Phase I clinical trial of the Src inhibitor dasatinib with dacarbazine in metastatic melanoma

Treatment of Metastatic Melanoma with a Combination of Immunotherapies and Molecularly Targeted Therapies

Simple Summary

Immunotherapies and molecularly targeted therapies have drastically changed the therapeutic approach for unresectable advanced or metastatic melanoma. The majority of melanoma patients have benefitted from these therapies; however, some patients acquire resistance to them. Novel combinations of immunotherapies and molecularly targeted therapies may be more efficient in treating these patients. In this review, we discuss various combination therapies under pre-clinical and clinical development which can reduce toxicity, enhance efficacy, and prevent recurrences in patients with metastatic melanoma.

Abstract

Melanoma possesses invasive metastatic growth patterns and is one of the most aggressive types of skin cancer. In 2021, it is estimated that 7180 deaths were attributed to melanoma in the United States alone. Once melanoma metastasizes, traditional therapies are no longer effective. Instead, immunotherapies, such as ipilimumab, pembrolizumab, and nivolumab, are the treatment options for malignant melanoma. Several biomarkers involved in tumorigenesis have been identified as potential targets for molecularly targeted melanoma therapy, such as tyrosine kinase inhibitors (TKIs). Unfortunately, melanoma quickly acquires resistance to these molecularly targeted therapies. To bypass resistance, combination treatment with immunotherapies and single or multiple TKIs have been employed and have been shown to improve the prognosis of melanoma patients compared to monotherapy. This review discusses several combination therapies that target melanoma biomarkers, such as BRAF, MEK, RAS, c-KIT, VEGFR, c-MET and PI3K. Several of these regimens are already FDA-approved for treating metastatic melanoma, while others are still in clinical trials. Continued research into the causes of resistance and factors influencing the efficacy of these combination treatments, such as specific mutations in oncogenic proteins, may further improve the effectiveness of combination therapies, providing a better prognosis for melanoma patients.

Unbiased High-Throughput Drug Combination Pilot Screening Identifies Synergistic Drug Combinations Effective against Patient-Derived and Drug-Resistant Melanoma Cell Lines

We describe the development, optimization, and validation of 384-well growth inhibition assays for six patient-derived melanoma cell lines (PDMCLs), three wild type (WT) for BRAF and three with V600E-BRAF mutations. We conducted a pilot drug combination (DC) high-throughput screening (HTS) of 45 pairwise 4×4 DC matrices prepared from 10 drugs in the PDMCL assays: two B-Raf inhibitors (BRAFi), a MEK inhibitor (MEKi), and a methylation agent approved for melanoma; cytotoxic topoisomerase II and DNA methyltransferase chemotherapies; and drugs targeting the base excision DNA repair enzyme APE1 (apurinic/apyrimidinic endonuclease-1/redox effector factor-1), SRC family tyrosine kinases, the heat shock protein 90 (HSP90) molecular chaperone, and histone deacetylases.Pairwise DCs between dasatinib and three drugs approved for melanoma therapy-dabrafenib, vemurafenib, or trametinib-were flagged as synergistic in PDMCLs. Exposure to fixed DC ratios of the SRC inhibitor dasatinib with the BRAFis or MEKis interacted synergistically to increase PDMCL sensitivity to growth inhibition and enhance cytotoxicity independently of PDMCL BRAF status. These DCs synergistically inhibited the growth of mouse melanoma cell lines that either were dabrafenib-sensitive or had acquired resistance to dabrafenib with cross resistance to vemurafenib, trametinib, and dasatinib. Dasatinib DCs with dabrafenib, vemurafenib, or trametinib activated apoptosis and increased cell death in melanoma cells independently of their BRAF status or their drug resistance phenotypes. These preclinical in vitro studies provide a data-driven rationale for the further investigation of DCs between dasatinib and BRAFis or MEKis as candidates for melanoma combination therapies with the potential to improve outcomes and/or prevent or delay the emergence of disease resistance.

The Role of Senescent Cells in Acquired Drug Resistance and Secondary Cancer in BRAFi-Treated Melanoma

Simple Summary

Advances in melanoma treatment include v-Raf murine sarcoma viral oncogene homolog B (BRAF) inhibitors that target the predominant oncogenic mutation found in malignant melanoma. Despite initial success of the BRAF inhibitor (BRAFi) therapies, resistance and secondary cancer often occur. Mechanisms of resistance and secondary cancer rely on upregulation of pro-survival pathways that circumvent senescence. The repeated identification of a cellular senescent phenotype throughout melanoma progression demonstrates the contribution of senescent cells in resistance and secondary cancer development. Incorporating senotherapeutics in melanoma treatment may offer a novel approach for potentially improving clinical outcome.

Abstract

BRAF is the most common gene mutated in malignant melanoma, and predominately it is a missense mutation of codon 600 in the kinase domain. This oncogenic BRAF missense mutation results in constitutive activation of the mitogen-activate protein kinase (MAPK) pro-survival pathway. Several BRAF inhibitors (BRAFi) have been developed to specifically inhibit BRAF^V600 mutations that improve melanoma survival, but resistance and secondary cancer often occur. Causal mechanisms of BRAFi-induced secondary cancer and resistance have been identified through upregulation of MAPK and alternate pro-survival pathways. In addition, overriding of cellular senescence is observed throughout the progression of disease from benign nevi to malignant melanoma. In this review, we discuss melanoma BRAF mutations, the genetic mechanism of BRAFi resistance, and the evidence supporting the role of senescent cells in melanoma disease progression, drug resistance and secondary cancer. We further highlight the potential benefit of targeting senescent cells with senotherapeutics as adjuvant therapy in combating melanoma.

RTK Inhibitors in Melanoma: From Bench to Bedside

MAPK (mitogen activated protein kinase) and PI3K/AKT (Phosphatidylinositol-3-Kinase and Protein Kinase B) pathways play a key role in melanoma progression and metastasis that are regulated by receptor tyrosine kinases (RTKs). Although RTKs are mutated in a small percentage of melanomas, several receptors were found up regulated/altered in various stages of melanoma initiation, progression, or metastasis. Targeting RTKs remains a significant challenge in melanoma, due to their variable expression across different melanoma stages of progression and among melanoma subtypes that consequently affect response to treatment and disease progression. In this review, we discuss in details the activation mechanism of several key RTKs: type III: c-KIT (mast/stem cell growth factor receptor); type I: EGFR (Epidermal growth factor receptor); type VIII: HGFR (hepatocyte growth factor receptor); type V: VEGFR (Vascular endothelial growth factor), structure variants, the function of their structural domains, and their alteration and its association with melanoma initiation and progression. Furthermore, several RTK inhibitors targeting the same receptor were tested alone or in combination with other therapies, yielding variable responses among different melanoma groups. Here, we classified RTK inhibitors by families and summarized all tested drugs in melanoma indicating the rationale behind the use of these drugs in each melanoma subgroups from preclinical studies to clinical trials with a specific focus on their purpose of treatment, resulted effect, and outcomes.

Src Family Kinases as Therapeutic Targets in Advanced Solid Tumors: What We Have Learned so Far

Src is the prototypal member of Src Family tyrosine Kinases (SFKs), a large non-receptor kinase class that controls multiple signaling pathways in animal cells. SFKs activation is necessary for the mitogenic signal from many growth factors, but also for the acquisition of migratory and invasive phenotype. Indeed, oncogenic activation of SFKs has been demonstrated to play an important role in solid cancers; promoting tumor growth and formation of distant metastases. Several drugs targeting SFKs have been developed and tested in preclinical models and many of them have successfully reached clinical use in hematologic cancers. Although in solid tumors SFKs inhibitors have consistently confirmed their ability in blocking cancer cell progression in several experimental models; their utilization in clinical trials has unveiled unexpected complications against an effective utilization in patients. In this review, we summarize basic molecular mechanisms involving SFKs in cancer spreading and metastasization; and discuss preclinical and clinical data highlighting the main challenges for their future application as therapeutic targets in solid cancer progression

Structure and Characterization of a Covalent Inhibitor of Src Kinase

Unregulated Src activity promotes malignant processes in cancer, but no Src-directed targeted therapies are used clinically, possibly because early Src inhibitors produce off-target effects leading to toxicity. Improved selective Src inhibitors may enable Src-directed therapies. Previously, we reported an irreversible Src inhibitor, DGY-06-116, based on the hybridization of dasatinib and a promiscuous covalent kinase probe SM1-71. Here, we report biochemical and biophysical characterization of this compound. An x-ray co-crystal structure of DGY-06-116: Src shows a covalent interaction with the kinase p-loop and occupancy of the back hydrophobic kinase pocket, explaining its high potency, and selectivity. However, a reversible analog also shows similar potency. Kinetic analysis shows a slow inactivation rate compared to other clinically approved covalent kinase inhibitors, consistent with a need for p-loop movement prior to covalent bond formation. Overall, these results suggest that a strong reversible interaction is required to allow sufficient time for the covalent reaction to occur. Further optimization of the covalent linker may improve the kinetics of covalent bond formation.

SIRT2 Contributes to the Resistance of Melanoma Cells to the Multikinase Inhibitor Dasatinib

Malignant melanoma is the most aggressive skin cancer and can only be cured if detected early. Unfortunately, later stages of the disease do not guarantee success due to the rapid rate of melanoma cell metastasis and their high resistance to applied therapies. The search for new molecular targets and targeted therapy may represent the future in the development of effective methods for combating this cancer. SIRT2 is a promising target; thus, we downregulated SIRT2 expression in melanoma cells in vertical growth and metastatic phases and demonstrated that sirtuin acts as regulator of the basic functions of melanoma cells. A detailed transcriptomic analysis showed that SIRT2 regulates the expression of multiple genes encoding the tyrosine kinase pathways that are molecular targets of dasatinib. Indeed, cells with low SIRT2 expression were more susceptible to dasatinib, as demonstrated by multiple techniques, e.g., neutral red uptake, 3/7 caspase activity, colony formation assay, and in vitro scratch assay. Furthermore, these cells showed an altered phosphorylation profile for proteins playing roles in the response to dasatinib. Thus, our research indicates new, previously unknown SIRT2 functions in the regulation of gene expression, which is of key clinical significance.

STAT3 enhances the constitutive activity of AGC kinases in melanoma by transactivating PDK1

Background

The PI3K/Akt and the STAT3 pathways are functionally associated in many tumor types. Both in vitro and in vivo studies have revealed that either biochemical or genetic manipulation of the STAT3 pathway activity induce changes in the same direction in Akt activity. However, the implicated mechanism has been poorly characterized. Our goal was to characterize the precise mechanism linking STAT3 with the activity of Akt and other AGC kinases in cancer using melanoma cells as a model.

Results

We show that active STAT3 is constitutively bound to the PDK1 promoter and positively regulate PDK1 transcription through two STAT3 responsive elements. Transduction of WM9 and UACC903 melanoma cells with STAT3-small hairpin RNA decreased both PDK1 mRNA and protein levels. STAT3 knockdown also induced a decrease of the phosphorylation of AGC kinases Akt, PKC, and SGK. The inhibitory effect of STAT3 silencing on Akt phosphorylation was restored by HA-PDK1. Along this line, HA-PDK1 expression significantly blocked the cell death induced by dacarbazine plus STAT3 knockdown. This effect might be mediated by Bcl2 proteins since HA-PDK1 rescued Bcl2, Bcl-XL, and Mcl1 levels that were down-regulated upon STAT3 silencing.

Conclusions

We show that PDK1 is a transcriptional target of STAT3, linking STAT3 pathway with AGC kinases activity in melanoma. These data provide further rationale for the ongoing effort to therapeutically target STAT3 and PDK1 in melanoma and, possibly, other malignancies.

Electronic supplementary material

The online version of this article (10.1186/s13578-018-0265-8) contains supplementary material, which is available to authorized users.

Post-treatment de-phosphorylation of p53 correlates with dasatinib responsiveness in malignant melanoma

BACKGROUND

Dasatinib (Sprycel) was developed as a tyrosine kinase inhibitor targeting Bcr-Abl and the family of Src kinases. Dasatinib is commonly used for the treatment of acute lymphoblastic and chronic myelogenous leukemia. Previous clinical studies in melanoma returned inconclusive results and suggested that patients respond highly heterogeneously to dasatinib as single agent or in combination with standard-of-care chemotherapeutic dacarbazine. Reliable biomarkers to predict dasatinib responsiveness in melanoma have not yet been developed.

RESULTS

Here, we collected comprehensive in vitro data from experimentally well-controlled conditions to study the effect of dasatinib, alone and in combination with dacarbazine, on cell proliferation and cell survival. Sixteen treatment conditions, covering therapeutically relevant concentrations ranges of both drugs, were tested in 12 melanoma cell lines with diverse mutational backgrounds. Melanoma cell lines responded heterogeneously and, importantly, dasatinib and dacarbazine did not synergize in suppressing proliferation or inducing cell death. Since dasatinib is a promiscuous kinase inhibitor, possibly affecting multiple disease-relevant pathways, we also determined if basal phospho-protein amounts and treatment-induced changes in phospho-protein levels are indicative of dasatinib responsiveness. We found that treatment-induced de-phosphorylation of p53 correlates with dasatinib responsiveness in malignant melanoma.

CONCLUSIONS

Loss of p53 phosphorylation might be an interesting candidate for a kinetic marker of dasatinib responsiveness in melanoma, pending more comprehensive validation in future studies.

Protein Tyrosine Signaling and its Potential Therapeutic Implications in Carcinogenesis

Protein tyrosine phosphorylation is a crucial signaling mechanism that plays a role in epithelial carcinogenesis. Protein tyrosine kinases (PTKs) control various cellular processes including growth, differentiation, metabolism, and motility by activating major signaling pathways including STAT3, AKT, and MAPK. Genetic mutation of PTKs and/or prolonged activation of PTKs and their downstream pathways can lead to the development of epithelial cancer. Therefore, PTKs became an attractive target for cancer prevention. PTK inhibitors are continuously being developed, and they are currently used for the treatment of cancers that show a high expression of PTKs. Protein tyrosine phosphatases (PTPs), the homeostatic counterpart of PTKs, negatively regulate the rate and duration of phosphotyrosine signaling. PTPs initially were considered to be only housekeeping enzymes with low specificity. However, recent studies have demonstrated that PTPs can function as either tumor suppressors or tumor promoters, depending on their target substrates. Together, both PTK and PTP signal transduction pathways are potential therapeutic targets for cancer prevention and treatment.

Synergistic anti-tumor effects of dasatinib and dendritic cell vaccine on metastatic breast cancer in a mouse model

Immunotherapy is currently considered as one of the major anti-tumor modalities, but its efficacy is limited. Dasatinib could improve the expansion and recruitment of cluster of differentiation (CD) 8⁺T cells and natural killer (NK) cells to the tumor microenvironment. The present study aimed to evaluate the synergistic anti-tumor effects of dasatinib with dendritic cell (DC) vaccine in metastatic breast cancer. Dasatinib with DC vaccine was administered to mice inoculated with 4T1 breast cancer cells. Thereafter, tumor volume was measured every other day. On day 34, lung metastasis was assessed with a stereomicroscope. Tumor proliferation and angiogenesis were determined by immunohistochemistry. Apoptosis in tumor tissues was assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling. The results showed that although there were no significant differences in tumor volumes between the untreated control, DC vaccine and dasatinib groups, the tumor volume was significantly decreased in the combined treatment group compared to the other three groups. Mice in the combined treatment group showed the longest survival time, while mice treated with either single treatment had a slightly increased survival time compared to the untreated control mice. Additionally, the number of metastatic lung nodules was significantly decreased in combined treatment group compared with the dasatinib alone, DC vaccine alone and untreated control groups. Furthermore, the combined treatment group showed significantly reduced intratumoral microvessel density compared to the other three groups. In addition, the ratios of CD8⁺ T and NK cells were significantly increased in the combined treatment group compared with the other three groups. These results suggest that dasatinib combined with the DC vaccine is a possible modality for the treatment of metastatic breast cancer.

Incidence, Diagnosis, and Management of QT Prolongation Induced by Cancer Therapies: A Systematic Review

Background

The cardiovascular complications of cancer therapeutics are the focus of the burgeoning field of cardio‐oncology. A common challenge in this field is the impact of cancer drugs on cardiac repolarization (ie, QT prolongation) and the potential risk for the life‐threatening arrhythmia torsades de pointes. Although QT prolongation is not a perfect marker of arrhythmia risk, this has become a primary safety metric among oncologists. Cardiologists caring for patients receiving cancer treatment should become familiar with the drugs associated with QT prolongation, its incidence, and appropriate management strategies to provide meaningful consultation in this complex clinical scenario.

Methods and Results

In this article, we performed a systematic review (using Preferred Reporting Items of Systematic Reviews and Meta‐Analyses (PRISMA) guidelines) of commonly used cancer drugs to determine the incidence of QT prolongation and clinically relevant arrhythmias. We calculated summary estimates of the incidence of all and clinically relevant QT prolongation as well as arrhythmias and sudden cardiac death. We then describe strategies to prevent, identify, and manage QT prolongation in patients receiving cancer therapy. We identified a total of 173 relevant publications. The weighted incidence of any corrected QT (QTc) prolongation in our systematic review in patients treated with conventional therapies (eg, anthracyclines) ranged from 0% to 22%, although QTc >500 ms, arrhythmias, or sudden cardiac death was extremely rare. The risk of QTc prolongation with targeted therapies (eg, small molecular tyrosine kinase inhibitors) ranged between 0% and 22.7% with severe prolongation (QTc >500 ms) reported in 0% to 5.2% of the patients. Arrhythmias and sudden cardiac death were rare.

Conclusions

Our systematic review demonstrates that there is variability in the incidence of QTc prolongation of various cancer drugs; however, the clinical consequence, as defined by arrhythmias or sudden cardiac death, remains rare.

A phase 2 trial of dasatinib in patients with locally advanced or stage IV mucosal, acral, or vulvovaginal melanoma: A trial of the ECOG-ACRIN Cancer Research Group (E2607)

BACKGROUND

KIT-directed tyrosine kinase inhibitors such as imatinib have demonstrated benefits in KIT-mutant (KIT+) mucosal, acral, vulvovaginal, and chronically sun-damaged (CSD) melanoma. Dasatinib has superior preclinical activity in comparison with other tyrosine kinase inhibitors against cells with the most common KIT mutation, exon 11^L576P . The ECOG-ACRIN E2607 trial assessed dasatinib in patients with these melanoma subtypes.

METHODS

Patients received 70 mg of oral dasatinib twice daily. The primary objective for this 2-stage phase 2 trial was response rate. Stage I was open to KIT+ and wild-type KIT (KIT-) mucosal, acral, and CSD melanoma (n = 57). Stage II accrued only KIT+ tumors (n = 30). To enrich the trial for KIT+ tumors, vulvovaginal melanoma was added, and CSD melanoma was removed from eligibility. Secondary objectives included progression-free survival (PFS), overall survival (OS), and safety.

RESULTS

From May 2009 to December 2010, the first stage enrolled 57 patients. Among the evaluable patients, 3 of 51 (5.9%) achieved a partial response: all were KIT-. Stage II closed early because of slow accrual (November 2011 to December 2015). In stage II, 4 of 22 evaluable patients (18.2%) had a partial response; the median duration was 4.2 months. The median PFS was 2.1 months (n = 73; 95% confidence interval [CI], 1.5-2.9 months). The median OS was 7.5 months (95% CI, 6.0-11.9 months). In exploratory analyses, no differences were seen in PFS or OS with the KIT status or subtype. Dasatinib was discontinued because of adverse events in 9 of 75 patients (12%).

CONCLUSIONS

The dasatinib response rate among KIT+ melanoma patients was low. In view of its clinical activity, it is recommended that imatinib remain the KIT tyrosine kinase inhibitor of choice for unresectable KIT+ melanoma. Cancer 2017;123:2688-97. © 2017 American Cancer Society.

Combinatorial approach to treatment of melanoma

There are multiple effective and well-tolerated systemic therapy treatments for the treatment of advanced melanoma, as well as new immunotherapy and targeted therapy agents in clinical trials. Traditional cytotoxic chemotherapy and targeted BRAF inhibitors can increase antigen presentation and can rebalance the intratumoral immune milieu. The combination of pulsed cytotoxic therapy and immunotherapy is a logical next step in designing treatment regimens. Combination radiotherapy and immunotherapy also has experimental and clinical support. The standard of care for patients with advanced melanoma remains participation in clinical trials in order to enhance understanding of the effectiveness and toxicities of combination regimens.

Dasatinib (BMS-35482) interacts synergistically with docetaxel, gemcitabine, topotecan, and doxorubicin in ovarian cancer cells with high SRC pathway activation and protein expression

PURPOSE

This study aimed to explore the activity of dasatinib in combination with docetaxel, gemcitabine, topotecan, and doxorubicin in ovarian cancer cells.

METHODS

Cells with previously determined SRC pathway and protein expression (SRC pathway/SRC protein IGROV1, both high; SKOV3, both low) were treated with dasatinib in combination with the cytotoxic agents. SRC and paxillin protein expression were determined pretreatment and posttreatment. Dose-response curves were constructed, and the combination index (CI) for drug interaction was calculated.

RESULTS

In the IGROV1 cells, dasatinib alone reduced phospho-SRC/total SRC 71% and p-paxillin/t-paxillin ratios 77%. Phospho-SRC (3%-33%; P = 0.002 to 0.04) and p-paxicillin (6%-19%; P = 0.01 to 0.05) levels were significantly reduced with dasatinib in combination with each cytotoxic agent. The combination of dasatinib and docetaxel, gemcitabine, or topotecan had a synergistic antiproliferative effect (CI, 0.49-0.68), whereas dasatinib combined with doxorubicin had an additive effect (CI, 1.08).In SKOV3 cells, dasatinib resulted in less pronounced reductions of phospho-SRC/total SRC (49%) and p-paxillin/t-paxillin (62%). Phospho-SRC (18%; P < 0.001) and p-paxillin levels (18%; P = 0.001; 9%; P = 0.007) were significantly decreased when dasatinib was combined with docetaxel and topotecan (p-paxillin only). Furthermore, dasatinib combined with the cytotoxics in the SKOV3 cells produced an antagonistic interaction on the proliferation of these cells (CI, 1.49-2.27).

CONCLUSIONS

Dasatinib in combination with relapse chemotherapeutic agents seems to interact in a synergistic or additive manner in cells with high SRC pathway activation and protein expression. Further evaluation of dasatinib in combination with chemotherapy in ovarian cancer animal models and exploration of the use of biomarkers to direct therapy are warranted.

Combination of dasatinib and gemcitabine reduces the ALDH1A1 expression and the proliferation of gemcitabine-resistant pancreatic cancer MIA PaCa-2 cells

Gemcitabine-based chemotherapy is the standard for treatment of pancreatic cancer; however, intrinsic and acquired resistance to gemcitabine commonly occurs. Aldehyde dehydrogenase 1A1 (ALDH1A1), one of the characteristic features of tumor-initiating and/or cancer stem cell (CSC) properties, is important in both intrinsic and acquired resistance to gemcitabine. In this study, we investigated the effectiveness of dasatinib, an SRC inhibitor, and gemcitabine combination to inhibit the survivals of parental (MIA PaCa-2/P) and gemcitabine-resistant (MIA PaCa-2/GR) cell lines. In MIA PaCa-2/GR cells, the levels of phospho-SRC and ALDH1A1 were increased compared to MIA PaCa-2/P cells. Inhibition of SRC by dasatinib or siRNA synergistically enhanced gemcitabine-induced anti-proliferative effects and induced apoptotic cell death in these cells. Furthermore, combination of SRC inhibition (either by dasatinib or siRNA) and gemcitabine significantly decreased the levels of ALDH1A1 expression. These results suggest that dasatinib and gemcitabine combination may be a potential therapeutic strategy to overcome gemcitabine resistance by decreasing the levels of ALDH1A1 expression.

Predictive biomarkers for dasatinib treatment in melanoma

Dasatinib has anti-proliferative and anti-invasive effects in melanoma cell lines. However clinical trials have shown modest activity for dasatinib in metastatic melanoma. Although dasatinib targets SRC kinase, neither expression nor phosphorylation of SRC appears to predict response to dasatinib. Identification of predictive biomarkers for dasatinib may facilitate selection of melanoma patients who are more likely to respond to dasatinib. We correlated the anti-proliferative effects of dasatinib in 8 melanoma cell lines with expression of a previously identified 6-gene biomarker panel. We examined the relationship between response to dasatinib and expression of each gene at both the mRNA and protein level. Dasatinib inhibited growth in 3 of the 8 cell lines tested. mRNA expression of the panel of 6 biomarkers did not correlate with response, whilst elevated protein expression of ANXA1, CAV-1 and EphA2 correlated significantly with response to dasatinib in the panel of cell lines. Expression of ANXA1, CAV-1 and EphA2 were analysed in 124 melanoma samples by immunohistochemistry. ANXA1 protein was detected in 81 % (97/120) of tumours, CAV-1 in 44 % (54/122) of tumours and EphA2 in 74 % (90/121) of tumours. Thirty one % (35/113) of tumours tested expressed all three markers and 19 % (21/112) had moderate or strong expression of ANXA1, CAV-1 and EphA2. Seventeen percent (19/112) of melanoma samples were positive for SRC kinase expression, combined with high expression of ANXA1, CAV-1 and EphA2. This subgroup may represent a population of melanoma patients who would be more likely to derive clinical benefit from dasatinib treatment.

Dasatinib promotes the expansion of a therapeutically superior T-cell repertoire in response to dendritic cell vaccination against melanoma

Dasatinib (DAS) is a potent inhibitor of the BCR-ABL, SRC, c-KIT, PDGFR, and ephrin tyrosine kinases that has demonstrated only modest clinical efficacy in melanoma patients. Given reports suggesting that DAS enhances T cell infiltration into the tumor microenvironment, we analyzed whether therapy employing the combination of DAS plus dendritic cell (DC) vaccination would promote superior immunotherapeutic benefit against melanoma. Using a M05 (B16.OVA) melanoma mouse model, we observed that a 7-day course of orally-administered DAS (0.1 mg/day) combined with a DC-based vaccine (VAC) against the OVA_257–264 peptide epitope more potently inhibited tumor growth and extended overall survival as compared with treatment with either single modality. The superior efficacy of the combinatorial treatment regimen included a reduction in hypoxic-signaling associated with reduced levels of immunosuppressive CD11b⁺Gr1⁺ myeloid-derived suppressor cells (MDSC) and CD4⁺Foxp3⁺ regulatory T (Treg) populations in the melanoma microenvironment. Furthermore, DAS + VAC combined therapy upregulated expression of Type-1 T cell recruiting CXCR3 ligand chemokines in the tumor stroma correlating with activation and recruitment of Type-1, vaccine-induced CXCR3⁺CD8⁺ tumor-infiltrating lymphocytes (TILs) and CD11c⁺ DC into the tumor microenvironment. The culmination of this bimodal approach was a profound “spreading” in the repertoire of tumor-associated antigens recognized by CD8⁺ TILs, in support of the therapeutic superiority of combined DAS + VAC immunotherapy in the melanoma setting.

Targeting of BRAF resistant melanoma via extracellular matrix metalloproteinase inducer receptor

BACKGROUND

The BRAF inhibitor vemurafenib (PLX) has shown promise in treating metastatic melanoma, but most patients develop resistance to treatment after 6 mo. We identified a transmembrane protein, extracellular matrix metalloproteinase inducer (EMMPRIN) as a cell surface receptor highly expressed by PLX-resistant melanoma. Using an S100A9 ligand, we created an EMMPRIN targeted probe and liposome that binds to melanoma cells in vivo, thus designing a novel drug delivery vehicle.

METHODS

PLX-resistant cells were established through continuous treatment with PLX-4032 over the course of 1 y. Both PLX-resistant and sensitive melanoma cell lines were evaluated for the expression of unique cell surface proteins, which identified EMMPRIN as an overexpressed protein in PLX0-resistant cells and S100A9 is a ligand for EMMPRIN. To design a probe for EMMPRIN, S100A9 ligand was conjugated to a CF-750 near-infrared (NIR) dye. EMMPRIN targeted liposomes were created to encapsulate CF-750 NIR dye. Liposomes were characterized by scanning electron microscopy, flow cytometry, and in vivo analysis. A2058PLX and A2058 cells were subcutaneously injected into athymic mice. S100A9 liposomes were intravenously injected and tumor accumulation was evaluated using NIR fluorescent imaging.

RESULTS

Western blot and flow cytometry demonstrated that PLX sensitive and resistant A2058 and A375 melanoma cells highly express EMMPRIN. S100A9 liposomes were 200 nm diameter and uniformly sized. Flow cytometry demonstrated 100X more intracellular dye uptake by A2058 cells treated with S100A9 liposomes compared with untargeted liposomes. In vivo accumulation of S100A9 liposomes within subcutaneous A2058 and A2058PLX tumors was observed from 6-48 h, with A2058PLX accumulating significantly higher levels (P = 0.001626).

CONCLUSIONS

EMMPRIN-targeted liposomes via an S100A9 ligand are a novel, targeted delivery system which could provide improved EMMPRIN specific drug delivery to a tumor.

Dasatinib

Dasatinib is an orally available short-acting dual ABL/SRC tyrosine kinase inhibitor (TKI). It potently inhibits BCR-ABL and SRC family kinases (SRC, LCK, YES, FYN), but also c-KIT, PDGFR-α and PDGFR-β, and ephrin receptor kinase. Dasatinib is an effective treatment for chronic myeloid leukemia (CML) and Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ ALL). Both diseases are characterized by a constitutively active tyrosine kinase; BCR-ABL. Dasatinib inhibits BCR-ABL with greater potency compared with other BCR-ABL inhibitors and is active in CML resistant or intolerant to imatinib. Dasatinib is approved for the treatment of CML (all phases) and for the treatment of Ph+ ALL, resistant or intolerant to prior imatinib treatment. Randomized trial data in CML show that first-line dasatinib provides superior responses compared with imatinib and enables patients to achieve early, deep responses, correlated with improved longer-term outcomes. A once-daily dose of 100 mg in chronic phase CML results in high hematologic and molecular remission rates and prolongation of survival. In accelerated and blastic phase of CML, as well as in Ph+ ALL, complete hematologic and cytogenetic remissions frequently occur. Remissions however are very short. In these patients, once-daily 140 mg is the recommended dose. The effect of dasatinib in other malignancies including solid tumors is subject of clinical studies. Regardless of many clinical trials in different tumor types and in different combinations of dasatinib with other agents, the role of dasatinib in the treatment of solid tumors has not yet been defined. Side effects of dasatinib are frequent but mostly moderate and manageable and include cytopenias and pleural effusions. The review presents the preclinical and clinical activity of dasatinib with a focus on clinical studies in CML.

Ligase-assisted, upconversion luminescence resonance energy transfer-based method for specific and sensitive detection of V600E mutation in the BRAF gene

We report a specific and sensitive detection of BRAF V600E mutation based on a ligase-assisted signal-amplifiable scheme using upconversion nanoparticles.

SRC family kinase inhibition as a novel strategy to augment melphalan-based regional chemotherapy of advanced extremity melanoma

BACKGROUND

Src kinase inhibition has been shown to augment the efficacy of chemotherapy. Dasatinib, a dual Src/Abl kinase inhibitor approved for the treatment of CML, is under investigation as monotherapy for tumors with abnormal Src signaling, such as melanoma. The goal of this study was to determine if Src kinase inhibition using dasatinib could enhance the efficacy of regionally administered melphalan in advanced extremity melanoma.

METHODS

The mutational status of c-kit and patterns of gene expression predictive of dysregulated Src kinase signaling were evaluated in a panel of 26 human melanoma cell lines. The effectiveness of dasatinib was measured by quantifying protein expression and activation of Src kinase, focal adhesion kinase, and Crk-associated substrate (p130(CAS)), in conjunction with in vitro cell viability assays using seven melanoma cell lines. Utilizing a rat model of regional chemotherapy, we evaluated the effectiveness of systemic dasatinib in conjunction with regional melphalan against the human melanoma cell line, DM443, grown as a xenograft.

RESULTS

Only the WM3211 cell line harbored a c-kit mutation. Significant correlation was observed between Src-predicted dysregulation by gene expression and sensitivity to dasatinib in vitro. Tumor doubling time for DM443 xenografts treated with systemic dasatinib in combination with regional melphalan (44.8 days) was significantly longer (p = 0.007) than either dasatinib (21.3 days) or melphalan alone (24.7 days).

CONCLUSIONS

Systemic dasatinib prior to melphalan-based regional chemotherapy markedly improves the efficacy of this alkylating agent in this melanoma xenograft model. Validation of this concept should be considered in the context of a regional therapy clinical trial.

C-kit-mutated melanomas: the Chinese experience

PURPOSE OF REVIEW

Malignant melanoma is the most frequent cause of mortality in skin cancer. Unlike Caucasians, mucosal and acral melanomas account for approximately 65% of all melanomas in Chinese. Genetic mutations of c-kit are detected in mucosal and acral melanomas, which thus can be regarded as molecular targets for treatments. This review describes the recent proceedings in the c-kit-targeted molecular therapy of melanoma, on the basis of our experiences in Chinese melanoma patients.

RECENT FINDINGS

Somatic mutations within c-kit gene have been detected in 10.8% of Chinese melanoma patients. Imatinib, a selective inhibitor targeting Abl as well as c-kit and the platelet-derived growth factor receptor, has been tested for the efficacy and toxicities in metastatic melanoma patients, suggesting that imatinib may increase the progression-free survival and overall survival in selected melanoma patients harboring mutations in c-kit gene. The current status of c-kit mutation and the standard for selection of imatinib-sensitive patients have been tentatively established.

SUMMARY

C-kit is a proto-oncogene that can serve as a potential target for molecular therapy of metastatic melanoma. Imatinib is effective and well tolerated in the treatment of metastatic melanoma patients. In selected subsets of melanoma patients harboring genetic alterations of c-kit, imatinib may be a promising agent.

Targeted therapy for melanoma: rational combinatorial approaches

The treatment of melanoma, the most aggressive form of skin cancer, is being revolutionized by the development of personalized targeted therapy approaches. Mutant-selective BRAF inhibitors and MEK inhibitors have demonstrated impressive clinical results in molecularly selected patients. However, emerging understanding of the molecular heterogeneity of this disease and the identification of multiple mechanisms of resistance to targeted therapies strongly support the rationale for combinatorial approaches. In this review, we will discuss the preclinical and clinical studies that are testing leading hypotheses and emerging combinatorial strategies for the future.

Activation of abl family kinases in solid tumors

Although c-Abl and Arg non-receptor tyrosine kinases are well known for driving leukemia development, their role in solid tumors has not been appreciated until recently. Accumulating evidence now indicates that c-Abl and/or Arg are activated in some solid tumor cell lines via unique mechanisms that do not involve gene mutation/translocation, and c-Abl/Arg activation promotes matrix degradation, invasion, proliferation, tumorigenesis, and/or metastasis, depending on the tumor type. However, some data suggest that c-Abl also may suppress invasion, proliferation, and tumorigenesis in certain cell contexts. Thus, c-Abl/Arg may serve as molecular switches that suppress proliferation and invasion in response to some stimuli (e.g., ephrins) or when inactive/regulated, or as promote invasion and proliferation in response to other signals (e.g., activated growth factor receptors, loss of inhibitor expression), which induce sustained activation. Clearly, more data are required to determine the extent and prevalence of c-Abl/Arg activation in primary tumors and during progression, and additional animal studies are needed to substantiate in vitro findings. Furthermore, c-Abl/Arg inhibitors have been used in numerous solid tumor clinical trials; however, none of these trials were restricted to patients whose tumors expressed highly activated c-Abl/Arg (targeted trial). Targeted trials are critical for determining whether c-Abl/Arg inhibitors can be effective treatment options for patients whose tumors are driven by c-Abl/Arg.

Sensitivity to the MEK inhibitor E6201 in melanoma cells is associated with mutant BRAF and wildtype PTEN status

Background

Melanoma is the most lethal form of skin cancer, but recent advances in molecularly targeted agents against the Ras/Raf/MAPK pathway demonstrate promise as effective therapies. Despite these advances, resistance remains an issue, as illustrated recently by the clinical experience with vemurafenib. Such acquired resistance appears to be the result of parallel pathway activation, such as PI3K, to overcome single-agent inhibition. In this report, we describe the cytotoxicity and anti-tumour activity of the novel MEK inhibitor, E6201, in a broad panel of melanoma cell lines (n = 31) of known mutational profile in vitro and in vivo. We further test the effectiveness of combining E6201 with an inhibitor of PI3K (LY294002) in overcoming resistance in these cell lines.

Results

The majority of melanoma cell lines were either sensitive (IC50 < 500 nM, 24/31) or hypersensitive (IC50 < 100 nM, 18/31) to E6201. This sensitivity correlated with wildtype PTEN and mutant BRAF status, whereas mutant RAS and PI3K pathway activation were associated with resistance. Although MEK inhibitors predominantly exert a cytostatic effect, E6201 elicited a potent cytocidal effect on most of the sensitive lines studied, as evidenced by Annexin positivity and cell death ELISA. Conversely, E6201 did not induce cell death in the two resistant melanoma cell lines tested. E6201 inhibited xenograft tumour growth in all four melanoma cell lines studied to varying degrees, but a more pronounced anti-tumour effect was observed for cell lines that previously demonstrated a cytocidal response in vitro. In vitro combination studies of E6201 and LY294002 showed synergism in all six melanoma cell lines tested, as defined by a mean combination index < 1.

Conclusions

Our data demonstrate that E6201 elicits a predominantly cytocidal effect in vitro and in vivo in melanoma cells of diverse mutational background. Resistance to E6201 was associated with disruption of PTEN and activation of downstream PI3K signalling. In keeping with these data we demonstrate that co-inhibition of MAPK and PI3K is effective in overcoming resistance inherent in melanoma.