of cell lines in vitro. When given p.o. to rodents, tributyrin produces substantial plasma butyrate concentrations. We treated 13 patients with escalating doses of tributyrin from 50 to 400 mg/kg/day. Doses were administered p.o. after an overnight fast, once daily for 3 weeks, followed by a 1-week rest. Intrapatient dose escalation occurred after two courses without toxicity greater than grade 2. The time course of butyrate in plasma was assessed on days 1 and 15 and after any dose escalation. Grade 3 toxicities consisted of nausea, vomiting, and myalgia. Grades 1 and 2 toxicities included diarrhea, headache, abdominal cramping, nausea, anemia, constipation, azotemia, lightheadedness, fatigue, rash, alopecia, odor, dysphoria, and clumsiness. There was no consistent increase in hemoglobin F with tributyrin treatment. Peak plasma butyrate concentrations occurred between 0.25 and 3 h after dose, increased with dose, and ranged from 0 to 0.45 mM. Peak concentrations did not increase in three patients who had dose escalation. Butyrate pharmacokinetics were not different on days 1 and 15. Because peak plasma concentrations near those effective in vitro (0.5-1 mM) were achieved, but butyrate disappeared from plasma by 5 h after dose, we are now pursuing dose escalation with dosing three times daily, beginning at a dose of 450 mg/kg/day.

Methods of creating pneumoperitoneum: a review of techniques and complications

The existence of numerous techniques for the creation of pneumoperitoneum at laparoscopy indicates that none have been proven totally efficacious or complication free. These methods include the standard technique of insufflation after insertion of the Veress needle via the umbilicus or less commonly via the transfundal or transforniceal routes, open laparoscopy involving dissection through the linea alba and opening of the peritoneum under direct vision, and direct trocar insertion as well as variations on these techniques. After reviewing the methods available and surveying the existing data concerning the rates of failure and complications, we conclude that no single technique can claim to be overwhelmingly superior, and that laparoscopists should, therefore, acquaint themselves with at least two of these techniques. Finally, we recommend a large-scale combined survey by the colleges of obstetricians and gynecologists and surgeons on rates of failure and complications of the varied approaches of abdominal entry for laparoscopy.

The safety of laparoscopic treatment for ovarian dermoid tumours

Whilst laparoscopic surgery has largely replaced laparotomy as the standard surgical option for the management of benign ovarian cysts, concern remains regarding the safety of laparoscopy for benign cystic teratomas. This is based on a higher rate of cyst content spillage compared to laparotomy and the known sequelae of chemical peritonitis and granuloma formation. We present 18 cases of laparoscopic dermoid cystectomy with recommendations for specimen removal from the peritoneal cavity. Our findings together with evidence from the literature confirms the safety of laparoscopy for the treatment of ovarian dermoid cysts.

Plasma concentrations and pharmacokinetics of dimethylsulfoxide and its metabolites in patients undergoing peripheral-blood stem-cell transplants

PURPOSE

Dimethylsulfoxide (DMSO) is used to cryopreserve hematopoietic stem cells and is obligatorily infused into patients who receive stem-cell transplants. This study characterized the plasma concentrations and pharmacokinetics of DMSO and its metabolites in patients who underwent peripheral-blood stem-cell transplants.

MATERIALS AND METHODS

Plasma concentrations of DMSO, dimethylsulfone (DMSO2), and dimethylsulfide (DMSH2) were assessed in 10 patients who underwent autologous transplants with stem cells, cryopreserved in 10% DMSO (vol/vol). Blood was sampled at multiple times after the stem-cell infusion. Urine was pooled during the 24 hours postinfusion. DMSO, DMSO2, and DMSH2 were assayed simultaneously by gas chromatography. A one-compartment model with saturable elimination proved most suitable for fitting plasma DMSO concentration-versus-time data.

RESULTS

Stem-cell volumes infused ranged between 180 and 585 mL (254 to 824 mmol DMSO). Infusions lasted between 20 and 120 minutes. Peak plasma DMSO concentrations were 19.1 +/- 6.3 mmol/L (mean +/- SD). Pharmacokinetic parameters for volume of the central compartment (Vc), maximum velocity (Vmax), and Michaels-Menten constant (Km) were 37.3 +/- 17 L, 0.99 +/- 0.57 mmol/L/h, and 5.2 +/- 5.0 mmol/L, respectively. Plasma DMSO2 concentrations increased during the first 24 hours, plateaued at 4.4 +/- 1.2 mmol/L, and remained there until 48 hours (the last sample). DMSH2 concentrations were at steady-state by 5 minutes and remained between 3 and 5 mmol/L for 48 hours. Urinary excretion of DMSO and DMSO2 accounted for 44% +/- 4% and 4% +/- 1%, respectively, of the administered DMSO dose. Renal clearance of DMSO was 14.1 +/- 3.4 mL/min.

CONCLUSION

These data (1) document plasma concentrations of DMSO and metabolites in patients following peripheral-blood stem-cell transplants; (2) allow consideration of potential effects of these concentrations on stem-cell engraftment and drug-drug interactions; and (3) can facilitate a concentration-guided phase I trial of DMSO.