Has mortality from melanoma stopped rising in Australia? Analysis of trends between 1931 and 1994.

OBJECTIVE--To describe recent trends in mortality from melanoma in Australia. DESIGN--An analysis of trends in age standardised and age and sex specific mortalities by year of death and median year of birth (cohort). SETTING--Australia. SUBJECTS--All deaths from melanoma registered in Australia between 1931 and 1994. RESULTS--Melanoma mortality rose steadily from 1931 to 1985. From 1959 the annual rate of increase was 6.3% in men and 2.9% in women, resulting in mortalities of 4.82 and 2.51 per 100,000 person years in 1985 and 1989, respectively. Mortalities for both sexes seem to have plateaued from June 1985 onwards. In 1990-4 the rate rose by 3.7% in men to 5.00 per 100,000 and in women it fell by 5.2% to 2.38 per 100,000. The non-significant increase after 1985 in mortality in men was restricted to those aged over 70 years of age, whereas the fall in rates in women was mostly in those aged under 55 years. This pattern was generally reflected in the state trends, though with some variation: rates for women in Queensland had peaked in the late 1970s; while rates for men in New South Wales continued to rise in 1990-4, placing them above those for Queensland. Examination of mortalities specific for age, period, and cohort for Australia as a whole showed several salient features. Rates in men rose steeply in cohorts born before about 1930; were stable in cohorts born between 1930 and 1950; and fell in more recent cohorts. Rates in women showed similar changes but about five years earlier. CONCLUSION--Melanoma mortality in Australia peaked in about 1985 and has now plateaued. On the basis of trends in cohorts it can be expected to fall in coming years.     

Regulating the response to targeted MEK inhibition in melanoma: Enhancing apoptosis in NRAS- and BRAF-mutant melanoma cells with Wnt/β-catenin activation

The limitations of revolutionary new mutation-specific inhibitors of BRAF^V600E include the universal recurrence seen in melanoma patients treated with this novel class of drugs. Recently, our lab showed that simultaneous activation of the Wnt/β-catenin signaling pathway and targeted inhibition of BRAF^V600E by PLX4720 synergistically induces apoptosis across a spectrum of BRAF^V600E melanoma cell lines. As a follow-up to that study, treatment of BRAF-mutant and NRAS-mutant melanoma lines with WNT3A and the MEK inhibitor AZD6244 also induces apoptosis. The susceptibility of BRAF-mutant lines and NRAS-mutant lines to apoptosis correlates with negative regulation of Wnt/β-catenin signaling by ERK/MAPK signaling and dynamic decreases in abundance of the downstream scaffolding protein, AXIN1. Apoptosis-resistant NRAS-mutant lines can sensitize to AZD6244 by pretreatment with AXIN1 siRNA, similar to what we previously reported in BRAF-mutant cell lines. Taken together, these findings indicate that NRAS-mutant melanoma share with BRAF-mutant melanoma the potential to regulate apoptosis upon MEK inhibition through WNT3A and dynamic regulation of cellular AXIN1. Understanding the cellular context that makes melanoma cells susceptible to this combination treatment will contribute to the study and development of novel therapeutic combinations that may lead to more durable responses.     

Tumor-infiltrating lymphocytes: apparently good for melanoma patients. But why?

Tumor-infiltrating T lymphocytes (TILs) are observed in a number of human primary or metastatic tumors. Recently, gene expression profiling experiments suggested that the presence of T cells in metastatic melanomas before vaccinating the patients with tumor antigens could be a biomarker for clinical benefit from the vaccines. In this context, we review results pertaining to TILs in human melanomas, their prognostic value, and some possible reasons why their presence could help in selecting melanoma patients for vaccination against tumor-specific antigens.     

Complete protection against melanoma in absence of autoimmune depigmentation after rejection of melanoma cells expressing α(1,3)galactosyl epitopes

The major barrier for xenotransplantation in humans is the presence of (1–3) Galactosyl epitopes (Gal) in xenogeneic tissue and the vast quantities of natural antibodies (Ab) produced by humans against this epitope. The binding of anti-Gal Ab to cells expressing Gal triggers a complement-mediated hyperacute rejection of target cells. The hyperacute rejection of whole cancer cells, modified to express Gal epitopes, could be exploited as a new cancer vaccine to treat human cancers. We tested this hypothesis in Galactosyltransferase knockout (GT KO) mice which, like humans, do not express Gal on their cell surfaces and can produce anti-Gal Ab. Forty-five percent of mice with preexisting anti-Gal Ab rejected Gal positive melanoma cells (B16Gal). These mice remained tumor-free for more than 90 days. The majority of control mice injected with B16Null, Gal negative cells succumbed to melanoma. The rejection of B16Gal induced strong long-lasting antitumor immunity against B16Null measured by the expansion of cytotoxic T lymphocytes. In addition, mice rejecting B16Gal were protected against melanoma since they survived a second rechallenge with B16Null. Protected mice developed antitumor immunity in the absence of autoimmune depigmentation (vitiligo). These results show that rejection of Gal positive melanoma cells can efficiently boost the immune response to other tumor associated antigens present in Gal negative melanoma cells. This study supports the concept of a novel anticancer vaccine to treat human malignancies.     

Decreased monocyte antibody-dependent cell-mediated toxicity in stage I–II malignant melanoma

Summary Lymphocyte and monocyte antibody-dependent cell-mediated cytotoxicity (ADCC) against human red blood cells was examined in 28 stage-I-II malignant melanoma patients. Eighteen were studied at various time intervals after receiving SC Corynebacterium parvum (C. parvum); 10 were untreated. Fifteen normal age-matched controls were also studied. Monocyte ADCC was significantly decreased in untreated patients compared with controls (P<0.005) and was significantly increased above controls and untreated patients in individuals treated with C. parvum (P<0.008). No significant differences in lymphocyte ADCC were seen. Optimal enhancement of monocyte ADCC by C. parvum occurred from 2 weeks to 1 month after treatment. Significant decreases in ADCC to baseline levels occurred in patients studied from 3 to 6 months beyond treatment.     

A prognostic signature of G₂ checkpoint function in melanoma cell lines

As DNA damage checkpoints are barriers to carcinogenesis, G₂ checkpoint function was quantified to test for override of this checkpoint during melanomagenesis. Primary melanocytes displayed an effective G₂ checkpoint response to ionizing radiation (IR)-induced DNA damage. Thirty-seven percent of melanoma cell lines displayed a significant defect in G₂ checkpoint function. Checkpoint function was melanoma subtype-specific with “epithelial-like” melanoma lines, with wild type NRAS and BRAF displaying an effective checkpoint, while lines with mutant NRAS and BRAF displayed defective checkpoint function. Expression of oncogenic B-Raf in a checkpoint-effective melanoma attenuated G₂ checkpoint function significantly but modestly. Other alterations must be needed to produce the severe attenuation of G₂ checkpoint function seen in some BRAF-mutant melanoma lines. Quantitative trait analysis tools identified mRNA species whose expression was correlated with G₂ checkpoint function in the melanoma lines. A 165 gene signature was identified with a high correlation with checkpoint function (p < 0.004) and low false discovery rate (≤ 0.077). The G₂ checkpoint gene signature predicted G₂ checkpoint function with 77–94% accuracy. The signature was enriched in lysosomal genes and contained numerous genes that are associated with regulation of chromatin structure and cell cycle progression. The core machinery of the cell cycle was not altered in checkpoint-defective lines but rather numerous mediators of core machinery function were. When applied to an independent series of primary melanomas, the predictive G₂ checkpoint signature was prognostic of distant metastasis-free survival. These results emphasize the value of expression profiling of primary melanomas for understanding melanoma biology and disease prognosis.     

Is it time to test biguanide metformin in the treatment of melanoma?

Metformin is the most widely used antidiabetic drug that belongs to the biguanide class. It is very well tolerated and has the major clinical advantage of not inducing hypoglycemia. Metformin decreases hepatic glucose production via a mechanism requiring liver kinase B1, which controls the metabolic checkpoint, AMP‐activated protein kinase‐mammalian target of rapamycin and neoglucogenic genes. The effects of metformin on this pathway results in reduced protein synthesis and cell proliferation. These observations have given the impetus for many investigations on the role of metformin in the regulation of tumor cell proliferation, cell‐cycle regulation, apoptosis, and autophagy. Encouraging results from these studies have shown that metformin could potentially be used as an efficient anticancer drug in various neoplasms such as prostate, breast, lung, pancreas cancers, and melanoma. These findings are strengthened by retrospective epidemiological studies that have found a decrease in cancer risk in diabetic patients treated with metformin. In this review, we have focused our discussion on recent molecular mechanisms of metformin that have been described in various solid tumors in general and in melanoma in particular.     

Clonal Differences in Photosynthesis in Hevea Brasiliensis Müll. Arg.

The objective of the present investigation was to examine the extent of variations in single leaf net photosynthetic rate (P_N) and its relative dependence on stomatal conductance (g_s) and the mesophyll capacity to fix carbon in 12 clones of the natural rubber plant. There were significant variations in P_N measured at low and saturating photon flux density (PFD); the extent of variation was larger at low than at saturating PFD. The compensation irradiance (CI) and apparent quantum yield of CO₂ assimilation (φ_c) calculated from the P_N/PFD response curves showed significant variations among the clones. P_N at low irradiance was positively correlated with φ_c. Thus a clone with large P_N at low irradiance, high φ_c, and low CI may tolerate shade better and thus produce a high tree stand per hectare. A strong positive correlation existed between P_N saturated with radiant energy (P_sat) and carboxylation efficiency (CE) estimated from the response curves of P_N on intercellular CO₂ concentration (C_i), but g_s showed a poor correlation with P_sat High CO₂ compensation concentration (Γ) led to low CE in Hevea clones. A clone with large P_sat, high CE, low g_s, and low Γ is the one in which photosynthesis is more dependent on the mesophyll factors than stomata. Such a clone may produce relatively high biomass and maintain high water use efficiency. This revised version was published online in September 2006 with corrections to the Cover Date.     

L1CAM from human melanoma carries a novel type of N-glycan with Galβ1-4Galβ1- motif. Involvement of N-linked glycans in migratory and invasive behaviour of melanoma cells

Dramatic changes in glycan biosynthesis during oncogenic transformation result in the emergence of marker glycans on the cell surface. We analysed the N-linked glycans of L1CAM from different stages of melanoma progression, using high-performance liquid chromatography combined with exoglycosidase sequencing, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, and lectin probes. L1CAM oligosaccharides are heavily sialylated, mainly digalactosylated, biantennary complex-type structures with galactose β1-4/3-linked to GlcNAc and with or without fucose α1-3/6-linked to GlcNAc. Hybrid, bisected hybrid, bisected triantennary and tetraantennary complex oligosaccharides, and β1-6-branched complex-type glycans with or without lactosamine extensions are expresses at lower abundance. We found that metastatic L1CAM possesses only α2-6-linked sialic acid and the loss of α2-3-linked sialic acid in L1CAM is a phenomenon observed during the transition of melanoma cells from VGP to a metastatic stage. Unexpectedly, we found a novel monoantennary complex-type oligosaccharide with a Galβ1-4Galβ1- epitope capped with sialic acid residues A1[3]G(4)2S_2-3. To our knowledge this is the first report documenting the presence of this oligosaccharide in human cancer. The novel and unique N-glycan should be recognised as a new class of human melanoma marker. In functional tests we demonstrated that the presence of cell surface α2-3-linked sialic acid facilitates the migratory behaviour and increases the invasiveness of primary melanoma cells, and it enhances the motility of metastatic cells. The presence of cell surface α2-6-linked sialic acid enhances the invasive potential of both primary and metastatic melanoma cells. Complex-type oligosaccharides in L1CAM enhance the invasiveness of metastatic melanoma cells.     

The paradox of T cell–mediated antitumor immunity in spite of poor clinical outcome in human melanoma

Human melanoma is hardly ever curable at an advanced stage, but overwhelming evidence from untreated or vaccinated patients indicates that this tumor is highly antigenic and frequently immunogenic. Here, we review recent results indicating that CD8⁺ T cell–mediated antitumor immunity is activated at the systemic and tumor level in the early clinical stages (AJCC stages I and II) and continues to be promoted, in a fraction of patients, even in metastatic disease (stages III and IV). This evidence was obtained by looking at frequency, differentiation phenotype, and function of antitumor T cells in periphery and tumor site of melanoma patients. On the other hand, the paradox of immunity in spite of poor clinical evolution of the disease, points toward a model of concurrent evolution of immunity and tumor escape. As melanoma progresses to metastatic disease, powerful mechanisms of tumor evasion from immune recognition, and of immunosuppression, are activated, thus tilting the balance between immunity and escape in favor of tumor resistance to host defense. Nevertheless, recent developments in our understanding of regulation of T cell–mediated immunity can provide clues to the prospects for improved immunotherapy approaches. By integrating the information from basic research in immunology, from murine tumor models, and from trials of immunotherapy, we discuss how the most relevant steps of the antitumor response should be manipulated with greater efficacy by future clinical trials. This article forms part of the Symposium in Writing Tumor escape from the immune response, published in Vol. 53.     

Salmonella typhimurium with γ-radiation induced H2AX phosphorylation and apoptosis in melanoma

To investigate the combinatorial effects using Salmonella and γ-radiation, the Salmonella typhimurium infection in combination with γ-radiation was investigated on melanoma. We showed that ROS expression and H₂AX phosphorylation increased during stress by γ-radiation irrespective of Salmonella infection, inducing apoptosis by caspase-3 and bcl2 in tumor cells. In addition, tumor growth was suppressed by this combinatory therapy suggesting candidates for radiation therapy against melanoma.