The emerging world of breast cancer immunotherapy.

Over the last few years, the developments around cancer immunotherapy (CIT) have led to a paradigm shift in the treatment of many different cancers, in particular melanoma, renal, bladder and lung cancers with a remarkable impact on response rate and, most importantly, overall survival. Breast cancer is most commonly considered to be a 'non-inflamed' cancer and so this shift has been less marked within its treatment. However, some subsets of breast cancer, most notably triple negative breast cancer, are deemed to be more 'inflamed' and therefore may prove to be an appropriate cohort for CIT. This review looks back at the theory of the cancer immunity cycle and mechanism of action behind immune checkpoint inhibitors and goes on to explore their role within the various subtypes of breast cancer. It looks at the first trials performed using CIT monotherapy which demonstrated that breast cancer could respond to CIT with a small population reaping considerable benefit. It then examines the continuing body of work being undertaken to explore CIT in combination with chemotherapy to try to increase the proportion of patients who might reap the considerable rewards on offer.

A Review of Fulvestrant in Breast Cancer.

Fulvestrant is a selective estrogen receptor degrader that binds, blocks and degrades the estrogen receptor (ER), leading to complete inhibition of estrogen signaling through the ER. This review article further explains the mechanism of action of the drug and goes on to review the trials carried out to optimize its dosing. Multiple trials have been undertaken to compare fulvestrant with other endocrine treatments, and results have shown it to have similar efficacy to anastrozole, tamoxifen and exemestane at 250 mg every 28 days. However, when given at 500 mg every 28 days, with an extra loading dose on day 14, it has demonstrated an improved progression-free survival (PFS) compared to anastrozole. We look at how fulvestrant has been used in combination with CDK4/6 inhibitors such as palbociclib (PALOMA-3) and ribociclib (MONALEESA-3) and drugs targeting the PI3K/AKT/mTOR pathway such as pictilisib (FERGI) and buparlisib (BELLE-2 and BELLE-3). We then go on to describe a selection of the ongoing clinical trials looking at combination therapy involving fulvestrant. Finally, we review the effect of fulvestrant in patients who have developed resistance to aromatase inhibitors via ESR1 mutation, where it has been shown to offer a PFS benefit that is further improved by the addition of the CDK4/6 inhibitor palbociclib. Whilst fulvestrant is clearly an effective drug as monotherapy, we believe that its role in the treatment of ER-positive breast cancer may be best reserved for combination therapy, and whilst there are multiple trials currently in progress, it would appear that the combination with CDK4/6 inhibitors would offer the greatest promise in terms of balancing benefit with toxicity.

Vessel co-option is common in human lung metastases and mediates resistance to anti-angiogenic therapy in preclinical lung metastasis models.

Anti-angiogenic therapies have shown limited efficacy in the clinical management of metastatic disease, including lung metastases. Moreover, the mechanisms via which tumours resist anti-angiogenic therapies are poorly understood. Importantly, rather than utilizing angiogenesis, some metastases may instead incorporate pre-existing vessels from surrounding tissue (vessel co-option). As anti-angiogenic therapies were designed to target only new blood vessel growth, vessel co-option has been proposed as a mechanism that could drive resistance to anti-angiogenic therapy. However, vessel co-option has not been extensively studied in lung metastases, and its potential to mediate resistance to anti-angiogenic therapy in lung metastases is not established. Here, we examined the mechanism of tumour vascularization in 164 human lung metastasis specimens (composed of breast, colorectal and renal cancer lung metastasis cases). We identified four distinct histopathological growth patterns (HGPs) of lung metastasis (alveolar, interstitial, perivascular cuffing, and pushing), each of which vascularized via a different mechanism. In the alveolar HGP, cancer cells invaded the alveolar air spaces, facilitating the co-option of alveolar capillaries. In the interstitial HGP, cancer cells invaded the alveolar walls to co-opt alveolar capillaries. In the perivascular cuffing HGP, cancer cells grew by co-opting larger vessels of the lung. Only in the pushing HGP did the tumours vascularize by angiogenesis. Importantly, vessel co-option occurred with high frequency, being present in >80% of the cases examined. Moreover, we provide evidence that vessel co-option mediates resistance to the anti-angiogenic drug sunitinib in preclinical lung metastasis models. Assuming that our interpretation of the data is correct, we conclude that vessel co-option in lung metastases occurs through at least three distinct mechanisms, that vessel co-option occurs frequently in lung metastases, and that vessel co-option could mediate resistance to anti-angiogenic therapy in lung metastases. Novel therapies designed to target both angiogenesis and vessel co-option are therefore warranted. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Preclinical Evidence That Trametinib Enhances the Response to Antiangiogenic Tyrosine Kinase Inhibitors in Renal Cell Carcinoma.

Sunitinib and pazopanib are antiangiogenic tyrosine kinase inhibitors (TKI) used to treat metastatic renal cell carcinoma (RCC). However, the ability of these drugs to extend progression-free and overall survival in this patient population is limited by drug resistance. It is possible that treatment outcomes in RCC patients could be improved by rationally combining TKIs with other agents. Here, we address whether inhibition of the Ras-Raf-MEK-ERK1/2 pathway is a rational means to improve the response to TKIs in RCC. Using a xenograft model of RCC, we found that tumors that are resistant to sunitinib have a significantly increased angiogenic response compared with tumors that are sensitive to sunitinib in vivo. We also observed significantly increased levels of phosphorylated ERK1/2 in the vasculature of resistant tumors, when compared with sensitive tumors. These data suggested that the Ras-Raf-MEK-ERK1/2 pathway, an important driver of angiogenesis in endothelial cells, remains active in the vasculature of TKI-resistant tumors. Using an in vitro angiogenesis assay, we identified that the MEK inhibitor (MEKI) trametinib has potent antiangiogenic activity. We then show that, when trametinib is combined with a TKI in vivo, more effective suppression of tumor growth and tumor angiogenesis is achieved than when either drug is utilized alone. In conclusion, we provide preclinical evidence that combining a TKI, such as sunitinib or pazopanib, with a MEKI, such as trametinib, is a rational and efficacious treatment regimen for RCC.