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Treating imatinib-resistant leukemia: the next generation targeted therapies.

Imatinib (Gleevec/STI-571/CGP57148B, Novartis) is a small-molecule, tyrosine kinase inhibitor developed to target BCR-ABL, c-Kit, and PDGF-R. Through inhibition of these oncogenic kinases, imatinib is effective in the treatment of BCR-ABL-positive leukemia, gastrointestinal stromal tumor, and hypereosinophilic syndrome, respectively. However, clinical success of imatinib is hampered by acquired resistance that may occur through several mechanisms including kinase domain mutation, target amplification, and activation of alternate signaling pathways. Strategies to overcome resistance have included targeting BCR-ABL stability and downstream signaling pathways important for tumor growth. Additional work has shown that new BCR-ABL kinase inhibitors with increased potency or alternate conformation-binding properties can target imatinib resistance. This review focuses on the mechanisms of imatinib resistance and the strategies currently being developed to overcome clinical resistance.

Antineoplastic Agents↗

Molecular targeted therapy in combination with chemotherapy for the treatment of platinum-resistant/refractory ovarian cancer (PROC): a systematic review and network meta-analysis.

BACKGROUND: Although single-agent chemotherapy is the most common approach for treating platinum-resistant or refractory ovarian cancer (PROC), there is growing evidence that combining molecular targeted agents with chemotherapy is beneficial, especially for certain patient groups. However, the most effective combination regimen remains elusive. OBJECTIVES: This Bayesian network meta-analysis (NMA) aims to identify the best combination therapy for PROC. METHODS: Relevant studies were searched in PubMed, EMBASE, Web of Science and the Cochrane Central Register of Controlled Trials from their inception until October 2024. The primary outcomes were overall survival (OS), progression-free survival (PFS) and adverse events (AEs). Statistical analyses were performed using the GEMTC package (1.0-2) and R 4.2.0. This review was registered in PROSPERO (CRD42023428414). RESULTS: Our analysis of 22 randomized controlled trials (RCTs) (n = 3408) demonstrated that chemotherapy combinations with bevacizumab (hazard ratio (HR) = 0.52-0.65), sorafenib (HR = 0.65, 95% confidence interval (CI): 0.45-0.93) or adavosertib (HR = 0.56, 95%CI: 0.35-0.90) significantly improved OS and PFS versus chemotherapy alone. Notably, adavosertib + gemcitabine was associated with an increased risk of grade 3-4 AEs (relative risk (RR) = 1.8, 95%CI: 1.3-2.7), but these were generally manageable. CONCLUSIONS: Bevacizumab-based combinations demonstrate consistent benefits across multiple regimens for PROC. Paclitaxel + bevacizumab emerges as the optimal balance of efficacy and safety. Topotecan + sorafenib could be an alternative for patients who are ineligible for anti-angiogenic therapy.

Humans↗

Activator protein 1-mediated transcriptional regulation strategy sustains long-term expression of a xenogeneic gene product in vivo: an implication for gene therapy targeting congenital protein deficiencies.

Maintenance of high-level transgene expression is the main challenge in current gene therapy. Although the cytomegalovirus (CMV) promoter/enhancer or its derivative the CAG promoter has been harnessed in current gene therapy vectors, transgene expression by these vectors is often transient and remains at suboptimal levels due to undefined mechanisms, possibly including the shortage of transcriptional machinery. To overcome this drawback, we designed a novel transcriptional control system, designated here as transcription factor-supercharging promoter system, in which transgene expression is regulated by the positive feedback circuit consisting of cis- and trans-acting elements of gene expression machinery. Among combinations of these elements, a plasmid composed of a target gene expression cassette driven by the chimeric CMV promoter containing repetitive 12-O-tetradecanoylphorbol-13-acetate-responsive elements as cis-acting elements (CMV-TTT) and expression cassettes for c-Fos and c-Jun genes as trans-acting elements facilitated high and long-term (>10 months) expression of a transgene after its intramuscular electroporation-mediated delivery in mice. Since human secretory alkaline phosphatase was used as a reporter, it was suggested that the immune evasion mechanism elicited by the CMV-TTT and/or c-Fos/ c-Jun expression also contributed to the sustained expression in mice. Our strategy may open a new avenue for a gene therapy that involves lifelong supplementation of a deficient protein that could be targeted by the host's immune system.

Animals↗

Molecularly targeted therapy for gastrointestinal cancer.

Receptor and non-receptor tyrosine kinases (TKs) have emerged as clinically useful drug target molecules for treating gastrointestinal cancer. Imatinib mesilate (STI-571, Gleevec(TM)), an inhibitior of bcr-abl TK, which was primarily designed to treat chronic myeloid leukemia is also an inhibitor of c-kit receptor TK, and is currently the drug of choice for the therapy of metastatic gastrointestinal stromal tumors (GISTs), which frequently express constitutively activated forms of the c-kit-receptor. The epidermal growth factor receptor (EGFR), which is involved in cell proliferation, metastasis and angiogenesis, is another important target. The two main classes of EGFR inhibitors are the TK inhibitors and monoclonal antibodies. Gefitinib (ZD1839, Iressa(TM)) has been on trial for esophageal and colorectal cancer (CRC) and erlotinib (OSI-774, Tarceva(TM)) on trial for esophageal, colorectal, hepatocellular, and biliary carcinoma. In addition, erlotinib has been evaluated in a Phase III study for the treatment of pancreatic cancer. Cetuximab (IMC-C225, Erbitux(TM)), a monoclonal EGFR antibody, has been FDA approved for the therapy of irinotecan resistant colorectal cancer and has been tested for pancreatic cancer. Vascular endothelial growth factor (VEGF) and its receptor (VEGFR) are critical regulators of tumor angiogenesis. Bevacizumab (Avastin(TM)), a monoclonal antibody against VEGF, was efficient in two randomized clinical trials investigating the treatment of metastatic colorectal cancer. It is also currently investigated for the therapy of pancreatic cancer in combination with gemcitabine. Other promising new drugs currently under preclinical and clinical evaluation, are VEGFR2 inhibitor PTK787/ZK 222584, thalidomide, farnesyl transferase inhibitor R115777 (tipifarnib, Zarnestra(TM)), matrix metalloproteinase inhibitors, proteasome inhibitor bortezomib (Velcade(TM)), mammalian target of rapamycin (mTOR) inhibitors, cyclooxygenase-2 (COX-2) inhibitors, platelet derived growth factor receptor (PDGF-R) inhibitors, protein kinase C (PKC) inhibitors, mitogen-activated protein kinase kinase (MEK) 1/2 inhibitors, Rous sarcoma virus transforming oncogene (SRC) kinase inhibitors, histondeacetylase (HDAC) inhibitors, small hypoxia-inducible factor (HIF) inhibitors, aurora kinase inhibitors, hedgehog inhibitors, and TGF-beta signalling inhibitors.

Animals↗

Molecularly targeted therapy for melanoma: current reality and future options.

Effective therapy for melanoma remains an unmet goal, with most traditional therapies representing inadequate trade-offs among the several goals of specificity, efficacy, and toxicity. Targeted molecular therapeutics are tailored to genetic abnormalities that are associated with tumor progression. Modulation of aberrant signaling pathways in cancer cells has the potential to provide more effective and potentially nontoxic therapy for a broad range of cancers, including melanoma. Among the possible targets in melanoma are the Ras-MAPK and PI3K/AKT signal transduction pathways, the proteasome, histone deacetylases, methyltransferases, and melanoma-induced angiogenesis.

Angiogenesis Inhibitors↗

Targeted therapy of human laryngeal squamous cell carcinoma in vitro by antisense oligonucleotides directed against telomerase reverse transcriptase mRNA.

A number of different approaches have been developed to inhibit telomerase activity in human cancer cells. In this study, the effect of antisense oligonucleotides (ODNs) by targeting human telomerase reverse transcriptase (hTERT) mRNA in a laryngeal cancer cell line (Hep-2) was investigated. A 20mer antisense oligodeoxynucleotide targeting the most open part of hTERT mRNA (anti-hTERT) and a mismatched control sequence were synthesized. Cells were treated daily with oligonucleotides for up to 72 hours. hTERT mRNA expression was measured by the reverse transcription polymerase chain reaction (RT-PCR) assay; telomerase activity by the telomerase PCR ELISA assay kit (TRAP; Boehringer Mannheim, GmbH, Mannheim, Germany). Cell viability after administration of ODNs was determined using the MTT assay. Morphological changes were examined by haematoxylin and eosin staining. The cell cycle was analyzed using flow cytometry. It was found that antisense treatment induced a decrease in hTERT mRNA expression, telomerase activity, cell growth rate, cell viability, and an increase in apoptosis. The results suggest that inhibition of telomerase activity in Hep-2 cells by short-term antisense treatment against the mRNA of hTERT results in apoptotic cell death. The treatment with anti-hTERT may be useful as a treatment modality for laryngeal squamous carcinoma.

Apoptosis↗

New concepts in the treatment of acute myeloid malignancies: selected pathways for targeted therapy.

Acute myeloid leukemia (AML) and myelodysplasia (MDS) continue to present formidable treatment challenges as there is not yet a "standard approach" that reliably and safely cures the majority of adults with these disorders. Understanding the basic cellular and molecular biology of leukemia is vital to the development of better treatment approaches. All malignant cells, including leukemias, carry survival advantages compared to their normal counterparts. These survival advantages are particularly evident when the cells face both normal environmental stressors as well as extreme stressors of potentially lethal DNA damage. The impact of such stressors is ultimately determined by the signaling pathways and resultant cellular activation, including alterations in cellular growth, differentiation, survival and death. It is our improving understanding of these signaling pathways, both normal and malignant, that provide the targets for novel therapies. In this review article, we will focus on several signaling pathways, as well as the regulation of the cell cycle, that not only represent potentially accessible sites for intervention in myeloid malignancies, but those that are actively being studied.

Antibodies, Monoclonal↗

Preclinical models for cell cycle-targeted therapies.

Deregulation of the cell cycle machinery is frequently associated to tumor development in most cell types. Many of these tumor-associated alterations result in the abnormal activation of cyclin-dependent protein kinases (Cdks) involved in the G1/S transition. Recent results from the genetic analysis of cyclins and Cdks in mouse models have raised some questions regarding the relevance of these molecules in cell cycle-targeted strategies for cancer therapy. The comprehensive evaluation of these biochemical and genetic data seems to be a necessary given the relevance of these and other new cell cycle kinases as targets for therapeutic approaches in cancer.

Animals↗

Monoclonal antibodies: new agents for cancer detection and targeted therapy.

Antibodies directed against markers on cancer cells are gaining in importance for the purpose of targeting diagnostic and therapeutic agents. In the past, this approach has had very limited success principally because the classical methods for producing antibodies from blood serum of animals immunized with cancer cells or extracts were unsatisfactory. The situation has changed dramatically since 1975 following the design of procedures for "immortalizing" antibody-producing cells (lymphocytes) by fusing them with cultured myeloma cells to form hybridomas which continuously secrete antibodies. Since these hybridomas produce antibodies coded for by a single antibody-producing cell, the antibodies are called monoclonal. Building on these advances in biomedical research, it is now possible to reproducibly manufacture monoclonal antibodies on a scale suitable for use in cancer detection and therapy.

Antibodies, Monoclonal↗

Intracellular targeting therapy of cisplatin-encapsulated transferrin-polyethylene glycol liposome on peritoneal dissemination of gastric cancer.

Peritoneal dissemination in gastric cancer is a common fatal clinical condition with few effective therapies available. We studied the therapeutic effect of a tumor-targeting drug delivery system that uses cisplatin-encapsulated and Tf-conjugated PEG liposomes (Tf-PEG liposomes) in nude mice with peritoneal dissemination of human gastric cancer cells. Small unilamellar Tf-PEG, PEG or DSPC/CH liposomes (bare liposomes) encapsulating cisplatin were prepared by reverse-phase evaporation followed by extrusion. Electron microscopic studies revealed that Tf-PEG liposomes were internalized into tumor cells by receptor-mediated endocytosis. To examine the biodistribution of each liposome and cisplatin level, nude mice were inoculated i.p. with 10(7) MKN45P human gastric tumor cells. On the fourth day after tumor inoculation, (3)H-CHE-labeled and cisplatin-encapsulated Tf-PEG, PEG or bare liposome were inoculated i.p. The Tf-PEG liposome-administered group maintained high liposome and cisplatin levels in ascites and showed a prolonged residence time in the peripheral circulation. Uptake of Tf-PEG liposomes into the liver and spleen was significantly lower than that of bare liposomes. Uptake of Tf-PEG liposomes in disseminated tumor cells of ascites and the greater omentum was significantly higher than that of PEG or bare liposomes and a significant increase in cisplatin levels was observed in these tumor cells. Mice receiving Tf-PEG liposomes 1 and 4 days after the day of tumor inoculation showed significantly higher survival rates compared with those receiving PEG liposomes without Tf, bare liposomes or free cisplatin solution. These results suggest that cisplatin-encapsulated Tf-PEG liposomes may be useful as a new intracellular targeting carrier for treatment of gastric cancer with peritoneal dissemination.

Animals↗

Degree of CD25 expression in T-cell lymphoma is dependent on tissue site: implications for targeted therapy.

PURPOSE: Using concurrent tumor samples from different anatomical sites, we compared expression of the therapeutic targets CD25 and CD30 in T-cell lymphoma (TCL). EXPERIMENTAL DESIGN: We examined levels of CD25 and CD30 by flow cytometry in tumor cells from peripheral blood and lymph node in 13 cutaneous TCL patients and by immunohistochemistry in concurrent lymph node and skin biopsy specimens in 17 additional TCL cases, mostly mycosis fungoides. Tumor cell expression was correlated with patterns of expression in nonneoplastic lymphocytes in 14 reactive lymph node and 10 skin samples showing chronic dermatitis. Expression of CD25 and CD30 in all biopsy samples was compared with that of cutaneous lymphocyte antigen (CLA), a mediator of skin homing. RESULTS: By flow cytometry, we noted significantly decreased expression of CD25 in lymph node compared with peripheral blood in 8 of 13 TCLs, with no changes in CD30 levels in 4 cases studied. Using immunohistochemistry, CD25 was strongly expressed in epidermotropic tumor cells in 13 of 17 (76%) TCL skin specimens but was decreased in the corresponding lymph node in 12 of these cases. CD30 was expressed at roughly equal intensity in tumor cells from both sites, except in 1 case. CLA showed a similar pattern to CD25, being expressed by tumor cells in 16 of 17 (94%) skin specimens, but was largely absent in tumor cells in the corresponding lymph node in 12 of these patients. In T cells from reactive lymph node biopsy specimens, CD25 was highly expressed only in dermatopathic lymphadenitis associated with transient skin rashes. CONCLUSIONS: We demonstrate in vivo that decreased levels of CD25 expression occur in TCL when it involves lymph node, similar to what is seen with CLA. This demonstrable variation related to anatomical localization has implications for the measurement of surface expression of CD25 and for understanding the response of patients with cutaneous TCL to interleukin 2 receptor-targeted immunotherapy.

Antigens, CD↗

Biology of progressive, castration-resistant prostate cancer: directed therapies targeting the androgen-receptor signaling axis.

Prostate cancers that are progressing on medical and surgical therapies designed to ablate the action of androgens continue to express androgen receptor (AR) and to depend on signaling through the receptor for growth. A more clinically relevant classification of castration-resistant disease focuses on the mechanisms of receptor activation, which include (1) changes in the level of ligand(s) in tumor tissue; (2) increased levels of the protein due to gene amplification or altered mRNA expression; (3) activating mutations in the receptor that affect structure and function; (4) changes in coregulatory molecules including coactivators and corepressors; and (5) factors that lead to activation of the receptor independent of the level of ligand or receptor allowing kinase cross talk. From an AR perspective, the term "hormone refractory" is inappropriate. On the basis of this schema, we discuss strategies that are focused on the AR either directly or indirectly, as single agents or in combination, that are in clinical development.

Androgen Receptor Antagonists↗

Targeted therapy of schwannoma cells in immunocompetent rats with an erbB2-specific antibody-toxin.

Over-expression of the erbB2-receptor tyrosine kinase is frequently observed in many human tumors of epithelial origin. Due to its causal involvement in malignant transformation and its presence on the tumor cell surface erbB2 is an attractive target for directed tumor therapy. We earlier described the potent anti-tumoral activity of the recombinant single-chain antibody toxin scFv(FRP5)-ETA in vitro and in nude mouse tumor models in vivo. This molecule consists of the variable domains of the heavy and light chains of an erbB2-specific antibody genetically fused to a truncated Pseudomonas exotoxin A. Here we have investigated the in vivo effects of this immunotoxin on erbB2 expressing NV2Cd schwannoma cells growing as s.c. tumors in syngeneic BDIX rats. Established tumors were treated either locally by intra-tumoral injection of scFv(FRP5)-ETA or systemically by injection into the tail vein. Both routes of application resulted in pronounced inhibition of tumor growth with local treatment being more effective. Treatment with 25 micrograms/day of scFv(FRP5)-ETA for 10 days suppressed tumor growth almost completely. Antibodies directed mainly against the toxin domain of the fusion protein developed in all animals treated.

ADP Ribose Transferases↗

Antiangiogenic gene therapy targeting the endothelium-specific receptor tyrosine kinase Tie2.

Angiogenesis is required for tumor growth and metastasis, and inhibition of angiogenesis is a promising approach for anticancer therapy. Tie2 (a.k.a Tek) is an endothelium-specific receptor tyrosine kinase known to play a role in tumor angiogenesis. To explore the therapeutic potential of blocking the Tie2 pathway, an adenoviral vector was constructed to deliver a recombinant, soluble Tie2 receptor (AdExTek) capable of blocking Tie2 activation. Two days after i.v. injection of AdExTek, the plasma concentration of ExTek exceeded 1 mg/ml and was maintained for about 8 days. Administration of AdExTek to mice with two different well established primary tumors, a murine mammary carcinoma (4T1) or a murine melanoma (B16F10.9), significantly inhibited the growth rate of both tumors (64% and 47%, respectively). To study the effect of ExTek on tumor metastasis, both tumor cell lines were coinjected i.v. with either AdExTek or a control virus. Mice coinjected with control virus developed numerous large, well vascularized lung metastases. In contrast, mice coinjected with AdExTek virus developed few, if any, grossly apparent metastases, and histologic examination revealed only small avascular clusters of tumor cells. Administration of AdExTek also inhibited tumor metastasis when delivered at the time of surgical excision of primary tumors in a clinically relevant model of tumor metastasis. This study demonstrates the potential utility of gene therapy for systemic delivery of an antiangiogenic agent targeting an endothelium-specific receptor, Tie2.

Adenoviridae↗

Targeted therapy for colorectal cancer: mapping the way.

In spite of the significant advances in conventional therapeutic approaches to colorectal cancer (CRC), most patients ultimately die of their disease. Dissecting the molecular mechanisms underlying CRC progression will not only accelerate the development of novel cancer-selective drugs but will also enable the therapeutic regimen to be personalized according to the molecular features of individual patients and tumors. Here, we report on the novel insights into CRC biology that are paving the way to the development of molecular therapies and summarize the results from recent clinical trials demonstrating that agents targeting tumor-specific molecular derangements can significantly improve the therapeutic efficacy of conventional chemotherapy. Only a broader clinical implementation of these concepts will provide patients with CRC the best chance of a cure.

Angiogenesis Inhibitors↗

Farnesyl protein transferase inhibitors as targeted therapies for hematologic malignancies.

Farnesyl protein transferase inhibitors (FTIs) represent a new class of anticancer agents specifically targeting aberrant biologic processes involved with cellular transformation and malignancy. Originally developed to inhibit tumors by preventing activation of oncogenic ras genes via suppression of their posttranslational farnesylation, their anticancer activity appears to stem from their ability to inhibit farnesylation of various proteins that mediate signal transduction, growth, apoptosis, and angiogenesis. The safety, biologic activity, clinical response, and pharmacokinetics of R115777, a potent, orally active FTI, were recently investigated in a phase I dose-ranging study in patients with acute leukemias. Patients with acute myelogenous leukemia (AML), acute lymphocytic leukemia (ALL), or chronic myelogenous leukemia (CML) in blast crisis received R115777 100 mg, 300 mg, 600 mg, 900 mg, or 1,200 mg twice daily for 21 days. Cycles were repeated every 28 to 31 days for up to four cycles. An overall response rate of 29% (10/34 evaluable patients) was observed across all R115777 doses. R115777 was well tolerated; common adverse events included fatigue, increased creatinine, nausea, and neutropenia. Dose-limiting toxicity occurred at 1,200 mg twice daily. Farnesylation of lamin A and HDJ-2, examined as biologic end points, was inhibited by R115777 doses > or = 600 mg twice daily. Pharmacokinetic evaluation suggests that R115777 is concentrated in bone marrow at steady state. The biologic and antitumor activity and favorable tolerability of R115777 support further clinical evaluation alone and in combination therapy in hematologic malignancies.

Alkyl and Aryl Transferases↗

Galectins as markers of aggressiveness of mouse mammary carcinoma: towards a lectin target therapy of human breast cancer.

Galectins, beta-galactoside binding proteins, expressed selectively in human breast carcinoma are attractive targets to employ lectin-aimed therapeutics. We examined beta-galactoside binding potency of neoplastic cells using fluorescein-labelled synthetic glycoconjugates as probes for flow cytometry. As a result, surface beta-galactoside binding proteins/galectins were discovered on mouse mammary carcinoma cells in vitro and in vivo unlike non-malignant cells from the several tissues; and asialo-GM1 ganglioside carbohydrate part--containing probe was the most specific one. However, in liver and lung metastatic cells galectins seem to be expressed within cytoplasm and/or nuclei. Galectin expression correlated directly with aggressive tumour potential in the A/Sn transplantable model similar to findings in several human breast carcinoma cell lines. However, galectin expression was reduced during tumour progression in more aggressive forms of spontaneous BLRB mammary carcinomas like it was shown for human breast carcinoma specimens. Analysis of the histopathological data led, however, to the conclusion that galectin expression hardly might be a suitable marker of aggressiveness of heterogeneous mammary carcinomas as the observed level of galectin expression is influenced by the amount of the stroma in a tumour sample and/or probably, galectin expression inversely correlates with tumour aggressiveness during the initial and advanced steps of mammary tumour progression. We conclude that surface beta-galactoside binding proteins/galectins that are selectively expressed during mouse mammary carcinoma progression, similarly to human breast carcinomas, seem to be proper targets for asialo-GM1-vectored cytotoxics and our mouse model system might be a relevant instrument to further test novel modes of anti-breast cancer therapy.

Animals↗