Expression of sorafenib targets in melanoma patients treated with carboplatin, paclitaxel and sorafenib

BACKGROUND

Sorafenib, a multitarget kinase inhibitor, inhibits members of the mitogen-activated protein kinase (MAPK) pathway and receptor tyrosine kinases, including vascular endothelial growth factor receptor 2 (VEGF-R2). Sorafenib, carboplatin, and paclitaxel (SCP) has antitumor activity in melanoma patients, but no association was found between response and activating B-Raf V600E mutations. We assessed the expression of sorafenib targets in SCP-treated patient specimens and evaluated the association with response and progression-free survival.

EXPERIMENTAL DESIGN

Using automated quantitative analysis, we quantified the expression of VEGF-R1, VEGF-R2, VEGF-R3, fibroblast growth factor receptor 1, platelet-derived growth factor receptor beta, c-Kit, B-Raf, C-Raf, meiosis-specific serine/threonine protein kinase 1, and extracellular regulated kinase 1/2 (ERK1/2) in pretreatment specimens from 46 patients. Furthermore, we assessed ERK1/2 expression in 429 archival melanomas.

RESULTS

VEGF-R2 expression was significantly higher in patients with a complete or partial response (P = 0.0435), whereas ERK1/2 was higher in patients who did not respond (P = 0.0417). High ERK1/2 was an independent predictor of poor survival. High ERK1/2 was associated with decreased survival in the archival melanoma cohort, suggesting that high ERK1/2-expressing tumors are biologically more aggressive. All of the six patients with both high VEGF-R2 and low ERK1/2 responded to SCP.

CONCLUSIONS

High VEGF-R2 expression is associated with response to SCP in melanoma, whereas high ERK1/2 is associated with resistance. Collection of specimens from SCP-treated melanoma patients in a cooperative group phase III trial comparing this regimen with the chemotherapy alone is ongoing, and confirmation of these findings is necessary. These markers might be useful for predicting response to sorafenib when given with other chemotherapies and in other diseases, resulting in the possible elimination of unnecessary treatment of patients unlikely to respond.

Molecular pathogenesis of cutaneous melanocytic neoplasms

Melanoma is the deadliest form of skin cancer without an effective treatment. An understanding of the genetic basis of melanoma has recently shed light on some of the mechanisms of melanomagenesis. This review explores the major genes involved in familial and sporadic cutaneous melanoma with an emphasis on CDKN2A, CDK4, MC1R, and MAPK pathway targets (e.g., RAS and BRAF), apoptosis regulators (e.g., BCL-2, AKT, and APAF-1), and the tumor-suppressor genes TP53 and PTEN. New directions for therapeutics based on our current knowledge of the genes implicated in melanoma are also discussed.

Melanoma genetics and therapeutic approaches in the 21st century: moving from the benchside to the bedside

Metastatic melanoma is notoriously one of the most difficult cancers to treat. Although many therapeutic regimens have been tested, very few achieve response rates greater than 25%. Given the rising incidence of melanoma and the paucity of effective treatments, there is much hope and excitement in leveraging recent genetic and molecular insights for therapeutic advantage. Over the past 30 years, elegant studies by many groups have helped decipher the complex genetic networks involved in melanoma proliferation, progression and survival, as well as several genes involved in melanocyte development and survival. Many of these oncogenic loci and pathways have become crucial targets for pharmacological development. In this article we review: (1) our current understanding of melanoma genetics within the context of signaling networks; (2) targeted therapies, including an extensive discussion of promising agents that act in the Bcl-2 signaling network; (3) future areas of research.

Genetics of melanoma tumorigenesis

Melanoma therapy is moving away from combinatorial approaches and towards newer targeted strategies. With the identification of mutations in various RAS pathway genes, there are now tremendous opportunities to bring inhibitors of RAS signalling to the clinical arena.

New approaches in metastatic melanoma: biological and molecular targeted therapies

Classical metastatic melanoma therapy is disappointing but important progress has been made in the understanding of melanoma biology. Genetic lesions and several intracellular signaling pathways that could serve as targets for novel therapy have been identified and a number of new agents are under evaluation. Promising tumor cell targets were identified in the cell membrane, cytoplasm and nucleus. New therapeutic approaches, besides monoclonal antibodies and vaccination, include an increasing number of small molecules that have been shown to interfere restrictively with intracellular signaling pathways in melanoma and decrease proliferation, survival, migration or invasion. Other agents can interfere with stromal components of melanoma, such as angiogenesis and components of the immune system.

Sorafenib: delivering a targeted drug to the right targets

Approved for the treatment of advanced renal cell carcinoma by the US FDA and other regulatory agencies, sorafenib is an agent with multiple targets that may also prove beneficial in other malignancies. Phase III trials are underway in melanoma, hepatocellular carcinoma and non-small-cell lung cancer. Scrutiny of the Phase II data and correlative studies conducted in that context suggests that inhibition of angiogenesis and signaling in tumor cells may play a part in the clinical efficacy of sorafenib. Although the vascular endothelial growth factor receptor inhibitors are the most populated class of targeted agents in cancer clinical trials, sorafenib may prove to have unique properties that distinguish it. A detailed discussion of the clinical trials in renal cell carcinoma, melanoma and hepatocellular carcinoma highlights what is known and what has yet to be understood about this agent.

Current topics in melanoma

PURPOSE OF REVIEW

New approaches to melanoma are emerging. This review summarizes developments over the past 12 months.

RECENT FINDINGS

Surgical, chemotherapeutic, immunologic and targeted therapies for melanoma are evolving. Sentinel lymph node sampling is now accepted as the standard of care for patients with intermediate thickness primary melanomas. Temozolomide continues to be widely used as part of combination therapy, and recent evidence suggests that a combination of temozolomide and interferon-alpha may be superior to temozolomide alone. Meanwhile, temozolomide and thalidomide carries unacceptable thrombosis risk. In the area of immunotherapy, anti-CTLA-4 continues to show promise, but special attention must be paid to gastrointestinal toxicity. Interferon-alpha, in addition, has shown efficacy in the neoadjuvant setting with inflammatory infiltrates demonstrated in tumors. A better understanding of the complex genetic regulation of melanoma cell growth is emerging and this is expected to lead to the development of novel targeted therapies.

SUMMARY

Research is producing a more complete understanding of melanoma genetics and immune regulation. These are beginning to produce therapeutics that are impacting clinical practice.

Sorafenib and sunitinib in the treatment of advanced non-small cell lung cancer

Despite the optimization of chemotherapy regimens, treatment outcomes for advanced non-small cell lung cancer (NSCLC) are still considered to be disappointing. Thus, clinical research of new treatment strategies is warranted. Several targeted agents have been introduced into clinical trials in NSCLC, but to date, only a few of these new agents can offer hope of a substantial impact on the natural history of the disease. One of the main reasons for the failure of several clinical trials of targeted therapy in lung cancer is that there is multilevel cross-stimulation among the targets of the new biological agents along several pathways of signal transduction that lead to neoplastic events; blocking only one of these pathways, as most first-generation targeted agents do, allows others to act as salvage or escape mechanisms for cancer cells. Sorafenib and sunitinib are two oral multitargeted receptor tyrosine kinase inhibitors. Sorafenib is a multikinase inhibitor that inhibits the kinase activity of both C-RAF and B-RAF and targets the vascular endothelial growth factor receptor family (VEGFR-2 and VEGFR-3) and platelet-derived growth factor receptor family (PDGFR-beta and stem cell factor receptor [KIT]). Sunitinib is a multitargeted inhibitor of PDGFR, KIT, fms-like tyrosine kinase 3, and VEGFR. The kinases targeted and inhibited by sorafenib and sunitinib directly and indirectly regulate tumor growth, survival, and angiogenesis, and this might be expected to result in broad antitumor efficacy. Sorafenib and sunitinib have been approved by the U.S. Food and Drug Administration for the treatment of metastatic renal cell carcinoma; sunitinib has also been approved for the treatment of gastrointestinal stromal tumors. Their mechanism of action, preclinical data, and phase II studies suggest efficacy in the treatment of advanced NSCLC.

Therapeutic targets in melanoma: MAPKinase pathway

Recent progress in our understanding of the genetic alterations that occur in the pathogenesis of melanoma provides exciting opportunities for therapy. The most important signaling pathways in melanoma lie downstream of NRAS: the RAS-BRAF-MAPK pathway. A great deal of attention has been focused on the high mutation rate in the BRAF oncogene, which approaches 60%, because BRAF itself is an appealing drug substrate and because of the central contribution of BRAF function to melanoma development that the mutation rate signifies. Agents that specifically target BRAF, such as sorafenib, as well as new molecules that function both upstream and downstream of BRAF, are being actively investigated.