Current Cancer Drug Targets - Volume 8, Issue 5, 2008

Inactivation of the FHIT and TP53 genes is frequently observed in primary non-small cell lung cancers (NSCLC) and cell lines and may contribute to resistance to apoptotic stimuli elicited by various anti-tumor drugs. To evaluate a possible relationship between FHIT and TP53 status and response to platinum-analogue regimens, we retrospectively selected 55 NSCLC patients treated with carboplatin/gemcitabine. Pre-treatment formalin fixed biopsies were analyzed for FHIT and p53 protein expression by immunohistochemistry and representative micro dissected tissue for TP53 mutations by DG-DGGE/sequencing. The FHIT-negative immunophenotype (FHIT-, pathologic) was found in 33 patients (60%) and p53 over expression/mutation (p53+, pathologic) in 25 patients (45%). The FHIT-/p53+ combination was present in 12 patients (22%). Overall, there was partial response in 21 patients (38%), with subgroup response rates of 33% in FHIT+/p53-, 46% in FHIT+/p53+, 38% in FHIT-/p53- and 33% in FHIT-/p53+ patients. Median progression-free survival (PFS) was 9.6, 7.9, 6.8 and 5.9 months and median overall survival (OS) was 12.8, 11.9, 10.5 and 8.7 months in the four groups, respectively. The Group comparison showed significantly worse PFS (p=0.04) in FHIT-/p53+ than the other groups. There was no significant difference in OS between the groups. A trend (p=0.07) for shorter OS was found in FHIT- cases suggesting that NSCLC tumors carrying this feature are less responsive to treatment. This retrospective study indicates that FHIT-/p53+ status might be a biological variable influencing the efficacy of carboplatin/ gemcitabine treatment in NSCLC.

Angiogenesis is an important factor for cancer development and progression in humans. Hereditary and sporadic renal cell carcinoma are characterized by inactivation of the Von-Hippel Lindau (VHL) gene, which results in hyperactivity of the hypoxia-inducible factor-a (HIFa). As a consequence, there is a production of angiogenic factors, such as vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF). The activity of these factors is associated with oncogenesis, growth, and metastatic potential of renal-cell carcinoma. These data indicate that angiogenic factors are the promising therapeutic targets in this disease. Surgery can cure the patients with renal cancer if disease is diagnosed at an early stage. On the contrary, inoperable or metastatic disease is not curable. Until recently, the only drugs approved for the treatment of advanced disease were the cytokines, interferon, and interleukin. Nevertheless, only a minority of patients (about 15%) would benefited from this treatment, while the toxicity was considerable. During the last 5 years a new era of biological agents, with considerable activity has been developed and tested in clinical trials and (some of them) have been approved in USA and Europe. These agents are: Sunitinib, Bevacizumab, Sorafenib and Temserolimus. Bevacizumab is an anti-VEGF monoclonal antibody, Sunitinib and Sorafenib are multi- tyrosine kinase inhibitors (TKIs), while Temserolimus is a mTOR inhibitor. The common these in their development is the inhibition of angiogenesis, which may explain their significant activity in renal-cell carcinoma. All the agents have been proven more effective than the interferon as first or second-line treatment. This review will focus in these recent developments and the intense continuing clinical research in this field.

Gastrointestinal Stromal Tumors (GISTs) are the most common mesenchimal tumors of the gastrointestinal tract. Such tumors usually have activating mutations in either KIT (75-80%) or Platelet Derived Growth Factor Receptor alpha (PDGFRa) (5-10%) which lead to ligand-independent signal transduction. Targeting these activated proteins with Imatinib mesylate, a small-molecule kinase inhibitor, has proven useful in the treatment of recurrent or metastatic GISTs. However, more than half of patients develop resistance to Imatinib after about 2 years. Therefore, other targets have been studying in order to implement the therapeutical armamentarium for this disease. Sunitinib malate is an oral multikinase inhibitor that targets several receptor tyrosine kinases and has proved to prolong survival in Imatinib-resistant patients. Other molecules, such as Nilotinib, Sorafenib and Dasatinib were shown to be useful in Imatinib resistant mutant cell lines and the results of their activity in humans are being awaited. Recent evidence suggests that GIST cells acquire the capability to escape from the control of KIT and PDGFRa through the activation of alternative pathways. Therefore, further effort should be invested in the discovery of new signaling pathways, such as AXL, MET, IGF-R, which might be involved in the evolution of the disease. After a description of KIT and PDGFRa as known targets of anti-GIST treatments, we review other mechanisms and mediators that might be potential targets of new therapies, providing a comprehensive revision of the new molecular strategies under investigation.

Thyroid cancer occurs three times more frequently in females than in males, and in females the incidence decreases after menopause. This gender difference suggests that the growth and progression of thyroid cancer may be influenced by female sex hormones, particularly estrogens. Experimental data have clearly demonstrated that estrogens can influence cancer cell growth. The action of estrogens on target sites is mediated through related but distinct estrogen receptors, designated estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), both of which are known to be expressed in thyroid cancer cells. The proliferation of thyroid cancer cells is promoted by an ERα agonist, whereas the proliferation is reduced by the enhanced expression of ERβ or by an ERβ agonist. When ERβ is down-regulated, the proliferation of thyroid cells is significantly increased. Studies have shown that the expression of ERα in thyroid cancer cells is increased while the expression of ERβ is either very low or absent. In conclusion, it appears that estrogens have opposite effects on the growth of thyroid cancer cells, depending on the balance between ERα and ERβ in the cells. The modulation of ERα and ERβ and the intervention of their pathways may open up new potential targets for the treatment of thyroid cancer.

In addition to well-established genetic abnormalities -particularly gene mutations, deletions or translocations -, epigenetic abnormalities are also implicated in the development and progression of hematological malignancies. As such, the constitutive pattern of DNA methylation and histone acetylation observed in normal hematopoietic cells is remarkably altered in both myeloid and lymphoid tumors. Recent advances in the understanding of these transcriptional and post-transcriptional mechanisms in normal B and T cells as well as malignant lymphoid cells have been instrumental in the development of novel diagnostic markers, prognostic classification and targeted therapeutic approaches. This review focuses on the most important epigenetic alterations discovered in lymphoma-derived cell lines and primary lymphoid tumors and how pharmacologic manipulation of these abnormalities could eventually change the way we treat them in the clinic.

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality worldwide. Although modest survival benefit has been observed with surgery, radiotherapy and platinum-based chemotherapy, an efficacy plateau has been reached. It has become obvious, therefore, that additional treatments are needed in order to provide an improved survival benefit for these patients. The use of molecular targeted therapies, particularly those against tumor capillaries, has the potential to improve outcomes for NSCLC patients. Bevacizumab, a recombinant humanized monoclonal antibody against vascular endothelial growth factor (VEGF), is the first targeted drug that has shown survival advantage when combined with chemotherapy in NSCLC. Other antivascular agents, including vascular disrupting agents (VDAs) and different small-molecule receptor tyrosine kinase inhibitors, have also shown promise in phase I and II trials in NSCLC. The aim of this study is to describe the clinical properties of these drugs and to discuss the evidence that supports their use in the treatment of NSCLC. Furthermore, we plan to review the main pitfalls of antivascular strategies in NSCLC cancer therapy as well as assess the future direction of these treatment methods with an emphasis on clarifying the molecular background of the effects of these drugs and defining the biomarkers.

The monoclonal antibody (mAb) 376.96 has been used for detection of micrometastatic tumor cells due to its high binding specificity for a wide range of tumor cells, but the identity and function of its target antigen have not been known. Here, using immunoprecipitation and siRNA technology, we demonstrate that the antigen is the human 4Ig-B7H3 (4Ig-hB7H3) protein, previously known as an immunoregulatory protein in immune cells. Immunoblots of whole cell lysates, subcellular fractionation and tunicamycin treatment of human tumor cells indicated that 4Ig-hB7H3 is a ∼100-kDa N-linked glycosylated membrane protein. The tumor promoter phorbol 12-myristate 13-acetate (PMA) enhanced the expression of 4Ig-hB7H3 in FEMX-I (melanoma), MA11 (breast cancer), and OHS (osteosarcoma) cells, suggesting that 4Ig-hB7H3 may be implicated in tumorigenesis. Most importantly, siRNA-downregulation of hB7H3 reduced cell adhesion to fibronectin of melanoma and breast cancer cells by up to 50 %, and migration and matrigel-invasion by more than 70 %, but surprisingly had no apparent impact on cell proliferation. In conclusion, our data present 4Ig-hB7H3 as a tumorassociated antigen and suggests a novel biological role of 4Ig-hB7H3 in tumor progression and metastasis.

Recent phase II randomised trials in colorectal cancer failed to demonstrate any advantage of celecoxib combined with standard chemotherapy; some authors even reported that the addition of celecoxib to irinotecan and oxaliplatin in colon cancer results in an inferior response rate. This observation leads to the hypothesis that there are pharmacokinetic interactions between celecoxib and chemotherapeutic drugs. The aim of the study was to investigate the induction by celecoxib of some multidrug resistance proteins, MRP1, MRP2, MRP4 and MRP5, involved in the transport of irinotecan and 5-FU. WiDr and COLO-205 cells were treated with celecoxib at a clinically relevant concentration. A viability assay was performed by treating cells with chemotherapy alone and chemotherapy plus celecoxib. The expression of MRP1, MRP2, MRP4 and MRP5 was analysed by RT-PCR and Western blot analysis. The sub cellular localization of MRP4 and MRP5 was investigated by cryoimmunoelectron microscopy. In both cell lines celecoxib induced MRP4 and MRP5 overexpression at RNA and protein levels. No induction of MRP1 and MRP2 was observed in treated cells compared to controls. Cryoimmunoelectron microscopy showed increased MRP4 and MRP5 immunolabeling in celecoxib treated cells both at cytoplasmic level and along the plasma membrane. Recent phase II randomised trials in colorectal cancer failed to demonstrate any advantage of celecoxib combined with standard chemotherapy; some authors even reported that the addition of celecoxib to irinotecan and oxaliplatin in colon cancer results in an inferior response rate. This observation leads to the hypothesis that there are pharmacokinetic interactions between celecoxib and chemotherapeutic drugs. The aim of the study was to investigate the induction by celecoxib of some multidrug resistance proteins, MRP1, MRP2, MRP4 and MRP5, involved in the transport of irinotecan and 5-FU. WiDr and COLO-205 cells were treated with celecoxib at a clinically relevant concentration. A viability assay was performed by treating cells with chemotherapy alone and chemotherapy plus celecoxib. The expression of MRP1, MRP2, MRP4 and MRP5 was analysed by RT-PCR and Western blot analysis. The sub cellular localization of MRP4 and MRP5 was investigated by cryoimmunoelectron microscopy. In both cell lines celecoxib induced MRP4 and MRP5 overexpression at RNA and protein levels. No induction of MRP1 and MRP2 was observed in treated cells compared to controls. Cryoimmunoelectron microscopy showed increased MRP4 and MRP5 immunolabeling in celecoxib treated cells both at cytoplasmic level and along the plasma membrane. Our findings suggest that the low response rate observed in clinical trials using celecoxib added to 5-fluorouracil and irinotecan may reflect celecoxib-mediated extrusion of chemotherapeutic drugs from cancer cells through the up regulation of ATP-binding cassette proteins. Our findings, together with the results of clinical trials, may suggest that the combined use of celecoxib and drugs that are substrate for MRP4/MRP5 should be avoided.

Nuclear protein 1 (NUPR1/com1/p8) has been shown to interact with transcriptional regulators such as p300, PTIP, estrogen receptor-β, and SMAD. NUPR1 also has been implicated in the regulation of cell cycle and apoptosis. An increase in NUPR1 expression has been seen with serum starvation and in response to compounds such as cycloheximide, ceramide, and staurosporine. There are several overtly conflicting reports about the exact role of NUPR1 in tumor biology. This work investigates the nature of the relationship between NUPR1 and the cdk-inhibitor p21 (Waf1/Cip1) expression. We show that the expression of resident and doxorubicin-induced p21 paralleled that of endogenous NUPR1 levels. NUPR1 formed a complex with p53 and p300 and bound the p21 promoter and transcriptionally upregulated p21 expression. Moreover, NUPR1 allowed cells to progress through cell cycle in presence of doxorubicin. Since NUPR1 upregulated p21, concomitant with phosphorylation of Rb and upregulation of the anti-apoptotic protein, Bcl-xL we propose that NUPR1 expression imparts a cell growth and survival advantage. Importantly, we also report that NUPR1 conferred resistance to two chemotherapeutic drugs, Taxol and doxorubicin.

The introduction of concepts proposing multiple cellular subgroups in the normal female breast leads to the hypothesis that distinct cellular phenotypes in the female breast give rise to different subtypes of breast carcinomas e.g. expressing ER, HER2 and EGFR differentially. Therefore, origin of breast carcinoma types may be based on the formation of a cancer prone field in which the committed progenitor cells pass mutations to their progenies, glandular as well as myoepithelial cells. The existence of such field within the human breast was inferred from the results on primary breast cancer obtained by PCR-based microsatellite analysis of allelic imbalance (AI) of the EGF receptor gene. Here, normal breast tissue shows egfr AI adjacent to breast cancer tissue also harboring egfr gene AI. The therapeutic implications of such a model are fundamental, as tumors may display different phenotypes which arise from transformation of different progenitor cells as well as from transformation of more differentiated progenies within a cancer prone field. Thereby they may show up with different clinical courses of the disease, higher rates of metastases and responses to therapy. In this review, we discuss this mechanism focusing on the EGF receptor as an example for regulators of progenitor cell growth in many tissues. Phylloides tumors serve as a putative model for embryonic differentiation stage ruled by EGFR signaling and give insights into the tumor-host-interaction. The inhibition of the EGF receptor by specific monoclonal antibodies (e.g. Erbitux) will give an answer in as far EGFR-signaling is decisive for the development of an invasive breast cancer. For this purpose new models have been inaugurated which vary in the EGF receptor gene dosage and protein expression. Moreover, we discuss the EGF receptor as a target for the treatment of pre-malignant lesions with a high risk for malignant growth, e.g. DCIS, which certainly will be detected more frequently by mammography screening programs soon.