First-in-human phase 1 study of the anti-TIGIT antibody vibostolimab as monotherapy or with pembrolizumab for advanced solid tumors, including non-small-cell lung cancer☆.

BACKGROUND: In this first-in-human phase 1 study (NCT02964013; MK-7684-001), we investigated the safety and efficacy of the anti-TIGIT (T cell immunoglobulin and ITIM domain) antibody vibostolimab as monotherapy or in combination with pembrolizumab. PATIENTS AND METHODS: Part A enrolled patients with advanced solid tumors, and part B enrolled patients with non-small-cell lung cancer (NSCLC). Patients received vibostolimab 2.1-700 mg alone or with pembrolizumab 200 mg in part A and vibostolimab 200 mg alone or with pembrolizumab 200 mg in part B. Primary endpoints were safety and tolerability. Secondary endpoints included pharmacokinetics and objective response rate (ORR) per RECIST v1.1. RESULTS: Part A enrolled 76 patients (monotherapy, 34; combination therapy, 42). No dose-limiting toxicities were reported. Across doses, 56% of patients receiving monotherapy and 62% receiving combination therapy had treatment-related adverse events (TRAEs); grade 3-4 TRAEs occurred in 9% and 17% of patients, respectively. The most common TRAEs were fatigue (15%) and pruritus (15%) with monotherapy and pruritus (17%) and rash (14%) with combination therapy. Confirmed ORR was 0% with monotherapy and 7% with combination therapy. In part B, 39 patients had anti-PD-1 (programmed cell death protein 1)/PD-L1 (programmed death-ligand 1)-naive NSCLC (all received combination therapy), and 67 had anti-PD-1/PD-L1-refractory NSCLC (monotherapy, 34; combination therapy, 33). In patients with anti-PD-1/PD-L1-naive NSCLC: 85% had TRAEs-the most common were pruritus (38%) and hypoalbuminemia (31%); confirmed ORR was 26%, with responses occurring in both PD-L1-positive and PD-L1-negative tumors. In patients with anti-PD-1/PD-L1-refractory NSCLC: 56% receiving monotherapy and 70% receiving combination therapy had TRAEs-the most common were rash and fatigue (21% each) with monotherapy and pruritus (36%) and fatigue (24%) with combination therapy; confirmed ORR was 3% with monotherapy and 3% with combination therapy. CONCLUSIONS: Vibostolimab plus pembrolizumab was well tolerated and demonstrated antitumor activity in patients with advanced solid tumors, including patients with advanced NSCLC.

A randomized, phase II trial of cetuximab with or without PX-866, an irreversible oral phosphatidylinositol 3-kinase inhibitor, in patients with relapsed or metastatic head and neck squamous cell cancer.

BACKGROUND: The phosphotidylinositol-3 kinase (PI3K)/serine-threonine kinase/mammalian target of rapamycin signaling pathway is frequently altered in head and neck squamous cell cancer (HNSCC). PX-866 is an oral, irreversible, pan-isoform inhibitor of PI3K. A phase I trial demonstrated tolerability of this combination. This randomized phase II study evaluated PX-866 combined with cetuximab in patients with advanced, refractory HNSCC. METHODS: Patients with recurrent or metastatic HNSCC who had received at least one and no more than two prior systemic treatment regimens were randomized (1 : 1) to cetuximab with or without PX-866 (8 mg p.o. daily; arms A and B, respectively). The primary end point was progression-free survival (PFS). Secondary end points included objective response rate (ORR), overall survival (OS), toxicity, and correlation of key biomarkers with efficacy outcomes. RESULTS: Eighty-three patients were enrolled. There was a similar response rate between arms (10% versus 7%). Of patients for whom tissue was assessable, 57% were human papillomavirus (HPV) positive. Median PFS was 80 days in both arms and there was no difference in OS between the two arms (211 versus 256 days). Overall toxicity was higher in arm A compared with arm B, especially in terms of nausea (53% versus 23%), vomiting (45% versus 15%), fatigue (43% versus 23%), diarrhea (40% versus 21%), and hypokalemia (25% versus 10%). Grade 3 or higher adverse events were infrequent, but more common in the combination arm although without a specific pattern. PIK3CA mutations were observed in 17% of the cases assessed, and PTEN loss was infrequently observed. CONCLUSION: The addition of PX-866 to cetuximab did not improve PFS, RR, or OS in patients with advanced, refractory HNSCC enrolled without molecular preselection. In this contemporary cohort, HPV-positive patients comprised the majority, and neither HPV-positive nor HPV-negative patients derived clinical benefit for the addition of cetuximab plus PX-866.

A phase II/III randomized study to compare the efficacy and safety of rigosertib plus gemcitabine versus gemcitabine alone in patients with previously untreated metastatic pancreatic cancer.

BACKGROUND: Rigosertib (ON 01910.Na), a first-in-class Ras mimetic and small-molecule inhibitor of multiple signaling pathways including polo-like kinase 1 (PLK1) and phosphoinositide 3-kinase (PI3K), has shown efficacy in preclinical pancreatic cancer models. In this study, rigosertib was assessed in combination with gemcitabine in patients with treatment-naïve metastatic pancreatic adenocarcinoma. MATERIALS AND METHODS: Patients with metastatic pancreatic adenocarcinoma were randomized in a 2:1 fashion to gemcitabine 1000 mg/m(2) weekly for 3 weeks of a 4-week cycle plus rigosertib 1800 mg/m(2) via 2-h continuous IV infusions given twice weekly for 3 weeks of a 4-week cycle (RIG + GEM) versus gemcitabine 1000 mg/m(2) weekly for 3 weeks in a 4-week cycle (GEM). RESULTS: A total of 160 patients were enrolled globally and randomly assigned to RIG + GEM (106 patients) or GEM (54). The most common grade 3 or higher adverse events were neutropenia (8% in the RIG + GEM group versus 6% in the GEM group), hyponatremia (17% versus 4%), and anemia (8% versus 4%). The median overall survival was 6.1 months for RIG + GEM versus 6.4 months for GEM [hazard ratio (HR), 1.24; 95% confidence interval (CI) 0.85-1.81]. The median progression-free survival was 3.4 months for both groups (HR = 0.96; 95% CI 0.68-1.36). The partial response rate was 19% versus 13% for RIG + GEM versus GEM, respectively. Of 64 tumor samples sent for molecular analysis, 47 were adequate for multiplex genetic testing and 41 were positive for mutations. The majority of cases had KRAS gene mutations (40 cases). Other mutations detected included TP53 (13 cases) and PIK3CA (1 case). No correlation between mutational status and efficacy was detected. CONCLUSIONS: The combination of RIG + GEM failed to demonstrate an improvement in survival or response compared with GEM in patients with metastatic pancreatic adenocarcinoma. Rigosertib showed a similar safety profile to that seen in previous trials using the IV formulation.

A multicenter phase 1 study of PX-866 in combination with docetaxel in patients with advanced solid tumours.

BACKGROUND: This phase I, dose-finding study determined the safety, maximum tolerated dose (MTD)/recommended phase 2 dose (RP2D), pharmacokinetics, and antitumour activity of PX-866, a phosphatidylinositol 3-kinase inhibitor, combined with docetaxel in patients with incurable solid tumours. METHODS: PX-866 was administered at escalating doses (4-8 mg daily) with docetaxel 75 mg m⁻² intravenously every 21 days. Archived tumour tissue was assessed for potential predictive biomarkers. RESULTS: Forty-three patients were enrolled. Most adverse events (AEs) were grade 1 or 2. The most frequent study drug-related AE was diarrhoea (76.7%), with gastrointestinal disorders occurring in 79.1% (docetaxel-related) and 83.7% (PX-866-related). No dose-limiting toxicities were observed. The RP2D was 8 mg, the same as the single-agent MTD. Co-administration of PX-866 and docetaxel did not affect either drug's PKs. Best responses in 35 evaluable patients were: 2 partial responses (6%), 22 stable disease (63%), and 11 disease progression (31%). Eleven patients remained on study for >180 days, including 8 who maintained disease control on single-agent PX-866. Overall median progression-free survival (PFS) was 73.5 days (range: 1-569). A non-significant association between longer PFS for PIK3CA-MUT/KRAS-WT vs PIK3CA-WT/KRAS-WT was observed. CONCLUSION: Treatment with PX-866 and docetaxel was well tolerated, without evidence of overlapping/cumulative toxicity. Further investigation with this combination is justified.

A phase I study of sorafenib and vorinostat in patients with advanced solid tumors with expanded cohorts in renal cell carcinoma and non-small cell lung cancer.

BACKGROUND: This phase I study evaluated the safety, tolerability and preliminary efficacy of sorafenib combined with vorinostat in patients with solid tumors. PATIENTS AND METHODS: Patients were treated with sorafenib 400 mg po bid daily and vorinostat 200-400 mg po days 1-14 of a 21 day cycle to establish the recommended phase II dose (RP2D). The tolerability and efficacy of the RP2D was further tested in two cohorts of 6-12 patients each with advanced RCC and NSCLC. RESULTS: 17 patients were treated in the dose escalation phase that established the RP2D at sorafenib 400 mg po bid daily, vorinostat 300 mg po days 1-14. Dose limiting toxicities (DLT) included intolerable grade 2 hand-foot syndrome and multiple grade 1 toxicities causing dose interruption for more than 14 days. Despite good tolerance in the all-comers population, the RP2D was poorly tolerated in the RCC and NSCLC cohorts with the majority being unable to finish 2 full cycles of therapy. Although there were no confirmed responses, 1 patient each with NSCLC adenocarcinoma and renal sarcoma had unconfirmed partial responses and 5 of 8 patients with RCC having durable minor responses (11-26 %), including 2 who were on treatment for nearly a year. CONCLUSIONS: Although tolerable in other tumor types, sorafenib 400 mg po bid with vorinostat 300 mg po daily days 1-14 of a 21-day cycle is not tolerable without dose reductions/delays in RCC and NSCLC patients. These patients may require lower doses than the RP2D explored within this study. No confirmed responses were seen but minor responses particularly in RCC were observed.

[Epidemic outbreak of Pseudomonas aeruginosa carbepenem-resistant producing metallo-beta-lactamase]. / Detección de un brote epidémico por Pseudomonas aeruginosa multirresistente productora de metalo-beta-lactamasa.

OBJECTIVE: To describe the nosocomial outbreak of multiresistant Pseudomonas aeruginosa producing metallo-beta-lactamase (MBL) in Cartagena (Murcia, Spain). MATERIAL AND METHODS: In May 2009, six consecutive isolations of multiresistant Pseudomonas aeruginosa were detected. These were characterized by their profile of resistance to imipenem and cephalosporins and sensibility to aztreonam, this suggesting the production of carbapenemases. The isolations were screened for MBL and a PCR for the detection of the VIM gene was performed. Secondary, all of the isolations having the same characteristics in the year 2009 were analyzed retrospectively in order to establish the possibility of an endemic infection. RESULTS: The molecular typing of the isolates revealed two clones in Pulsed Field Gel Electrophoresis (PFGE), the most frequent (Type 1) being represented by 4 isolates. All of them came from patients who were in the Intensive Care Unit. All (100%) of the isolates of the outbreak were considered to be multiresistant. PCR confirmed the presence of the VIM gene related with the production of MBL in 100% of the isolates corresponding to pulsotype 1. CONCLUSIONS: We detected the existence of an outbreak of carbapenem-resistant Pseudomonas aeruginosa producing metallo-beta-lactamase. Am evident therapeutic problem as well as a problem of nosocomial infection was considered. The isolation means should be maximized and routine controls performed for the presence of MBL given its elevated prevalence in our setting.

Capmatinib for non-small cell lung cancer.

Molecular profiling of non-small cell lung cancer (NSCLC) in the past decade has revealed numerous oncogenic driver events in NSCLC leading to several highly effective therapies. While a promising target, small-molecule inhibition of MET signaling has proven difficult. Capmatinib is a specific inhibitor of MET with Food and Drug Administration (FDA) accelerated approval in 2020 for the treatment of NSCLC harboring MET exon 14 skipping mutations. As a first-line therapy, 68% of patients in phase II clinical trials responded to capmatinib with a median duration of 12.6 months and a manageable safety profile. Although FDA approval is currently limited to MET exon 14 skipping mutations, capmatinib has shown potential in other subsets of MET-dysregulated NSCLC for which ongoing studies are underway. This review covers the preclinical and early clinical data leading to capmatinib's approval, discusses the management of treatment-related toxicities, and offers potential avenues of further research.

Naxitamab: a humanized anti-glycolipid disialoganglioside (anti-GD2) monoclonal antibody for treatment of neuroblastoma.

Therapy for high-risk neuroblastoma (HR NBL) is comprised of multimodal therapy including chemotherapy, surgery, radiation therapy, myeloablative therapy followed by autologous hematopoietic stem cell transplant, and immunotherapy. GD2 is a disialoganglioside that is highly expressed on the surface of neuroblastoma cells, with limited expression on normal tissues, which makes it an attractive target for immunologic therapy. The combination of immunotherapy with murine and chimeric anti-GD2 antibody formulations has improved outcomes compared with standard therapy in HR NBL patients. Naxitamab (Danyelza), a fully humanized anti-GD2 antibody, was developed at Memorial Sloan Kettering Cancer Center (MSKCC) to mitigate adverse reactions related to intolerance of foreign murine and chimeric antigens. Phase I and II studies demonstrating the tolerability and efficacy of naxitamab in patients with relapsed/refractory (r/r) HR NBL prompted its approval by the U.S. Food and Drug Administration (FDA) in 2020 for HR NBL with bone or bone marrow involvement. Initial outcomes with naxitamab are encouraging; however, future trials to maximize drug tolerance and elucidate its optimal role in neuroblastoma therapy in conjunction with other treatment strategies are needed. This review discusses the use of naxitamab in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF) for the treatment of r/r HR NBL.

The EMA assessment of avapritinib in the treatment of gastrointestinal stromal tumours harbouring the PDGFRA D842V mutation.

Avapritinib is a protein kinase inhibitor designed to selectively inhibit oncogenic KIT and platelet-derived growth factor receptor alpha (PDGFRA) mutants by targeting the active conformation of the kinase. On 24 September 2020, a marketing authorisation valid through the European Union was issued for avapritinib as treatment of adult patients with unresectable or metastatic gastrointestinal stromal tumours (GIST) harbouring the PDGFRA D842V mutation. The drug was evaluated in an open-label, phase I, first-in-human, dose-escalation, open-label study to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and efficacy of avapritinib in adults with unresectable or metastatic GIST. The benefit of avapritinib was observed in patients with GIST harbouring the PDGFRA D842V mutation. The overall response rate was 95% (95% confidence interval 82.3%-99.4%), with a median duration of response of 22.1 months (95% confidence interval 14.1-not estimable months). The most common adverse events were nausea, fatigue, anaemia, periorbital and face oedema, hyperbilirubinaemia, diarrhoea, vomiting, increased lacrimation, and decreased appetite. Most of the reported cognitive effects were mild memory impairment. Rarer events were cases of severe encephalopathy and intracranial or gastrointestinal bleeding. The aim of this manuscript is to summarise the scientific review of the application leading to regulatory approval in the European Union.

Integrated preclinical and clinical development of mTOR inhibitors in pancreatic cancer.

BACKGROUND: The purpose of this work was to determine the efficacy of inhibiting mammalian target of rapamycin (mTOR) in pancreatic cancer preclinical models and translate preclinical observations to the clinic. METHODS: Temsirolimus (20 mg Kg(-1) daily) was administered to freshly generated pancreatic cancer xenografts. Tumour growth inhibition was determined after 28 days. Xenografts were characterised at baseline by gene expression and comparative genomic hybridisation. Patients with advanced, gemcitabine-resistant pancreatic cancer were treated with sirolimus (5 mg daily). The primary end point was 6-month survival rate (6mSR). Correlative studies included immunohistochemistry assessment of pathway expression in baseline tumours, drug pharmacokinetics (PKs), response assessment by FDG-PET and pharmacodynamic effects in peripheral-blood mononuclear cells (PBMCs). RESULTS: In all, 4 of 17 xenografts (23%) responded to treatment. Sensitive tumours were characterised by gene copy number variations and overexpression of genes leading to activation of the PI3K/Akt/mTOR pathway. Activation of p70S6K correlated with drug activity in the preclinical studies. Sirolimus was well tolerated in the clinic, showed predictable PKs, exerted pathway inhibition in post-treatment PBMCs and resulted in a 6mSR of 26%. No correlation, however, was found between activated p70S6K in tumour tissues and anti-tumour effects. CONCLUSION: Sirolimus activity in pancreatic cancer was marginal and not predicted by the selected biomarker.

Glial reactivity after antipsychotic treatment. An experimental study in rats and its implications for psychiatry.

INTRODUCTION: The importance of the glial cells in the function of the nervous system and in its pathology has been the object of multiple studies in the last years. Specifically, their role in the action of the antipsychotics is debated. Our study has analyzed glial reactivity in rats treated with antipsychotics. METHODOLOGY: In a first ultrastructural study of the arcuate nucleus of the hypothalamus, the animals were treated with chlorpromazine for 40 days, and were sacrificed at the end of the treatment, after 20 days of rest without treatment. In another series of studies, with the light microscope and immunohistochemistry we evaluated the immunoreactivity of the glial fibrillary acidic protein (GFAP) in six regions of the central nervous system of rats treated with typical and atypical antipsychotics. RESULTS: With the electron microscope, the animals treated with chlorpromazine showed a significant reduction of the axosomatic synapses on the neurons of the hypothalamic arcuate nucleus and an increase of glial presence, as noted by the greater amount of astrocyte processes. The mentioned modifications were reversible, tending to normalize in a group of animals sacrificed 20 days after completion of the treatment. In the immunohistochemical study, the glial reaction was important in the territory of the nucleus accumbens with all the antipsychotics, moderate in the cingulate cortex, although only with atypical antipsychotics, and scarcely significant in the rest of the regions. CONCLUSIONS: Our results confirm that the glial cells are targets of the antipsychotic action, and this will allow us to better understand the action of these drugs and the role of the glial cells in the normal function of the nervous system and in the mental disease.

Zanubrutinib: a new BTK inhibitor for treatment of relapsed/refractory mantle cell lymphoma.

Mantle cell lymphoma (MCL) has historically been an aggressive disease with poor long-term survival. In the last decade, Bruton tyrosine kinase (BTK) inhibition has emerged as a new treatment strategy for MCL, especially in the relapsed/refractory (r/r) setting. Zanubrutinib, a second-generation BTK inhibitor, was approved by the U.S. Food and Drug Administration (FDA) in late 2019 for r/r MCL on the basis of combined overall response rate of 84% in a total of 118 patients from two multicenter clinical trials, BGB-3111-AU-003 and BGB-3111-206. Duration of response was 14-18 months. Although 57% of patients developed grade 3 and 4 adverse side effects including anemia, pneumonia and neutropenia, only 8% discontinued treatment suggesting zanubrutinib monotherapy was fairly well tolerated. As compared to first-generation ibrutinib, zanubrutinib has higher BTK selectivity which may result in fewer off-target effects and improved potential for combination with other targeted therapies. In addition to a confirmatory phase III trial, there are multiple ongoing studies evaluating zanubrutinib as part of two- and three-drug regimens in MCL and other B-cell malignancies. These current results and areas of further interest indicate an exciting future for zanubrutinib in the treatment of MCL.

Avapritinib for metastatic or unresectable gastrointestinal stromal tumors.

Avapritinib is a tyrosine kinase inhibitor (TKI) that has recently received Food and Drug Administration (FDA) approval for the treatment of metastatic or unresectable gastrointestinal stromal tumors harboring a platelet-derived growth factor receptor alpha (PDGFRA) exon 18 mutation. Mutations in the activation loop of PDGFRA or KIT confer resistance to conventional TKIs due to structural changes in the receptor. Avapritinib was developed to selectively target these mutations, thereby offering a new treatment option for patients in whom imatinib, sunitinib, and regorafenib have failed. This review covers the basic science and preclinical studies that guided avapritinib's development, in addition to the data currently available from early clinical studies as well as those later-stage trials that led to its approval.

Tazemetostat for the treatment of multiple types of hematological malignancies and solid tumors.

Epigenetic alterations contributing to malignancy have become a more prominent field of investigation over the past several years, as several hallmarks of cancer are substantially altered by changes in the epigenome. Enhancer of zeste homologue 2 (EZH2), an enzyme involved in silencing the transcription of various genes, is overexpressed or mutated in multiple cancers and can lead to proliferation of dedifferentiated cells. Both gain-of-function and loss-of-function mutations have been noted in hematologic cancers, with gain-of-function mutations prevalent among non-Hodgkin lymphomas. Tazemetostat is a first-in-class EZH2 inhibitor developed to target this overexpression. Phase I trials have shown it is generally well tolerated and efficacious in solid tumors as well as hematological malignancies. Tazemetostat was approved by the U.S. Food and Drug Administration (FDA) for use in epithelioid sarcoma in January 2020 on the basis of the results of a recent phase II trial, but with several clinical trials ongoing, the use of tazemetostat for hematological malignancies is a promising avenue for treatment.

Polatuzumab vedotin to treat relapsed or refractory diffuse large B-cell lymphoma, in combination with bendamustine plus rituximab.

Diffuse large B-cell lymphoma (DLBCL) is the most common non Hodgkin lymphoma (NHL) in adults, and it accounts for about 30% of adult NHL cases. Newly diagnosed patients are treated with rituximab in combination with anthracycline-containing chemotherapy, but a significant number of patients relapse after initial treatment. New strategies for relapsed lymphomas are in development among which antibody-drug conjugates (ADCs) are currently in clinical trials. Polatuzumab vedotin is a novel ADC which binds to the commonly expressed B-cell antigen CD79b, and it delivers monomethyl auristatin E, a small molecule with anti-tubulin activity. Polatuzumab vedotin in combination with bendamustine and rituximab (BR) has been approved in the U.S. and the E.U. for use in patients with relapsed or refractory DLBCL ineligible for transplant. These approvals were based on a randomized study of patients treated with either polatuzumab vedotin plus BR or BR alone, where complete response was 40% in the polatuzumab vedotin + BR group versus 18% in the BR group. The most common adverse events of this treatment were cytopenias and peripheral neuropathy.

Effects of amine molecular structure on carbon nanotubes functionalization.

Three amines with different molecular structure, triethylenetetramine (TETA) and two polyetheramines (Jeffamine D-230 and Jeffamine T-403) were employed to functionalize multi-walled carbon nanotubes (MWCNT) previously oxidized by acid treatment. The functionalized MWCNT were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, UV-vis spectroscopy and the surface modification was investigated by field emission scanning electron microscopy (FE-SEM). Thermogravimetric analysis (TGA) was employed to quantify the amount of amine groups anchored to MWCNTs. The results have shown that the efficiency of amine functionalization is in the order TETA > D-230 > T-403, thus showing that amine chemical structure and molecular weight are important parameters on functionalization of carbon nanotubes.

Abiraterone acetate to treat metastatic castration-resistant prostate cancer in combination with prednisone.

Prostate cancer is one of the most common cancers in the United States, with an estimated incidence of 164,690 cases, accounting for 9.5% of all new cancer diagnoses. The mainstay of therapy for metastatic prostate cancer involves suppressing testosterone production through androgen deprivation therapy. However, nearly all patients on androgen deprivation therapy will develop resistance to hormone therapy. An improved understanding of the biology of castration resistance has allowed for the development of novel inhibitors of the androgen axis. Agents such as abiraterone acetate, which provides additional androgen suppression by inhibiting cytochrome P450 17A (CYP17A), have improved survival outcomes of patients with advanced prostate cancer. The longest experience with abiraterone acetate is in the metastatic castration-resistant setting. However, more recent trials have demonstrated that abiraterone acetate is an option for treatment earlier in the prostate cancer paradigm. This review will cover the current use of abiraterone acetate in combination with prednisone for the treatment of castration-resistant prostate cancer.

Macrophages Promote Growth of Squamous Cancer Independent of T cells.

Oral cancers, primarily squamous cell carcinomas (SCCs), progress either slowly or aggressively. Here we assessed the role of macrophages in SCC behavior. We used mouse SCC cells derived from tumors harboring a KrasG12D activation mutation and Smad4 deletion in keratin 15-positive stem cells and a human oral SCC cell line, FaDu, which has NRAS amplification and SMAD4 deletion. SCC cells were transplanted into immune-compromised or immune-competent (syngeneic) recipients. After tumors were established, we used clodronate liposomes to ablate macrophages. We found that the number of tumor-associated macrophages (TAMs) was not affected by the presence of T cells but differed considerably among tumors derived from different SCC lines. Clodronate significantly reduced TAMs and splenic macrophages, resulting in reduced SCC volumes. Tumors with clodronate treatment did not show decreased proliferation but did exhibit increased apoptosis and reduced vascular density. FLIP (Fas-associated via death domain-like interleukin 1ß-converting enzyme inhibitory protein), an apoptosis inhibitor abundantly produced in tumor cells and TAMs, was reduced in tumor cells of clodronate-treated mice. Reduced FLIP levels correlated with reductions in phosphorylated nuclear NFκB p65 and NFκB inhibitor attenuated FLIP protein levels in SCC cells. Furthermore, TGFß1 serum levels and pSmad3 were reduced in clodronate-treated mice, but their reductions were insufficient to reverse epithelial-mesenchymal transition or TGFß-mediated angiogenesis in endothelial cells. Consequently, metastasis was not significantly reduced by macrophage reduction. However, reduced pSmad3 correlated with reduction of its transcriptional target, vascular endothelial growth factor A, in clodronate-treated tumor cells, which correlated with reduced vascular density in clodronate-treated tumors. Taken together, our study revealed that macrophages contribute to SCC expansion through interactions with tumor cells but are dispensable for SCC metastasis. Our study provides novel insights into understanding the contributions and limitations of TAMs in SCC progression.