An erythematous facial rash

Two months of treatment with doxycycline provided no improvement. A biopsy of the patient's cheek led to a proper diagnosis.

Merkel Cell Carcinoma, Version 1.2018, NCCN Clinical Practice Guidelines in Oncology

This selection from the NCCN Guidelines for Merkel Cell Carcinoma (MCC) focuses on areas impacted by recently emerging data, including sections describing MCC risk factors, diagnosis, workup, follow-up, and management of advanced disease with radiation and systemic therapy. Included in these sections are discussion of the new recommendations for use of Merkel cell polyomavirus as a biomarker and new recommendations for use of checkpoint immunotherapies to treat metastatic or unresectable disease. The next update of the complete version of the NCCN Guidelines for MCC will include more detailed information about elements of pathology and addresses additional aspects of management of MCC, including surgical management of the primary tumor and draining nodal basin, radiation therapy as primary treatment, and management of recurrence.

Abstract LB-085: PTPN11 plays oncogenic roles and is a therapeutic target for BRAF wild-type melanomas

Melanoma is one of the most highly mutated cancer types. To identify functional drivers of melanoma, we searched for cross-species conserved mutations utilizing a mouse melanoma model driven by loss of PTEN and CDKN2A, and identified mutations in Kras, Erbb3, and Ptpn11. PTPN11 encodes the SHP2 protein tyrosine phosphatase (PTP) that activates the RAS/RAF/MAPK pathway. Although PTPN11 is an oncogene in leukemia, lung, and breast cancers, its roles in melanoma are not clear. In this study, we found that PTPN11 is frequently activated in human melanoma specimens and cell lines and is required for full RAS/RAF/MAPK signaling activation in BRAF wild-type (either NRAS mutant or wild-type) melanoma cells. PTPN11 played oncogenic roles in melanoma by driving anchorage-independent colony formation and tumor growth. In Pten and Cdkn2a null mice, tet-inducible and melanocyte-specific PTPN11 E76K expression significantly enhanced melanoma tumorigenesis. Melanoma cells derived from this mouse model showed doxycycline-dependent tumor growth in nude mice. Silencing PTPN11 E76K expression by doxycycline withdrawal caused regression of established tumors by induction of apoptosis and senescence, and suppression of proliferation. Moreover, the PTPN11 inhibitor (SHP099) also caused regression of NRAS Q61K-mutant melanoma. Using a quantitative tyrosine phosphoproteomics approach, we identified GSK3α/β as one of the key substrates that were differentially tyrosine-phosphorylated in these experiments modulating PTPN11. This study identifies PTPN11 as an oncogenic driver and a novel and actionable therapeutic target for BRAF wild-type melanoma.

Citation Format: Kristen Hill, Jane Messina, Jie Wu, Charles E. Chalfant, Minjung Kim. PTPN11 plays oncogenic roles and is a therapeutic target for BRAF wild-type melanomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-085.

Abstract 3800: HDAC8 regulates plasticity and escape from therapy in BRAF mutant melanoma

Melanoma cells are highly plastic and have the ability to switch to a dedifferentiated, invasive phenotype in response to multiple stimuli. We here show that exposure to melanoma cell lines and patient specimens to multiple stresses including BRAF-MEK inhibitor therapy, hypoxia and UV-irradiation leads to an increase in HDAC8 expression/activity, and in turn, the adoption of a drug-resistant, invasive phenotype. Systems level analyses using mass spectrometry-based phosphoproteomics and RNA-Seq demonstrated HDAC8 to be involved in pathways that regulated cell cycle entry, ribosome function, RNA binding, regulation of the cytoskeleton and MAPK pathway signaling. Introduction of HDAC8 into drug-naïve melanoma cells conveyed resistance in vitro and in in vivo xenograft models. The HDAC8-mediated BRAF inhibitor resistance was mediated through upstream receptor tyrosine kinase (RTK) activation, Ras/CRAF/MEK/ERK signaling and the suppression of apoptosis through increased stabilization of Mcl-1 and the inhibition of pro-apoptotic BIM. Among the multiple RTKs increased by HDAC8, EGFR emerged as a direct transcriptional target, and it was found that EGFR inhibition could overcome HDAC8-mediated tolerance to BRAF inhibition. Although it is known that HDACs primarily function at the histone level, they can also regulate signaling through the modulation of cytoplasmic protein acteylation. In line with this, we observed that HDAC8 introduction decreased the acetylation of c-JUN, leading to an increase in its transcriptional activity and the enrichment for an AP-1 gene signature. Mutation of putative acetylation sites in c-JUN (K268R, K271R, K273R) reduced the transcriptional activation of c-JUN in melanoma cells and conveyed resistance to BRAF inhibition through increased MAPK pathway activity. In vivo xenograft studies confirmed the key role of HDAC8 in therapeutic adaptation, with either a pan-HDAC inhibitor (panobinostat) or an HDAC8 inhibitor (PCI-34051) enhancing the durability of response to BRAF inhibitor therapy. We have thus identified HDAC8 as a key driver of phenotype switching in melanoma that regulates the responses to multiple cellular stresses and conveys resistance to BRAF inhibition. Our studies demonstrate that isoform-specific HDAC8 inhibitors could be an excellent strategy to limit the adaptation of melanoma cells to multiple stresses and therapeutic interventions, including the BRAF-MEK inhibitor combination.

Citation Format: Michael Emmons, Fernanda Flores, John Koomen, Edward Seto, Jane Messina, Eric Lau, Jonathan Licht, Keiran Smalley. HDAC8 regulates plasticity and escape from therapy in BRAF mutant melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3800.

Testicular tissue cryopreservation: 8 years of experience from a coordinated network of academic centers

STUDY QUESTION

Is it feasible to disseminate testicular tissue cryopreservation with a standardized protocol through a coordinated network of centers and provide centralized processing/freezing for centers that do not have those capabilities?

SUMMARY ANSWER

Centralized processing and freezing of testicular tissue from multiple sites is feasible and accelerates recruitment, providing the statistical power to make inferences that may inform fertility preservation practice.

WHAT IS KNOWN ALREADY

Several centers in the USA and abroad are preserving testicular biopsies for patients who cannot preserve sperm in anticipation that cell- or tissue-based therapies can be used in the future to generate sperm and offspring.

STUDY DESIGN, SIZE, DURATION

Testicular tissue samples from 189 patients were cryopreserved between January 2011 and November 2018. Medical diagnosis, previous chemotherapy exposure, tissue weight, and presence of germ cells were recorded.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human testicular tissue samples were obtained from patients undergoing treatments likely to cause infertility. Twenty five percent of the patient's tissue was donated to research and 75% was stored for patient's future use. The tissue was weighed, and research tissue was fixed for histological analysis with Periodic acid-Schiff hematoxylin staining and/or immunofluorescence staining for DEAD-box helicase 4, and/or undifferentiated embryonic cell transcription factor 1.

MAIN RESULTS AND THE ROLE OF CHANCE

The average age of fertility preservation patients was 7.9 (SD = 5) years and ranged from 5 months to 34 years. The average amount of tissue collected was 411.3 (SD = 837.3) mg and ranged from 14.4 mg-6880.2 mg. Malignancies (n = 118) were the most common indication for testicular tissue freezing, followed by blood disorders (n = 45) and other conditions (n = 26). Thirty nine percent (n = 74) of patients had initiated their chemotherapy prior to undergoing testicular biopsy. Of the 189 patients recruited to date, 137 have been analyzed for the presence of germ cells and germ cells were confirmed in 132.

LIMITATIONS, REASONS FOR CAUTION

This is a descriptive study of testicular tissues obtained from patients who were at risk of infertility. The function of spermatogonia in those biopsies could not be tested by transplantation due limited sample size.

WIDER IMPLICATIONS OF THE FINDINGS

Patients and/or guardians are willing to pursue an experimental fertility preservation procedure when no alternatives are available. Our coordinated network of centers found that many patients request fertility preservation after initiating gonadotoxic therapies. This study demonstrates that undifferentiated stem and progenitor spermatogonia may be recovered from the testicular tissues of patients who are in the early stages of their treatment and have not yet received an ablative dose of therapy. The function of those spermatogonia was not tested.

STUDY FUNDING/COMPETING INTEREST(S)

Support for the research was from the Eunice Kennedy Shriver National Institute for Child Health and Human Development grants HD061289 and HD092084, the Scaife Foundation, the Richard King Mellon Foundation, the Departments of Ob/Gyn & Reproductive Sciences and Urology of the University of Pittsburgh Medical Center, United States-Israel Binational Science Foundation (BSF), and the Kahn Foundation. The authors declare that they do not have competing financial interests.

Phase I study of vemurafenib (VEM) and cobimetinib (COB) with heat shock protein 90 (HSP90) inhibitor XL888 in advanced BRAFV600 mutant melanoma

9553

Background: Resistance to BRAF+MEK inhibitors(i) in BRAF-mutant melanoma is common. Multiple resistance mechanisms involve HSP90 clients, and a phase 1 study of VEM with XL888 showed PFS rates similar to the combination of BRAF+MEKi (Eroglu, CCR, 2018). Methods: Combination of VEM (960 mg PO BID) and COB (60 mg QD for 21 of 28 days) with escalating dose cohorts of XL888 (30, 45, 60 or 90 mg PO twice weekly) was investigated in a phase 1 study of advanced melanoma, with a modified Ji dose escalation design. Dose-limiting toxicity (DLT) was defined as related grade ≥3 adverse event or inability to deliver 75% of XL888 in first 4 weeks. Results: 25 pts (9 female, median age 62, 15 with M1C disease, 6 with prior anti-PD-1 therapy) were enrolled. After 2 DLTs (rash and acute kidney injury) in first cohort, a lower dose of VEM 720 mg BID and COB 40 mg, with the same XL888 cohorts was investigated. 3 DLTs (rash) in 12 pts were observed in the XL888 60 mg cohort, which was determined as the maximum tolerated dose. Most common grade 3 toxicities included diarrhea (8), hypertension (6), rash (5), alkaline phosphate/GGT elevation (4). 11 patients required dose reductions of VEM and/or COB. Objective responses (PR/CR) were observed in 18 of 25 pts (72%; 95% CI: 51-88%). Median PFS was 8.1 months (4.7 – NA); median overall survival was not reached, with 1-year OS of 71% (45-86%). Single cell RNA-Seq (10X genomics) was performed on baseline and on-treatment tumor biopsies; 8 days of treatment was associated with an increase in immune cell influx (CD4+ and CD8+) and a decrease in number of melanoma cells. At day 8, one patient (now without progression for nearly 2 years) had no tumor cells remaining with only immune cells and stromal fibroblasts left. Further analyses will be presented. Serial plasma BRAF circulating tumor (ct)DNA levels were obtained, with decrease in ctDNA levels corresponding with response and 83% of patients with disease progression showing an elevation in ctDNA from baseline. Conclusions: VEM/COB plus XL888 had significant toxicity, requiring dose-reductions that may have contributed to the low PFS rate despite high response rate. Caution must be used in combination of BRAF+MEKi with other agents. Clinical trial information: NCT02721459.

Association Between Recent Ultraviolet Radiation Exposure and Cutaneous Beta Human Papillomavirus Infection

Keratinocyte carcinoma (KC), comprised of squamous cell carcinoma and basal cell carcinoma, is the most common cancer in the United States. The effects of ultraviolet radiation (UVR), an established risk factor for KC, on cutaneous human papillomavirus (HPV) infection, a suggested risk factor currently under investigation, are not well established. We assessed cross sectional associations between UVR exposure and cutaneous beta HPV infection, using data obtained from the Viruses in Skin Cancer Study (VIRUSCAN), a prospective cohort study conducted at the Moffitt Cancer Center and the University of South Florida. Methods: Eyebrow hairs (EBH), skin swabs (SSW) and spectrophotometer-based measurements of recent UVR exposure were obtained from 1,179 skin cancer screening patients enrolled in the VIRUSCAN study. Viral DNA was measured using a multiplex PCR assay for 46 beta HPV types in both skin swab samples and eyebrow hair follicles. Logistic regression was used to examine the association between UVR exposure and cutaneous HPV infection in individual sites. Ordinal logistic regression was used to examine the effect of UVR exposure on the trend of having the same HPV infection across two sites, adjusted for age and sex. Results: Patients with higher UVR exposure were more likely to test positive for beta HPV 19, 47, 100 and 145 in EBH. In SSW, beta 38, 49, 76, 100, 124 were positively associated with UVR exposure. When considering viral infection across two sites, we found UVR exposure to be significantly associated with the odds of having infection in both EBH and SSW for beta HPV 19 (OR = 1.12, 95% CI: 1.03–1.23, p-trend = 0.04), 38 (OR = 1.08, 95% CI: 1.04–1.13, p-trend < 0.01), 76 (OR = 1.06, 95% CI: 1.00–1.12, p-trend = 0.01), and 100 (OR = 1.10, 95% CI: 1.04–1.17, p-trend = 0.01). Conclusions: UVR exposure is positively associated with beta cutaneous HPV at the type level, in both individual sites and across skin swab and eyebrow hair. Future research is needed to better understand the biological mechanisms mediating the associations between UVR and cutaneous HPV infection.

Abstract 2387: The oncogenic role and therapeutic potential of PTPN11 in melanoma

The RAS/RAF/MEK/ERK signaling pathway, which is intricately regulated by multiple proteins including PTPN11 (Tyrosine-Protein Phosphatase Non-Receptor Type 11, encoding SHP2), is frequently activated in melanoma. Although implicated as an oncogene in multiple cancer types, the oncogenic role of PTPN11 has not been established in melanoma. Recently, we preformed whole exome sequencing on tumors generated by a mouse model driven by loss of PTEN and CDKN2A (INK4A/ARF) and identified several conserved cross-species orthologous mutations in Kras, Erbb3, and Ptpn11. In this study, we addressed the functional roles of PTPN11 in melanoma tumorigenesis and tumor maintenance; as well as, PTPN11's effect on the RAS/RAF/MEK/ERK signaling pathway and its activation status in human melanoma.

PTPN11 can be activated by receptor tyrosine kinases (RTKs) or by point mutations. We observed activating phosphorylation on Tyr 542 of PTPN11 in 40% (n=15/38) of melanoma specimens and the majority of human melanoma cell lines (n=14), supporting frequent activation of PTPN11 in human melanoma even though the mutation rate is low (1~3%). PTPN11 knock-down suppressed ERK activation in NRAS mutant and BRAF/NRAS wild-type melanoma cells, but not in BRAF mutant cells. Moreover, we have shown that expression of active PTPN11E76K mutant drives soft-agar colony growth in vitro, tumor growth in nude mice, RAS/RAF/MEK/ERK activation, and resistance to MEK inhibition. Alternatively, knock-down of Ptpn11 reduces colony growth and ERK activation. We generated a tet-inducible, melanocyte-specific, PTPN11E76K transgenic mouse model in a PTEN and CDKN2A null background and observed melanoma formation. Implantation of melanoma cells derived from this model showed doxycycline dependent tumor growth in nude mice. Doxycycline withdrawal and subsequent extinction of PTPN11E76K caused regression of established tumors, supporting the tumor maintenance role of PTPN11. Subsequently, tumor tissue from this model underwent phosphor-tyrosine proteomic analysis to identify downstream effectors of PTPN11's protein tyrosine phosphatase activity. The proteins identified in this analysis are currently being confirmed. These data support the oncogenic roles of PTPN11 in melanoma by regulating RAS/RAF/MAPK pathway activation and the value of PTPN11 as a novel and actionable therapeutic target.

Citation Format: Kristen Suzanne Hill, Evan Roberts, Ellen Marin, Xue Wang, Jamie Teer, Jane Messina, Jerry Wu, Minjung Kim. The oncogenic role and therapeutic potential of PTPN11 in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2387.

Abstract 3025: Ligand-independent EphA2 signaling drives an amoeboid phenotype that promotes melanoma brain metastasis development

The majority of melanoma patients treated with BRAF inhibitors (BRAFi) ultimately develop resistance and fail on therapy. It has previously been shown that BRAFi resistance is highly correlated with the adoption of a strongly invasive phenotype through ligand-independent EphA2 signaling.

In this study, we used comprehensive mass spectrometry-based proteomic approaches to delineate the global signaling changes associated with the aggressive phenotype driven by ligand-independent EphA2 signaling. Preliminary data have identified new signaling adaptations associated with a mesenchymal-to-amoeboid transition (MAT) phenotype, which was confirmed in 3D collagen cultures. Functional experiments demonstrated that the amoeboid phenotype promoted cell migration and invasion, which was mediated through the interaction of EphA2 and CDC42. These findings were confirmed by expressing a constitutively activated form of CDC42. BRAFi resistant cell lines also exhibited the MAT phenotype and were more invasive compared to their treatment-naïve counterparts, in line with their dependence upon ligand-independent EphA2 signaling following BRAFi selection pressure.

To further demonstrate the metastatic potential of these amoeboid cells driven by ligand-independent EpHA2 signaling in vivo, we performed intracardiac injections in mice with cell lines expressing either EpHA2 S897A (inactive) or S897E (constitutively active phosphomimetic). Interestingly, we found a preferential homing of EphA2 S897E cells to the brain, but no difference in metastasis to other organs including the lung and liver. An analysis of brain metastasis specimens from patients failing BRAF and BRAF/MEK inhibitor therapy showed strong staining for the amoeboid phenotype marker EphA2.

To investigate whether the amoeboid phenotype may confer a survival advantage in circulation, we carried out shear stress assays. These experiments demonstrated that the amoeboid phenotype driven by ligand-independent EphA2 signaling promoted the survival of melanoma cells under shear stress. Cell attachment assays, trans-endothelial invasion assays and vascular permeability assays show that these cells are better suited to attach to and permeate an endothelial monolayer. We further show that inhibiting PI3K reversed the amoeboid phenotype and limited the EphA2-driven invasive capacity.

In summary, we show for the first time that BRAFi resistance is associated with the adoption of an MAT phenotype that increases the metastatic seeding of melanoma cells to the brain, which can be reversed through inhibition of PI3K signaling.

Citation Format: Chao Zhang, Inna Smalley, Ritin Sharma, Michael Emmons, Jane Messina, John Koomen, Keiran Smalley. Ligand-independent EphA2 signaling drives an amoeboid phenotype that promotes melanoma brain metastasis development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3025.

Abstract 4364: R-Ras activation cooperates with BRAF mutation in melanoma tumorigenesis

The Ras family of small GTP binding proteins are tightly regulated through a complex network of proteins. In melanoma the Ras signaling pathway is frequently activated by mutations in NRAS (20%), KRAS (2%) and HRAS (1%); alternatively, Ras can also be activated by the inactivation of Ras GTPase activating proteins (RasGAPs) such as NF1, RASA1, and RASA2. Recently, we observed that inactivation of RASA1 (RAS p21 protein activator 1, also called p120RasGAP) suppressed melanoma via its RasGAP activity toward the R-Ras (related RAS viral (r-ras) oncogene homolog) isoform and that R-Ras was required to promote anchorage-independent growth driven by RASA1 inactivation. Moreover, a low level of RASA1 mRNA expression is associated with decreased overall survival in melanoma patients with BRAF mutations. Based on these observations, we hypothesized that, although not mutated, R-Ras is activated in melanoma by inactivation of RasGAPs and that BRAF activation cooperates with this RasGAP/R-Ras pathway activation in melanoma tumorigenesis.

In this study, we addressed the importance of R-Ras, a previously less appreciated member of the Ras small GTPases family, in melanoma tumorigenesis. We observed frequent activation of R-Ras in BRAF mutant human melanoma cell lines and human melanoma specimens. In addition, RNAi-mediated knockdown of R-Ras suppressed anchorage-independent colony growth and tumor growth. Of the 3 major RAS effector pathways, specifically MEK/ERK, AKT and Ral-A, reduced R-Ras expression suppressed Ral-A activation, which may explain the mechanism of Ral-A activation in BRAF mutant melanoma. Interestingly, anchorage-independent growth driven by R-Ras activation downstream of RASA1 inactivation was suppressed by both genetic (siRNA targeting Ral-A) and pharmacological (Ral inhibitor BQU57) inhibition of Ral-A. To further investigate the impact of RASA1 loss, and thus R-Ras activation, on BRAF mutant melanoma development in vivo, we generated a Rasa1L/L; BRAFCA/CA; Tyr-CreERT2 mouse model in which treatment with 4OHT results in expression of constitutively activated mutant BRAF and deletion of Rasa1 in melanocytic lineage cells. Preliminary analysis shows hyperpigmentation of the ear, tail, and foot pad in Rasa1L/L BRAFCA/CA mice compared to Rasa1+/+ BRAFCA/CA littermates; as well as, the development of cutaneous melanoma in Rasa1 deficient mice. Tumors generated in this animal model will be analyzed to determine the extent of R-Ras and Ral-A activity in vivo. This study demonstrates the importance of the RASA1/R-Ras/Ral-A signaling pathway in BRAF mutant melanoma and supports the possible combinatorial treatment strategy targeting both the BRAF/MAPK and Ral signaling pathways.

Citation Format: Kristen S. Hill, Evan R. Roberts, Xue Wang, Youngchul Kim, Jane Messina, Minjung Kim. R-Ras activation cooperates with BRAF mutation in melanoma tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4364.

Abstract B12: The importance of the RASA1/R-Ras/Ral-A signaling axis in melanoma tumorigenesis

The Ras family of small GTP-binding proteins is frequently activated by mutations, including NRAS (20%), KRAS (2%), and HRAS (1%), in melanoma. In addition to mutations, Ras isoforms can also be activated by the inactivation of Ras GTPase activating proteins (RasGAPs), such as NF1, RASA1, and RASA2. In our recent study, we observed that the inactivation of RASA1 (RAS p21 protein activator 1, also called p120RasGAP) suppressed melanoma via its RasGAP activity toward the R-Ras (related RAS viral (r-ras) oncogene homolog) isoform. We hypothesized that, although not mutated, R-Ras is activated in melanoma through the inactivation of RasGAPs and that RasGAP/R-Ras pathway activation cooperates with BRAF activation in melanoma tumorigenesis.

In this study, we addressed the importance of R-Ras, a previously less-appreciated member of the Ras family, in melanoma tumorigenesis and investigated the molecular mechanisms underlying R-Ras signaling in BRAF mutant melanoma. We observed frequent activation of R-Ras in BRAF mutant human melanoma cell lines. In addition, RNAi-mediated reduced expression of R-Ras suppressed anchorage-independent colony growth and tumor growth. Moreover, among the three major RAS effector pathways, reduced R-Ras expression suppressed Ral-A activation, which may explain the mechanism of Ral-A activation in BRAF mutant melanoma. Interestingly, anchorage-independent growth driven by RASA1 inactivation and subsequent R-Ras activation was suppressed by both genetic (siRNA targeting Ral-A) and pharmacologic (Ral inhibitor BQU57) inhibition of Ral-A. To further investigate the impact of RASA1 loss, and thus R-Ras activation, on BRAF mutant melanoma development in vivo, we generated a RASA1 L/L; BRAF CA/CA; Tyr-CreERT2 mouse model in which treatment with 4OHT results in the expression of constitutively activated mutant BRAF and the deletion of RASA1 in melanocytic lineage cells. Preliminary analysis shows hyperpigmentation of the ear, tail, and foot pad in RASA1 L/L BRAF CA/CA mice compared to RASA1 +/+ BRAF CA/CA littermates and the development of melanoma in RASA1 mutant mice. This study demonstrates the importance of the RASA1/R-Ras/Ral-A signaling pathway in BRAF mutant melanoma and supports the possible combinatorial treatment strategy targeting both the BRAF/MAPK and Ral signaling pathways.

Citation Format: Kristen S. Hill, Xue Wang, Evan R. Roberts, Youngchul Kim, Jane Messina, Minjung Kim. The importance of the RASA1/R-Ras/Ral-A signaling axis in melanoma tumorigenesis [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr B12.

Abstract A04: Cross-species oncogenomics approach identifies PTPN11 as an oncogene and potential therapeutic target in melanoma

Melanoma is a deadly disease carrying many genetic mutations. A major challenge to the development of effective targeted therapies in melanoma is the identification of true “driver” mutations among numerous “passenger” alterations. Several previous studies support using cross-species comparative oncogenomic approaches for cancer gene discovery. Specifically, it has been shown that mice and humans share several genetic events in the development of cancer and that these events that are conserved across different species may point to functionally important and evolutionary conserved alterations targeting “driver” genes. Recently, we analyzed melanoma genomes from a mouse model driven by the loss of PTEN and CDKN2A (INK4A/ARF), commonly observed alterations in human melanoma patients, by whole-exome sequencing. This study identified several conserved cross-species orthologous mutations in Kras, Erbb3, and Ptpn11. In this study, we addressed the functional roles of PTPN11 in melanoma tumorigenesis and tumor maintenance, its effect on RAS/RAF/MEK/ERK signaling pathway, and its activation status in human melanoma.

Melanoma displays frequent activation of the RAS/RAF/MEK/ERK signaling pathway, which is intricately regulated by multiple proteins including PTPN11 (Tyrosine-Protein Phosphatase Non-Receptor Type 11, encoding SHP2). Although implicated as an oncogene in multiple cancer types, the oncogenic role of PTPN11 has not been fully established in melanoma. PTPN11 can be activated by receptor tyrosine kinases (RTKs) and/or by point mutations. Although the mutation rate is low (1~3%), we observed activating phosphorylation on Tyr 542 of PTPN11 in 40% (n=15/38) of melanoma specimens and the majority of human melanoma cell lines (n=14), indicating the potential frequent activation of PTPN11 in human melanoma. PTPN11 knock-down suppressed ERK activation in NRAS mutant (WM1361A, 1366, 1346) and BRAF/NRAS wt (WM3211, MeWo, CHL1) melanoma cells, but not in BRAF mutant (1205Lu, IGR1, 983C) cells. Moreover, we have shown that the expression of active PTPN11 E76K mutant drives soft-agar colony growth in vitro, tumor growth in nude mice, RAS/RAF/MEK/ERK activation, and resistance to MEK inhibition, whereas knock-down of Ptpn11 reduces colony growth and ERK activation. We generated a tet-inducible, melanocyte-specific, PTPN11 E76K transgenic mouse model in a Pten and Cdkn2a null background and observed melanoma formation. Implantation of melanoma cells derived from this model showed doxycycline-dependent tumor growth in nude mice; additionally, withdrawal of doxycycline and subsequent extinction of PTPN11 E76K caused regression of established tumors, supporting a tumor-maintenance role of PTPN11. These data support the oncogenic roles of PTPN11 in melanoma by regulating RAS/RAF/MAPK pathway activation and the value of PTPN11 as a novel and actionable therapeutic target.

Citation Format: Kristen S. Hill, Xue Wang, Evan R. Roberts, Ellen M. Marin, Jamie K. Teer, Youngchul Kim, Jane Messina, Jie Wu, Minjung Kim. Cross-species oncogenomics approach identifies PTPN11 as an oncogene and potential therapeutic target in melanoma [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr A04.

Second Opinion Reviews for Cancer Diagnoses in Anatomic Pathology: A Comprehensive Cancer Center's Experience

AIM

The objective of this study was to define the rates of discrepancy between outside pathological diagnoses and secondary reviews.

MATERIALS AND METHODS

We assessed the rates of discordance between outside diagnoses and secondary reviews, categorizing by organ site and minor or major (affecting patient care) discordances.

RESULTS

A total of 9,289 consecutive surgical pathology (SP) and cytopathology (CP) cases reviewed in 2015 were identified. For 8,191 outside SP cases reviewed, the overall discordance rate (DR) was 14.2% (2.2% major, 12.0% minor). Specifically, neuropathology had the highest DR (10.9%), cutaneous and breast the lowest (1.1% each). Among 1,098 CP cases, the total DR was 13.7% (3.0% major, 10.7% minor). The majority of CP cases (1,066) were non-gynecological and had a total DR of 13.4% (2.7% major, 10.7% minor).

CONCLUSION

While major DR was low, certain subspecialties had high DRs. This project can help identify areas where focused education could help improve pathological diagnostic accuracy for cancer.

Eccrine squamous syringometaplasia in an allogenic stem cell transplant patient undergoing chemotherapy

Eccrine squamous syringometaplasia (ESS) is a rare finding defined as metaplastic change of the cuboidal epithelial cells of eccrine glands into two or more layers of squamous epithelial cells. We present a patient who developed ESS after induction of CLAG chemotherapy [2-Chlorodeoxyadenosine (2-CdA) with cytarabine (Ara-C) and (granulocyte-colony stimulating factor) G-CSF] for management of the blast crisis of his chronic myelogenous leukemia (CML). Our patient's ESS eruption presented with a variety of morphologies, thus multiple skin biopsies were taken to determine the possible diagnosis(es). All skin biopsies showed ESS and the eruption resolved with topical corticosteroids after CLAG therapy was finished.

Abstract 365: Cross-talk between BRAF and Hippo/YAP1 signaling in melanoma

Hippo/YAP1 signaling pathway is a tumor suppressive pathway that controls the organ size by modulating the cell growth, proliferation and apoptosis and is conserved from Drosophila to mammals. In mammals, the Hippo tumor suppressor pathway consists of cascade of kinases in which MST1/2 phosphorylates and activates LATS1/2. The latter phosphorylates the oncogenic transcriptional coactivators YAP1 and TAZ, leading to their cytoplasmic retention by 14-3-3 proteins and/or degradation. Inactivation of MST and LATS kinases allows YAP1 and/ or TAZ nuclear translocation and subsequent activation of their target genes.

Deregulation of Hippo pathway can induce tumors in model organisms and occurs in wide range of human cancers including melanoma. Merlin, a key component of this pathway which inhibits YAP1, is mutated/deleted in 8% of melanoma. Majority of uveal melanomas are driven by Gq/11 mutations that trigger YAP1 nuclear translocation, promoting tumor growth. High levels of YAP1 in BRAFV600E mutant tumors confer resistance to RAF- and MEK- targeted therapy in patients.

Our results show that YAP1 level is elevated in melanoma and the YAP1 inhibitor verteporfin alone or in combination with B-RAF inhibitor PLX4720 reduces the viability, invasion and anchorage-independent growth of B-RAF V600E mutant SK-MEL-28 and SK-MEL-5 cells. In addition, verteporfin treatment also reduced the viability of PLX4720 resistant 1205 cells. Western blot analysis of verteporfin and PLX4720 treated SK-MEL-28 and SK-MEL-5 cells displayed reduced levels of YAP1, B-RAF, pERK, MEK and pMEK.

We also report a novel physical interaction between YAP1 and B-RAF; this could be detected using double immunofluorescence and immunoprecipitation-western blotting techniques in both B-RAF V600E mutant and N-Ras mutant melanoma cells. Proximity ligation assays on tissue microarray showed that YAP1-B-RAF interaction is elevated in metastatic melanoma compared to normal skin. These novel findings highlight the crosstalk between B-RAF and Hippo/YAP1 signaling which might have a

potential role in melanoma development and progression. Further, experiments are in progress to elucidate the functional significance of YAP1-B-RAF interaction in melanoma.

Citation Format: Mohan Kumar Durai Raj, Jonathan Nguyen, Namrata Bora-singhal, Jane Messina, Geoffrey Gibney, Srikumar Chellappan. Cross-talk between BRAF and Hippo/YAP1 signaling in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 365. doi:10.1158/1538-7445.AM2017-365

Patterns of histologic response to neoadjuvant targeted therapy in patients with BRAF mutant melanoma

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Background: While BRAF and MEK inhibitors are approved for patients with BRAF V600 + unresectable/metastatic melanoma, their role in the neoadjuvant setting is less well defined. Results from small trials have noted robust response rates, but less is known about histological patterns of response in resected tumor specimens and relation to outcome in these patients (pts). Methods: In a retrospective study, we analyzed the clinical and pathologic patterns of response to neoadjuvant BRAF ± MEK inhibitor therapy in pts with locally advanced melanoma subsequently rendered disease free with surgery. Results: Twenty pts were identified, nine with stage IIIC and 11 with stage IV melanoma. Seven patients received neoadjuvant vemurafenib (VEM), 12 received dabrafenib + trametinib (D+T), and one encorafenib + binimetinib. The median duration of treatment was 7.8 months. Seven patients (35%) had a pathologic complete response (pCR); six of them had received combination therapy, 5 with D+T, 1 VEM with an HSP90 inhibitor. Four distinct histologic patterns were observed in the resected tumor specimens: necrotic, fibrotic/melanotic (tumoral melanosis), hyalinized, or mixed. With median follow-up of 25 months (range 1-60), six pts (30%) had experienced recurrence; three developed CNS metastases. Four of the six patients had received neoadjuvant D+T; three were restarted on their prior targeted therapy at recurrence and all responded. All 6 pts with recurrence had residual disease in the surgical specimen; three had no necrosis identified. In contrast to the 13 pts with persistent tumor, none of the 7 pCR pts has relapsed (p = 0.05). There was a trend towards improved relapse-free-survival (RFS) with a pCR, with a 1 yr of RFS-rate of 50.4% vs 100% in pCR.(p = 0.08) Of the 14 patients without subsequent recurrence, 9 had either a pure necrotic histology, or a mixed histological pattern that included necrosis. Conclusions: In locally advanced or M1a BRAF mutant melanoma, attaining a pCR to neoadjuvant targeted therapy may correlate with improved patient outcomes and be more likely achieved with combination therapy. Presence of necrosis in the surgical specimen appears be a favorable prognostic factor.

Epidermal programmed cell death-ligand 1 expression in TEN associated with nivolumab therapy

Nivolumab is a programmed cell death receptor-1 (PD-1) antibody used in the treatment of metastatic or unresectable melanoma. Cutaneous reactions are the most common adverse events reported with these agents and are rarely severe or life-threatening. Here we present a case report describing the clinicopathological findings of a patient with a fatal toxic epidermal necrolysis (TEN) eruption associated with use of nivolumab for treatment of metastatic melanoma. The patient developed a pruritic, morbiliform eruption, which slowly progressed over 3 months to a tender, exfoliative dermatosis. Histology initially showed interface dermatitis and subsequently revealed full thickness epidermal necrosis. The diagnosis of TEN was made. From initial biopsy to TEN presentation, there was an increase in the number of CD8+ lymphocytes within the dermal-epidermal junction and an increase of programmed death ligand 1 (PD-L1) expression in both lymphocytes and keratinocytes. Despite treatment with infliximab, high-dose steroids and intravenous immunoglobulin, the patient expired. Herein we describe what we believe is the second case of TEN associated with anti-PD1 therapy reported in the literature. Increased expression of PD-L1 by immunohistochemistry was observed as the eruption progressed to TEN. Early diagnosis and treatment is necessary in these fatal TEN reactions secondary to the anti-PD-1 antibody therapies.