Stergios J. Moschos

Survival in BRAF V600–Mutant Advanced Melanoma Treated with Vemurafenib

BACKGROUND Approximately 50% of melanomas harbor activating (V600) mutations in the serine-threonine protein kinase B-RAF (BRAF). The oral BRAF inhibitor vemurafenib (PLX4032) frequently produced tumor regressions in patients with BRAF V600-mutant metastatic melanoma in a phase 1 trial and improved overall survival in a phase 3 trial. METHODS We designed a multicenter phase 2 trial of vemurafenib in patients with previously treated BRAF V600-mutant metastatic melanoma to investigate the efficacy of vemurafenib with respect to overall response rate (percentage of treated patients with a tumor response), duration of response, and overall survival. The primary end point was the overall response rate as ascertained by the independent review committee; overall survival was a secondary end point. RESULTS A total of 132 patients had a median follow-up of 12.9 months (range, 0.6 to 20.1). The confirmed overall response rate was 53% (95% confidence interval [CI], 44 to 62; 6% with a complete response and 47% with a partial response), the median duration of response was 6.7 months (95% CI, 5.6 to 8.6), and the median progression-free survival was 6.8 months (95% CI, 5.6 to 8.1). Primary progression was observed in only 14% of patients. Some patients had a response after receiving vemurafenib for more than 6 months. The median overall survival was 15.9 months (95% CI, 11.6 to 18.3). The most common adverse events were grade 1 or 2 arthralgia, rash, photosensitivity, fatigue, and alopecia. Cutaneous squamous-cell carcinomas (the majority, keratoacanthoma type) were diagnosed in 26% of patients. CONCLUSIONS Vemurafenib induces clinical responses in more than half of patients with previously treated BRAF V600-mutant metastatic melanoma. In this study with a long follow-up, the median overall survival was approximately 16 months. (Funded by Hoffmann-La Roche; ClinicalTrials.gov number, NCT00949702.).

Leptin in Immunology

Leptin is an adipokine which conveys information on energy availability. In humans, leptin influences energy homeostasis and regulates neuroendocrine function primarily in states of energy deficiency. As a cytokine, leptin also affects thymic homeostasis and, similar to other proinflammatory cytokines, leptin promotes Th1 cell differentiation and cytokine production. We review herein recent advances on the role of leptin in the pathophysiology of immune responses.

Leptin and reproduction: a review

OBJECTIVE To review recent advances in understanding the role of leptin in the physiology and pathophysiology of reproduction, with a focus on relevant clinical situations. DESIGN A MEDLINE computer search was performed to identify relevant articles. RESULT(S) Leptin, an adipocyte hormone important in regulating energy homeostasis, interacts with the reproductive axis at multiple sites, with stimulatory effects at the hypothalamus and pituitary and inhibitory actions at the gonads. More recently, leptin has been shown to play a role in other target reproductive organs, such as the endometrium, placenta, and mammary gland, with corresponding influences on important physiologic processes such as menstruation, pregnancy, and lactation. As a marker of whether nutritional stores are adequate, leptin may act in concert with gonadotropins and the growth hormone axis to initiate the complex process of puberty. Conditions in which nutritional status is suboptimal, such as eating disorders, exercise-induced amenorrhea, and functional hypothalamic amenorrhea, are associated with low serum leptin levels; and conditions with excess energy stores or metabolic disturbances, such as obesity and polycystic ovarian syndrome, often have elevated serum or follicular fluid leptin levels, raising the possibility that relative leptin deficiency or resistance may be at least partly responsible for the reproductive abnormalities that occur with these conditions. CONCLUSION(S) Leptin may act as the critical link between adipose tissue and the reproductive system, indicating whether adequate energy reserves are present for normal reproductive function. Future interventional studies involving leptin administration are expected to further clarify this role of leptin and may provide new therapeutic options for the reproductive dysfunction associated with states of relative leptin deficiency or resistance.

The Role of the IGF System in Cancer: From Basic to Clinical Studies and Clinical Applications

Insulin-like growth factors (IGFs) are important mediators of growth, development, and survival, are synthesized by almost any tissue in the body, and their action is modulated by a complex network of molecules, including binding proteins, proteases and receptors, which all comprise the IGF system. Evidence from in vitro and animal studies suggests that overexpression of IGFs by cancer cells and/or the nearby stroma as well as the type IGF-I receptor by the cancer cells may play a significant role in establishing a transformed phenotype in an increasing number of malignancies. More specifically, IGFs may promote cell cycle progression and inhibition of apoptosis either by directly associating with other growth factors or indirectly by interacting with other molecular systems which have an established role in carcinogenesis and cancer promotion, such as the steroid hormones and integrins. In addition, a growing number of epidemiologic studies suggest that increased serum levels of IGFs and/or altered levels of their binding proteins are associated with increased risk for developing several malignancies. These data indicate that IGF dysregulation should now be considered as an important independent factor for cancer risk, and a potential target for novel antineoplastic therapies and/or preventative strategies in high-risk groups.

Leptin Concentrations in Relation to Body Mass Index and the Tumor Necrosis Factor-α System in Humans

The expression of leptin, an adipocyte-derived protein whose circulating levels reflect energy stores, can be induced by tumor necrosis factor (TNF)alpha in rodents, but an association between the TNF alpha system and leptin levels has not been reported in humans. To evaluate the potential association between serum leptin and the TNF alpha system, we measured the levels of soluble TNF alpha-receptor (sTNF alpha-R55), which has been validated as a sensitive indicator of activation of the TNF alpha system. We studied two groups: 1) 82 young healthy normal controls and 2) 48 patients with noninsulin dependent diabetes mellitus (NIDDM) and 24 appropriately matched controls. By simple regression analysis in controls, there was a strong positive association between leptin and 3 parameters: body mass index, sTNF alpha-R55, and insulin levels. In a multiple regression analysis model, leptin remained significantly and strongly associated with body mass index, and the association of leptin with both insulin and sTNF alpha-R55, although weakened, remained significant. Patients with NIDDM had leptin concentrations similar to controls of similar weight. Importantly, serum levels of sTNF alpha-R55 were also positively and independently associated with leptin in this group of diabetic subjects and matched controls. These data are consistent with the hypothesis that the TNF alpha system plays a role in regulating leptin levels in humans. Further elucidation of a possible role of the TNF alpha system in leptin expression and circulating levels may have important implications for our understanding of obesity and cachexia in humans.

Human Merkel cell polyomavirus infection II. MCV is a common human infection that can be detected by conformational capsid epitope immunoassays.

Merkel cell polyomavirus (MCV) is a newly‐discovered human tumor virus found in ∼80% of Merkel cell carcinoma (MCC). The rate of MCV infection among persons without MCC is unknown. We developed a MCV virus‐like particle (VLP) enzyme‐linked immunoassay (EIA) that does not cross‐react with human BK or murine polyomaviruses. Peptide mapping of the MCV VP1 gene and immunoblotting with denatured MCV VLP are less sensitive than the MCV EIA in detecting MCV antibodies suggesting antibody reactivity in this assay primarily targets conformational but not linear epitopes. Among MCC patients, all 21 (100%) patients tested with MCV‐positive tumors had high serum MCV IgG but not high MCV IgM levels. Only 3 of 6 (50%) MCC patients with MCV‐negative tumors were positive for MCV antibodies. Sera from most adults, including 107 of 166 (64%) blood donors, 63 of 100 (63%) commercial donors and 37 of 50 (74%) systemic lupus erythematosus patients, show evidence for prior MCV exposure. Age‐specific MCV prevalence was determined by examining a cross‐sectional distribution of 150 Langerhans cell histiocytosis (an unrelated neoplasm) patient sera. MCV prevalence increases from 50% among children age 15 years or younger to 80% among persons older than 50 years. We did not find evidence for vertical transmission among infants. Although past exposure to MCV is common among all adult groups, MCC patients have a markedly elevated MCV IgG response compared with control patients. Our study demonstrates that MCV is a widespread but previously unrecognized human infection.

Pharmacodynamic Effects and Mechanisms of Resistance to Vemurafenib in Patients With Metastatic Melanoma

PURPOSE To assess pharmacodynamic effects and intrinsic and acquired resistance mechanisms of the BRAF inhibitor vemurafenib in BRAF(V600)-mutant melanoma, leading to an understanding of the mechanism of action of vemurafenib and ultimately to optimization of metastatic melanoma therapy. METHODS In the phase II clinical study NP22657 (BRIM-2), patients received oral doses of vemurafenib (960 mg twice per day). Serial biopsies were collected to study changes in mitogen-activated protein kinase (MAPK) signaling, cell-cycle progression, and factors causing intrinsic or acquired resistance by immunohistochemistry, DNA sequencing, or somatic mutation profiling. Results Vemurafenib inhibited MAPK signaling and cell-cycle progression. An association between the decrease in extracellular signal-related kinase (ERK) phosphorylation and objective response was observed in paired biopsies (n = 22; P = .013). Low expression of phosphatase and tensin homolog showed a modest association with lower response. Baseline mutations in MEK1(P124) coexisting with BRAF(V600) were noted in seven of 92 samples; their presence did not preclude objective tumor responses. Acquired resistance to vemurafenib associated with reactivation of MAPK signaling as observed by elevated ERK1/2 phosphorylation levels in progressive lesions and the appearance of secondary NRAS(Q61) mutations or MEK1(Q56P) or MEK1(E203K) mutations. These two activating MEK1 mutations had not previously been observed in vivo in biopsies of progressive melanoma tumors. CONCLUSION Vemurafenib inhibits tumor proliferation and oncogenic BRAF signaling through the MAPK pathway. Acquired resistance results primarily from MAPK reactivation driven by the appearance of secondary mutations in NRAS and MEK1 in subsets of patients. The data suggest that inhibition downstream of BRAF should help to overcome acquired resistance.

Neoadjuvant Treatment of Regional Stage IIIB Melanoma With High-Dose Interferon Alfa-2b Induces Objective Tumor Regression in Association With Modulation of Tumor Infiltrating Host Cellular Immune Responses

PURPOSE Adjuvant high-dose interferon-alfa-2b (HDI) improves disease-free and overall survival in patients with high-risk melanoma. However, its mechanism of action is largely unknown. Therefore, HDI was investigated in the neoadjuvant setting to assess clinical and pathologic responses after 4 weeks of HDI and to perform immunohistochemical evaluation of immune cell subsets and melanoma-associated antigens. PATIENTS AND METHODS Patients with palpable regional lymph node metastases from melanoma (American Joint Committee on Cancer stage IIIB-C) underwent surgical biopsy at study entry and then received standard intravenous HDI (20 million units/m2, 5 days per week) for 4 weeks followed by complete lymphadenectomy and standard maintenance subcutaneous HDI (10 million units/m2 3 times per week) for 48 weeks. Biopsy samples were obtained before and after intravenous HDI and subjected to immunohistochemical analysis as well as routine pathologic study. RESULTS Twenty patients were enrolled, and biopsy samples were informative for 17. Eleven patients (55%) demonstrated objective clinical response, and 3 patients (15%) had complete pathologic response. At a median follow-up of 18.5 months (range, 7 months to 50 months) 10 patients had no evidence of recurrent disease. Clinical responders had significantly greater increases in endotumoral CD11c+ and CD3+ cells and significantly greater decreases in endotumoral CD83+ cells compared with nonresponders. No changes in the expression of melanoma-associated lineage antigens, tumor cell proliferation, angiogenesis, or apoptosis were evident. CONCLUSION Neoadjuvant HDI is highly effective for the treatment of palpable stage IIIB-C melanoma, and the findings of this study implicate an indirect immunomodulatory mechanism rather than a direct antitumor mechanism.

Next Generation of Immunotherapy for Melanoma

PURPOSE Immunotherapy has a long history with striking but limited success in patients with melanoma. To date, interleukin-2 and interferon-alfa2b are the only approved immunotherapeutic agents for melanoma in the United States. DESIGN Tumor evasion of host immune responses, and strategies for overcoming tumor-induced immunosuppression are reviewed. Several novel immunotherapies currently in worldwide phase III clinical testing for melanoma are discussed. RESULTS The limitations of immunotherapy for melanoma stem from tumor-induced mechanisms of immune evasion that render the host tolerant of tumor antigens. For example, melanoma inhibits the maturation of antigen-presenting cells, preventing full T-cell activation and downregulating the effector antitumor immune response. New immunotherapies targeting critical regulatory elements of the immune system may overcome tolerance and promote a more effective antitumor immune response. These include monoclonal antibodies that block the cytotoxic T lymphocyte-associated antigen 4 (CTLA4) and toll-like receptor 9 (TLR9) agonists. Blockade of CTLA4 prevents inhibitory signals that downregulate T-cell activation. TLR9 agonists stimulate dendritic cell maturation and ultimately induce a more effective immune response. These approaches have been shown to stimulate acute immune activation with concomitant appearance of transient adverse events mediated by the immune system. The pattern and duration of immune responses associated with these new modalities differ from those associated with cytokines and cytotoxic agents. In addition, vaccines are being developed that may ultimately target melanoma either alone or in combination with these immunomodulatory therapies. CONCLUSION The successes of cytokine and interferon therapy of melanoma, coupled with an array of new approaches, are generating new enthusiasm for the immunotherapy of melanoma.

Leptin: in search of role(s) in human physiology and pathophysiology.

Obesity, a health problem reaching epidemic proportions in western countries, is an important risk factor for the most frequent diseases in the western world, i.e. diabetes, hypertension, cardiovascular diseases and certain types of cancer. Thus, significant research efforts have been focusing on its aetiology, prevention and treatment. The recent discovery of leptin (from the Greek wordleptos: i.e. thin), the product of theob gene (Zhanget al., 1994), has greatly advanced our understanding of body adiposity and energy balance regulation. This hormone, produced mainly by adipose tissue, conveys to the brain information about the size of energy stores and activates hypothalamic centres that regulate energy intake and expenditure (Flier, 1997). Moreover, leptin affects several neuroendocrine mechanisms and regulates multiple hypothalamic– pituitary axes (Flier, 1997). The realization that adipose tissue is not simplyastorage depot, butalsoan important endocrine gland, has created new opportunities for the investigation and, possibly, treatment of diseases such as obesity and eating disorders. In this review, we discuss the biology of leptin secretion and regulation, as well as our current knowledge of the role leptin plays in various physiological and pathophysiological states. Although most available research studies have been based on animal models, a substantial amount of information has been accumulated over the last 3 years on the role of leptin in humans. Thus, this article mainly focuses on our current knowledge about the role of leptin in human physiology and pathophysiology. Finally, some of the important unanswered questions about leptin physiology are discussed and future directions for leptin research are suggested.