Cooperative inhibition of renal cancer growth by anti-epidermal growth factor receptor antibody and protein kinase A antisense oligonucleotide

Multiomics surface receptor profiling of the NCI-60 tumor cell panel uncovers novel theranostics for cancer immunotherapy

BACKGROUND

Immunotherapy with immune checkpoint inhibitors (ICI) has revolutionized cancer therapy. However, therapeutic targeting of inhibitory T cell receptors such as PD-1 not only initiates a broad immune response against tumors, but also causes severe adverse effects. An ideal future stratified immunotherapy would interfere with cancer-specific cell surface receptors only.

METHODS

To identify such candidates, we profiled the surface receptors of the NCI-60 tumor cell panel via flow cytometry. The resulting surface receptor expression data were integrated into proteomic and transcriptomic NCI-60 datasets applying a sophisticated multiomics multiple co-inertia analysis (MCIA). This allowed us to identify surface profiles for skin, brain, colon, kidney, and bone marrow derived cell lines and cancer entity-specific cell surface receptor biomarkers for colon and renal cancer.

RESULTS

For colon cancer, identified biomarkers are CD15, CD104, CD324, CD326, CD49f, and for renal cancer, CD24, CD26, CD106 (VCAM1), EGFR, SSEA-3 (B3GALT5), SSEA-4 (TMCC1), TIM1 (HAVCR1), and TRA-1-60R (PODXL). Further data mining revealed that CD106 (VCAM1) in particular is a promising novel immunotherapeutic target for the treatment of renal cancer.

CONCLUSION

Altogether, our innovative multiomics analysis of the NCI-60 panel represents a highly valuable resource for uncovering surface receptors that could be further exploited for diagnostic and therapeutic purposes in the context of cancer immunotherapy.

Identification of biological targets through the correlation between cell line chemosensitivity and protein expression pattern

Matching biological data sequences is one of the most interesting ways to discover new bioactive compounds. In particular, matching cell chemosensitivity with a protein expression profile can be a useful approach to predict the activity of compounds against definite biological targets. In this review, we discuss this correlation. First, we analyze case studies in which some known drugs, acting on known targets, show a good correlation between their antiproliferative activities and protein expression when a large panel of tumor cells is considered. Then, we highlight how the application of in silico methods based on the correlation between cell line chemosensitivity and gene/protein expression patterns might be a quick, cheap, and interesting approach to predict the biological activity of investigated molecules.

Epidermal growth factor receptor: Structure-function informing the design of anticancer therapeutics

Research on the epidermal growth factor (EGF) family and the family of receptors (EGFR) has progressed rapidly in recent times. New crystal structures of the ectodomains with different ligands, the activation of the kinase domain through oligomerisation and the use of fluorescence techniques have revealed profound conformational changes on ligand binding. The control of cell signaling from the EGFR-family is complex, with heterodimerisation, ligand affinity and signaling cross-talk influencing cellular outcomes. Analysis of tissue homeostasis indicates that the control of pro-ligand processing is likely to be as important as receptor activation events. Several members of the EGFR-family are overexpressed and/or mutated in cancer cells. The perturbation of EGFR-family signaling drives the malignant phenotype of many cancers and both inhibitors and antagonists of signaling from these receptors have already produced therapeutic benefits for patients. The design of affibodies, antibodies, small molecule inhibitors and even immunotherapeutic drugs targeting the EGFR-family has yielded promising new approaches to improving outcomes for cancer patients. In this review, we describe recent discoveries which have increased our understanding of the structure and dynamics of signaling from the EGFR-family, the roles of ligand processing and receptor cross-talk. We discuss the relevance of these studies to the development of strategies for designing more effective targeted treatments for cancer patients.

Application of nano-surface and molecular-orientation limited proteolysis to LC–MS bioanalysis of cetuximab

Background: We recently reported the principle of nano-surface and molecular-orientation limited (nSMOL) proteolysis, which is useful for LC–MS bioanalysis of antibody drugs. Methodology: The nSMOL is a Fab-selective limited proteolysis which utilizes the difference of protease-immobilized nanoparticle diameter (200 nm) and antibody collection resin pore (100 nm). We have demonstrated the full validation for chimeric antibody cetuximab bioanalysis in human plasma using nSMOL. Signature peptides (SQVFFK, ASQSIGTNIHWYQQR and YASESISGIPSR) in cetuximab complementarity-determining region were simultaneously quantitated by LC–MS multiple reaction monitoring. Conclusion: This nSMOL quantification showed sensitivity of 0.586 µg/ml and linearity of 0.586 to 300 µg/ml. Full validation study archived the guideline criteria of low Mw drug compounds. These results indicate that nSMOL is also significant method for cetuximab bioanalysis.

Blockade of phospholipid scramblase 1 with its N-terminal domain antibody reduces tumorigenesis of colorectal carcinomas in vitro and in vivo

Background

Membrane-bound phospholipid scramblase 1 (PLSCR1) is involved in both lipid trafficking and cell signaling. Previously, we showed that PLSCR1 is overexpressed in many colorectal carcinomas (CRCs). In the present study, we investigated the tumorigenic role of PLSCR1 in CRC and suggest that it is a potential therapeutic target.

Methods

To identify PLSCR1 as a therapeutic target, we studied the tumorigenic properties of CRC cell lines treated with a monoclonal antibody (NP1) against the N-terminus of PLSCR1 in vitro and in vivo. We also investigated cell cycle status and epidermal growth factor receptor–related pathways and downstream effectors of PLSCR1 after blocking its function with NP1.

Results

Treating CRC cells with NP1 in vitro and in vivo decreased cell proliferation, anchorage-independent growth, migration, and invasion. Adding NP1 to the CRC cell line HT29 caused arrest at G1/S. Treating HT29 cells with NP1 significantly decreased the expression of cyclin D1 and phosphorylation levels of Src, the adaptor protein Shc, and Erks. The reduced level of cyclin D1 led to an increase in the activated form of the tumor suppressor retinoblastoma protein via dephosphorylation. These actions led to attenuation of tumorigenesis.

Conclusions

Therefore, PLSCR1 may serve as a potential therapeutic target for CRC.

Identification of genes differentially expressed as result of adenovirus type 5- and adenovirus type 12-transformation

BACKGROUND

Cells transformed by human adenoviruses (Ad) exhibit differential capacities to induce tumours in immunocompetent rodents; for example, Ad12-transformed rodent cells are oncogenic whereas Ad5-transformed cells are not. The E1A gene determines oncogenic phenotype, is a transcriptional regulator and dysregulates host cell gene expression, a key factor in both cellular transformation and oncogenesis. To reveal differences in gene expression between cells transformed with oncogenic and non-oncogenic adenoviruses we have performed comparative analysis of transcript profiles with the aim of identifying candidate genes involved in the process of neoplastic transformation.

RESULTS

Analysis of microarray data revealed that a total of 232 genes were differentially expressed in Ad12 E1- or Ad5 E1-transformed BRK cells compared to untransformed baby rat kidney (BRK) cells. Gene information was available for 193 transcripts and using gene ontology (GO) classifications and literature searches it was possible to assign known or suggested functions to 166 of these identified genes. A subset of differentially-expressed genes from the microarray was further examined by real-time PCR and Western blotting using BRK cells immortalised by Ad12 E1A or Ad5 E1A in addition to Ad12 E1- or Ad5 E1-transformed BRK cells. Up-regulation of RelA and significant dysregulation of collagen type I mRNA transcripts and proteins were found in Ad-transformed cells.

CONCLUSION

These results suggest that a complex web of cellular pathways become altered in Ad-transformed cells and that Ad E1A is sufficient for the observed dysregulation. Further work will focus on investigating which splice variant of Ad E1A is responsible for the observed dysregulation at the pathway level, and the mechanisms of E1A-mediated transcriptional regulation.

The use of xenograft models for the selection of cancer treatments with the EGFR as an example

Mouse models of cancer have consistently been used to qualify new anti-cancer drugs for development of human clinical trials. The most used models are xenografts of human tumors grown subcutaneously in immunodeficient mice such as athymic (nude) or severe combined immune deficient (SCID) mice. However, the number of anti-cancer agents that fail in the clinic far outweighs those considered effective, suggesting that the selection procedure for progression of molecules into the clinic requires improvement. This has provoked considerable skepticism about the value of using such preclinical models. As a result, a shift has occurred towards developing and using spontaneous mouse tumor arising in transgenic and/or knockout mice engineered to recapitulate various genetic alterations thought to be causative of specific types of human cancers. Alternatively, the option has been to improve human tumor xenograft models by using orthotopic transplantation and, therefore, promotion of metastatic spread of the resultant 'primary' tumors. Here we review the value and the limitations of xenograft models and their role in developing new anti-cancer treatments.

Potential pharmacological interventions in polycystic kidney disease

Polycystic kidney diseases (autosomal dominant and autosomal recessive) are progressive renal tubular cystic diseases, which are characterised by cyst expansion and loss of normal kidney structure and function. Autosomal dominant polycystic kidney disease (ADPKD) is the most common life- threatening, hereditary disease. ADPKD is more prevalent than Huntington's disease, haemophilia, sickle cell disease, cystic fibrosis, myotonic dystrophy and Down's syndrome combined. Early diagnosis and treatment of hypertension with inhibitors of the renin-angiotensin-aldosterone system (RAAS) and its potential protective effect on left ventricular hypertrophy has been one of the major therapeutic goals to decrease cardiac complications and contribute to improved prognosis of the disease. Advances in the understanding of the genetics, molecular biology and pathophysiology of the disease are likely to facilitate the improvement of treatments for these diseases. Developments in describing the role of intracellular calcium ([Ca(2+)](i)) and its correlation with cellular signalling systems, Ras/Raf/mitogen extracellular kinase (MEK)/extracellular signal-regulated protein kinase (ERK), and interaction of these pathways with cyclic adenosine monophosphate (cAMP) levels, provide new insights on treatment strategies. Blocking the vasopressin V(2) receptor, a major adenylyl cyclase agonist, demonstrated significant improvements in inhibiting cytogenesis in animal models. Because of activation of the mammalian target of rapamycin (mTOR) pathway, the use of sirolimus (rapamycin) an mTOR inhibitor, markedly reduced cyst formation and decreased polycystic kidney size in several animal models. Caspase inhibitors have been shown to decrease cytogenesis and renal failure in rats with cystic disease. Cystic fluid secretion results in cyst enlargement and somatostatin analogues have been shown to decrease renal cyst progression in patients with ADPKD. The safety and efficacy of these classes of drugs provide potential interventions for experimental and clinical trials.

Targeted cancer therapies based on antibodies directed against epidermal growth factor receptor: status and perspectives

Compelling experimental and clinical evidence suggests that epidermal growth factor receptor (EGFR) plays an important role in the pathogenesis of a variety of human cancers; thus, providing a strong rationale for the development of receptor antagonists as effective and specific therapeutic strategies for the treatment of EGFR-expressing cancers. Monoclonal antibodies (mAb), owing to their high specificity towards a given target, represent a unique class of novel cancer therapeutics. A number of anti-EGFR mAb are currently being developed in our clinic, including two that have been approved by the United States Food and Drug Administration for the treatment of refractory metastatic colorectal cancer (mCRC) and squamous cell carcinomas of the head and neck (SCCHN). Cetuximab (Erbitux, IMC-C225), an IgG1 mAb, has demonstrated significant antitumor activity, both as a single agent and in combination with chemotherapeutics and radiation, in patients with refractory mCRC and SCCHN, respectively. Panitumumab (Vectibix), an IgG2 mAb, has been approved as a single agent for the treatment of patients with refractory mCRC. These mAb, via blocking ligand/receptor interactions, exert their biological activity via multiple mechanisms, including inhibition of cell cycle progression, potentiation of cell apoptosis, inhibition of DNA repair, inhibition of angiogenesis, tumor cell invasion and metastasis and, potentially, induction of immunological effector mechanisms. Anti-EGFR antibodies have demonstrated good safety profiles and potent anticancer activity in our clinic and may prove to be efficacious agents in the treatment of a variety of human malignancies.

Bee venom secretory phospholipase A2 and phosphatidylinositol-homologues cooperatively disrupt membrane integrity, abrogate signal transduction and inhibit proliferation of renal cancer cells

Bee venom secretory phospholipase A2 (bv-sPLA2) and phosphatidylinositol-(3,4)-bisphosphate (PtdIns(3,4)P2) act synergistically to induce cell death in tumour cells of various origins with concomitant stimulation of the immune system. Here, we investigated the mechanisms involved in such actions and examined structural requirements of PtdIns-homologues to inhibit tumour cells in combination with bv-sPLA2. Renal cancer cells were treated with bv-sPLA2 alone or in combination with PtdIns-homologues. Inhibitory effects on [(3)H] thymidine incorporation and intracellular signal transduction pathways were tested. Reaction products generated by bv-sPLA2 interaction with PtdIns(3,4)P2 were identified by mass spectrometry. Among the tested PtdIns-homologues those with a phosphate esterified to position 3 of the inositol head group, were most efficient in cooperating with bv-sPLA2 to block tumour cell proliferation. Growth inhibition induced by the combined action of bv-sPLA2 with either PtdIns(3,4)bisphosphate or PtdIns(3,4,5)trisphosphate were synergistic and accompanied by potent cell lysis. In contrast, PtdIns, which lacked the phosphate group at position 3, failed to promote synergistic growth inhibition. The combined administration of PtdIns(3,4)P2 and bv-sPLA2 abrogated signal transduction mediated by extracellular signal regulated kinase 1 and 2 and prevented transduction of survival signals mediated by protein kinase B. Surface expression of the epidermal growth factor (EGF)-receptor was reduced after PtdIns(3,4)P2-bv-sPLA2 administration and associated with a blockade of EGF-induced signalling. In addition, mass spectroscopy revealed that bv-sPLA2 cleaves PtdIns(3,4)P2 to generate lyso-PtdIns(3,4)P2. In conclusion, we suggest that the cytotoxic activity mediated by PtdIns(3,4)P2 and bv-sPLA2 is due to cell death that results from disruption of membrane integrity, abrogation of signal transduction and the generation of cytotoxic lyso-PtdIns(3,4)P2.

Efficacy of ablative high-dose-per-fraction radiation for implanted human renal cell cancer in a nude mouse model

OBJECTIVES

Stereotactic body radiation therapy (SBRT) is a new therapeutic paradigm that uses a very large dose per fraction treatments (ablative hypofractionation). We investigated the use of ablative hypofractionation in treating human renal cell carcinoma using a nude mouse model.

METHODS

Nude mice were injected subcutaneously with A498 human renal carcinoma cells. Tumour-bearing animals were radiated with three fractions (one per week) for a total dose of 48 Gy (n = 12), while untreated animals served as controls (n = 7). The mice were weighed, and tumour volumes were measured at baseline and weekly until 7 weeks post-treatment.

RESULTS

Control animals demonstrated progressive tumour growth and were sacrificed because of either tumour size or ulceration. Tumours in the treatment group grew to three times their initial size over the 3 weeks of treatment but subsequently decreased progressively to less than 30% of their initial volume. All treated tumours exhibited marked cytologic changes. Tumours from mice sacrificed before post-treatment week 4 had a mitotic count of 1-4/10 hpf. Tumours from mice sacrificed more than 4 weeks post-treatment (n = 4) demonstrated no mitoses.

CONCLUSIONS

Treatment with high-dose-per-fraction radiation to 48 Gy resulted in a sustained decrease in tumour volume and marked cytologic changes. These results are preliminary--but promising--and encourage further research into this application of ablative hypofractionated radiation for kidney cancer.

Mechanism of von Hippel-Lindau protein-mediated suppression of nuclear factor kappa B activity

Biallelic inactivating mutations of the von Hippel-Lindau tumor suppressor gene (VHL) are a hallmark of clear cell renal cell carcinoma (CCRCC), the most common histologic subtype of RCC. Biallelic VHL loss results in accumulation of hypoxia-inducible factor alpha (HIFalpha). Restoring expression of the wild-type protein encoded by VHL (pVHL) in tumors with biallelic VHL inactivation (VHL(-)(/)(-)) suppresses tumorigenesis, and pVHL-mediated degradation of HIFalpha is necessary and sufficient for VHL-mediated tumor suppression. The downstream targets of HIFalpha that promote renal carcinogenesis have not been completely elucidated. Recently, VHL loss was shown to activate nuclear factor kappa B (NF-kappaB), a family of transcription factors that promotes tumor growth. Here we show that VHL loss drives NF-kappaB activation by resulting in HIFalpha accumulation, which induces expression of transforming growth factor alpha, with consequent activation of an epidermal growth factor receptor/phosphatidylinositol-3-OH kinase/protein kinase B (AKT)/IkappaB-kinase alpha/NF-kappaB signaling cascade. We also show that components of this signaling pathway promote the growth of VHL(-)(/)(-) tumor cells. Members of this pathway represent viable drug targets in VHL(-)(/)(-) tumors, such as those associated with CCRCC.

Immunohistochemically determined total epidermal growth factor receptor levels not of prognostic value in newly diagnosed glioblastoma multiforme: Report from the Radiation Therapy Oncology Group

PURPOSE

The Radiation Therapy Oncology Group (RTOG) performed an analysis of patterns of immunohistochemically detected total epidermal growth factor receptor (EGFR) protein expression levels and their prognostic significance on archival tissue in newly diagnosed glioblastoma multiforme (GBM) patients from prior prospective RTOG clinical trials.

METHODS AND MATERIALS

Patients in this study had been treated on previous RTOG GBM trials (RTOG 7401, 7918, 8302, 8409, 9006, 9305, 9602, and 9806). Tissue microarrays were prepared from 155 patients enrolled in these trials. These specimens were stained using a mouse monoclonal antibody specific for the extracellular binding domain of EGFR to detect total EGFR (including both wild-type phosphorylated and wild-type unphosphorylated isoforms with some cross-reactivity with EGFRvIII). The intensity of total EGFR protein expression was measured by computerized quantitative image analysis using the SAMBA 4000 Cell Image Analysis System. The parameters measured were the mean optical densities over the labeled areas and the staining index, which represents the proportion of stained area relative to the mean stain concentration. Both parameters were correlated with the clinical outcome.

RESULTS

No differences in either overall or progression-free survival could be demonstrated by the mean optical density class or mean optical density quartile or the staining index of total EGFR immunostaining among the representative RTOG GBM cases.

CONCLUSION

Total EGFR protein expression levels, as measured immunohistochemically, do not appear to be of prognostic value in newly diagnosed GBM patients. Given the accumulating clinical evidence of the activity of anti-EGFR agents in GBM and the preclinical data suggesting the important role of downstream mediators as effectors of EGFR signaling, the RTOG is conducting additional investigations into the prognostic value of activation patterns of EGFR signaling, both at the level of the receptor (e.g., EGFRvIII, phospho-EGFR) and at the level of downstream signal transduction pathways (e.g., PI3K, Ras/MAPK pathways).

A Src family inhibitor (PP1) potentiates tumor-suppressive effect of connexin 32 gene in renal cancer cells

Connexin (Cx) genes exert negative growth effects on tumor cells with certain cell specificity. We have recently reported that Cx32 acts as a tumor suppressor gene in renal cancer cells due to the inhibition of Src-dependent signaling. In line with the previous study, here we examined if a Src family inhibitor (PP1) could potentiate tumor-suppressive effect of Cx32 in Caki-2 cell from human renal cell carcinoma. In order to clarify the potentialization of PP1, using Cx32-transfected Caki-2 cells and mock-transfected Caki-2 cells, we estimated difference in cytotoxic effect of PP1 on the two cell clones in vitro as well as in vivo. PP1 showed more cytotoxic effect on Caki-2 cells having Cx32 positive expression than that of Cx32 negative expression at lower doses. This potentialization was also observed in xenograft model of nude mice. The potentialization of the effect mainly depended on the induction of apoptosis but not the control of cell growth. In conjugation with this event, the reduction of anti-apoptotic molecules (Bcl-2 and Bcl-xL) was caused by the combination of Cx32 expression and PP1 treatment in Caki-2 cells. These results suggest that PP1 potentiates tumor-suppressive effect of connexin 32 gene in renal cancer cells through the reduction of anti-apoptotic molecules.

Epidermal growth factor receptor tyrosine kinase inhibitors in late stage clinical trials

The epidermal growth factor receptor (EGFR) is a cell membrane receptor that plays a key role in cancer development and progression. Ligand-activated EGFR-dependent signalling is involved in cell proliferation, apoptosis, angiogenesis and metastatic spread. Targeting the EGFR, therefore, represents a promising molecular approach in cancer treatment. Several anti-EGFR agents are in clinical development. Three drugs are currently in Phase II and III development as single agents, or in combination with other anticancer modalities: IMC-225 (cetuximab/Erbitux; ImClone), a chimaeric human-mouse monoclonal IgG(1) antibody, which blocks ligand binding and functional activation of the EGFR; OSI-774 (erlotinib/Tarceva; Genentech/OSI/Roch) and ZD1839 (gefitinib/Iressa; AstraZeneca), two small molecule EGFR-selective inhibitors of tyrosine kinase enzymatic activity, which prevent EGFR autophosphorylation and activation. Iressa is the first EGFR-targeting agent to be registered as an anticancer drug in Japan, in Australia and in the US for the third-line treatment of chemoresistant non-small cell lung cancer (NSCLC) patients. This review will focus on the preclinical background and on the results from the first series of clinical trials with these drugs. Furthermore, continuing clinical trials and a series of open clinical issues for the development of optimal strategies of using EGFR-targeting agents will be discussed.

Molecular biological design of novel antineoplastic therapies

Novel therapies represent a new strategy for the development of anticancer agents. New targets derived from the knowledge of the molecular structure and genetic defects has been useful in developing anticancer drugs that prolong or stabilise the progression of tumours with minimal systemic toxicities. In this review, the mechanism of action and the most significant trials regarding monoclonal antibodies, tyrosine kinase inhibitors, angiogenesis and cyclooxygenase inhibitor-based therapies, farnesyl transferase inhibitors and proteasome inhibitors are discussed. The potential biological end points and toxicities are also described. In conclusion, novel therapies present a promising class of anticancer agents, acting through different mechanisms and offering a new perspective in the treatment of cancer.

Targeting multiple signaling pathways as a strategy for managing prostate cancer: multifocal signal modulation therapy

The aberrant behavior of cancer reflects upregulation of certain oncogenic signaling pathways that promote proliferation, inhibit apoptosis, and enable the cancer to spread and evoke angiogenesis. Theoretically, it should be feasible to decrease the activity of these pathways-or increase the activity of pathways that oppose them-with noncytotoxic agents. Since multiple pathways are dysfunctional in most cancers, and cancers accumulate new oncogenic mutations as they progress, the greatest and most durable therapeutic benefit will likely be achieved with combination regimens that address several targets. Thus, a multifocal signal modulation therapy (MSMT) of cancer is proposed. This concept has already been documented by researchers who have shown that certain combinations of signal modulators-of limited utility when administered individually-can achieve dramatic suppression of tumor growth in rodent xenograft models. The present essay attempts to guide development of MSMTs for prostate cancer. Androgen ablation is a signal-modulating measure already in standard use in the management of delocalized prostate cancer. The additional molecular targets considered here include the type 1 insulin-like growth factor receptor, the epidermal growth factor receptor, mammalian target of rapamycin, NF-kappaB, hypoxia-inducible factor-1alpha, hsp90, cyclooxygenase-2, protein kinase A type I, vascular endothelial growth factor, 5-lipoxygenase, 12-lipoxygenase, angiotensin II receptor type 1, bradykinin receptor type 1, c-Src, interleukin-6, ras, MDM2, bcl-2/bclxL, vitamin D receptor, estrogen receptor-beta, and PPAR-. Various nutrients and phytochemicals suspected to have potential utility in prostate cancer prevention and therapy, but whose key molecular targets are still unknown, might reasonably be incorporated into MSMTs for prostate cancer; these include lycopene, selenium, green tea polyphenols, genistein, and silibinin. MSMTs can be developed systematically by testing various combinations of signal-modulating agents, in concentrations that can feasibly be achieved and maintained clinically, on human prostate cancer cell lines; combinations that appear promising can then be tested in xenograft models and, ultimately, in the clinic. Some signal modulators can increase response to cytotoxic drugs by upregulating effectors of apoptosis. When MSMTs fail to raise the spontaneous apoptosis rate sufficiently to achieve tumor stasis or regression, incorporation of appropriate cytotoxic agents into the regimen may improve the clinical outcome.

Antitumor Activity of ZD6474, a Vascular Endothelial Growth Factor-2 and Epidermal Growth Factor Receptor Small Molecule Tyrosine Kinase Inhibitor, in Combination with SC-236, a Cyclooxygenase-2 Inhibitor

Purpose: The epidermal growth factor receptor (EGFR) autocrine pathway plays an important role in cancer cell growth. Vascular endothelial growth factor (VEGF) is a key regulator of tumor-induced endothelial cell proliferation and vascular permeability. Enhanced cyclooxygenase-2 (COX-2) expression has been linked to cancer cell proliferation, EGFR activation, VEGF secretion, and tumor-induced angiogenesis. ZD6474 is an orally available, small molecule, dual VEGF receptor-2 (VEGFR-2) and EGFR tyrosine kinase inhibitor. We investigated the activity of ZD6474 in combination with SC-236, a selective COX-2 inhibitor, to determine the antitumor activity of the simultaneous blockade of EGFR, COX-2, and VEGF functions.

Experimental Design: The antitumor activity in vitro and in vivo of ZD6474 and/or SC-236 was tested in human cancer cell lines with a functional EGFR autocrine pathway.

Results: The combination of ZD6474 and SC-236 determined supra-additive growth inhibition in all cancer cell lines tested. In nude mice bearing established human colon (GEO) or lung adenocarcinoma (A549) cancer xenografts and treated with ZD6474 and/or SC-236 for 3 weeks, a reversible tumor growth inhibition was seen with each agent, whereas a more prolonged growth inhibition that lasted for 3 to 5 weeks following the end of treatment resulted from the combination of the two agents. A long-term, 10-week treatment with ZD6474 plus SC-236 resulted in sustained tumor growth inhibition in all mice with tumor eradication in 3 of 10 GEO tumor–bearing mice and in 4 of 10 A549 tumor–bearing mice.

Conclusions: This study provides a rationale for evaluating the simultaneous blockade of EGFR, COX-2, and VEGF signaling as cancer therapy in a clinical setting.

Angiogenesis inhibitors: a rational strategy for radiosensitization in the treatment of non-small-cell lung cancer?

Angiogenesis is a precondition to invasion and metastasis for all solid tumors. Vascular endothelial growth factor (VEGF) and its family of receptors (VEGFR) play a critical role in cancer progression by promoting new blood vessel formation. Overexpression of VEGF and VEGFR has been correlated with poor prognosis in a variety of malignancies. In this era of targeted therapies for cancer, inhibiting angiogenesis through antiangiogenic and/or vascular targeting agents seems logical. Disturbing the angiogenesis process is an alternative or complementary strategy to inhibition of growth factor signaling. Blocking angiogenesis may enhance conventional anticancer treatments such as radiation therapy in situations where tumors are unresponsive to current antigrowth factor efforts. Compounds currently under investigation in cancer therapy include anti-VEGF/VEGFR antibodies, small molecule VEGFR tyrosine kinase inhibitors, antisense suppression of VEGF, immunotherapy, viral-directed targeting of VEGFR signaling, ribozymes, and various toxin conjugates. Preclinical investigations are exploring the benefits of combining angiogenic inhibitors with radiation. This article will provide an overview of these preclinical studies and the rationale for this therapeutic strategy in the treatment of non-small-cell lung cancer.

Inhibition of bcl-2 enhances the efficacy of chemotherapy in renal cell carcinoma

OBJECTIVES

Renal cell cancer (RCC) is highly resistant to chemotherapy. Increased expression of the antiapoptotic gene bcl-2 in tumors is known to be associated with poor responses to systemic treatment of cancer. Down-regulation of bcl-2 expression using antisense oligonucleotides (asON) has been shown to increase chemosensitivity in clinical phase I-III studies with various cancers. However, no studies on the efficacy of this approach in RCC have been reported so far. This study aimed to evaluate whether bcl-2 asON could enhance efficacy of chemotherapy in human RCC.

MATERIAL AND METHODS

Expression of bcl-2 mRNA and protein was analyzed in different RCC cell lines by RT-PCR and Western blot. Cells with high or low bcl-2 mRNA and protein expression were treated with different concentrations of bcl-2 asON in combination with cisplatin. AsON-induced down-regulation of bcl-2 mRNA and protein was documented by RT-PCR and Western blot. Treatment effects on cell viability were analyzed by colorimetric tetrazolium (MTT) assay. Immunohistochemical staining of M30-positive cells was performed for quantification of apoptotic cells.

RESULTS

Transfection of high bcl-2 expressing cells with bcl-2 asON alone induced no reduction of cell viability at a concentration range from 100-1000 nM. In combination therapy, pretreatment with asON significantly enhanced MTT reduction after cisplatin treatment. IC50 concentrations of cisplatin were 1 microg/ml with and 2.7 microg/ml without prior incubation. The marked reduction of cell viability correlated with an 8-fold increase of apoptotic cells after combination treatment. Only a minor increase of cisplatin effectivity was noted after asON preincubation of cells with lower bcl-2 expression.

CONCLUSIONS

The combination of cisplatin and bcl-2 antisense ON exerts significantly greater effects on cell viability and apoptosis than either agent used alone on human RCC cells. These data indicate that inhibition of bcl-2 expression may be an attractive therapeutic strategy in RCC tumors with high bcl-2 expression.

A phase II trial of gefitinib (Iressa, ZD1839) in stage IV and recurrent renal cell carcinoma

PURPOSE

The epidermal growth factor receptor (EGFR) is overexpressed in 75 to 90% of renal cell carcinomas and may play a role in tumor initiation and progression. Gefitinib (Iressa, ZD1839) is a potent, selective EGFR-tyrosine kinase inhibitor. This trial was undertaken to assess the efficacy and toxicity of gefitinib in advanced renal cell carcinoma.

EXPERIMENTAL DESIGN

Oral gefitinib, 500 mg once daily, was given continuously. A single-dose reduction to 250 mg daily was allowed for toxicity. The primary end point was response rate (defined as complete remission + partial remission + stable disease). Secondary end points were progression-free survival, overall survival, toxicity, and correlation of response with EGFR status.

RESULTS

Twenty-one patients were enrolled on this study, and all are evaluable for response and toxicity. Patient characteristics were median age 61 (range, 35-78 years); 17 males, 4 females; median performance status 0 (range 0-2); median number of prior systemic therapies 1 (range, 0-3). The median and mean number of cycles of therapy received was 3 and 4.7 (range, 1-14+). The best response was stable disease in eight patients (38%). Median progression-free survival was 2.7 months. Median overall survival was 8.3 months. The difference in overall survival was significantly different between patients with progressive disease versus stable disease (6.1 months versus 16+ months; Log-Rank test P value < 0.0001). Three patients required a dose reduction, all for grade 3 diarrhea. There was no apparent correlation between EGFR status and stability of disease or progression of disease.

CONCLUSIONS

Gefitinib is without significant conventional activity in renal cell carcinoma. The relation of "stable disease" to treatment or to disease-related prognostic heterogeneity remains to be defined.

Antitumor activity of ZD6474, a vascular endothelial growth factor receptor tyrosine kinase inhibitor, in human cancer cells with acquired resistance to antiepidermal growth factor receptor therapy

PURPOSE

The epidermal growth factor receptor (EGFR) autocrine signaling pathway is involved in cancer development and progression. EGFR inhibitors such as C225 (cetuximab), a chimeric human-mouse anti-EGFR monoclonal antibody, and ZD1839 (gefitinib), a small molecule EGFR-selective tyrosine kinase inhibitor, are in advanced clinical development. The potential emergence of cancer cell resistance in EGFR-expressing cancers treated with EGFR inhibitors could determine lack of activity of these drugs in some cancer patients. Vascular endothelial growth factor (VEGF) is secreted by cancer cells and plays a key role in the regulation of tumor-induced endothelial cell proliferation and permeability. ZD6474 is a small molecule VEGF flk-1/KDR (VEGFR-2) tyrosine kinase inhibitor that also demonstrates inhibitory activity against EGFR tyrosine kinase.

EXPERIMENTAL DESIGN

The antitumor activity of ZD1839, C225, and ZD6474 was tested in athymic mice bearing human GEO colon cancer xenografts. GEO cell lines resistant to EGFR inhibitors were established from GEO xenografts growing in mice treated chronically with ZD1839 or C225. Expression of EGFR was evaluated by flow cytometry. Expression of various proteins involved in intracellular cell signaling was assessed by Western blotting. Tumor growth data were evaluated for statistical significance using the Student's t test. All Ps were two-sided.

RESULTS

Although chronic administration of optimal doses of C225 or ZD1839 efficiently blocked GEO tumor growth in the majority of mice, tumors slowly started to grow within 80-90 days, despite continuous treatment. In contrast, continuous treatment of mice bearing established GEO xenografts with ZD6474 resulted in efficient tumor growth inhibition for the entire duration of dosing (up to 150 days). ZD6474 activity was also determined in mice pretreated with ZD1839 or C225. When GEO growth was apparent after 4 weeks of treatment with EGFR inhibitors, mice were either re-treated with EGFR inhibitors or treated with ZD6474. GEO tumor growth was blocked only in mice treated with ZD6474, whereas tumor progression was observed in mice re-treated with C225 or ZD1839. GEO tumors growing during treatment with C225 or with ZD1839 were established as cell lines (GEO-C225-RES and GEO-ZD1839-RES, respectively). Cell membrane-associated EGFR expression was only slightly reduced in these cell lines compared with parental GEO cells. Western blotting revealed no major change in the expression of the EGFR ligand transforming growth factor alpha of bcl-2, bcl-xL, p53, p27, MDM-2, akt, activated phospho-akt, or mitogen-activated protein kinase. However, both GEO-C225-RES and GEO-ZD1839-RES cells exhibited a 5-10-fold increase in activated phospho-mitogen-activated protein kinase and in the expression of cyclooxygenase-2 and of VEGF compared with GEO cells. GEO-C225-RES and GEO-ZD1839-RES growth as xenografts in nude mice was not significantly affected by treatment with either C225 or ZD1839 but was efficiently inhibited by ZD6474.

CONCLUSIONS

Long-term treatment of GEO xenografts with selective EGFR inhibitors results in the development of EGFR inhibitor-resistant cancer cells. Growth of EGFR inhibitor-resistant tumors can be inhibited by ZD6474. These data indicate that inhibition of VEGF signaling has potential as an anticancer strategy, even in tumors that are resistant to EGF inhibitors.

Antitumor activity of ZD6126, a novel vascular-targeting agent, is enhanced when combined with ZD1839, an epidermal growth factor receptor tyrosine kinase inhibitor, and potentiates the effects of radiation in a human non-small cell lung cancer xenograft model

Objective: Targeting the tumor vasculature may offer an alternative or complementary therapeutic approach to targeting growth factor signaling in lung cancer. The aim of these studies was to evaluate the antitumor effects in vivo of the combination of ZD6126, a tumor-selective vascular-targeting agent; ZD1839 (gefitinib, Iressa), an epidermal growth factor receptor tyrosine kinase inhibitor; and ionizing radiation in the treatment of non-small cell lung cancer xenograft model. Methods: Athymic nude mice with established flank A549 human non-small cell lung cancer xenograft model xenografts were treated with fractionated radiation therapy, ZD6126, ZD1839, or combinations of each treatment. ZD6126 (150 mg/kg) was given i.p. the day after each course of radiation. Animals treated with ZD1839 received 100 mg/kg per dose per animal, 5 or 7 days/wk for 2 weeks. Immunohistochemistry was done to evaluate the effects on tumor growth using an anti-Ki67 monoclonal antibody. Effects on tumor-induced vascularization were quantified using an anti–factor VIII–related antigen monoclonal antibody. Results: ZD6126 attenuated the growth of human A549 flank xenografts compared with untreated animals. Marked antitumor effects were observed when animals were treated with a combination of ZD6126 and fractionated radiation therapy with protracted tumor regression. ZD6126 + ZD1839 resulted in a greater tumor growth delay than either agent alone. Similar additive effects were seen with ZD1839 + fractionated radiation. Finally, the addition of ZD6126 to ZD1839 and radiation therapy seemed to further improve tumor growth control, with a significant tumor growth delay compared with animals treated with single agent or with double combinations. Immunohistochemistry showed that ZD1839 induced a marked reduction in A549 tumor cell proliferation. Both ZD1839 and ZD6126 treatment substantially reduced tumor-induced angiogenesis. ZD6126 caused marked vessel destruction through loss of endothelial cells and thrombosis, substantially increasing the level of necrosis seen when combined with radiation therapy. The combination of radiation therapy, ZD6126, and ZD1839 induced the greatest effects on tumor growth and angiogenesis. Conclusion: This first report shows that a selective vascular-targeting agent (ZD6126) + an anti–epidermal growth factor receptor agent (ZD1839) and radiation have additive in vivo effects in a human cancer model. Targeting the tumor vasculature offers an excellent strategy to enhance radiation cytotoxicity. Polytargeted therapy with agents that interfere with both growth factor and angiogenic signaling warrants further investigation.

Negative growth control of renal cell carcinoma cell by connexin 32: possible involvement of Her-2

Connexin (Cx) genes have negative growth effects on tumor cells with certain cell specificity. We have previously reported that Cx32 is specifically downregulated in human renal cell carcinoma cell (RCC) lines as well as cancerous regions of kidneys and that the Cx is expressed in the progenitor cells of the carcinoma. However, the precise role of Cx32 in growth control of RCC cells remains unknown. In this study, we examined whether Cx32 could act in growth control against a human RCC cell, Caki-2 cell. In order to estimate the cell growth control, we established Caki-2 cells that have stable expression of Cx32 genes. Cx32 expression in Caki-2 cells induced contact inhibition of growth and reduced anchorage-independent growth ability, but did not significantly affect lag phase growth rates. This growth control by Cx32 was dependent on the inhibition of the cell-cycle transition from G1 to S phase at high cell density, and the inhibition of the cell-cycle transition related to the suppression of Her-2 activation. Furthermore, the suppression of Cx32 expression in Caki-2 cells by short interfering RNA induced the activation of Her-2. These data suggest that Cx32 has negative growth control of Caki-2 cells, partly due to the inhibition of the Her-2 activation.

Antisense targeting protein kinase A type I as a drug for integrated strategies of cancer therapy

We have studied the role of protein kinase A (PKA) and its type I isoform (PKAI) in the transduction of mitogenic signaling, apoptosis, and angiogenesis. We have contributed to the development of selective inhibitors of PKAI, including a hybrid DNA/RNA mixed backbone oligonucleotide (AS-PKAI). We, and others, have demonstrated that AS-PKAI has a cooperative antitumor effect with a selected class of cytotoxic drugs and with radiotherapy in vitro and in vivo and that these effects can also be obtained following oral adinistration. Previously, we developed a series of therapeutic models based on the pleiotropic role played by PKAI in cell proliferation, apoptosis, and angiogenesis. On the basis of our former demonstration of functional and structural interactions of PKAI and the activated epidermal growth factor receptor (EGFR), we have shown that the combined blockade of both signaling molecules by AS-PKAI and either the monoclonal antibody C225 (erbitux) or the small molecule ZD1839 (gefitinib), results in a marked cooperative antitumor effect in a variety of human tumor models. A further cooperative antitumor effect can be obtained when AS-PKAI is used in combination with both EGFR inhibitors and either cytotoxic drugs or radiotherapy. The antitumor activity is associated with inhibition of growth factors and angiogenic factors production and to induction of apoptosis. In light of the recently demonstrated role of PKAI on the bcl-2-dependent apoptotic pathway, we have recently shown a synergistic antitumor, antiangiogenic, and proapoptotic effect of AS-PKAI in combination with antisense bcl-2 (oblimersen) or with a bispecific bcl-2/bcl-xL second generation antisense. A connection between COX-2, EGFR and PKAI was established, and we demonstrated that the combination of AS-PKAI with gefitinib and a COX-2 inhibitor, all adminstered orally, can result in a potent antitumor and antiangiogenic activity. These studies support the development of AS-PKAI as a novel anticancer agent and suggest its potentially relevant role when integrated with conventional treatments and/or other signaling inhibitors in novel therapeutic strategies.

Hypoxia inducible factor activates the transforming growth factor-alpha/epidermal growth factor receptor growth stimulatory pathway in VHL(-/-) renal cell carcinoma cells

Bi-allelic-inactivating mutations of the VHL tumor suppressor gene are found in the majority of clear cell renal cell carcinomas (VHL(-/-) RCC). VHL(-/-) RCC cells overproduce hypoxia-inducible genes as a consequence of constitutive, oxygen-independent activation of hypoxia inducible factor (HIF). While HIF activation explains the highly vascularized nature of VHL loss lesions, the relative role of HIF in oncogenesis and loss of growth control remains unknown. Here, we report that HIF plays a central role in promoting unregulated growth of VHL(-/-) RCC cells by activating the transforming growth factor-alpha (TGF-alpha)/epidermal growth factor receptor (EGF-R) pathway. Dominant-negative HIF and enzymatic inhibition of EGF-R were equally efficient at abolishing EGF-R activation and serum-independent growth of VHL(-/-) RCC cells. TGF-alpha is the only known EGF-R ligand that has a VHL-dependent expression profile and its overexpression by VHL(-/-) RCC cells is a direct consequence of HIF activation. In contrast to TGF-alpha, other HIF targets, including vascular endothelial growth factor (VEGF), were unable to stimulate serum-independent growth of VHL(-/-) RCC cells. VHL(-/-) RCC cells expressing reintroduced type 2C mutants of VHL, and which retain the ability to degrade HIF, fail to overproduce TGF-alpha and proliferate in serum-free media. These data link HIF with the overproduction of a bona fide renal cell mitogen leading to activation of a pathway involved in growth of renal cancer cells. Moreover, our results suggest that HIF might be involved in oncogenesis to a much higher extent than previously appreciated.

Understanding the mechanisms of action of EGFR inhibitors in NSCLC: what we know and what we do not know

The development of rationally designed agents targeting specific biological pathways in tumor development has been heralded as a major paradigm shift in the approach to the treatment of cancer. The application of these agents has lead to promising pre-clinical findings in a variety of human cancer pre-clinical models including lung cancer. Results from initial clinical trials employing targeted agents have shown that in contrast to what was expected, only selected patients may benefit. Determining which patients will benefit remains a major challenge. Findings from the 'Iressa' Dose Evaluation in Lung Cancer and INTACT trials for non-small cell lung cancer (NSCLC) require investigators to return to the laboratory to design relevant pre-clinical studies that improve our ability to predict response to targeted agents in the clinic.

Epidermal growth factor receptor (EGFR) as a target in cancer therapy: understanding the role of receptor expression and other molecular determinants that could influence the response to anti-EGFR drugs

The epidermal growth factor receptor (EGFR) is a rational target for cancer therapy because it is commonly expressed at a high level in a variety of solid tumours and it has been implicated in the control of cell survival, proliferation, metastasis and angiogenesis. However, despite evidence to suggest that EGFR expression is associated with a poor prognosis in some tumours (e.g. breast, head and neck carcinomas), the situation is by no means clear-cut. A number of issues are worthy of particular consideration, including how EGFR is measured and whether these assays are sensitive and reproducible, which mechanisms other than increased EGFR expression might cause the EGFR signalling drive to be increased, and the relationship, if any, between EGFR expression and the response to EGFR-targeted agents.

Antisense oligonucleotide therapy for urologic tumors

Modulation of gene expression using antisense oligonucleotides has advanced from the laboratory to the clinic. Numerous companies can, at least partially, attribute their success to the development of antisense techniques, and one antisense drug is currently on the market. Antisense compounds have been used in clinical trials that included patients with urologic tumors, mostly directed at proliferation- or apoptosis-related targets. Furthermore, therapeutic inhibition of many new identified genes is being investigated in preclinical tests. This review provides a contemporary overview of current preclinical and clinical antisense oligonucleotide concepts for the treatment of urologic tumors.

Monoclonal antibody therapy for genitourinary oncology: promise for the future

PURPOSE

Metastatic or recurrent cancer continues to be the bane of the urological oncologist. Despite recent improvements in therapeutic strategies and outcomes for clinically localized disease overall survival in patients with the majority of metastatic and recurrent genitourinary malignancies remains relatively unchanged. Modern advances in the field of immunotherapy hold the promise of providing the clinical urologist/oncologist with new tools to fight urological cancer. In this review we discuss the various mAb based strategies currently under investigation for urological oncology as well as the lessons learned from similar approaches in other fields.

MATERIALS AND METHODS

We reviewed the literature on mAb based immunotherapy with a particular emphasis on target antigens, mAb design and potential applications in the field of urology.

RESULTS

Early trials with mAb therapy for solid tumor oncology met with limited success due to difficulty with mAb design and production, the development of host immunological responses against murine monoclonal antibodies (that is human anti-mouse antibodies), suboptimal target antigen selection, and poor monoclonal antibody pharmacokinetics and tumor tissue penetration. Recent advances in the fields of immunology and oncology have sought to circumvent these obstacles. Today several preliminary studies have shown the effectiveness and usefulness of mAb based strategies for urological oncology.

CONCLUSIONS

The field of mAb based immunotherapy continues to evolve. New discoveries in this burgeoning area of cancer therapy show promise for the future.

Antisense therapy for cancer--the time of truth

The recent acceleration in the identification and characterisation of new molecular targets for cancer and the limited effectiveness of conventional treatment strategies has focused considerable interest on the development of new types of anticancer agents. These new drugs are hoped to be highly specific for malignant cells with a favorable side-effect profile due to well-defined mechanisms of action. Antisense oligonucleotides are one such class of new agent--they are short, synthetic stretches of DNA which hybridise with specific mRNA strands that correspond to target genes. By binding to the mRNA, the antisense oligonucleotides prevent the sequence of the target gene being converted into a protein, thereby blocking the action of the gene. Several genes known to be important in the regulation of apoptosis, cell growth, metastasis, and angiogenesis, have been validated as molecular targets for antisense therapy. Furthermore, new targets are rapidly being uncovered through coordinated functional genomics and proteomics initiatives. Phosphorothioate oligonucleotides are the current gold standard for antisense therapy; they have acceptable physical and chemical properties and show reasonable resistance to nucleases. Recently, new generations of these phosphorothioate oligonucleotides that contain 2'-modified nucleoside building blocks to enhance RNA binding affinity and decrease indirect toxic effects have been developed. Antisense therapeutics are, after decades of difficulties, finally close to fulfilling their promise in the clinic.

Molecular basis of the VHL hereditary cancer syndrome

The von Hippel-Lindau hereditary cancer syndrome was first described about 100 years ago. The unusual clinical features of this disorder predicted a role for the von Hippel-Lindau gene (VHL) in the oxygen-sensing pathway. Indeed, recent studies of this gene have helped to decipher how cells sense changes in oxygen availability, and have revealed a previously unappreciated role of prolyl hydroxylation in intracellular signalling. These studies, in turn, are laying the foundation for the treatment of a diverse set of disorders, including cancer, myocardial infarction and stroke.

Protein kinase A as target for novel integrated strategies of cancer therapy

We have studied the role of protein kinase A (PKA) in neoplastic transformation, apoptosis, and angiogenesis and its relationship with other signaling molecules, as a basis for developing novel therapeutic strategies. We demonstrated the involvement of PKA type I (PKA-I) in the transduction of mitogenic signals from different sources and demonstrated functional and structural interactions between PKA-I and the activated epidermal growth factor receptor (EGFR). We contributed to the identification and development of several selective inhibitors of PKA-I, such as 8-Cl-cAMP and a hybrid DNA/RNA antisense oligonucleotide of a novel class (AS-PKA-I) and of EGFR, including mAbC225 and ZD1839 (Iressa). All these agents have been investigated in cancer patients. We demonstrated the therapeutic potential of the combined blockade of PKA-I and EGFR, reporting a synergistic antitumor effect when their inhibitors are used in combination. We have also shown that PKA-I and EGFR inhibitors are able to cooperate with selected class of cytotoxic drugs and with ionizing radiation, causing a synergistic inhibition of tumor growth in vitro and in vivo, accompanied by inhibition of expression of growth and angiogenic factors and by suppression of vessel production. Moreover, PKA-I is implicated in a bcl-2-dependent apoptotic pathway, and we have recently reported a cooperative antitumor and proapoptotic effect of AS-PKA-I in combination with an AS-bcl-2. Finally, we have shown that AS-PKA-I also has antitumor and antiangiogenic effects following oral administration and that they can be greatly enhanced in combination with oral ZD1839 and oral taxanes.

Anti-epidermal growth factor receptor drugs in cancer therapy

The epidermal growth factor receptor is a cell membrane growth factor receptor that plays a key role in cancer development and progression. Epidermal growth factor receptor-activated signalling pathways control cell proliferation, apoptosis, angiogenesis and metastatic spread in the majority of human epithelial cancers. Targeting the epidermal growth factor receptor represents a valuable molecular approach to cancer therapy. Promising strategies in clinical development include monoclonal antibodies which block ligand binding and small molecule inhibitors of the tyrosine kinase enzymatic activity which prevent epidermal growth factor receptor autophosphorylation and propagation of downstream intracellular signals. Several anti-epidermal growth factor receptor agents are in clinical development for cancer therapy. Among these, IMC-225 (cetuximab), a chimeric human-mouse monoclonal IgG1 antibody, OSI-774 (Tarceva) and ZD1839 (Iressa), two small molecule epidermal growth factor receptor-selective tyrosine kinase inhibitors, are currently in Phase II and III development as single agents or in combination with conventional therapies, such as radiotherapy or chemotherapy. Results from Phase I - II trials in advanced cancer demonstrate that these drugs have an acceptable tolerability and an interesting clinical activity in patients with a variety of tumour types.

cAMP-dependent protein kinase and proliferation differ in normal and polycystic kidney epithelia

Developmental control of cell proliferation is crucial, and abnormal principal cell proliferation may contribute to cystogenesis in polycystic kidney disease. This study investigates roles of cAMP and its primary effector, cAMP-dependent protein kinase (protein kinase A; PKA), in control of cell proliferation in filter-grown noncystic (NC) and cystic (CY)-derived principal cell cultures. These cultures had similar cAMP pathway characteristics upstream of PKA subunit distribution but differed in predicted PKA subtype distribution. Functionally, cultures were proliferative before polarization, with constitutively higher proliferation in CY cultures. NC cultures achieved levels similar to those of CY cultures on pharmacological manipulation of cAMP production or PKA activation or inhibition of PKA subtype I activity. Inhibition of overall PKA activity, or of PKA subtype II anchoring, diminished cAMP/PKA-mediated proliferation in NC cultures but had no effect on CY cultures. Polarized CY monolayers remained proliferative, but NC monolayers lost responsiveness. No large proliferation changes resulted from treatments of polarized cultures; however, polarized NC and CY cultures differed in poststimulation handling of PKA catalytic and type IIalpha regulatory subunits. Our results support PKA subtype regulation of prepolarization proliferation in NC principal cells and altered regulation of PKA in CY cells and suggest that differences at or downstream of PKA can contribute to altered proliferation in a developmental renal disease.

New agents for the treatment of renal cell carcinoma

One-third of patients with renal cell carcinoma present with unresectable or metastatic disease. Immunotherapy, the current standard treatment, induces response in only 10-20% of patients. Chemotherapy with current agents is minimally effective. Other approaches including allogeneic stem cell transplant, vaccine and gene therapy and signal transduction inhibitors, offer promise in early Phase studies. This paper reviews the current treatment options and promising new agents in development.

Treatment prospects for autosomal-dominant polycystic kidney disease

An increased understanding of the molecular genetic and cellular pathophysiologic mechanisms responsible for the development of autosomal-dominant polycystic kidney disease (ADPKD), made possible by the advances in molecular biology and genetics of the last three decades, has laid the foundation for the development of effective therapies. As the concept that a polycystic kidney is a neoplasm in disguise is becoming increasingly accepted, the development of therapies for ADPKD may benefit greatly from the expanding body of information on cancer chemoprevention and chemosuppression. This review summarizes the observations that already have been made and discusses therapies for PKD that deserve investigation.

Renal cell cultures for the study of growth factor interactions underlying kidney organogenesis

The present study was performed in four renal cell lines to evaluate their capability to: (1) produce and express transforming growth factor alpha (TGFalpha), its respective receptor, the epidermal growth factor receptor (EGFr) and the small G protein, RhoA, and (2) exhibit morphogenetic properties when grown on Matri-cell substrates. The cell lines were derived from normal (Madin-Darby canine kidney cells), embryonic (SK-NEP-1 and 293 cells), and cancerous (human renal adenocarcinoma cells) kidneys. TGFalpha messenger ribonucleic acid, evaluated by a nonradioactive in situ hybridization technique, was found to be expressed in all the cell lines. Large amounts of TGFalpha peptide were observed in all four cell lines, while EGFr was highly expressed only in cancerous ACHN and embryonic-tumor SK-NEP-1 cells. RhoA peptide was found in appreciable amounts in SK-NEP-1 and 293 cells (compared to the other two cell lines). The morphogenetic properties of the four cell lines were assessed, by culturing them on Matri-cell dishes: SK-NEP-1 cells alone were found to grow in three-dimensional structures forming clusters and worm-like cellular aggregates. This feature was displayed by SK-NEP-1 cells but not by the other three cell lines, and may be connected with the contemporary presence of RhoA, EGFr, and TGFalpha found in significant amounts only in the SK-NEP-1 cell line.

Role of transforming growth factor-alpha in von Hippel--Lindau (VHL)(-/-) clear cell renal carcinoma cell proliferation: a possible mechanism coupling VHL tumor suppressor inactivation and tumorigenesis

Mutations of the VHL tumor suppressor gene occur in patients with VHL disease and in the majority of sporadic clear cell renal carcinomas (VHL(-/-) RCC). Loss of VHL protein function is associated with constitutive expression of mRNAs encoding hypoxia-inducible proteins, such as vascular endothelial growth factor. Overproduction of angiogenic factors might explain why VHL(-/-) RCC tumors are so highly vascularized, but whether this overproduction is sufficient for oncogenesis still remains unknown. In this report, we examined the activity of transforming growth factor-alpha (TGF-alpha), another VHL-regulated growth factor. We show that TGF-alpha mRNA and protein are hypoxia-inducible in VHL(-/-) RCC cells expressing reintroduced VHL. In addition to its overexpression by VHL(-/-) RCC cells, TGF-alpha can also act as a specific growth-stimulatory factor for VHL(-/-) RCC cells expressing reintroduced wild-type VHL, as well as primary renal proximal tubule epithelial cells, the likely site of origin of RCC. This role is in contrast to those of other growth factors overexpressed by VHL(-/-) RCC cells, such as vascular endothelial growth factor and TGF-beta1, which do not stimulate RCC cell proliferation. A TGF-alpha-specific antisense oligodeoxynucleotide blocked TGF-alpha production in VHL(-/-) RCC cells, which led to the dependence of those cells on exogenous growth factors to sustain growth in culture. Growth of VHL(-/-) RCC cells was also significantly reduced by a drug that specifically inhibits the epidermal growth factor receptor, the receptor through which TGF-alpha stimulates proliferation. These results suggest that the generation of a TGF-alpha autocrine loop as a consequence of VHL inactivation in renal proximal tubule epithelial cells may provide the uncontrolled growth stimulus necessary for the initiation of tumorigenesis.

Role of transforming growth factor-alpha in von Hippel--Lindau (VHL)(-/-) clear cell renal carcinoma cell proliferation: a possible mechanism coupling VHL tumor suppressor inactivation and tumorigenesis

Mutations of the VHL tumor suppressor gene occur in patients with VHL disease and in the majority of sporadic clear cell renal carcinomas (VHL(-/-) RCC). Loss of VHL protein function is associated with constitutive expression of mRNAs encoding hypoxia-inducible proteins, such as vascular endothelial growth factor. Overproduction of angiogenic factors might explain why VHL(-/-) RCC tumors are so highly vascularized, but whether this overproduction is sufficient for oncogenesis still remains unknown. In this report, we examined the activity of transforming growth factor-alpha (TGF-alpha), another VHL-regulated growth factor. We show that TGF-alpha mRNA and protein are hypoxia-inducible in VHL(-/-) RCC cells expressing reintroduced VHL. In addition to its overexpression by VHL(-/-) RCC cells, TGF-alpha can also act as a specific growth-stimulatory factor for VHL(-/-) RCC cells expressing reintroduced wild-type VHL, as well as primary renal proximal tubule epithelial cells, the likely site of origin of RCC. This role is in contrast to those of other growth factors overexpressed by VHL(-/-) RCC cells, such as vascular endothelial growth factor and TGF-beta1, which do not stimulate RCC cell proliferation. A TGF-alpha-specific antisense oligodeoxynucleotide blocked TGF-alpha production in VHL(-/-) RCC cells, which led to the dependence of those cells on exogenous growth factors to sustain growth in culture. Growth of VHL(-/-) RCC cells was also significantly reduced by a drug that specifically inhibits the epidermal growth factor receptor, the receptor through which TGF-alpha stimulates proliferation. These results suggest that the generation of a TGF-alpha autocrine loop as a consequence of VHL inactivation in renal proximal tubule epithelial cells may provide the uncontrolled growth stimulus necessary for the initiation of tumorigenesis.

TGF-alpha antisense gene therapy inhibits head and neck squamous cell carcinoma growth in vivo

Unlike normal mucosal squamous epithelial cells, head and neck squamous cell carcinomas (HNSCCs) overexpress TGF-alpha mRNA and protein which is required to sustain the proliferation of HNSCC cells in vitro. To determine whether TGF-alpha expression contributes to tumor growth in vivo, cationic liposome-mediated gene transfer was used to deliver an antisense expression construct targeting the human TGF-alpha gene into human head and neck tumor cells, grown as subcutaneous xenografts in nude mice. The TGF-alpha antisense gene was immediately detected in the cytoplasm of the tumor cells, translocated to the nucleus by 12 h and remained localized to the nucleus for up to 3 days. Direct inoculation of the TGF-alpha antisense (but not the corresponding sense) construct into established HNSCC tumors resulted in inhibition of tumor growth. Sustained antitumor effects were observed for up to 1 year after the treatments were discontinued. Down-modulation of TGF-alpha was accompanied by increased apoptosis in vivo. These experiments indicate that interference with the TGF-alpha/EGFR autocrine signaling pathway may be an effective therapeutic strategy for cancers which overexpress this ligand/receptor pair.

Intratumoral pharmacokinetics of oligonucleotides in a tissue-isolated tumor perfusion system

The intratumoral pharmacokinetics of model oligonucleotides were studied in Walker 256 tissue-isolated tumor preparations using an in situ single-pass vascular perfusion technique. A 20-mer phosphodiester (PO) oligonucleotide, its fully phosphorothioated (PS) oligonucleotide counterpart, and an 18-mer phosphorothioated oligonucleotide containing four 2'-O-methylribonucleosides at both the 3'-end and 5'-end (PS-OMe) were used. These oligonucleotides were administered to the tumor in two ways, by constant arterial infusion and by direct intratumoral injection. In the case of constant arterial infusion, the experiments were carried out using perfusate with or without 4.7% bovine serum albumin (BSA). The protein binding of PO, PS, and PS-OMe to BSA was 46%, 87%, and 94%, respectively. No marked difference was observed between the degree of accumulation of the three types of oligonucleotides in the tumor when BSA was present in the perfusate. PS and PS-OMe showed higher degrees of accumulation in tumors compared with PO when no BSA was present. These results indicate that free (i.e., protein unbound) PS-OMe and PS have superior tumor accumulation characteristics. In the intratumoral injection experiments, PS-OMe was retained longer in tumor tissue compared with PS, suggesting that it might be useful for direct local injection into solid tumors. Thus, the present study provides useful information about the basic disposition characteristics of oligonucleotides in solid tumors.

The cAMP signaling pathway as a therapeutic target in lymphoid malignancies

Certain subsets of lymphoid cells, such as thymocytes or peripheral B cells, undergo apoptosis after treatment with agents which elevate intracellular 3',5' cyclic adenosine monophosphate (cAMP). Investigators have also noted induction of apoptosis of chronic lymphocytic leukemia (CLL) cells following treatment with methylxanthines, a phenomenon that may, at least in part, be due to the activity of these drugs as non-specific phosphodiesterase (PDE) inhibitors. We discuss three general strategies for altering cAMP-mediated signal transduction in lymphoid cells. After a review of what is known about the expression and regulation of PDE families in human lymphoid cells, we focus on the use of isoform-specific PDE inhibitors as potential therapeutic agents in CLL. Our work has suggested that despite the presence of PDE1, PDE3B, PDE4 and PDE7 enzymes in CLL, inhibition of PDE4 results in uniquely potent induction of apoptosis in CLL cells. This effect is relatively specific as comparable treatment of human peripheral blood T cells does not induce apoptosis. Clinical trials utilizing PDE4 inhibitors are indicated in the therapy of CLL patients resistant to standard therapy.