Hyper-Dependence on NHEJ Enables Synergy between DNA-PK Inhibitors and Low-Dose Doxorubicin in Leiomyosarcoma.

PURPOSE: Leiomyosarcoma (LMS) is an aggressive sarcoma for which standard chemotherapies achieve response rates under 30%. There are no effective targeted therapies against LMS. Most LMS are characterized by chromosomal instability (CIN), resulting in part from TP53 and RB1 co-inactivation and DNA damage repair defects. We sought to identify therapeutic targets that could exacerbate intrinsic CIN and DNA damage in LMS, inducing lethal genotoxicity. EXPERIMENTAL DESIGN: We performed clinical targeted sequencing in 287 LMS and genome-wide loss-of-function screens in 3 patient-derived LMS cell lines, to identify LMS-specific dependencies. We validated candidate targets by biochemical and cell-response assays in vitro and in seven mouse models. RESULTS: Clinical targeted sequencing revealed a high burden of somatic copy-number alterations (median fraction of the genome altered =0.62) and demonstrated homologous recombination deficiency signatures in 35% of LMS. Genome-wide short hairpin RNA screens demonstrated PRKDC (DNA-PKcs) and RPA2 essentiality, consistent with compensatory nonhomologous end joining (NHEJ) hyper-dependence. DNA-PK inhibitor combinations with unconventionally low-dose doxorubicin had synergistic activity in LMS in vitro models. Combination therapy with peposertib and low-dose doxorubicin (standard or liposomal formulations) inhibited growth of 5 of 7 LMS mouse models without toxicity. CONCLUSIONS: Combinations of DNA-PK inhibitors with unconventionally low, sensitizing, doxorubicin dosing showed synergistic effects in LMS in vitro and in vivo models, without discernable toxicity. These findings underscore the relevance of DNA damage repair alterations in LMS pathogenesis and identify dependence on NHEJ as a clinically actionable vulnerability in LMS.

Assessing the risk of thromboembolism in cancer patients receiving immunotherapy.

Malignancy has long been implicated with hypercoagulability, leading to an increased rate of both venous and arterial thromboembolic events (VTE and ATE). Immunotherapy has established itself as a cornerstone of modern cancer therapy by promoting antitumor immune responses, though there have been some suggestions that immune-related adverse events could include increased rates of VTE and ATE. In this review, we examine the available evidence regarding the use of immune checkpoint inhibitors (ICIs) and thrombosis. First, we describe the potential mechanisms by which ICIs might lead to thrombophilia given the overlap between the immune system, coagulation cascade, and platelet adhesion and activation. In addition, while there are some preclinical data evaluating immunotherapy-associated ATEs in animal models, there is a paucity of evidence exploring potential mechanism of VTEs in ICIs. Second, we review the incidence of ATE and VTE in patients receiving ICIs in the published literature. Finally, we discuss current limitations in understanding, areas of conflicting evidence, and approaches to further investigation.

Aspirin and antiplatelet treatments in cancer.

Platelets have been hypothesized to promote certain neoplastic malignancies; however, antiplatelet drugs are still not part of routine pharmacological cancer prevention and treatment protocols. Paracrine interactions between platelets and cancer cells have been implicated in potentiating the dissemination, survival within the circulation, and extravasation of cancer cells at distant sites of metastasis. Signals from platelets have also been suggested to confer epigenetic alterations, including upregulating oncoproteins in circulating tumor cells, and secretion of potent growth factors may play roles in promoting mitogenesis, angiogenesis, and metastatic outgrowth. Thrombocytosis remains a marker of poor prognosis in patients with solid tumors. Experimental data suggest that lowering of platelet count may reduce tumor growth and metastasis. On the basis of the mechanisms by which platelets could contribute to cancer growth and metastasis, it is conceivable that drugs reducing platelet count or platelet activation might attenuate cancer progression and improve outcomes. We will review select pharmacological approaches that inhibit platelets and may affect cancer development and propagation. We begin by presenting an overview of clinical cancer prevention and outcome studies with low-dose aspirin. We then review current nonclinical development of drugs targeted to platelet binding, activation, and count as potential mitigating agents in cancer.

Phase I trials and therapeutic intent in the age of precision oncology: What is a patient's chance of response?

The advancement of therapeutic strategies in oncology such as precision oncology has generated significant interest in better estimating the response of modern phase I cancer clinical trials. These estimates have varied widely. In this commentary, we provide an umbrella review of phase I response rates and discuss methodological reasons for variation in prior estimates which include limited use of unpublished data, the inclusion of expansion cohorts that artificially raise response rates of cumulative response rates, varying enrolment of haematologic malignancies, and increased next in class drugs.

Correction: Complementary activity of tyrosine kinase inhibitors against secondary kit mutations in imatinib-resistant gastrointestinal stromal tumours.

The additional information of this manuscript originally stated that the authors declare no competing interests. This statement was incorrect, and should instead have stated the following:M.C.H. has the following competing interests to declare: Equity interest at Molecular MD; Consulting at Molecular MD, Blueprint Medicines, Deciphera Pharmaceuticals; Expert Testimony at Novartis; Licensed patent with royalty payments at Novartis. The remaining authors have no competing interests to declare.The authors apologise for any convenience this may have caused.

Complementary activity of tyrosine kinase inhibitors against secondary kit mutations in imatinib-resistant gastrointestinal stromal tumours.

BACKGROUND: Most patients with KIT-mutant gastrointestinal stromal tumours (GISTs) benefit from imatinib, but treatment resistance results from outgrowth of heterogeneous subclones with KIT secondary mutations. Once resistance emerges, targeting KIT with tyrosine kinase inhibitors (TKIs) sunitinib and regorafenib provides clinical benefit, albeit of limited duration. METHODS: We systematically explored GIST resistance mechanisms to KIT-inhibitor TKIs that are either approved or under investigation in clinical trials: the studies draw upon GIST models and clinical trial correlative science. We subsequently modelled in vitro a rapid TKI alternation approach against subclonal heterogeneity. RESULTS: Each of the KIT-inhibitor TKIs targets effectively only a subset of KIT secondary mutations in GIST. Regorafenib and sunitinib have complementary activity in that regorafenib primarily inhibits imatinib-resistance mutations in the activation loop, whereas sunitinib inhibits imatinib-resistance mutations in the ATP-binding pocket. We find that rapid alternation of sunitinib and regorafenib suppresses growth of polyclonal imatinib-resistant GIST more effectively than either agent as monotherapy. CONCLUSIONS: Our data highlight that heterogeneity of KIT secondary mutations is the main mechanism of tumour progression to KIT inhibitors in imatinib-resistant GIST patients. Therapeutic combinations of TKIs with complementary activity against resistant mutations may be useful to suppress growth of polyclonal imatinib-resistance in GIST.

Molecular Testing in Patients With Castration-Resistant Prostate Cancer and Its Impact on Clinical Decision Making.

PURPOSE: Metastatic castration-resistant prostate cancer (CRPC) is the lethal form of the disease. Many groups have performed mutational or immunohistochemistry (IHC) testing in metastatic CRPC to identify treatment targets. However, the frequency with which mutational or IHC data have an impact on clinical decision making and the outcomes of molecularly guided therapy in CRPC are largely unknown. We report our institution's experience with mutational and IHC testing in patients with metastatic CRPC and its impact on clinical decision making and patient outcomes. METHODS: Between 2012 and 2015, 59 patients with CRPC underwent metastatic tissue biopsies and were genotyped with a 37-cancer gene panel in a Clinical Laboratory Improvement Amendments-certified laboratory. PTEN expression by IHC testing was also measured in 35 of these samples. A retrospective chart review was performed to determine whether the genomic information was acted upon and the outcome of patients whose treatment was guided by molecular testing. RESULTS: Forty-six of 59 patients with CRPC (78.0%) had biopsies with adequate tumor for mutational testing. Thirty-one of 46 subjects (67.4%) had mutations identified by sequencing. Of the 35 patients with CRPC whose biopsies were evaluated for PTEN expression by IHC testing, 13 had PTEN loss. Two patients had treatment on the basis of molecular testing, and one of these subjects had greater tumor control with molecularly guided therapy than his immediate prior therapy. CONCLUSION: Targeted sequencing and IHC can identify clinically informative molecular abnormalities in CRPC. Despite this, a small minority of patients in our series underwent therapies guided by mutational or IHC testing. Actionability of abnormalities identified in metastatic CRPC may be improved with access to clinical trials, insurance approval for unapproved uses of existing anticancer drugs, and larger gene sequencing panels that include more frequently mutated genes.