Pathogenesis of cancers derived from thyroid follicular cells

The genomic simplicity of differentiated cancers derived from thyroid follicular cells offers unique insights into how oncogenic drivers impact tumour phenotype. Essentially, the main oncoproteins in thyroid cancer activate nodes in the receptor tyrosine kinase-RAS-BRAF pathway, which constitutively induces MAPK signalling to varying degrees consistent with their specific biochemical mechanisms of action. The magnitude of the flux through the MAPK signalling pathway determines key elements of thyroid cancer biology, including differentiation state, invasive properties and the cellular composition of the tumour microenvironment. Progression of disease results from genomic lesions that drive immortalization, disrupt chromatin accessibility and cause cell cycle checkpoint dysfunction, in conjunction with a tumour microenvironment characterized by progressive immunosuppression. This Review charts the genomic trajectories of these common endocrine tumours, while connecting them to the biological states that they confer.

Conjunctival Melanoma: Current Treatments and Future Options

Conjunctival melanoma is a rare tumor of the conjunctival epithelium with a heterogenous clinical presentation and a propensity for regional and distant metastatic spread. Guidelines for the treatment of local conjunctival melanoma are well-established, but there are no standard efficacious therapies for metastatic disease. Given that conjunctival melanoma is genetically similar to cutaneous melanoma and mucosal melanomas, targeted therapies effective in the treatment of these diseases, such as BRAF inhibitors and KIT inhibitors, may be effective in the treatment of patients with metastatic conjunctival melanoma. Other targeted small-molecule drugs in the drug development pipeline for the treatment of more prevalent melanomas could also be applicable to conjunctival melanoma. Furthermore, systemic immunotherapy treatments that are now a mainstay in the treatment of cutaneous melanoma, such as programmed cell death-1 and cytotoxic T lymphocyte-associated antigen-4 inhibitors, could also stand to benefit patients with metastatic conjunctival melanoma. Limited case reports provide clues about the effectiveness of both targeted small-molecule inhibitors and immunotherapy in patients with advanced local and metastatic conjunctival melanoma and give credence to the argument that conjunctival melanoma patients should be included in major trials studying new therapies in both cutaneous and mucosal melanomas where applicable.

Current and emerging systemic therapies for cutaneous metastatic melanoma

INTRODUCTION

Melanoma therapies have evolved rapidly, and initial successes have translated into survival gains for patients with advanced melanoma. Both targeted and immune-therapy now have evidence in earlier stage disease. There are many new agents and combinations of treatments in development as potential future treatment options. This highlights the need for a reflection on current treatment practice trends that are guiding the development of potential new therapies.

AREAS COVERED

In this review, the authors discuss the evidence for currently approved therapies for cutaneous melanoma, including adjuvant therapy, potential new biomarkers, and emerging treatments with early phase clinical trial data. The authors have searched both the PubMed and clinicaltrials.gov databases for published clinical trials and discuss selected landmark trials of current therapies and of investigational treatment strategies with early evidence for the treatment of melanoma.

EXPERT OPINION

Significant efficacy has been demonstrated with both immune checkpoint inhibitors and targeted therapies in treating advanced melanoma. A multitude of novel therapies are in development and there is need for instructive biomarker assessment to identify patients likely to respond or be refractory to current therapies, to identify mechanisms of resistance and to direct further treatment options to patients based on individual disease biology.

DPS-2: A Novel Dual MEK/ERK and PI3K/AKT Pathway Inhibitor with Powerful Ex Vivo and In Vivo Anticancer Properties

Development of novel bioactive compounds against KRAS and/or BRAF mutant colorectal cancer (CRC) is currently an urgent need in oncology. In addition, single or multitarget kinase inhibitors against MEK/ERK and PI3K/AKT pathways are of potential therapeutic advantage. A new compound based on the benzothiophene nucleus was synthesized, based on previous important outcomes on other pharmaceutical preparations, to be tested as potential anticancer agent. Treatments by 2-5 μM DPS-2 of several CRC and melanoma cell lines bearing either BRAF or KRAS mutations have shown a remarkable effect on cell viability in 2D and 3D cultures. More detailed analysis has shown that DPS-2 can kill cancer cells by apoptosis, reducing at the same time their autophagy properties. After testing activities of several signaling pathways, the compound was found to have a dual inhibition of two major proliferative/survival pathways, MEK/ERK and PI3K/AKT, in both CRC and melanoma, thus providing a mechanistic evidence for its potent anticancer activity. Antitumor activity of DPS-2 was further validated in vivo, as DPS-2 treatment of mouse xenografts of Colo-205 colorectal cancer cells remarkably reduced their tumor formation properties. Our findings suggest that DPS-2 has significant anti-KRAS/ anti-BRAF mutant CRC activity in preclinical models, potentially providing a novel treatment strategy for these difficult-to-treat tumors, which needs to be further exploited.

A Multicenter Phase I Study Evaluating Dual PI3K and BRAF Inhibition with PX-866 and Vemurafenib in Patients with Advanced BRAF V600-Mutant Solid Tumors

Purpose: The objectives of the study were to evaluate the safety of daily oral PX-866 in combination with twice daily vemurafenib and to identify potential predictive biomarkers for this novel combination.Experimental Design: We conducted a phase I, open-label, dose-escalation study in patients with advanced BRAF V600-mutant solid tumors. PX-866 was administered on a continuous schedule in combination with vemurafenib. Patients underwent a baseline and on-treatment biopsy after 1-week of PX-866 monotherapy for biomarker assessment.Results: Twenty-four patients were enrolled. The most common treatment-related adverse events were gastrointestinal side effects. One dose-limiting toxicity (DLT) of grade 3 rash and one DLT of grade 3 pancreatitis were observed in cohort 2 (PX-866 6 mg daily; vemurafenib 960 mg twice daily) and cohort 3 (PX-866 8 mg daily; vemurafenib 960 mg twice daily), respectively. Of 23 response-evaluable patients, seven had confirmed partial responses (PR), 10 had stable disease, and six had disease progression. Decreases in intratumoral pAKT expression were observed following treatment with PX-866. Patients who achieved PRs had higher rates of PTEN loss by IHC (80% vs. 58%) and pathogenic PTEN mutations and/or deletions (57% vs. 25%). Two patients with durable PRs had an increase in intratumoral CD8⁺ T-cell infiltration following treatment with PX-866.Conclusions: PX-866 was well tolerated at its maximum tolerated single-agent dose when given in combination with a modified dose of vemurafenib (720 mg twice daily). Response to treatment appeared to be associated with PTEN loss and treatment with PX-866 seemed to increase CD8⁺ T-cell infiltration in some patients. Clin Cancer Res; 24(1); 22-32. ©2017 AACR.

PI3K Pathway Inhibition Achieves Potent Antitumor Activity in Melanoma Brain Metastases In Vitro and In Vivo

PURPOSE

Great advances have recently been made in treating patients with metastatic melanoma. However, existing therapies are less effective on cerebral than extracerebral metastases. This highlights the potential role of the brain environment on tumor progression and drug resistance and underlines the need for "brain-specific" therapies. We previously showed that the PI3K-AKT survival pathway is hyperactivated in brain but not extracerebral melanoma metastases and that astrocyte-conditioned medium activates AKT in melanoma cells in vitro We therefore tested the PI3K inhibitor buparlisib as an antitumor agent for melanoma brain metastases.

EXPERIMENTAL DESIGN AND RESULTS

Buparlisib inhibited AKT activity, decreased proliferation, and induced apoptosis in metastatic melanoma cell lines and short-term brain melanoma cells, irrespective of their BRAF and NRAS mutation status. In addition, buparlisib inhibited hyperactivated AKT and induced apoptosis in melanoma cells that were stimulated with astrocyte-conditioned medium. The growth of tumors induced by injecting human BRAF- and NRAS-mutant metastatic melanoma cells into the brain of mice was significantly inhibited by buparlisib.

CONCLUSIONS

These results emphasize the value of targeting the PI3K pathway as a strategy to develop drugs for melanoma brain metastases. Clin Cancer Res; 22(23); 5818-28. ©2016 AACR.

Targeted therapies in melanoma

Advances in the biology of melanoma have provided insights about chemoresistance and its genetic heterogeneity in parallel with advances in drug design, culminating in recent major treatment breakthroughs. Although clinical benefit of targeted therapies has been unquestionable, future advances are only possible if we understand the interplay between genetic aberrations and role of other crucial nongenetic changes yet to be identified by such projects as the Cancer Genome Atlas Project in Melanoma. Combination therapies, either among small molecule inhibitors themselves and/or with immunotherapies, may be the optimal strategy to prevent development of drug resistance inherently linked with such targeted therapies.