Chemotherapy for metastatic gastric cancer: past, present, and future

Despite the numerous efforts of randomized studies on advanced gastric cancer, no globally accepted standard regimen has yet been established. Two triplet regimens have already demonstrated significant survival prolongation in Western studies. However, the benefit seems to be marginal, and these regimens may be replaced by recently published newer generation regimens for which favorable survival is reported. At present, the combination of 5-fluorouracil (5-FU) and platinum analog is still the most widely accepted standard regimen worldwide: 5-FU can be replaced by S-1 or capecitabine, and cisplatin by oxaliplatin. In Japan, S-1 plus cisplatin is the most reasonable first-line standard, based on recent randomized studies. Some early clinical studies using molecular targeting agents have shown promising activity, particularly in combination with cytotoxic agents for gastric cancer. Several targeting agents such as trastuzumab, bevacizumab, and lapatinib are now under investigation in international randomized studies, including in Japan. These agents have shown a survival benefit in other tumor types. The next-generation targeting agents, including mammalian target of rapamycin inhibitor and a c-Met tyrosine kinase inhibitor, are also being evaluated in early clinical studies in association with biology research. Such agents can be advantageously used in gastric cancer studies, which, because of the ease with which tumor tissues can be obtained by endoscopy and the high incidence of gastric cancer in Japan, might advance the frontiers of biologic therapy. These efforts should result not only in further clinical advances but also in tailored medicine.

Targeting the Raf-MEK-ERK mitogen-activated protein kinase cascade for the treatment of cancer

Mitogen-activated protein kinase (MAPK) cascades are key signaling pathways involved in the regulation of normal cell proliferation, survival and differentiation. Aberrant regulation of MAPK cascades contribute to cancer and other human diseases. In particular, the extracellular signal-regulated kinase (ERK) MAPK pathway has been the subject of intense research scrutiny leading to the development of pharmacologic inhibitors for the treatment of cancer. ERK is a downstream component of an evolutionarily conserved signaling module that is activated by the Raf serine/threonine kinases. Raf activates the MAPK/ERK kinase (MEK)1/2 dual-specificity protein kinases, which then activate ERK1/2. The mutational activation of Raf in human cancers supports the important role of this pathway in human oncogenesis. Additionally, the Raf-MEK-ERK pathway is a key downstream effector of the Ras small GTPase, the most frequently mutated oncogene in human cancers. Finally, Ras is a key downstream effector of the epidermal growth factor receptor (EGFR), which is mutationally activated and/or overexpressed in a wide variety of human cancers. ERK activation also promotes upregulated expression of EGFR ligands, promoting an autocrine growth loop critical for tumor growth. Thus, the EGFR-Ras-Raf-MEK-ERK signaling network has been the subject of intense research and pharmaceutical scrutiny to identify novel target-based approaches for cancer treatment. In this review, we summarize the current status of the different approaches and targets that are under evaluation and development for the therapeutic intervention of this key signaling pathway in human disease.

Epidermal growth factor receptor – targeted molecular therapeutics for head and neck squamous cell carcinoma

Several molecular-targeted therapeutics have been tested in clinical trials for the treatment of head and neck squamous cell carcinoma (HNSCC). Of these, therapeutics targeting the epidermal growth factor receptor (EGFR) have been studied most extensively and some agents have demonstrated measurable clinical effectiveness. However, molecular studies designed to define HNSCC patient subcohorts of likely responders to EGFR-targeted therapy have not identified molecular signatures that correlate with clinical response. Here, the authors summarise the relevant clinical findings and highlight reported molecular correlative studies for EGFR-targeted therapeutics for HNSCC. The authors focus especially on molecular markers evaluated for association with clinical response and include data from EGFR-targeted clinical studies in other cancer sites that they anticipate will be of interest to the head and neck cancer research and treatment communities.

Epidermal growth factor receptor inhibitors in development for the treatment of non-small cell lung cancer

The epidermal growth factor receptor (EGFR) inhibitors erlotinib, gefitinib, and cetuximab have undergone extensive clinical testing and have established clinical activity in non-small cell lung cancer and other types of solid tumors. A number of newer inhibitors are currently in clinical development with different spectra of activity or mechanisms of receptor inhibition. These include monoclonal antibodies, such as panitumumab and matuzumab; dual inhibitors of EGFR and vascular endothelial growth factor receptor, such as ZD6474 and AEE788; inhibitors of multiple EGFR family members, such as lapatinib; and irreversible inhibitors, such as canertinib and HKI272. Preclinical studies suggest that several of these agents may have activity in tumors refractory to erlotinib or gefitinib. Among these agents, ZD6474 has undergone the most extensive clinical testing. The antitumor activity of ZD6474 in these two randomized phase II clinical trials in patients with non-small cell lung cancer was felt to be sufficiently promising to warrant phase III clinical testing. Several of the other EGFR inhibitors are also undergoing advanced clinical testing, either alone or in combination with other agents. EGFR has now been validated as a clinically relevant target, and several different types of agents inhibiting this receptor are currently in development. Future research will be needed to elucidate the role of these agents in patients with EGFR inhibitor-naive and EGFR inhibitor-refractory disease, to define the molecular characteristics that predict response, and to determine whether these drugs should be used in combination with other targeted agents or chemotherapy.

Overview of monoclonal antibodies and small molecules targeting the epidermal growth factor receptor pathway in colorectal cancer

The epidermal growth factor receptor (EGFR) provides survival signals and is overexpressed in the majority of colorectal cancers. As more is learned about the molecular details of EGFR signaling, antibodies can be designed to interfere with specific domains of the EGFR molecule. In this review, we analyze preclinical and current clinical data on EGFR-targeting molecules and their potential role in the treatment of colorectal cancer. Cetuximab binds to domain III of EGFR and hinders ligand binding. It is now approved by the US Food and Drug Administration for metastatic colorectal cancer treatment. Panitumumab is another widely studied anti-EGFR antibody with similar properties. Bispecific antibodies are modified immunoglobulin molecules containing 2 different binding specificities. These antibodies can redirect the immune response against tumor cells by tethering effector cells such as CD3e-expressing T cells or CD16-expressing natural killer cells and granulocytes to the surface of cancer cells. Tyrosine kinase inhibitors are quinazoline-derived, low molecular weight synthetic molecules that can block the intracellular tyrosine kinase domain of several receptors, including EGFR, Erb2, and vascular endothelial growth factor receptor, and thereby inhibit ligand-induced receptor phosphorylation and abrogate the biologic effect of EGFR signaling. The presence of skin rash and EGFR gene amplification have been advanced as possible predictors of clinical effectiveness of targeted anti-EGFR therapies.