Activation of Grm1 expression by mutated BRaf (V600E) in vitro and in vivo

Our laboratory previously showed that ectopic expression of Grm1 is sufficient to induce spontaneous melanoma formation with 100% penetrance in transgenic mouse model, TG-3, which harbors wild-type BRaf. Studies identified Grm1 expression in human melanoma cell lines and primary to secondary metastatic melanoma biopsies having wild-type or mutated BRaf, but not in normal melanocytes or benign nevi. Grm1 expression was detected in tissues from mice genetically engineered with inducible melanocyte-specific BRaf^V600E. Additionally, stable clones derived from introduction of exogenous BRaf^V600E in mouse melanocytes also showed Grm1 expression, which was not detected in the parental or empty vector-derived cells, suggesting that expression of BRaf^V600E could activate Grm1 expression. Despite aberrant Grm1 expression in the inducible, melanocyte-specific BRaf^V600E mice, no tumors formed. However, in older mice, the melanocytes underwent senescence, as demonstrated previously by others. It was proposed that upregulated p15 and TGFβ contributed to the senescence phenotype. In contrast, in older TG-3 mice the levels of p15 and TGFβ remained the same or lower. Taken together, these results suggest the temporal regulation on the expression of "oncogenes" such as Grm1 or BRaf^V600E is critical in the future fate of the cells. If BRaf^V600E is turned on first, Grm1 expression can be induced, but this is not sufficient to result in development of melanoma; the cells undergo senescence. In contrast, if ectopic expression of Grm1 is turned on first, then regardless of wild-type or mutated BRaf in the melanocytes melanoma development is the consequence.

Abstract 5172: Developing a lung metastasis gene signature using a lung tropism model in melanoma

A patient with metastatic melanoma has a 5-year survival rate of only 15%. As with most cancers, approximately 90% of fatalities are caused by metastatic spread of tumor cells to vital organs like the liver, lung, brain, bone, etc. Lung is one of the leading metastatic sites of melanoma at initial presentation, yet the mechanisms that lead to melanoma lung metastases are not well understood. For our study we have developed an in vivo ‘spontaneous lung-metastasis model’ using two human melanoma cell lines, UACC903 and C8161, with different genetic backgrounds. Parental melanoma cells were injected subcutaneously into nude mice. After the tumors reached the maximum allowable size of 1.5 cm, survival surgery was performed to remove the subcutaneous tumors and the animals were observed for an additional 4 weeks or until the animals appeared ill. The animals were sacrificed and lung metastases were surgically removed and re-cultured. The two new cell lines were designated as UACC903-LM and C8161-LM. This process was repeated using these new cell lines to obtain a second round of lung metastasizing lines we designated as UACC903-LMM and C8161-LMM. Using the parental and metastasizing cell lines we have been able to identify a lung metastasis gene signature using PCR array analysis, validated by PCR and Western Blot. This lung metastasis gene signature was further supported by the identification of increased expression of the same set of genes in lung metastasis as compared to primary tumors from patients with melanoma. We have also observed increased migration in metastasizing cell lines as compared to the parental lines using a trans-well migration assay with fetal bovine serum as chemo-attractant. CXCR-4 was one of gene products up-regulated in the metastasizing cell lines and the FDA-approved CXCR-4 antagonist, AMD-3100, inhibited trans-well migration of the metastasizing cell lines far more than parental cell lines. Our ongoing studies are examining the potential of inhibiting CXCR-4, and other gene products from our metastasis gene signature, as a therapeutic option in patients with advanced melanoma.

Funding: NIH RO1-563057

Note: This abstract was not presented at the meeting.

Citation Format: Yu Wen, Maung Naing Lin Shan, Jiadong Li, James Goydos. Developing a lung metastasis gene signature using a lung tropism model in melanoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5172. doi:10.1158/1538-7445.AM2015-5172

Abstract 4199: Riluzole modulates the production of exosomes in melanoma cells

Exosomes are naturally occurring small membrane enclosed microvesicles generated constitutively and released by various cell types and more frequently released by tumor cells. It was postulated that exosomes may facilitate communication within the local microenvironment and the primary tumor, supporting melanoma cell dissemination and early events in metastasis. A gain-of-function mutation of a neuronal receptor, metabotropic glutamate receptor 1 (GRM1), when ectopically expressed in melanocytes, was sufficient to induce in vitro melanocytic transformation and spontaneous malignant melanoma development in vivo in a transgenic mouse model. Normal mouse melanocytes transformed with an expression vector containing GRM1 showed production and secretion of exosomes confirmed by electron microscopy, while the parental normal melanocytes showed no detectable presence of exosomes. In light of this data, It was hypothesized that over-expression of GRM1 in melanoma cells normally expressing a moderate amount of the protein, may promote elevated levels of exosome formation, while inhibitors to the receptor or limiting the levels of available ligand may suppress exosome production. Preliminary results demonstrated the working hypothesis is correct. Our earlier studies showed that inhibitors of the receptor modulated GRM1-mediated signaling events interfere with downstream effectors resulting in a decrease in both cell proliferation in vitro and tumor progression in vivo. It is not known if GRM1 acts directly, via its signaling cascade, or by another route, on exosome production regulation, this will be investigated. In addition to the pharmacological inhibitors we will also use a genetic approach with silencing RNA to modulate GRM1 expression levels.

Citation Format: Allison L. Isola, Yvonne Wen, James Goydos, Suzie Chen. Riluzole modulates the production of exosomes in melanoma cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4199. doi:10.1158/1538-7445.AM2014-4199

Metabotropic glutamate receptor 1 mediates melanocyte transformation via transactivation of insulin-like growth factor 1 receptor

Our laboratory previously described the oncogenic properties of metabotropic glutamate receptor 1 (mGluR1) in melanocytes. mGluR1 transformed immortalized mouse melanocytes in vitro and induced vigorous tumor formation in vivo. Subsequently, we observed the activation of PI3K/AKT in mGluR1-mediated melanocytic tumorigenesis in vivo. In particular, we identified AKT2 being the predominant isoform contributing to the activation of AKT. Suppression of Grm1 or AKT2 using an inducible Tet-R siRNA system resulted in a 60 or 30% reduction, respectively, in in vivo tumorigenesis. We show that simultaneous downregulation of Grm1 plus AKT2 results in a reduction of approximately 80% in tumor volumes, suggesting that both mGluR1 and AKT2 contribute to the tumorigenic phenotype in vivo. The discrepancy between the mild in vitro transformation characteristics and the aggressive in vivo tumorigenic phenotypes of these stable mGluR1-melanocytic clones led us to investigate the possible involvement of other growth factors. Here, we highlight a potential crosstalk network between mGluR1 and tyrosine kinase, insulin-like growth factor 1 receptor (IGF-1R).

Abstract 3889: GRM1 over-expression in melanoma cells promotes microvesicle formation which functions in stimulating angiogenesis

Our group has reported that metabotropic glutamate receptor 1 (GRM1) as an oncogene and a potential therapeutic target for melanoma. More than 60% of human melanoma expresses GRM1, while normal melanocytes do not. In a Phase-0 trial of riluzole (an oral inhibitor of GRM1) in patients with advanced melanoma we showed suppression of the PI3K/AKT and MAPK pathways in melanoma specimens in 34% of the patients.

Our group found that enhanced expression of GRM1 in a subclone of a melanoma cell line (UACC903) that normally expresses low levels of GRM1 stimulated angiogenesis via activation of the AKT-mTOR-HIF1-IL8, VEGF signaling pathway. Increasing GRM1 expression promoted membrane blebbing (a phenomenon that appears to lead to microvesicle formation) and riluzole treatment inhibited this effect. Suppression of GRM1 expression using an inducible siRNA construct inhibits the blebbing phenomena and microvesicle formation. Therefore, we hypothesize that GRM1 expression promotes microvesicle formation that may be involved in stimulating angiogenesis and tumor progression. Through electron-microscope and flow cytometry analysis, we have confirmed that increased GRM1 expression enhanced microvesicle secretion into the medium in cell culture and that knocking down GRM1 expression significantly reduced the quantity of microvesicle secretion. Furthermore, intra-tumor injection of collected microvesicles into two different melanoma xenograft tumors (UACC903 and C8161) demonstrated that the microvesicles formed from high GRM1 expressing cells promoted tumor growth and angiogenesis. We also showed that microvesicles from high GRM1 expressing cells increased endothelial cell proliferation exhibited measured using a BrdU incorporation assay.

Our preliminary data demonstrate that GRM1 expression promotes microvesicle formation and that these microvesicles are associated with angiogenesis. Research on the molecular events associated with the phenomenon is ongoing.

Citation Format: Jasmine J. Koo, Yu Wen, Jiadong Li, Suzie Chen, James Goydos. GRM1 over-expression in melanoma cells promotes microvesicle formation which functions in stimulating angiogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3889. doi:10.1158/1538-7445.AM2013-3889

MDM4 is a key therapeutic target in cutaneous melanoma

The inactivation of the p53 tumor suppressor pathway, which often occurs through mutations in TP53 (encoding tumor protein 53) is a common step in human cancer. However, in melanoma-a highly chemotherapy-resistant disease-TP53 mutations are rare, raising the possibility that this cancer uses alternative ways to overcome p53-mediated tumor suppression. Here we show that Mdm4 p53 binding protein homolog (MDM4), a negative regulator of p53, is upregulated in a substantial proportion (∼65%) of stage I-IV human melanomas and that melanocyte-specific Mdm4 overexpression enhanced tumorigenesis in a mouse model of melanoma induced by the oncogene Nras. MDM4 promotes the survival of human metastatic melanoma by antagonizing p53 proapoptotic function. Notably, inhibition of the MDM4-p53 interaction restored p53 function in melanoma cells, resulting in increased sensitivity to cytotoxic chemotherapy and to inhibitors of the BRAF (V600E) oncogene. Our results identify MDM4 as a key determinant of impaired p53 function in human melanoma and designate MDM4 as a promising target for antimelanoma combination therapy.

Abstract A28: Apoptosis induction with the MEK inhibitor AZD6244 and BH3 mimetic ABT-737 in melanoma

Over sixty percent of patients with melanoma have the activating B-RAFV600E mutation leading to increased activation of the mitogen activated protein kinase (MAPK) pathway. The downstream effects of MAPK pathway activation are increased proliferation, invasiveness, and survival through the regulation of down-stream targets such as the pro-apoptotic protein BIM. Prior studies have shown that inhibiting MAPK kinase (MEK), downstream of constitutively active B-RAF, can up-regulate BIM, leading to increased apoptosis in melanoma cell lines. However, single agent MEK inhibition has had limited effectiveness in the clinical setting for late-stage melanoma patients, likely due to an inadequate induction of apoptosis. We hypothesized that combining the clinically relevant MEK inhibitor, AZD6244 (ARRY142886) with a BCL-2 inhibitor, ABT-737, would lead to increased apoptosis over single agent therapies in melanoma cells via BIM activation and pan-BCL-2 inhibition. We compared single treatments of AZD6244 and ABT737 to the combination of these agents in a panel of melanoma tumor cell lines chosen by mutational status in both a monolayer system and an anchorage independent system. The combination of AZD6244 and ABT-737 had a synergistic effect on decreasing cell viability and increasing apoptosis compared to single agent treatments regardless of B-RAF mutational status. Western blotting revealed dramatic increases in cleaved caspase 3 and PARP with combinational treatment compared to single agent therapy. These early pre-clinical experiments indicate that AZD6244 combined with ABT-737 may be an effective combination therapy for patients with late-stage melanoma. Currently, we have plans to conduct in vivo studies to translate these results into the clinic.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A28.

Abstract 315: Human metabotropic glutamate receptor 1 (GRM1) may be essential for melanoma cell survival and activation of angiogenic signaling

Our group has demonstrated that ectopic expression of murine GRM1 results in transformation of mouse melanocyte cells, and we have found that human GRM1 is ectopically expressed in more than 60% human melanomas. We recently reported on the results of a Phase 0 preclinical trial targeting GRM1 signaling using a glutamate release-inhibitor, Riluzole. We demonstrated inhibition of signaling through the PI3K/AKT and MAPK pathways and a reduction in tumor size in 40% of patients treated. To better examine the mechanisms of Riluzole treatment effect and to begin to understand the function of GRM1 signal transduction in melanoma, cell lines that over-express GRM1 (UACC903 G2 and UACC903G4) were constructed using the native, low GRM1-expressing, UACC903 human melanoma cell line. We found that UACC903G2 and G4 cells produce elevated levels of GRM1 and were much more sensitive to treatment with 25uM Riluzole than the vector transfected control cell line UACC903V1. We also found that UACC903G2 and G4 cells produced much larger tumors in nude mice than the vector control cells. Tumors formed by UACC903G2 and G4 xenografts also do not demonstrate areas of hemorrhage necrosis as is found in UACC903V1 xenografts, and there are significantly more tumor blood vessels in the GRM1-overexpressing xenograft tumors. To confirm the angiogenic effect of GRM1 over-expression in UACC903 cells, an endothelial cell migration assay was performed. We found that culturing UACC903G2 and G4 cells in serum-free basic medium stimulated HMVECnd endothelial cell migration, an effect not seen with the vector control UACC903V1 cells. We next examined whether increased GRM1 expression in UACC903 cells resulted in the release of angiogenesis factor(s) from these cells. An angiogenesis antibody array (from Affymetrix) experiment was performed and we found that the conditioned medium from UACC903G2 and G4 cells had significantly higher levels of IL8 and VEGF (angiogenesis promoters), but decreased level of TIMP-2 and TIMP-1 (angiogenesis inhibitors) as compared to the conditioned medium from the UACC903V1 vector control cells. We conclude that over-expression of human GRM1 promotes proliferation, activates angiogenesis signaling, and renders cells more susceptible to the inhibitory effects of the glutamate-release inhibitor Riluzole. Further experiments examining the molecular mechanism of GRM1 in cell survival and angiogenesis are need to better understand the mechanisms at work.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 315. doi:10.1158/1538-7445.AM2011-315

The regulation of miRNA-211 expression and its role in melanoma cell invasiveness

The immediate molecular mechanisms behind invasive melanoma are poorly understood. Recent studies implicate microRNAs (miRNAs) as important agents in melanoma and other cancers. To investigate the role of miRNAs in melanoma, we subjected human melanoma cell lines to miRNA expression profiling, and report a range of variations in several miRNAs. Specifically, compared with expression levels in melanocytes, levels of miR-211 were consistently reduced in all eight non-pigmented melanoma cell lines we examined; they were also reduced in 21 out of 30 distinct melanoma samples from patients, classified as primary in situ, regional metastatic, distant metastatic, and nodal metastatic. The levels of several predicted target mRNAs of miR-211 were reduced in melanoma cell lines that ectopically expressed miR-211. In vivo target cleavage assays confirmed one such target mRNA encoded by KCNMA1. Mutating the miR-211 binding site seed sequences at the KCNMA1 3'-UTR abolished target cleavage. KCNMA1 mRNA and protein expression levels varied inversely with miR-211 levels. Two different melanoma cell lines ectopically expressing miR-211 exhibited significant growth inhibition and reduced invasiveness compared with the respective parental melanoma cell lines. An shRNA against KCNMA1 mRNA also demonstrated similar effects on melanoma cells. miR-211 is encoded within the sixth intron of TRPM1, a candidate suppressor of melanoma metastasis. The transcription factor MITF, important for melanocyte development and function, is needed for high TRPM1 expression. MITF is also needed for miR-211 expression, suggesting that the tumor-suppressor activities of MITF and/or TRPM1 may at least partially be due to miR-211's negative post transcriptional effects on the KCNMA1 transcript. Given previous reports of high KCNMA1 levels in metastasizing melanoma, prostate cancer and glioma, our findings that miR-211 is a direct posttranscriptional regulator of KCNMA1 expression as well as the dependence of this miRNA's expression on MITF activity, establishes miR-211 as an important regulatory agent in human melanoma.

Abstract 3299: Expression of exchange protein activated by cAMP (Epac) in melanoma and its role in cell migration

Background: We previously reported that Epac, a guanine nucleotide exchange factor directly activated by cAMP, increases cell migration in melanoma. Epac1, a major isoform of Epac, increases melanoma cell migration via production of heparan sulfate (HS), a major extracellular glycosaminoglycan. However, the frequency and level of expression of Epac1 in human melanoma tissues is largely unknown. Furthermore, it is still unclear if Epac1's role in heparan sulfate production and cell migration is universal among different melanomas. Methods: Epac1 mRNA expression was examined in melanoma cell lines at different melanoma progression stages, and in human fresh frozen tissue of four different stages, i.e., primary melanoma, regional dermal metastatic melanoma, lymph node metastatic melanoma and distant metastatic melanoma. Also, melanoma and melanocyte cell lines were subjected to cell migration assay with the Boyden chambers. Epac1 expression was ablated by shRNA to examine involvement of Epac1 in cell migration and HS production. Results: There was a tendency toward higher Epac1 mRNA expression with progression of melanoma stage, i.e., Epac1 mRNA was higher in metastatic melanoma (MM) and vertical growth phase (VGP) melanoma cell lines than in a melanocyte cell line. In human melanoma samples, Epac1 mRNA expression was higher in regional dermal (p=0.04, n=10) and lymph node (p=0.03, n=10) metastatic melanoma than in primary melanoma, but not in distant metastatic melanoma; however, 4 out of 10 distant metastatic melanoma showed more than 2-fold increase of Epac1 mRNA expression compared to primary melanoma. These data suggest that Epac1 expression correlates with melanoma stage. When cells were incubated with 8-pMeOPT-2′-O-Me-cAMP, an Epac-specific agonist, cell migration was increased in melanoma cell lines but not in melanocytes. Heparatinase, a heparan sulfate-degrading enzyme, inhibited 8-pMeOPT-2′-O-Me-cAMP-induced cell migration in 2 metastatic melanoma cell lines, SK-Mel-2 (64.6±7.5 vs. 35.2±5.5 cells/field, p<0.05, n=4) and SK-Mel-187 (70.2±6.6 vs 43.2±9 cells/field, p<0.05, n=4) in parallel with decreased HS production. When Epac1 expression was ablated by shRNA, cell migration was decreased (SK-Mel-2, 92.6±4 vs. 49.3±1 cells/field, p<0.05, n=4; SK-Mel-187, 77.9±9 vs. 31.6±5 cells/field, p<0.05, n=4) in parallel with decreased HS production (SK-Mel-2,13 vs. 6.8±0.6 μg/ml, p<0.05, n=4; SK-Mel-187, 46.6±6.2 vs. 26.1±8.2 μg/ml, p<0.05, n=4). These data suggest that Epac1 expression plays a major role in melanoma cell migration through heparan sulfate production, and Epac's role is universal in metastatic melanoma cells.

Conclusion: Epac1 expression increases with the progression of melanoma. Epac1 mediates melanoma cell migration via HS production in different melanoma cell lines. These data suggest that Epac1 could be a target for treating patients with melanoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3299.

Abstract C81: Preclinical evaluation of riluzole for the treatment of mantle cell lymphoma

Purpose: Emerging evidence suggests a role for glutamate and its receptors in the pathogenesis of several forms of cancer. Investigators from our institution have recently shown that the metabotropic glutamate receptor 1 plays a significant role in the pathogenesis of melanoma and that inhibition of this pathway by the glutamate release inhibitor Riluzole results in suppression of cell growth. In this study we test the hypothesis that inhibition of metabotropic glutamate receptors by Riluzole in mantle cell lymphoma cells will result in a reduction of cell proliferation/survival.

Experimental Design: Mantle cell lymphoma (MCL) cell lines (MINO, JEKO and Rec-1) were treated with several concentration of the glutamate release inhibitor Riluzole. Samples were collected after 24, 48 and 72 hours of treatment and evaluated for cell viability and cell number by trypan blue exclusion, and cell proliferation and cell cycle analysis by flow cytometry. Apoptosis was evaluated by PARP cleavage and staining for Annexin V.

Results: All three MCL cell lines treated with Riluzole demonstrated a significant decrease in cell number and cell viability with an IC50=25uM. MCL cells treated with Riluzole showed a block in S and G2/M of the cell cycle followed by apoptosis. Apoptosis was confirmed by annexin V expression and by PARP cleavage.

Conclusions: Our date demonstrates that glutamate blockade with Riluzole results in the inhibition of mantle cell lymphoma proliferation, cell viability and the induction of cell cycle arrest at S and G2/M phases of the cell cycle. In addition, we show that the loss of cell viability is due to the activation of the apoptotic pathway. These preliminary findings suggest that expression of metabotropic glutamate receptors may be important in the pathogenesis and that targeting this pathway may provide a novel and effective therapy.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C81.

c-Jun regulates phosphoinositide-dependent kinase 1 transcription: implication for Akt and protein kinase C activities and melanoma tumorigenesis

Mutations in N-RAS and B-RAF, which commonly occur in melanomas, result in constitutive activation of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated protein kinase (ERK) signaling. Active ERK increases expression and activity of the c-Jun transcription factor, linking ERK and Jun N-terminal kinase (JNK) cascades. Here, we show that c-Jun regulates transcription of phosphoinositide-dependent kinase 1 (PDK1) with a concomitant impact on Akt and protein kinase C (PKC) activity and related substrates. Inhibition of c-Jun reduces PDK1 expression and attenuates Akt and PKC activity, which can be restored by exogenous PDK1. c-Jun regulation of PDK1 in melanoma contributes to growth rate and the ability to form tumors in mice. Correspondingly, increased levels of c-Jun in melanoma cell lines coincide with up-regulation of PDK1 and phosphorylation of PKC and Akt. The identification of c-Jun as a transcriptional regulator of PDK1 expression highlights key mechanisms underlying c-Jun oncogenic activity, and provides new insight into the nature of up-regulated Akt and PKC in melanoma.

Effects of riluzole (RZ) and ionizing radiation (IR) in metabotropic glutamate receptor-1 (GRM1) positive human melanoma

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Background: Melanoma has long been known to be relatively radio-resistant. GRM1 is a metabotropic glutamate receptor that has been detected in human melanoma cell lines and biopsies. Riluzole (RZ), a glutamate release inhibitor, has been shown to arrest GRM1 positive human melanoma cells in G2/M and sub-G1 phases of the cell cycle. The purpose of this study was to determine if RZ enhances the lethal effects of IR in human melanoma. Methods: ATP luminescence assays were performed. Clonogenic assays were performed and cell survival curves generated. Cell cycle analysis was performed utilizing flow cytometry. Western blot analysis was performed utilizing cleaved PARP and caspase-3 antibodies as markers of apoptosis. Results: Luminescence assays revealed 25uM Riluzole to be the necessary concentration for clonogenic assays. At 2Gy, there was a 48% reduction (p≤0.05) in cell survival in RZ-treated cells. At 4 Gy, there was a 19% reduction (p≤0.05) in cell survival in RZ-treated cells. No differences were seen at 6 and 8 Gy. Cell cycle analysis showed that the combination of IR and RZ was superior to IR alone in increasing the number of cells in sub-G1, which represents apoptotic death. Western blot analysis showed that the combination of IR and RZ showed yielded increased cleaved PARP and caspase-3 activity when compared to IR alone. Conclusions: Riluzole is a FDA approved drug that has long been used in ALS. It is relatively non-toxic and crosses the blood brain barrier. Our data shows that Riluzole in combination with radiation eliminates the radio-resistant shoulder of the C8161 survival curve. RZ and IR, as combination therapy are more lethal than IR or RZ alone in human melanoma, as demonstrated by flow cytometry and WB analysis. This data has promising implications for melanoma patients with brain metastases.

No significant financial relationships to disclose.

Extracellular cAMP-dependent protein kinase (ECPKA) in melanoma

Melanoma is one of the fastest rising malignancies in the United States. When detected early, primary melanomas are curable through surgery. However, despite significant improvements in diagnosis and surgical, local and systemic therapy, mortality rate in metastatic melanoma remains high. Furthermore, genetic alterations associated with the development and stepwise progression of melanoma, are still unclear. Previous reports show that the catalytic kinase subunit of the cAMP-dependent protein kinase is secreted by tumor cells and can be detected in the serum of cancer patients. We examine in this report the clinical significance of this secreted C subunit kinase termed extracellular protein kinase (ECPKA) in melanoma patients. Our results showed the presence of ECPKA activity in the serum of melanoma patients and correlate with the appearance and size of the tumor. Most importantly, surgical removal of melanoma causes a precipitous decrease in ECPKA activity in the sera of patients, suggesting that ECPKA may be a novel predictive marker in melanoma.

Melanoma mouse model implicates metabotropic glutamate signaling in melanocytic neoplasia

To gain insight into melanoma pathogenesis, we characterized an insertional mouse mutant, TG3, that is predisposed to develop multiple melanomas. Physical mapping identified multiple tandem insertions of the transgene into intron 3 of Grm1 (encoding metabotropic glutamate receptor 1) with concomitant deletion of 70 kb of intronic sequence. To assess whether this insertional mutagenesis event results in alteration of transcriptional regulation, we analyzed Grm1 and two flanking genes for aberrant expression in melanomas from TG3 mice. We observed aberrant expression of only Grm1. Although we did not detect its expression in normal mouse melanocytes, Grm1 was ectopically expressed in the melanomas from TG3 mice. To confirm the involvement of Grm1 in melanocytic neoplasia, we created an additional transgenic line with Grm1 expression driven by the dopachrome tautomerase promoter. Similar to the original TG3, the Tg(Grm1)EPv line was susceptible to melanoma. In contrast to human melanoma, these transgenic mice had a generalized hyperproliferation of melanocytes with limited transformation to fully malignant metastasis. We detected expression of GRM1 in a number of human melanoma biopsies and cell lines but not in benign nevi and melanocytes. This study provides compelling evidence for the importance of metabotropic glutamate signaling in melanocytic neoplasia.

Lymphatic mapping and intraoperative lymphoscintigraphy for identifying the sentinel node in penile tumors

Lymph node mapping has become an integral part of the management of melanoma and breast cancer with regard to both staging and treatment. We report our technique for lymphatic mapping and intraoperative lymphoscintigraphy applied to a patient with penile melanoma. This technique may improve the sensitivity of identifying the sentinel lymph node in patients with malignant penile lesions.

Unrecognized pertussis infection in adolescents

Little information is available regarding the level of immunity to Bordetella pertussis among adolescents. We measured serum antibodies in 156 healthy adolescents to the following pertussis antigens: pertussis toxin, filamentous hemagglutinin, and 69-kd outer membrane protein. In an attempt to identify intercurrent pertussis infections, we also obtained a total of 43 repeated samples during the following 5 years. Using a 50% or greater rise in IgG enzyme-linked immunosorbent assay titers to define seroconversion, we found an annual incidence of 6.1%; by alternative definitions of seropositivity, the predicted annual incidence of infection ranged from 1.2% to 8.2%. These data suggest that infection with B pertussis is common in the adolescent population.