Establishment of Canine Transitional Cell Carcinoma Cell Lines Harboring BRAF V595E Mutation as a Therapeutic Target

Transitional cell carcinoma (TCC) is the most common malignant tumor of the canine urinary tract and tends to have a poor prognosis due to its invasive potential. Recent studies have reported that up to 80% of canine urothelial carcinoma has the BRAF V595E mutation, which is homologous to the human V600E mutation. Activating the BRAF mutation is an actionable target for developing effective therapeutic agents inhibiting the BRAF/mitogen-activated protein kinase (MAPK) pathway in canine cancer as well as human cancer. We established novel canine TCC cell lines from two tumor tissues and one metastatic lymph node of canine TCC patients harboring the BRAF V595E mutation. Tumor tissues highly expressed the BRAF mutant and phosphorylated extracellular signal-related kinases (ERK)1/2 proteins. The derived cell lines demonstrated activated MAPK pathways. We also evaluated the cell lines for sensitivity to BRAF inhibitors. Sorafenib, a multiple kinase inhibitor targeting RAF/vascular endothelial growth factor receptor (VEGFR), successfully inhibited the BRAF/MAPK pathway and induced apoptosis. The established canine TCC cell lines responded with greater sensitivity to sorafenib than to vemurafenib, which is known as a specific BRAF inhibitor in human cancer. Our results demonstrated that canine TCC cells showed different responses compared to human cancer with the BRAF V600E mutation. These cell lines would be valuable research materials to develop therapeutic strategies for canine TCC patients.

BRAF inhibitors: resistance and the promise of combination treatments for melanoma

Identification of mutations in the gene encoding the serine/threonine-protein kinase, BRAF, and constitutive activation of the mitogen-activated protein kinase (MAPK) pathway in around 50% of malignant melanomas have led to the development and regulatory approval of targeted pathway inhibitor drugs. A proportion of patients are intrinsically resistant to BRAF inhibitors, and most patients who initially respond, acquire resistance within months. In this review, we discuss pathway inhibitors and their mechanisms of resistance, and we focus on numerous efforts to improve clinical benefits through combining agents with disparate modes of action, including combinations with checkpoint inhibitor antibodies. We discuss the merits of combination strategies based on enhancing immune responses or overcoming tumor-associated immune escape mechanisms. Emerging insights into mechanisms of action, resistance pathways and their impact on host-tumor relationships will inform the design of optimal combinations therapies to improve outcomes for patients who currently do not benefit from recent treatment breakthroughs.

The Treatment of Melanoma Brain Metastases

Melanoma is the malignancy with the highest rate of dissemination to the central nervous system once it metastasizes. Until recently, the prognosis of patients with melanoma brain metastases (MBM) was poor. In recent years, however, the prognosis has improved due to high-resolution imaging that facilitates early detection of small asymptomatic brain metastases and early intervention with local modalities such as stereotactic radiosurgery. More recently, a number of systemic therapies have been approved by the Food and Drug Administration for metastatic melanoma, resulting in improved survival for many MBM patients. Registration trials for these newer therapies excluded patients with untreated brain metastases, and a number of studies specifically tailored to this population of patients have been conducted or are underway. Herein, we review contemporary locoregional and systemic therapies and describe the unique challenges posed by treatment of brain metastases, such as radionecrosis, cerebral edema, and pseudoprogression. Since the number of systemic and combined modality clinical trials has increased, we expect that the treatment landscape for patients with melanoma brain metastasis will change dramatically. In addition to ongoing clinical trials, which show great promise, we conclude that our understanding of intracranial metastasis remains quite limited. In addition to inter-disciplinary, multi-modality studies, bench-side work to better understand the process of cerebrotropism is needed to fuel more drug development and further improve outcomes.

Challenges in the delivery of therapies to melanoma brain metastases

Brain metastases are a major cause of morbidity and mortality in patients with advanced melanoma. Recent approval of several molecularly-targeted agents and biologics has brought hope to patients with this previously untreatable disease. However, patients with symptomatic melanoma brain metastases have often been excluded from pivotal clinical trials. This may be in part attributed to the fact that several of the approved small molecule molecularly-targeted agents are substrates for active efflux at the blood-brain barrier, limiting their effective delivery to brain metastases. We believe that successful treatment of melanoma brain metastases will depend on the ability of these agents to traverse the blood-brain barrier and reach micrometastases that are often not clinically detectable. Moreover, overcoming the emergence of a unique pattern of resistance, possibly through adequate delivery of combination targeted therapies in brain metastases will be important in achieving a durable response. These concepts, and the current challenges in the delivery of new treatments to melanoma brain metastases, are discussed in this review.

Evolving treatment options for melanoma brain metastases

Melanoma is a leading cause of lost productivity due to premature cancer mortality. Melanoma frequently spreads to the brain and is associated with rapid deterioration in quality and quantity of life. Until now, treatment options have been restricted to surgery and radiotherapy, although neither modality has been well studied in clinical trials. However, the new immune checkpoint inhibitors and molecularly targeted agents that have been introduced for treatment of metastatic melanoma are active against brain metastases and offer new opportunities to improve disease outcomes. New challenges arise, including how to integrate or sequence multiple treatment modalities, and current practice varies widely. In this Review, we summarise evidence for the treatment of melanoma brain metastases, and discuss the rationale and evidence for combination modalities, highlighting areas for future research.

Multidisciplinary approach to brain metastasis from melanoma: the emerging role of systemic therapies

Melanoma brain metastases are common, difficult to treat, and carry a poor prognosis. Until recently, systemic therapy was ineffective. Local therapy (including surgery, stereotactic radiotherapy, and whole brain radiotherapy) was considered the only option for a chance of disease control in the brain, and was highly dependent on the patient's performance status and age, number and size of brain metastases, and the presence of extracranial metastases. Since 2010, three drugs have demonstrated activity in progressing or "active" brain metastases including the anti-CTLA4 antibody ipilimumab (phase II study of 72 patients), and the BRAF inhibitors dabrafenib (phase II study of 172 patients, both previously treated and untreated brain metastases) and vemurafenib (a pilot study of 24 patients with heavily pretreated brain metastases). The challenge and unanswered question for clinicians is how to sequence all the available therapies, both local and systemic, to optimize the patient's quality of life and survival. This is an area of intense clinical research. The treatment of patients with melanoma brain metastases should be discussed by a multidisciplinary team of melanoma experts including a neurosurgeon, medical oncologist, and radiation oncologist. Important clinical features that help determine appropriate first line therapy include single compared with solitary brain metastasis, resectablity, BRAF mutation status of melanoma, rate of progression/performance status, and the presence of extracranial disease.

Successful (neo)adjuvant BRAF-targeted therapy in a patient with locally advanced BRAF V600E mutant melanoma

The treatment of locally advanced metastasized melanoma is challenging because there is no level 1 evidence to guide clinical decision-making. Moreover, the treatment options available fail to improve overall survival and are associated with considerable morbidity. Here, we show that systemic treatment with BRAF inhibitor vemurafenib substituted by dual BRAF/MEK inhibition (dabrafenib and trametinib) before surgery can offer the potential to cure the initially difficult or inoperable melanoma. A 62-year-old woman was diagnosed with an AJCC stage IIIB melanoma harboring the BRAF V600E mutation after a complete initial evaluation. Clinically, the patient presented a large primary lesion that was surrounded by ∼25 secondary epidermotropic lesions both satellite and 'in transit' with a diameter between 1 and 6 mm. Following multidisciplinary consultation, the patient was started on 960 mg twice-daily vemurafenib, which was stopped and resumed at 720 mg twice daily, and finally substituted with the combination dabrafenib and trametinib to reduce the persistent side effects. Successive clinical examinations had shown a progressive reduction in the thickness of the melanoma lesions. After about 5 months of therapy, surgery was performed and the histopathological analysis showed an almost complete regression of tumor cells. The treatment with dabrafenib/trametinib was continued only 3 months after surgery and stopped at the patient's request. The patient currently remains in complete remission at 8 months after surgery. The case presented here supports the use of neoadjuvant treatment with BRAF inhibitors in advanced 'in transit' melanoma.

Oral Targeted Therapies and Central Nervous System (CNS) Metastases

The purpose of our review is to summarize the clinical activity of oral targeted agents against brain metastases. This includes BRAF inhibitors (dabrafenib and vemurafenib), human epidermal growth factor receptor inhibitors (lapatinib, gefitinib, erlotinib, and afatinib), multi-kinase angiogenesis inhibitors (sorafenib, sunitinib, pazopanib, and vandetanib), and ALK/c-MET (crizotinib) and ALK/IGF-1 (ceritinib) inhibitors. Effective systemic therapies are needed for long-term benefit in brain metastases and documentation of intracranial activity for many therapies is poor. Our review provides a summary of the literature with pertinent data for clinicians. This is needed as subjects with brain metastases are often prevented from enrolling in clinical trials and investigations focused on systemic therapies for brain metastases are rare.

Intralesional administration of L19-IL2/L19-TNF in stage III or stage IVM1a melanoma patients: results of a phase II study

The intratumoral injection of cytokines, in particular IL2, has shown promise for cutaneous melanoma patients with unresectable disease or continuous recurrence despite surgery. We recently reported that the intralesional injection of L19-IL2, an immunocytokine combining IL2 and the human monoclonal antibody fragment L19, resulted in efficient regional control of disease progression, increased time to distant metastasis and evidence of effect on circulating immune cell populations. We have also shown in preclinical models of cancer a remarkable synergistic effect of the combination of L19-IL2 with L19-TNF, a second clinical-stage immunocytokine, based on the same L19 antibody fused to TNF. Here, we describe the results of a phase II clinical trial based on the intralesional administration of L19-IL2 and L19-TNF in patients with stage IIIC and IVM1a metastatic melanoma, who were not candidate to surgery. In 20 efficacy-evaluable patients, 32 melanoma lesions exhibited complete responses upon intralesional administration of the two products, with mild side effects mainly limited to injection site reactions. Importantly, we observed complete responses in 7/13 (53.8 %) non-injected lesions (4 cutaneous, 3 lymph nodes), indicating a systemic activity of the intralesional immunostimulatory treatment. The intralesional administration of L19-IL2 and L19-TNF represents a simple and effective method for the local control of inoperable melanoma lesions, with a potential to eradicate them or make them suitable for a facile surgical removal of the residual mass.

Metastasectomy for stage IV melanoma

Metastatic melanoma has an unpredictable natural history but a predictably high mortality. Despite recent advances in systemic therapy, many patients do not respond, or develop resistance to drug therapy. Surgery has consistently shown good outcomes in appropriately selected patients. It is likely to be even more successful in the era of more effective medical treatment. Surgery should remain a strongly considered option for metastatic melanoma.

Advances in the management of low-grade gliomas

Low-grade gliomas (LGGs) represent the most common childhood brain tumors and are a histologically heterogenous group of tumors. Most LGGs are surgically resectable with excellent 10-year overall survival outcomes of more than 90 % with surgery alone. Tumors not amenable to surgical resection and those with an aggressive biology are more challenging to treat. Conventional radiotherapy is a more efficacious method of long-term tumor control than chemotherapy. However, radiation is associated with significant cognitive, endocrine, and cerebrovascular late effects, making chemotherapy an often-preferred modality over radiotherapy, especially in younger children. Multiple chemotherapy regimens have been evaluated over the past few decades with comparable survival outcomes and differing toxicity profiles. Newer regimens containing antiangiogenic agents also show promise. Recent molecular studies have implicated the BRAF oncogene, a key regulator of the MAPK pathway, and the AKT/mTOR pathway in pediatric LGG tumorigenesis. This has opened up promising new avenues for targeted therapy, with many agents currently under investigation.

Radiation necrosis mimicking rapid intracranial progression of melanoma metastasis in two patients treated with vemurafenib

Optimal treatment of metastases to the central nervous system (CNS) in patients with malignant melanoma remains a clinical challenge. In particular, for patients with BRAF-mutant melanoma and CNS metastases, much remains unknown about the safety and efficacy of the novel BRAF-targeted agents when administered in close sequence with radiation. We report two cases of rapid development of CNS radiation necrosis in patients with metastatic melanoma treated with the BRAF inhibitor, vemurafenib, closely sequenced with stereotactic radiosurgery or fractionated stereotactic radiation therapy. In the absence of prospective safety data from clinical trials, we advise vigilance in monitoring patients with BRAF-mutant melanoma whose treatment plan includes CNS radiation and vemurafenib and caution when assessing treatment response within the CNS in these patients.

Neoadjuvant therapy for locally advanced melanoma: new strategies with targeted therapies

Neoadjuvant chemotherapy has been successfully tested in several bulky solid tumors, but it has not been utilized in advanced cutaneous melanoma, primarily because effective medical treatments for this disease have been lacking. However, with the development of new immunotherapies (monoclonal antibodies specific for cytotoxic T lymphocyte-associated antigen 4 [anti-CTLA-4] and programmed death protein-1 [anti-PD1]) and small molecules interfering with intracellular pathways (anti-BRAF and mitogen-activated protein kinase kinase [anti- MEK]) the use of this approach is becoming a viable treatment strategy for locally advanced melanoma. The neoadjuvant setting provides a double opportunity for a better knowledge of these drugs: a short-term evaluation of their intrinsic activity, and a deeper analysis of their action and resistance-induction mechanisms. BRAF inhibitors seem to be ideal candidates for the neoadjuvant setting, because of their prompt, repeatedly confirmed response in V600E BRAF-mutant metastatic melanoma. In this report we summarize studies focused on the neoadjuvant use of traditional medical treatments in advanced melanoma and anecdotal cases of this approach with the use of biologic therapies. Moreover, we discuss our experience with neoadjuvant targeted therapy as a priming for radical surgery in a patient with BRAF V600E mutation-positive advanced melanoma.

In vitro treatment of melanoma brain metastasis by simultaneously targeting the MAPK and PI3K signaling pathways

Malignant melanoma is the most lethal form of skin cancer, with a high propensity to metastasize to the brain. More than 60% of melanomas have the BRAF^V600E mutation, which activates the mitogen-activated protein kinase (MAPK) pathway [1]. In addition, increased PI3K (phosphoinositide 3-kinase) pathway activity has been demonstrated, through the loss of activity of the tumor suppressor gene, PTEN [2]. Here, we treated two melanoma brain metastasis cell lines, H1_DL2, harboring a BRAF^V600E mutation and PTEN loss, and H3, harboring WT (wild-type) BRAF and PTEN loss, with the MAPK (BRAF) inhibitor vemurafenib and the PI3K pathway associated mTOR inhibitor temsirolimus. Combined use of the drugs inhibited tumor cell growth and proliferation in vitro in H1_DL2 cells, compared to single drug treatment. Treatment was less effective in the H3 cells. Furthermore, a strong inhibitory effect on the viability of H1_DL2 cells, when grown as 3D multicellular spheroids, was seen. The treatment inhibited the expression of pERK1/2 and reduced the expression of pAKT and p-mTOR in H1_DL2 cells, confirming that the MAPK and PI3K pathways were inhibited after drug treatment. Microarray experiments followed by principal component analysis (PCA) mapping showed distinct gene clustering after treatment, and cell cycle checkpoint regulators were affected. Global gene analysis indicated that functions related to cell survival and invasion were influenced by combined treatment. In conclusion, we demonstrate for the first time that combined therapy with vemurafenib and temsirolimus is effective on melanoma brain metastasis cells in vitro. The presented results highlight the potential of combined treatment to overcome treatment resistance that may develop after vemurafenib treatment of melanomas.

A new role of vemurafenib as a neoadjuvant treatment of axillary and brain melanoma metastases

Vemurafenib is approved by the FDA for the management of unresectable or metastatic melanoma. However, its role as a neoadjuvant therapy has not been determined. We present the first documented case in which vemurafenib induced complete tumor necrosis of both lymph node and brain metastases within one month or less, an outcome that indicated that the patient was a good candidate for excisional surgery.

Neoadjuvant treatment of melanoma: case reports and review

Neoadjuvant therapy is an under-utilized regimen for the treatment of metastatic melanoma. The use of this approach has been increasing in other tumor types. Neoadjuvant therapy may reduce occult circulating tumor cell burden in the face of bulky disease and afford a real time evaluation of treatment effectiveness. Neoadjuvant approach can also provide preoperative histologic and molecular analysis of treated tissue that may guide the postoperative treatment planning in patients with resectable metastatic melanoma lesions. The putative benefits of better margin control and clearance of occult systemic disease would theoretically improve surgical outcome. With the advent of effective agents against metastatic melanoma, this common approach to the treatment of rectal cancer, metastatic colon cancer, and breast cancer should also be evaluated as a viable treatment strategy for advanced stage melanoma.