Suresh Mohan

A Cdc42 activation cycle coordinated by PI 3-kinase during Fc receptor-mediated phagocytosis

During Fc receptor-mediated phagocytosis in macrophages, PI 3-kinase mediates transitions in the signaling by Rho-family GTPases. Receptor-activated Cdc42 increases PI 3-kinase activity. Increased 3′ phosphoinositide concentrations in phagocytic cups then deactivate Cdc42.

The PI3K/Akt/mTOR axis in head and neck cancer: functions, aberrations, cross-talk, and therapies

Head and neck squamous cell carcinoma (HNSCC) is one of the most morbid, mortal, and genetically diverse malignancies. Although HNSCC is heterogeneous in nature, alterations in major components of the PI3K/Akt/mTOR pathway are consistently observed throughout the majority of HNSCC cases. These alterations include genetic aberrations, such as mutations or DNA copy number variations, and dysregulation of mRNA or protein expression. In normal physiology, the PI3K/Akt/mTOR axis regulates cell survival, growth, and metabolism. However, alterations in this pathway lead to the malignant phenotype which characterizes HNSCC, among many other cancers. For this reason, both pharmaceutical companies and academic institutions are actively developing and investigating inhibitors of PI3K, Akt, and mTOR in preclinical and clinical studies of HNSCC. Many of these inhibitors have shown promise, while the effects of others are tempered by the mechanisms through which HNSCC can evade therapy. As such, current research aimed at elucidating the interactions between PI3K/Akt/mTOR and other important signaling pathways which may drive resistance in HNSCC, such as p53, NF-κB, and MAPK, has become a prominent focus toward better understanding how to most effectively treat HNSCC.

MEK Inhibitor PD-0325901 Overcomes Resistance to PI3K/mTOR Inhibitor PF-5212384 and Potentiates Antitumor Effects in Human Head and Neck Squamous Cell Carcinoma

Purpose: Head and neck squamous cell carcinomas exhibit variable sensitivity to inhibitors of the PI3K/mTOR pathway, an important target of genomic alterations in this cancer type. The mitogen-activated protein kinase kinase (MEK)/ERK/activator protein 1 (AP-1) and nuclear factor-κB (NF-κB) pathways are also frequently co-activated, but their roles in resistance mechanisms to PI3K/mTOR inhibitors and as therapeutic targets in head and neck squamous cell carcinoma (HNSCC) are not well defined. Experimental Design: We determined the IC50s of dual PI3K/mTOR inhibitor PF-05212384 (PF-384) by XTT assays in 14 HNSCC lines with PI3K/Akt/mTOR cascade alterations. In two resistant models, we further characterized the molecular, cellular, and in vivo attributes and effects of combining PF-384 with MEK inhibitor PD-0325901 (PD-901). Results: PF-384 IC50s varied between 0.75 and 133 nmol/L in 14 HNSCC lines with overexpression or mutations of PIK3CA, and sensitivity correlated with increased phospho-AKT(T308/S473). In resistant UMSCC-1 and -46 models, PF-384 increased G0-/G1-phase accumulation but weakly induced sub-G0 cell death. PF-384 inhibited direct targets of PI3K/mTOR, but incompletely attenuated co-activated ERK and UMSCC-1 xenograft growth in vivo. PD-901 strongly inhibited MEK/ERK targets, and the combination of PF-384 and PD-901 inhibited downstream NF-κB and AP-1 transactivation, and IL8 and VEGF production in vitro. PD-901 potently inhibited tumor growth alone and with PF384, enhanced antiproliferative, apoptotic, and anti-angiogenesis activity in vivo. Conclusions: PI3K/mTOR inhibitor PF-384 exhibits variable activity in a panel of HNSCC cell lines with differing PIK3CA expression and mutation status. MEK inhibitor PD-901 overcomes resistance and enhances antitumor effects observed with PF-384 in vivo. Clin Cancer Res; 21(17); 3946–56. ©2015 AACR.

MEK Inhibitor PD-0325901 Overcomes Resistance to CK2 Inhibitor CX-4945 and Exhibits Anti-Tumor Activity in Head and Neck Cancer

The serine-threonine kinase CK2 exhibits genomic alterations and aberrant overexpression in human head and neck squamous cell carcinomas (HNSCC). Here, we investigated the effects of CK2 inhibitor CX-4945 in human HNSCC cell lines and xenograft models. The IC50s of CX-4945 for 9 UM-SCC cell lines measured by MTT assay ranged from 3.4-11.9 μM. CX-4945 induced cell cycle arrest and cell death measured by DNA flow cytometry, and inhibited prosurvival mediators phospho-AKT and p-S6 in UM-SCC1 and UM-SCC46 cells. CX-4945 decreased NF-κB and Bcl-XL reporter gene activities in both cell lines, but upregulated proapoptotic TP53 and p21 reporter activities, and induced phospho-ERK, AP-1, and IL-8 activity in UM-SCC1 cells. CX-4945 exhibited modest anti-tumor activity in UM-SCC1 xenografts. Tumor immunostaining revealed significant inhibition of PI3K-Akt-mTOR pathway and increased apoptosis marker TUNEL, but also induced p-ERK, c-JUN, JUNB, FOSL1 and proliferation (Ki67) markers, as a possible resistance mechanism. To overcome the drug resistance, we tested MEK inhibitor PD-0325901 (PD-901), which inhibited ERK-AP-1 activation alone and in combination with CX-4945. PD-901 alone displayed significant anti-tumor effects in vivo, and the combination of PD-901 and CX-4945 slightly enhanced anti-tumor activity when compared with PD-901 alone. Immunostaining of tumor specimens after treatment revealed inhibition of p-AKT S129 and p-AKT T308 by CX-4945, and inhibition of p-ERK T202/204 and AP-1 family member FOSL-1 by PD-901. Our study reveals a drug resistance mechanism mediated by the MEK-ERK-AP-1 pathway in HNSCC. MEK inhibitor PD-0325901 is active in HNSCC resistant to CX-4945, meriting further clinical investigation.

SMAC Mimetic Birinapant plus Radiation Eradicates Human Head and Neck Cancers with Genomic Amplifications of Cell Death Genes FADD and BIRC2

Comparison of tumors from The Cancer Genome Atlas (TCGA) reveals that head and neck squamous cell carcinomas (HNSCC) harbor the most frequent genomic amplifications of Fas-associated death domain (FADD), with or without Baculovirus inhibitor of apoptosis repeat containing BIRC2 (cIAP1), affecting about 30% of patients in association with worse prognosis. Here, we identified HNSCC cell lines harboring FADD/BIRC2 amplifications and overexpression by exome sequencing, RT-PCR, and Western blotting. In vitro, FADD or BIRC2 siRNA knockdown inhibited HNSCC displaying amplification and increased expression of these genes, supporting their functional importance in promoting proliferation. Birinapant, a novel SMAC mimetic, sensitized multiple HNSCC lines to cell death by agonists TNFα or TRAIL and inhibited cIAP1>XIAP>IAP2. Combination of birinapant and TNFα induced sub-G0 DNA fragmentation in sensitive lines and birinapant alone also induced significant G2-M cell-cycle arrest and cell death in UM-SCC-46 cells. Gene transfer and expression of FADD sensitized resistant UM-SCC-38 cells lacking FADD amplification to birinapant and TNFα, supporting a role for FADD in sensitization to IAP inhibitor and death ligands. HNSCC varied in mechanisms of cell death, as indicated by reversal by inhibitors or protein markers of caspase-dependent apoptosis and/or RIPK1/MLKL-mediated necroptosis. In vivo, birinapant inhibited tumor growth and enhanced radiation-induced TNFα, tumor responses, and host survival in UM-SCC-46 and -11B xenograft models displaying amplification and overexpression of FADD+/- BIRC2 These findings suggest that combination of SMAC mimetics such as birinapant plus radiation may be particularly active in HNSCC, which harbor frequent FADD/BIRC2 genomic alterations. Cancer Res; 76(18); 5442-54. ©2016 AACR.

A Case of Trigeminocardiac Reflex During Infrastructure Maxillectomy

IMPORTANCE The trigeminocardiac reflex refers to the sudden development of bradycardia or even asystole with arterial hypotension from manipulation of any sensory branches of the trigeminal nerve. Although it has only rarely been associated with morbidity and tends to be self-limited with removal of the stimulus, it is an important phenomenon for head and neck surgeons to recognize and respond to. OBSERVATIONS We present the case of a woman in her late 60s with maxillary alveolar ridge squamous cell carcinoma who developed episodes of asystole and bradycardia during posterior maxillary manipulation for an infrastructure maxillectomy at a tertiary academic medical center. Administration of atropine and removal of the inciting stimulus sufficed to extinguish the episodes and allow procedure completion. CONCLUSIONS AND RELEVANCE The trigeminocardiac reflex can be provoked by a number of head and neck and skull base procedures including parotidectomy and posterior maxillectomy. Surgeons and anesthesiologists should be wary of inciting the reflex during manipulation of trigeminal branches. Careful dissection for prevention and early intervention with stimulus removal and anticholinergic use as needed are paramount to ensure good outcomes.

Abstract 3821: Targeted therapy for head and neck squamous cell carcinoma using the novel SMAC-mimetic birinapant

Head and neck squamous cell carcinoma (HNSCC) is the most prevalent cancer affecting the upper aerodigestive tract, with an annual incidence of 600,000 patients and a five year survival of approximately 60% worldwide. Molecular mechanisms driving the development of HNSCC have recently begun to be discovered, with The Cancer Genome Atlas (TCGA) uncovering the genomic landscape of 279 cases of HNSCC. Alterations in cell death pathways were commonly found in the TCGA analysis, with ∼30% of samples harboring 11q13/22 amplifications and overexpression of genes encoding for Fas-associated death domain (FADD) and/or cellular Inhibitor of Apoptosis Proteins 1/2 (cIAP1/2). While overexpression of cIAP1 has been implicated in resistance to cytotoxic therapies, the role of FADD amplification as a target for therapy and in mechanisms of cell death is not well understood. Birinapant is a novel second mitochondria-derived activator of caspases (SMAC)-mimetic that targets and promotes degradation of cIAPs. Its clinical efficacy is currently being investigated in phase II trials of patients with ovarian cancer and leukemia. However, its preclinical and clinical efficacies have not been tested in HNSCC and genomic markers of sensitivity remain to be defined. Here we hypothesized that overexpression of FADD and cIAP1/2 could modulate birinapant sensitivity in HNSCC. To test this hypothesis, we have treated a panel of 11 HPV(-) and 8 HPV(+) HNSCC cell lines with birinapant alone and in combination with death agonists TNFα or TRAIL. UMSCC-46, an HPV(-) cell line which possesses high FADD expression, was the only cell line to reach half maximal inhibitory concentration (IC50) 72 hours post treatment with birinapant alone (IC50 = 10.7 nM); however, 8 of 11 HPV(-) cell lines and all 8 HPV(+) cell lines attained an IC50 (range: 0.1 - 794 nM) when treated with birinapant in combination with either TNFα or TRAIL. We further demonstrated that forced FADD overexpression in a previously resistant cell line (UMSCC-38) led to sensitization when treated with birinapant and TNFα. In vivo, two FADD/cIAP1 overexpressing murine xenograft models of HNSCC, UMSCC-46 and UMSCC-11B, were treated with birinapant at 15 mg/kg or 30 mg/kg every 3 days for a total of 10 treatments. The single modality regimen led to tumor growth inhibition and prolonged host survival. Additionally, combination treatment with birinapant 15 mg/kg and radiation 2Gy/day M-F for 2 weeks synergistically induced TNFα and led to a cure of animals bearing UMSCC-46 xenografts. Mechanistically, birinapant enhanced degradation of cIAP1 and modulated caspase apoptotic or MLKL necroptotic cell death markers in vitro and in vivo. These results suggest that patients harboring genomic alterations in FADD and/or cIAP overexpression may be candidates for treatment with birinapant and radiation. Supported by NIDCD intramural projects ZIA-DC-000073, and 74. Citation Format: Adeeb Derakhshan, Danielle Eytan, Grace Snow, Sophie Carlson, Anthony Saleh, Hui Cheng, Stephen Schiltz, Suresh Mohan, Shaleeka Cornelius, Jamie Coupar, Anastasia Sowers, Lydia Hernandez, James Mitchell, Christina Annunziata, Zhong Chen, Carter Van Waes. Targeted therapy for head and neck squamous cell carcinoma using the novel SMAC-mimetic birinapant. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3821.

Ossifying Parotid Carcinoma ex Pleomorphic Adenoma.

We present a unique case of an extensively ossified carcinoma ex pleomorphic adenoma (CXPA) in a 76-year-old man with a five-year history of a slowly growing parotid mass. Fine-needle aspiration of the mass was nondiagnostic. A computed tomography (CT) scan of the lesion revealed a well-circumscribed mass with peripheral calcification. Initial pathological analysis suggested a benign parotid mass, but rigorous decalcification revealed noninvasive CXPA. The patient underwent complete resection of the mass and remained disease-free nine months later. Extensive ossification of a seemingly benign parotid mass may mask areas of carcinoma that may progress if left untreated.

Abstract 2687: CK2 inhibitor CX-4945 modulates AKT, NF-kB, TP53 and MEK inhibitor PD-325901 targets AP1 mediated CK2 inhibitor drug resistance in head and neck cancer

We previously identified upregulated kinase CK2 as an activator of NF-B and repressor of TP53 in promoting the malignant phenotype of head and neck squamous cell carcinoma (HNSCC). Here, we investigate the anti-tumor effects of a small molecule CK2 inhibitor CX-4945, alone and in combination with MEK inhibitor PD-0325901 (PD-901), in human HNSCC models in vitro and in vivo. CX-4945 IC 50 s ranged from 3.4 µM to 11.9 µM in 9 UMSCC cell lines. CX-4945 caused S and G2/M cell cycle arrest, and induced sub-G0 DNA fragments, indicating cell death. CX-4945 inhibited NF-B and BcL-XL prosurvival reporter genes in wild type (wt) TP53 (UMSCC1) and mutant (mt) TP53 (UMSCC46) cell lines, and concurrently upregulated proapoptotic TP53, p21 and prosurvival AP-1 activity only in the wtTP53 cell line. Correspondingly, CK2 phosphorylation of AKT S129 as well as T308 and S473 prosurvival signaling was reduced in both cell lines, but AP-1 inducing p-Erk1/2 Thr202/204 was increased in the wtTP53 cell line. In the UMSCC1 xenografts, CX-4945 treatment significantly decreased PI3K/Akt/mTOR pathway signaling by immunostaining. While CX-4945 increased TP53 and TUNEL apoptosis marker staining at early time points (13 days after CX4945 treatment), an opposing increase in p-Erk, FosL1, cJun, JunB, and proliferation (Ki67) were also observed. Consistent with these opposing effects, no significant tumor reduction or improvement in survival was observed by CX-4945 alone. However, combination of CX-4945 with MEK/ERK inhibitor PD-901 exhibited significant synergistic anti-proliferative effects in vitro. Significant anti-tumor effects were observed with MEK inhibitor alone and in combination with CX-4945 in vivo, further supporting a role for MEK/ERK/AP-1 in resistance to CX-4945 in this HNSCC model. Supported by NIH Medical Research Scholars Program and NIDCD intramural projects ZIA-DC-000016, 73 and 74. Citation Format: Yansong Bian, Jiawei Han, Vishnu Kannabiran, Suresh Mohan, Jay Friedman, Kenna Anderes, Zhong Chen, Carter Van Waes. CK2 inhibitor CX-4945 modulates AKT, NF-kB, TP53 and MEK inhibitor PD-325901 targets AP1 mediated CK2 inhibitor drug resistance in head and neck cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2687. doi:10.1158/1538-7445.AM2014-2687

Long-Term Outcomes of Free Gracilis Muscle Transfer for Smile Reanimation in Children

Objective To evaluate long‐term outcomes of free gracilis muscle transfer (FGMT) for smile reanimation on smile excursion, facial symmetry, and quality of life in a cohort of children with facial palsy. Study design A retrospective analysis of 40 pediatric patients who underwent FGMT for facial palsy at the Massachusetts Eye and Ear Infirmary Facial Nerve Center was performed. Preoperative and postoperative photography and videography were used to quantify smile excursion and facial symmetry. Preoperative and postoperative quality of life was assessed with the Facial Clinimetric Evaluation (FaCE) survey, a validated, patient‐based instrument for evaluating facial impairment and disability. Results Of the 40 patients who underwent FGMT for facial palsy, 38 patients had complete data including preoperative and postoperative photography and videography from 3 months to 10 years following surgery; 13 cases had >5 years of follow‐up. FGMT resulted in significant improvements in smile excursion within several months, with continued improvements in smile excursion and symmetry demonstrated more than 5 years later. Fifteen patients completed preoperative and postoperative FaCE surveys, which demonstrated significant improvement in quality of life scores following FGMT. Conclusions FGMT significantly improves smile, facial asymmetry, and quality of life for years after this surgery for facial palsy.