Diane Tseng

Inhibition of Mac-1 (CD11b/CD18) enhances tumor response to radiation by reducing myeloid cell recruitment

Despite recent advances in radiotherapy, loco-regional failures are still the leading cause of death in many cancer patients. We have previously reported that bone marrow-derived CD11b+ myeloid cells are recruited to tumors grown in irradiated tissues, thereby restoring the vasculature and tumor growth. In this study, we examined whether neutralizing CD11b monoclonal antibodies could inhibit the recruitment of myeloid cells into irradiated tumors and inhibit their regrowth. We observed a significant enhancement of antitumor response to radiation in squamous cell carcinoma xenografts in mice when CD11b antibodies are administered systemically. Histological examination of tumors revealed that CD11b antibodies reduced infiltration of myeloid cells expressing S100A8 and matrix metalloproteinase-9. CD11b antibodies further inhibited bone marrow-derived cell adhesion and transmigration to C166 endothelial cell monolayers and chemotactic stimuli, respectively, to levels comparable to those from CD11b knockout or CD18 hypomorphic mice. Given the clinical availability of humanized CD18 antibodies, we tested two murine tumor models in CD18 hypomorphic or CD11b knockout mice and found that tumors were more sensitive to irradiation when grown in CD18 hypomorphic mice but not in CD11b knockout mice. When CD18 hypomorphism was partially rescued by reconstitution with the wild-type bone marrow, the resistance of the tumors to irradiation was restored. Our study thus supports the rationale of using clinically available Mac-1 (CD11b/CD18) antibodies as an adjuvant therapy to radiotherapy.

Anti-CD47 antibody–mediated phagocytosis of cancer by macrophages primes an effective antitumor T-cell response

Mobilization of the T-cell response against cancer has the potential to achieve long-lasting cures. However, it is not known how to harness antigen-presenting cells optimally to achieve an effective antitumor T-cell response. In this study, we show that anti-CD47 antibody–mediated phagocytosis of cancer by macrophages can initiate an antitumor T-cell immune response. Using the ovalbumin model antigen system, anti-CD47 antibody–mediated phagocytosis of cancer cells by macrophages resulted in increased priming of OT-I T cells [cluster of differentiation 8-positive (CD8+)] but decreased priming of OT-II T cells (CD4+). The CD4+ T-cell response was characterized by a reduction in forkhead box P3-positive (Foxp3+) regulatory T cells. Macrophages following anti-CD47–mediated phagocytosis primed CD8+ T cells to exhibit cytotoxic function in vivo. This response protected animals from tumor challenge. We conclude that anti-CD47 antibody treatment not only enables macrophage phagocytosis of cancer but also can initiate an antitumor cytotoxic T-cell immune response.

Cancer Stem Cell–Directed Therapies: Recent Data From the Laboratory and Clinic

Cancer stem cells (CSCs) are defined by their ability to (i) fully recapitulate the tumor of origin when transplanted into immunodeficient mouse hosts, and (ii) self-renew, demonstrated by their ability to be serially transplanted. These properties suggest that CSCs are required for tumor maintenance and metastasis; thus, it has been predicted that CSC elimination is required for cure. This prediction has profoundly altered paradigms for cancer research, compelling investigators to prospectively isolate CSCs to characterize the molecular pathways regulating their behavior. Many potential strategies for CSC-directed therapy have been proposed, but few studies have rigorously demonstrated their efficacy using in vivo models. Herein, we highlight recent studies that demonstrate the utility of CSC-directed therapies and discuss the implications of the CSC hypothesis to experimental design and therapeutic strategies.

Naive and Memory T Cells Induce Different Types of Graft-versus-Host Disease

The goal of this study was to compare the ability of donor naive and alloantigen-primed effector memory T cells to induce graft-vs-host disease after bone marrow transplantation in MHC-mismatched irradiated host mice. Purified CD4+ naive (CD62LhighCD44low) T cells and CD4+ effector memory (CD62LlowCD44high) T cells obtained from unprimed donors and donors primed to host alloantigens, respectively, were injected into host mice, and the rapidity, severity, and pattern of tissue injury of graft-vs-host disease was assessed. Unexpectedly, the naive T cells induced a more acute and severe colitis than the primed memory cells. Whereas the naive T cells expressing CD62L and CCR7 lymph node homing receptors vigorously expanded in mesenteric lymph nodes and colon by day 6 after transplantation, the primed memory T cells without these receptors had 20- to 100-fold lower accumulation at this early time point. These differences were reflected in the significantly more rapid decline in survival and weight loss induced by naive T cells. The primed memory T cells had a greater capacity to induce chronic colitis and liver injury and secrete IL-2 and IFN-γ in response to alloantigenic stimulation compared with memory T cells from unprimed donors. Nevertheless, the expected increase in potency as compared with naive T cells was not observed due to differences in the pattern and kinetics of tissue injury.

Targeting SDF-1/CXCR4 to inhibit tumour vasculature for treatment of glioblastomas

Local recurrence of glioblastomas is a major cause of patient mortality after definitive treatment. This review discusses the roles of the chemokine stromal cell-derived factor-1 and its receptor CXC chemokine receptor 4 (CXCR4) in affecting the sensitivity of glioblastomas to irradiation. Blocking these molecules prevents or delays tumour recurrence after irradiation by inhibiting the recruitment of CD11b+ monocytes/macrophages that participate in revascularising the tumour. We review the literature pertaining to the mechanism by which revascularisation occurs following tumour irradiation using experimental models. Areas of interest and debate in the literature include the process by which endothelial cells die after irradiation and the identity/origin of the cells that reconstitute the tumour blood vessels after injury. Understanding the processes that mediate tumour revascularisation will guide the improvement of clinical strategies for preventing recurrence of glioblastoma after irradiation.

Inhibition of CXCR7 extends survival following irradiation of brain tumours in mice and rats

Background:In experimental models of glioblastoma multiforme (GBM), irradiation (IR) induces local expression of the chemokine CXCL12/SDF-1, which promotes tumour recurrence. The role of CXCR7, the high-affinity receptor for CXCL12, in the tumour’s response to IR has not been addressed.Methods:We tested CXCR7 inhibitors for their effects on tumour growth and/or animal survival post IR in three rodent GBM models. We used immunohistochemistry to determine where CXCR7 protein is expressed in the tumours and in human GBM samples. We used neurosphere formation assays with human GBM xenografts to determine whether CXCR7 is required for cancer stem cell (CSC) activity in vitro.Results:CXCR7 was detected on tumour cells and/or tumour-associated vasculature in the rodent models and in human GBM. In human GBM, CXCR7 expression increased with glioma grade and was spatially associated with CXCL12 and CXCL11/I-TAC. In the rodent GBM models, pharmacological inhibition of CXCR7 post IR caused tumour regression, blocked tumour recurrence, and/or substantially prolonged survival. CXCR7 expression levels on human GBM xenograft cells correlated with neurosphere-forming activity, and a CXCR7 inhibitor blocked sphere formation by sorted CSCs.Conclusions:These results indicate that CXCR7 inhibitors could block GBM tumour recurrence after IR, perhaps by interfering with CSCs.

Interim-treatment quantitative PET parameters predict progression and death among patients with hodgkin's disease

PurposeWe hypothesized that quantitative PET parameters may have predictive value beyond that of traditional clinical factors such as the International Prognostic Score (IPS) among Hodgkins disease (HD) patients.MethodsThirty HD patients treated at presentation or relapse had staging and interim-treatment PET-CT scans. The majority of patients (53%) had stage III-IV disease and 67% had IPS ≥ 2. Interim-treatment scans were performed at a median of 55 days from the staging PET-CT. Chemotherapy regimens used: Stanford V (67%), ABVD (17%), VAMP (10%), or BEACOPP (7%). Hypermetabolic tumor regions were segmented semiautomatically and the metabolic tumor volume (MTV), mean standardized uptake value (SUVmean), maximum SUV (SUVmax) and integrated SUV (iSUV) were recorded. We analyzed whether IPS, absolute value PET parameters or the calculated ratio of interim- to pre-treatment PET parameters were associated with progression free survival (PFS) or overall survival (OS).ResultsMedian follow-up of the study group was 50 months. Six of the 30 patients progressed clinically. Absolute value PET parameters from pre-treatment scans were not significant. Absolute value SUVmax from interim-treatment scans was associated with OS as determined by univariate analysis (p < 0.01). All four calculated PET parameters (interim/pre-treatment values) were associated with OS: MTVint/pre (p < 0.01), SUVmeanint/pre (p < 0.05), SUVmaxint/pre (p = 0.01), and iSUVint/pre (p < 0.01). Absolute value SUVmax from interim-treatment scans was associated with PFS (p = 0.01). Three calculated PET parameters (int/pre-treatment values) were associated with PFS: MTVint/pre (p = 0.01), SUVmaxint/pre (p = 0.02) and iSUVint/pre (p = 0.01). IPS was associated with PFS (p < 0.05) and OS (p < 0.01).ConclusionsCalculated PET metrics may provide predictive information beyond that of traditional clinical factors and may identify patients at high risk of treatment failure early for treatment intensification.

Involution of Eruptive Melanocytic Nevi on Combination BRAF and MEK Inhibitor Therapy

IMPORTANCE Eruptive melanocytic nevi (EMN) are characterized by the sudden onset of numerous melanocytic nevi and have been traditionally described in the setting of immunosuppression. Selective BRAF inhibitors such as vemurafenib cause multiple cutaneous adverse effects, including the formation of cutaneous squamous cell carcinoma, as well as EMN. We describe the first reported case, to our knowledge, of involution of BRAF inhibitor-induced EMN following the concomitant addition of a MEK inhibitor, cobimetinib. OBSERVATIONS A woman in her 20s with a history of metastatic melanoma developed EMN while receiving therapy with vemurafenib, a selective BRAF inhibitor. After disease progression, the patient was placed on a clinical trial that combined vemurafenib with a MEK inhibitor, cobimetinib. Within months, we noted clinical involution of many of her EMN. In addition, numerous preexisting nevi were noted to fade in color on the dual regimen. Over a year after initiating this combination therapy, most of the patients EMN were no longer clinically evident. CONCLUSIONS AND RELEVANCE Our case report describing the involution of EMN supports data from previous clinical trials indicating that combination BRAF and MEK inhibition may reduce cutaneous proliferative effects that arise on BRAF inhibitor monotherapy. Further studies are necessary to characterize the biological mechanisms underlying this phenomenon.

Patterns of Metastatic Spread and Mechanisms of Resistance to Crizotinib in ROS1-Positive Non–Small-Cell Lung Cancer

PURPOSE The ROS1 tyrosine kinase is activated through ROS1 gene rearrangements in 1-2% of non-small cell lung cancer (NSCLC), conferring sensitivity to treatment with the ALK/ROS1/MET inhibitor crizotinib. Currently, insights into patterns of metastatic spread and mechanisms of crizotinib resistance among ROS1-positive patients are limited. PATIENTS AND METHODS We reviewed clinical and radiographic imaging data of patients with ROS1- and ALK-positive NSCLC in order to compare patterns of metastatic spread at initial metastatic diagnosis. To determine molecular mechanisms of crizotinib resistance, we also analyzed repeat biopsies from a cohort of ROS1-positive patients progressing on crizotinib. RESULTS We identified 39 and 196 patients with advanced ROS1- and ALK-positive NSCLC, respectively. ROS1-positive patients had significantly lower rates of extrathoracic metastases (ROS1 59.0%, ALK 83.2%, P=0.002), including lower rates of brain metastases (ROS1 19.4%, ALK 39.1%; P = 0.033), at initial metastatic diagnosis. Despite similar overall survival between ALK- and ROS1-positive patients treated with crizotinib (median 3.0 versus 2.5 years, respectively; P=0.786), ROS1-positive patients also had a significantly lower cumulative incidence of brain metastases (34% vs. 73% at 5 years; P<0.0001). Additionally, we identified 16 patients who underwent a total of 17 repeat biopsies following progression on crizotinib. ROS1 resistance mutations were identified in 53% of specimens, including 9/14 (64%) non-brain metastasis specimens. ROS1 mutations included: G2032R (41%), D2033N (6%), and S1986F (6%). CONCLUSIONS Compared to ALK rearrangements, ROS1 rearrangements are associated with lower rates of extrathoracic metastases, including fewer brain metastases, at initial metastatic diagnosis. ROS1 resistance mutations, particularly G2032R, appear to be the predominant mechanism of resistance to crizotinib, underscoring the need to develop novel ROS1 inhibitors with activity against these resistant mutants.

Oncogenic mutations in melanomas and benign melanocytic nevi of the female genital tract

BACKGROUND The genetic heterogeneity of melanomas and melanocytic nevi of the female genital tract is poorly understood. OBJECTIVE We aim to characterize the frequency of mutations of the following genes: BRAF, NRAS, KIT, GNA11, and GNAQ in female genital tract melanomas. We also characterize the frequency of BRAF mutations in female genital tract melanomas compared with melanocytic nevi. METHODS Mutational screening was performed on the following female genital tract melanocytic neoplasms: 25 melanomas, 7 benign melanocytic nevi, and 4 atypical melanocytic nevi. RESULTS Of the 25 female genital tract melanoma specimens queried, KIT mutations were detected in 4 (16.0%), NRAS mutations in 4 (16.0%), and BRAF mutations in 2 (8.0%) samples. Two of the tumors with KIT mutations harbored double mutations in the same exon. No GNAQ or GNA11 mutations were identified among 11 melanomas screened. BRAF V600E mutations were detected in 7 of 7 benign melanocytic genital nevi (100%) and 3 of 4 atypical genital nevi (75%). LIMITATIONS Our study is limited by the small sample size of this rare subset of melanomas. CONCLUSION KIT, NRAS, and BRAF mutations are found in a subset of female genital tract melanomas. Screening for oncogenic mutations is important for developing and applying clinical therapies for melanomas of the female genital tract.