Eva Muñoz-Couselo

The Hippo effector YAP promotes resistance to RAF- and MEK-targeted cancer therapies

Resistance to RAF- and MEK-targeted therapy is a major clinical challenge. RAF and MEK inhibitors are initially but only transiently effective in some but not all patients with BRAF gene mutation and are largely ineffective in those with RAS gene mutation because of resistance. Through a genetic screen in BRAF-mutant tumor cells, we show that the Hippo pathway effector YAP (encoded by YAP1) acts as a parallel survival input to promote resistance to RAF and MEK inhibitor therapy. Combined YAP and RAF or MEK inhibition was synthetically lethal not only in several BRAF-mutant tumor types but also in RAS-mutant tumors. Increased YAP in tumors harboring BRAF V600E was a biomarker of worse initial response to RAF and MEK inhibition in patients, establishing the clinical relevance of our findings. Our data identify YAP as a new mechanism of resistance to RAF- and MEK-targeted therapy. The findings unveil the synthetic lethality of combined suppression of YAP and RAF or MEK as a promising strategy to enhance treatment response and patient survival.

Trastuzumab-related cardiotoxicity in the elderly: a role for cardiovascular risk factors

BACKGROUNDnElderly breast cancer patients are usually excluded from clinical trials. Nevertheless, with the increasing use of trastuzumab, there is a need to address trastuzumab-related cardiotoxicity in this population.nnnPATIENTS AND METHODSnRecords for patients ≥ 70 years treated with trastuzumab since 2005 were reviewed. New York Heart Association classification was used to document symptomatic cardiotoxicity. Asymptomatic cardiotoxicity was defined as an absolute drop ≥ 10% with a final left ventricular ejection fraction < 50% or an absolute drop > 20%.nnnRESULTSnForty-five patients, median age 75.9 years (range 70-92), were identified. Three of 24 (12.5%) early breast cancer patients and 5 of 21 (23.8%) with advanced disease experienced asymptomatic cardiotoxicity. Four of 45 patients (8.9%), all with advanced breast cancer, developed symptomatic congestive heart failure. All but one of them recovered in a median time of 5 weeks (range 3-21). Patients with trastuzumab-related cardiotoxicity presented more often with cardiovascular risk factors, such as history of cardiac disease (33% versus 9.1%, P = 0.017) and diabetes (33.3% versus 6.1%, P = 0.010), compared with those without.nnnCONCLUSIONSnElderly breast cancer patients with a history of cardiac disease and/or diabetes treated with trastuzumab have an increased incidence of cardiotoxicity. Continuous cardiac monitoring is especially advised in this population.

Epigenetic activation of a cryptic TBC1D16 transcript enhances melanoma progression by targeting EGFR

Metastasis is responsible for most cancer-related deaths, and, among common tumor types, melanoma is one with great potential to metastasize. Here we study the contribution of epigenetic changes to the dissemination process by analyzing the changes that occur at the DNA methylation level between primary cancer cells and metastases. We found a hypomethylation event that reactivates a cryptic transcript of the Rab GTPase activating protein TBC1D16 (TBC1D16-47 kDa; referred to hereafter as TBC1D16-47KD) to be a characteristic feature of the metastatic cascade. This short isoform of TBC1D16 exacerbates melanoma growth and metastasis both in vitro and in vivo. By combining immunoprecipitation and mass spectrometry, we identified RAB5C as a new TBC1D16 target and showed that it regulates EGFR in melanoma cells. We also found that epigenetic reactivation of TBC1D16-47KD is associated with poor clinical outcome in melanoma, while conferring greater sensitivity to BRAF and MEK inhibitors.

HER2 and hormone receptor-positive breast cancer—blocking the right target

HER2-positive tumors have a worse prognosis than HER2-negative cancers. Although the standard treatment for HER2-positive metastatic breast cancer is chemotherapy and trastuzumab, the combination of aromatase inhibitors with anti-HER2 therapies has become an available strategy in patients with HER2-positive and hormone receptor-positive tumors. However, although this new treatment option is more effective than hormone therapy alone, it has not been compared with the standard chemotherapy and trastuzumab-based regimens. In fact, the activity observed in randomized clinical trials with chemotherapy and anti-HER2 therapies seems to be higher than that observed with aromatase inhibitors and trastuzumab-based or lapatinib-based therapies. In this article, we highlight the importance of considering chemotherapy and anti-HER2 therapy as the standard of care in HER2-positive and hormone receptor-positive tumors.

NRAS -mutant melanoma: current challenges and future prospect

Melanoma is one of the most common cutaneous cancers worldwide. Activating mutations in RAS oncogenes are found in a third of all human cancers and NRAS mutations are found in 15%–20% of melanomas. The NRAS-mutant subset of melanoma is more aggressive and associated with poorer outcomes, compared to non-NRAS-mutant melanoma. Although immune checkpoint inhibitors and targeted therapies for BRAF-mutant melanoma are transforming the treatment of metastatic melanoma, the ideal treatment for NRAS-mutant melanoma remains unknown. Despite promising preclinical data, current therapies for NRAS-mutant melanoma remain limited, showing a modest increase in progression-free survival but without any benefit in overall survival. Combining MEK inhibitors with agents inhibiting cell cycling and the PI3K–AKT pathway appears to provide additional benefit; in particular, a strategy of MEK inhibition and CDK4/6 inhibition is likely to be a viable treatment option in the future. Patients whose tumors had NRAS mutations had better response to immunotherapy and better outcomes than patients whose tumors had other genetic subtypes, suggesting that immune therapies – especially immune checkpoint inhibitors – may be particularly effective as treatment options for NRAS-mutant melanoma. Improved understanding of NRAS-mutant melanoma will be essential to develop new treatment strategies for this subset of patients with melanoma.

Eribulin mesylate as a microtubule inhibitor for treatment of patients with metastatic breast cancer

Metastatic breast cancer (MBC) remains an incurable disease, with the goals of care aimed at maximizing the patient’s duration and quality of life. Treatment options for MBC have become more efficacious and numerous. In addition to endocrine and chemotherapy agents, a number of targeted agents, including trastuzumab and bevacizumab, have further enhanced the landscape of therapeutic options. Eribulin mesylate (E7389) is a nontaxane microtubule dynamics inhibitor, and a structurally simplified synthetic analog of the natural marine product, halichondrin B, with a novel mechanism of action that has shown antitumor activity in pretreated MBC. Eribulin has shown a manageable tolerability profile in Phase I–II clinical trials and an improvement in overall survival compared with treatment of physician’s choice, without relevant toxicities in a recently published Phase III trial. This review will focus on eribulin as a new active agent for MBC and its role in the management of breast disease.

Trabectedin combined with liposomal doxorubicin in women with relapsed ovarian cancer

In the absence of a curative treatment for patients with recurrent ovarian cancer, many agents have shown different levels of activity in the control of this disease. Trabectedin is an antineoplastic agent originally derived from the Caribbean marine tunicate Ecteinascidia turbinate. This drug has a new mechanism of action based on DNA minor-groove binding. Following the encouraging results from Phase I and II studies of trabectedin monotherapy or in combination in patients with relapsed ovarian cancer, a Phase III trial investigating the use of trabectedin plus liposomal doxorubicin versus liposomal doxorubicin was launched. This study demonstrated a benefit for the combination in terms of progression-free survival that was consistent with published data of platinum-based regimens. This study has opened up the possibility of effective, nonplatinum, trabectedin-based combination therapy in patients with advanced or recurrent ovarian cancer.

Targeting FGFR pathway in breast cancer

Developments in breast cancer biology over the last years have permitted deconstructing the molecular profile of the most relevant breast cancer subtypes. This has led to an increase in therapeutic options, including more effective personalized therapy for breast cancer and substantial improvements in patient outcomes. Although currently there are only a few targeted therapies approved for metastatic breast cancer, the discovery of druggable kinase gene alterations has radically changed cancer treatment by providing novel and successfully actionable drug targets. Fibroblast growth factors and their receptors (FGFRs) participate in different physiologic processes and also play an essential role in cancer cell proliferation, survival, differentiation, migration, and apoptosis. This article summarizes the main molecular alterations of FGFRs, as well as the available preclinical and clinical data with FGFR inhibitors in breast cancer, and discusses new opportunities for the clinical development of these agents in patients with breast cancer.

Loss of USP28-mediated BRAF degradation drives resistance to RAF cancer therapies

RAF kinase inhibitors are clinically active in patients with BRAF (V600E) mutant melanoma. However, rarely do tumors regress completely, with the majority of responses being short-lived. This is partially mediated through the loss of negative feedback loops after MAPK inhibition and reactivation of upstream signaling. Here, we demonstrate that the deubiquitinating enzyme USP28 functions through a feedback loop to destabilize RAF family members. Loss of USP28 stabilizes BRAF enhancing downstream MAPK activation and promotes resistance to RAF inhibitor therapy in culture and in vivo models. Importantly, we demonstrate that USP28 is deleted in a proportion of melanoma patients and may act as a biomarker for response to BRAF inhibitor therapy in patients. Furthermore, we identify Rigosertib as a possible therapeutic strategy for USP28-depleted tumors. Our results show that loss of USP28 enhances MAPK activity through the stabilization of RAF family members and is a key factor in BRAF inhibitor resistance.

Bone metastases: Causes, consequences and therapeutic opportunities

Although the skeleton is a common site of metastasis for many solid tumours, metastatic bone disease is particularly relevant in prostate and breast cancers. Thus, bone is the most frequent – and often the only – location of metastasis in patients with advanced prostate cancer. Moreover, up to 70% of patients with metastatic breast cancer develop bone metastases over the course of their disease. n nMetastatic bone involvement usually results in multiple skeletal complications leading to a significant deterioration in the quality of life for cancer patients. Pain, hypercalcemia and skeletal-related events (SREs) – such as the use of radiotherapy or surgery of bone, pathological fractures and spinal cord compression – are problems typically derived from bone metastases [1]. n nThe pathogenesis of bone metastases is a complex process involving many interactions between tumour cells and osteoclasts and osteoblasts. Receptor activator of nuclear factor-κb (RANK) ligand (RANKL), which is expressed by osteoblasts and marrow stromal cells, is a potent inducer of osteoclast formation. In bone metastases, cytokines and growth factors secreted by tumour cells (interleukins 1 and 6, parathyroid-hormone-related peptide, tumour necrosis factor, prostaglandin E2, and macrophage-colony-stimulating factor, amongst others) increase the expression of RANKL on marrow stromal cells and osteoblasts [2]. Following this, RANKL binds to its receptor, RANK, on the surface of osteoclast precursors and stimulates the differentiation of these cells to mature osteoclasts. This excessive RANKL-induced osteoclast activity results in increased bone resorption and local bone destruction, leading to the release of growth factors from the bone matrix that subsequently promotes tumour progression. This relationship between tumour and bone cells constitutes the vicious cycle of bone metastases. n nFor all these reasons, patients with metastatic bone involvement who show higher levels of bone turnover markers have a particularly high risk for SREs in addition to worse clinical outcomes [3]. n nTreatment of bone metastases requires a broad strategy with different therapeutic options, including both local and systemic therapies. External-beam radiotherapy remains the mainstay of treatment for symptomatic bone metastases. However, considering that osteoclast-mediated bone resorption plays a critical role in the development of metastatic bone disease, its inhibition represents an attractive target for treating bone metastases. Below, some of the major management approaches are very briefly summarised.