Head and neck squamous cell carcinoma is a heterogeneous

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1 TARGETING THE PI3K PATHWAY IN HNSCC Targeting the PI3K Pathway in Head and Neck Squamous Cell Carcinoma Pedro Henrique Isaacsson Velho, MD, Gilberto Castro Jr, MD, PhD, and Christine H. Chung, MD OVERVIEW Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous disease arising from the mucosal epithelia in the head and neck region. The most common risk factors are tobacco use, alcohol consumption, and HPV infection, particularly in the oropharynx. The HPV-positive HNSCC is biologically and clinically distinct from the HPV-negative HNSCC; however, deregulations within the phosphatidylinositol 3-kinase (PI3K) pathway are frequent in both HPV-positive and HPV-negative HNSCC as it is the most frequently altered oncogenic pathway with a gain-of-function in HNSCC. This article reviews the basic biology and clinical data from the trials involving anticancer agents targeting the PI3K pathway in HNSCC. It also discusses the difficulties of translating the preclinical data to tangible clinical efficacy of these agents in patients with HNSCC even when there is significant preclinical data suggesting the PI3K pathway is a promising therapeutic target in HNSCC. We conclude that additional studies to determine appropriate patient selection for the activation of PI3K pathway and to develop targeted agents either as a monotherapy or combination therapy with favorable toxicity profiles are required before a broader clinical application. Head and neck squamous cell carcinoma is a heterogeneous disease originating from the mucosal epithelia in the head and neck region, most commonly the oral cavity, oropharynx, hypopharynx, and larynx. The risk factors are tobacco use, alcohol consumption, and HPV infection, particularly in the oropharynx. 1,2 The HPV-positive HNSCC is now established as a separate entity with distinct clinical characteristics, including younger age of onset, better performance status, less smoking history, and its association with high-risk sexual behaviors compared to the HPV-negative HNSCC. 3,4 In addition, the HPV-positive HNSCC has a distinct molecular profıle compared to the HPV-negative HNSCC, including lack of TP53 and CDKN2A mutations; however, mutations or copy number variations of genes within the PI3K pathway are frequent in both HPV-positive and HPV-negative HNSCC as it is the most frequently altered oncogenic pathway with a gain-of-function in HNSCC. 5 This article reviews the basic biology and clinical data from trials involving the PI3K pathway inhibitors in patients with HNSCC. BASIC BIOLOGY OF THE PI3K PATHWAY P13Ks are divided into three classes: class I, II, and III. The differences in these classes are comprehensively reviewed by Thorpe et al. 6 Class I is further divided into subclass IA and IB in mammals. Class IA PI3Ks are heterodimeric kinases consisting of a p110 catalytic subunit (p110-alpha, p110-beta, and p110-delta encoded by PIK3CA, PIK3CB, and PIK3CD, respectively) and a p85 regulatory subunit (p85-alpha and its splice variants, p55-alpha and p50-alpha, encoded by PIK3R1; p85-beta encoded by PIK3R2; and p55-gamma encoded by PIK3R3). These three p110 catalytic subunit isoforms can form a heterodimer with any of the fıve p85 regulatory subunits. Class IB PI3Ks are heterodimeric kinases consisting of a p110-gamma catalytic subunit encoded by PIK3CG and a p101 or p87 regulatory subunit encoded by PIK3R5 and PIK3R6, respectively. Unlike class I PI3Ks, class II PI3Ks are monomeric lipid kinases without a regulatory subunit. There are three class II isoforms, including PI3K- C2-alpha, PIK3-C2-beta, and PIK3-C2-gamma encoded by PIK3C2A, PIK3C2B, and PIK3C2G, respectively. VPS34 is the sole Class III PI3K encoded by PIK3C3 and forms a heterodimer with VPS15 encoded by PIK3R4. Activation of the PI3K signaling pathway is highly regulated. PI3K activation is initiated by activated receptor tyrosine kinases such as ErbB family receptors, fıbroblast growth factor receptors, insulin-like growth factor 1 receptor and others, as well as G protein-coupled receptors. 6,7 On activation, class I PI3Ks translocate to the plasma membrane where inhibition by the p85 regulatory subunit is relieved, and the p110 catalytic subunit catalyzes the phosphorylation From the Department of Clinical Oncology, Instituto do Câncer do Estado de São Paulo, Faculdade de Medicina da Universidade de Sao Paulo, Sao Paulo, Brazil; Department of Oncology and Department of Head and Neck Surgery-Otolaryngology, The Johns Hopkins Medical Institutions, Baltimore, MD. Disclosures of potential conflicts of interest are found at the end of this article. Corresponding author: Christine H. Chung, MD, Department of Oncology and Department of Head and Neck Surgery-Otolaryngology, Johns Hopkins University School of Medicine, Sidney Kimmel Comprehensive Cancer Center, 1550 Orleans St. CRB-2 Room 546, Baltimore, MD ; cchung11@jhmi.edu by American Society of Clinical Oncology. asco.org/edbook 2015 ASCO EDUCATIONAL BOOK 123

2 ISAACSSON VELHO, CASTRO JR, AND CHUNG FIGURE 1. The PI3K Network RTK GPCR PIP 3 PIP 2 P P 2 2 P P P RAS RAF MEK P P p85 Class I Pi3K RICTOR mtor GβL P AKT PTEN P PDK1 TSC1/2 PRAS40 SGK PKA PKC P70S6K IRS1 ERK Cyclin D1 Cell cycle, progression n GSK3β Forkhead BAD p27 FAS L BCL2 RAPTOR mtor GβL 4EBP EIF4B EEF2K RPS6 n of protein synthesis and cell growth Glucose metabolism Survival Class I PI3Ks are heterodimeric kinases consisting of a p110 catalytic subunit (class 1A-p110-alpha, p110-beta, and p110-delta, and class 1B-p110-gamma proteins) and a p85 regulatory subunit. PI3Ks are activated by receptor tyrosine kinases and GPCRs. PI3Ks phosphorylate PIP 2 to PIP 3, which functions as a second messenger. PIP 3 acts by recruiting downstream protein kinases, such as PDK1 and AKT, to the cell membrane that results in their activation. Subsequently, further downstream signaling network is activated and influence important cellular functions, such as cell proliferation, cell cycle, metabolism, and cell survival. Abbreviations: 4EBP1, 4E binding protein 1; BCL-2, B-cell lymphoma 2; EEF2K, eukaryotic elongation factor-2 kinase; EIF4B, eukaryotic translation initiation factor 4B; ERK, extracellular signalregulated kinase; FASL, Fas ligand; GPCR, G-protein coupled receptor; IRS1, insulin receptor substrate 1; mtor, mammalian target of rapamycin; PI3K, phosphatidylinositol 3-kinase; PIP 2, phosphatidylinositol-4,5-bisphosphate; PIP 3, phosphatidylinositol-3,4,5-trisphosphate; PTEN, phosphatase and tensin homolog; RICTOR, rapamycin-insensitive companion of mtor; RPS6, ribosomal protein S6; SGK3, serine/threonine-protein kinase 3; TSC, tuberous sclerosis protein. of phosphatidylinositol 4,5-bisphosphate (PIP 2 ) to phosphatidylinositol 3,4,5-trisphosphate (PIP 3 ). In turn, PIP 3 acts as a second messenger and triggers AKT-dependent and AKTindependent signaling pathways (Fig. 1). 6-8 Activated AKT further phosphorylates downstream targets, including mammalian target of rapamycin (mtor), 9 a master regulator of cellular proliferation, metabolism, and protein translation. Activation of the PI3K pathway is negatively regulated by a lipid phosphatase, phosphatase and tensin homolog (PTEN), which catalyzes the dephosphorylation of PIP 3 to PIP 2 and governs numerous cellular processes. 10 Although class I PI3Ks are extensively studied, physiological roles of class II and class III PI3Ks are poorly understood; therefore, they will KEY POINTS Deregulations within the phosphatidylinositol 3-kinase (PI3K) pathway are frequent in both HPV-positive and HPVnegative HNSCC. PIK3CA is the most commonly mutated oncogene in HNSCC. There are numerous clinical trials involving PI3K and mammalian target of rapamycin (mtor) inhibitors, but clinical benefits of these agents in unselected patients with HNSCC are unclear. Predictive biomarkers of PI3K and mtor inhibitor response are still under development. Further studies are required to develop the PI3K pathway targeted agents with favorable toxicity profiles. not be discussed in this review because they are beyond the scope of this article. THE PI3K PATHWAY DEREGULATION IN HEAD AND NECK SQUAMOUS CELL CARCINOMA With advancements in sequencing technology, HNSCC have been extensively sequenced through whole-genome sequencing, whole-exome sequencing, and targeted sequencing of cancer-related genes. 5,11-14 Collective data estimate the mutations and/or copy number variations of PIK3CA are detected in 32% of HNSCC (130/480 [27%] of HPV-negative and 63/171 [37%] of HPV-positive HNSCC). 14 Furthermore, a loss of PTEN, the PI3K negative regulator, also is frequently seen in patients with HNSCC, resulting in unrestrained activation of the pathway. Earlier studies showed 14% to 40% of patients with HNSCC to have PTEN loss of function because of a loss of heterozygosity or mutation, whereas recent tumor DNA sequencing studies show mutations or copy number variations in approximately 11% of HPV-positive and 5% of HPV-negative HNSCC When the mitogenic pathways (MAPK, JAK/STAT, and PI3K) relevant to HNSCC were evaluated, genes in the PI3K pathway were most frequently altered (30.5%). 17 In addition to the detectable genomic alteration by tumor sequencing, suffıcient data suggest that deregulation of the PI3K pathway plays an important role in the development and metastasis of HNSCC associating with poor prognosis For patients with HPV-positive HNSCC, recent studies also have demonstrated that epidermal growth factor recep ASCO EDUCATIONAL BOOK asco.org/edbook

3 TARGETING THE PI3K PATHWAY IN HNSCC tor (EGFR) and PI3K signaling are required for the viral entry into the cells that may be pertinent in this HNSCC subtype. 21,22 Pretreatment of patients with keratinocytes or cervical cancer cells in vitro with an EGFR inhibitor (gefıtinib) and two different PI3K inhibitors (PI-103 and wortmannin) is suffıcient to inhibit HPV-16 endocytosis and capable of preventing viral entry. In addition, PI3K/mTOR activation and suppression of autophagy in the early stages of patients with HPV16 infection are crucial for viral entry and infection. 22 Following HPV infection, the PI3K pathway appears to play an important role in established HPV-positive HNSCC as well. Gene-expression profıle analysis of HNSCC has determined that HPV-positive HNSCC upregulates genes within the 3q26 29 chromosomal region, which is the locus containing PIK3CA. Further analyses by RT-PCR and reverse phase protein arrays confırm that PIK3CA is upregulated in patients with HPV-positive HNSCC compared to HPV-negative HNSCC. 20,23 CLINICAL DEVELOPMENT OF PI3K INHIBITORS IN HEAD AND NECK SQUAMOUS CELL CARCINOMA As PIK3CA, which encodes the catalytic subunit of PI3K, is overall the most frequently altered oncogene in human cancers, numerous PI3K-targeted agents currently are in clinical development. In a preclinical study using HNSCC patient tumor-derived xenografts (PDXs), PDXs harboring PIK3CA mutations were shown to be more sensitive to the PI3K and mtor dual inhibitor, NVP-BEZ235, as compared with those lacking PIK3CA mutations. 17 Encouraged by the effıcacy data seen in preclinical models such as these PDX studies, a number of clinical trials in patients with HNSCC currently are underway to evaluate the effıcacy of small molecules that inhibit key points of this pathway (Table 1). PI3K inhibitors are under evaluation as a monotherapy or in combination with previously established radiation and/or chemotherapy regimens in patients with HNSCC. PI3K inhibitors, such as buparlisib, BYL-719, or PX-866, are being investigated in phase II trials in patients with HNSCC in combination with chemotherapy or cetuximab. PI3K and mtor share similarities in their kinase domain. Some compounds are developed to inhibit Class I PI3K isoforms, as well as mtorc1 and mtorc2, and many of these multikinase inhibitors are in clinical development (e.g., NVP-BEZ235). 24 However, although the biologic rationale is strong for the use of PI3K inhibitors, the effıcacy of these agents presently is unclear in unselected patients with HNSCC. In a randomized phase II trial in recurrent and/or metastatic patients with HNSCC, PX-866 was administered with cetuximab, and it showed no evidence of clinically meaningful benefıts. 25 Eightythree patients were randomly assigned 1:1 to receive cetuximab once a week with or without PX-866; there were no complete responses. The objective response rates were 10% in the combination therapy and 7% in the cetuximab monotherapy, without any differences in disease control rates (55% vs. 56%), median progression-free survival (80 days for both groups), and overall survival (211 days in the PX-866 and cetuximab arm vs. 256 days in the cetuximab alone arm). In addition, although there was no clear benefıt of adding PX-866 in these previously heavily treated patients with HNSCC, the toxicities were more pronounced in the combination arm compared to the cetuximab alone arm. These toxicities included worse nausea (53% vs. 23%), vomiting (45% vs. 15%), fatigue (43% vs. 23%), diarrhea (40% vs. 21%), rash (45% vs. 31%), hypokalemia (25% vs. 10%), and dysphagia (18% vs. 3%). The clinical development of NVP-BEZ235 has been halted because of intolerable toxicities. For the further development, additional studies with appropriate patient selection with the activation of PI3K pathway and improved toxicity profıles are required. Furthermore, numerous mtor inhibitors also are being evaluated in patients with HNSCC. These mtor inhibitors include everolimus and temsirolimus through phase II studies in neoadjuvant (or induction) chemotherapy and recurrent and/or metastatic settings. Rapamycin analogs, such as temsirolimus and everolimus, specifıcally inhibit mtorc1 and already are approved by the U.S. Food and Drug Administration in renal cell carcinoma, subependymal giant cell astrocytoma, pancreatic neuroendocrine tumors, and hormone receptor positive, HER2-negative breast cancer in combination with exemestane in the United States In a phase II trial, a combination of temsirolimus and low-dose weekly carboplatin and paclitaxel was well tolerated in patients with recurrent and/or metastatic HNSCC. 31 When 30 patients were treated with the combination regimen, the overall radiological response rate was 43% with one complete response and 12 partial responses; median overall survival was 12.9 months. Overall, this regimen was well tolerated. The most common (greater than three) adverse events were neutropenia, dysphagia, and anemia. However, other combination trials evaluating temsirolimus and erlotinib in a similar recurrent and/or metastatic population of patients with HNSCC revealed intolerable toxicities such as fatigue, diarrhea, and infection, which resulted in early closure of the study. 32 There are additional drugs that target other proteins within the PI3K pathway beyond PI3Ks and mtors. Novel Akt inhibitors, such as MK2206, AZD5363, and GSK690693, are in development through phase I and II clinical trials. 33 Although it is not a direct inhibitor of mtor, metformin, which is commonly used in type II diabetes, also is being investigated as an anticancer agent in patients with HNSCC. 34 Metformin indirectly inhibits mtorc1 by increasing intracellular adenosine monophosphate (AMP) levels mediated by AMP-activated protein kinase (AMPK) dependent and independent mechanisms, and may play a role in management of HNSCC. 35,36 ACTIVATION OF THE PI3K PATHWAY AS A BIOMARKER OF TREATMENT RESPONSE Development of PI3K pathway inhibitors has not been straightforward because of the demonstrated lack of effıcacy in unselected patient populations and unexpected degrees of asco.org/edbook 2015 ASCO EDUCATIONAL BOOK 125

4 ISAACSSON VELHO, CASTRO JR, AND CHUNG Table 1. Active Clinical Trials Evaluating PI3K/AKT/mTOR Targeted Agents in Patients with Locally Advanced, Recurrent, and/or Metastatic HNSCC* Targeted Agent Additional Targeted Agent Additional Therapy Inclusion Criteria Phase Clinical Trial Identifier PI3K Inhibitor PX Docetaxel Recurrent or metastatic HNSCC/NSCLC I/II NCT PX-866 Cetuximab - Recurrent or metastatic HNSCC/CRC I/II NCT BYL Recurrent or metastatic HNSCC II NCT BYL-719 Cetuximab - Recurrent or metastatic HNSCC I/II NCT BYL-719 Paclitaxel Recurrent or metastatic HNSCC/BRC I NCT Buparlisib - - Recurrent or metastatic HNSCC II NCT Buparlisib Cetuximab - Recurrent or metastatic HNSCC I/II NCT Buparlisib - Paclitaxel Recurrent or metastatic HNSCC II NCT Buparlisib - IMRT, cisplatin Locally advanced HNSCC Ib NCT PI3K/mTOR Inhibitor NVP-BEZ Recurrent or metastatic solid tumors I NCT NVP-BEZ235 NVP-BKM120 Paclitaxel Recurrent or metastatic solid tumors I NCT NVP-BEZ235 MEK Recurrent or metastatic solid tumors I NCT NVP-BEZ235 Everolimus - Recurrent or metastatic solid tumors I/II NCT mtor Inhibitor Everolimus - - Recurrent or metastatic HNSCC II NCT Everolimus - - Recurrent or metastatic HNSCC II NCT Everolimus Cetuximab Carboplatin Recurrent or metastatic HNSCC I/II NCT Everolimus Erlotinib - Recurrent or metastatic HNSCC II NCT Everolimus Vatalinib - Recurrent or metastatic solid tumors I NCT Everolimus - IMRT, cisplatin Locally advanced HNSCC I NCT Everolimus - Docetaxel, cisplatin Locally advanced HNSCC I NCT Everolimus - Carboplatin, paclitaxel Locally advanced HNSCC I/II NCT Everolimus Cetuximab Cisplatin, paclitaxel Locally advanced HNSCC II NCT Temsirolimus - - Recurrent or metastatic HNSCC II NCT Temsirolimus - Carboplatin, paclitaxel Recurrent or metastatic HNSCC I/II NCT Temsirolimus Cetuximab - Recurrent or metastatic HNSCC II NCT Temsirolimus Cetuximab Cisplatin Recurrent or metastatic HNSCC I/II NCT Temsirolimus Erlotinib - Recurrent or metastatic HNSCC II NCT Sirolimus - - Recurrent or metastatic HNSCC I/II NCT Sirolimus - Grapefruit juice Recurrent or metastatic solid tumors I NCT Ridaforolimus Cetuximab - Recurrent or metastatic HNSCC/NSCLC/CRC I NCT Metformin - Paclitaxel Recurrent or metastatic HNSCC II NCT Abbreviations: HNSCC, head and neck squamous cell carcinoma; IMRT, intensity modulated radiation therapy; NSCLC, non-small cell lung cancer; CRC, colorectal cancer; BRC, breast cancer. *All trial data are available at toxicity. Because of the ease of tumor DNA testing for PIK3CA mutations, many have proposed that the PIK3CA mutations are an integral biomarker for screening patient populations with PI3K pathway activation for future clinical trials. 37 Some studies suggest that patients with HPV-positive HNSCC would be more sensitive because of frequent PIK3CA mutations and enrich the trial. 17 However, in a recent study of cetuximab with or without PX-866, tumor HPV status was assessed by p16 immunohistochemistry. 25 Twenty-six patients (57%) of 46 with available tissue were HPV positive and 20 patients (43%) were HPV negative. There was no association between the tumor HPV status and response. PIK3CA mutations were detected in 17% of patients, but no response was seen in these eight patients with the PIK3CA mutation-harboring tumors. In addition, the PI3K pathway activation through compensatory receptor tyrosine kinase activation, such as MET and HER3, has been proposed as one of the resistance mechanisms of EGFR inhibitors in preclinical studies, suggesting PI3K/mTOR inhibitors may be developed in patients who are EGFR inhibitor resistant in addition to patients with the PIK3CA mutations. 38,39 In a recent preclinical study, the combined activity of cetuximab and mtor inhibitors in patients with HNSCC was evaluated. Cetuximab-sensitive ASCO EDUCATIONAL BOOK asco.org/edbook

5 TARGETING THE PI3K PATHWAY IN HNSCC HNSCC cells were transduced to express PIK3CA and RAS oncogenes, and tumor xenografts were treated with control, cetuximab, or rapamycin. The in vivo study showed that patients with HNSCC tumor xenografts expressing mutant PI3K and Ras proteins relapsed a few weeks after the initial response to cetuximab treatments. However, the addition of rapamycin dramatically increased antitumor activity in these cetuximab-resistant tumors, supporting the rationale to evaluate a combination of cetuximab/mtor inhibitors for treatment of patients with HNSCC. 39 However, a vast majority of the model systems use the H1047R PI3KCA mutation that does not reflect the most commonly seen mutations. 5 For example, there are differences in the PIK3CA mutation hotspots between patients with HPV-positive and HPV-negative HNSCC. Greater than 90% of HPV-positive patients with HNSCC have mutations in the helical domain (i.e., E542K or E545K), whereas patients with HPV-negative HNSCC have mutations throughout the entire gene, although the hotspot mutations in the helical and kinase domains (i.e., H1047R) are relatively more frequent. 14 The site of the mutations and resulting amino acid substitutions might produce functionally different mutant proteins and further differ depending on the genetic background of patients with HPV-positive and HPVnegative HNSCC. These phenotypical differences may result in varied responses to the PI3K targeted agents and substantially affect the development of predictive biomarkers. This concern is validated in the PX-866 trial in which the PIK3CA mutations were not associated with response to cetuximab or cetuximab and PX-866 combination. 25 In addition, patients with HNSCC have PTEN loss and other functional gain or loss of genes/proteins within the pathway that may affect the pathway in the absence of the PIK3CA mutations. 14 The functional signifıcance of these features must be adequately characterized before applying them to clinical trials. CONCLUSION Advancements in genomic and proteomic technology are providing a glimpse of the complexity of cancer biology and generating rich hypotheses for potential therapeutic targets. In addition, respective companion diagnostic biomarkers are being developed for clinical application. Currently, a large body of preclinical data indicate the PI3K pathway is important and a promising therapeutic target in patients with HNSCC. However, they have not always translated to clinically meaningful effıcacy in clinical studies. Additional studies to determine an appropriate method of patient selection with the activation of PI3K pathway and to develop targeted agents with favorable toxicity profıles are required. Existing data on PIK3CA mutations as a predictive biomarker to PI3K/mTOR inhibitor response or the EGFR inhibitor resistance are not yet fully developed. Potential differences in the gene/protein function based on the location and amino acid changes resulting from the PIK3CA mutations in appropriate genetic context of other coexisting pathologic signaling network, must be delineated further before proceeding with a broader clinical application. Disclosures of Potential Conflicts of Interest Relationships are considered self-held and compensated unless otherwise noted. Relationships marked L indicate leadership positions. Relationships marked I are those held by an immediate family member; those marked B are held by the author and an immediate family member. Institutional relationships are marked Inst. Relationships marked U are uncompensated. Employment: None. Leadership Position: None. Stock or Other Ownership Interests: None. Honoraria: None. Consulting or Advisory Role: Christine H. Chung, Novartis. Gilberto Castro, Teva, Boehringer Ingelheim, Eurofarma, Pfizer, Bayer. Speakers Bureau: Gilberto Castro, Speakers Bureau (Lilly, AstraZeneca, Bayer, Novartis, Roche, Eurofarma, Merck Serono). Research Funding: Christine H. Chung, Boehringer Ingelheim, Immunogen. Patents, Royalties, or Other Intellectual Property: None. Expert Testimony: None. Travel, Accommodations, Expenses: Christine H. Chung, Merck. Gilberto Castro, Merck Sharp & Dohme, Lilly, Novartis, Pfizer, Roche, AstraZeneca, Boehringer Ingelheim, Eurofarma, Bayer. Other Relationships: None. References 1. Maier H, Dietz A, Gewelke U, et al. Tobacco and alcohol and the risk of head and neck cancer. Clin Investig. 1992;70: D Souza G, Kreimer AR, Viscidi R, et al. Case-control study of human papillomavirus and oropharyngeal cancer. N Engl J Med. 2007;356: Ang KK, Harris J, Wheeler R, et al. Human papillomavirus and survival of patients with oropharyngeal cancer. N Engl J Med. 2010;363: Gillison ML, D Souza G, Westra W, et al. Distinct risk factor profıles for human papillomavirus type 16-positive and human papillomavirus type 16-negative head and neck cancers. J Natl Cancer Inst. 2008;100: Cancer Genome Atlas Network. Comprehensive genomic characterization of head and neck squamous cell carcinomas. Nature. 2015;517: Thorpe LM, Yuzugullu H, Zhao JJ. PI3K in cancer: divergent roles of isoforms, modes of activation and therapeutic targeting. Nat Rev Cancer. 2015;15: Lee JY, Engelman JA, Cantley LC. Biochemistry. PI3K charges ahead. Science. 2007;317: Clarke PA, Workman P. Phosphatidylinositide-3-kinase inhibitors: addressing questions of isoform selectivity and pharmacodynamic/predictive biomarkers in early clinical trials. J Clin Oncol. 2012;30: Hardt M, Chantaravisoot N, Tamanoi F. Activating mutations of TOR (target of rapamycin). Genes Cells. 2011;16: asco.org/edbook 2015 ASCO EDUCATIONAL BOOK 127

6 ISAACSSON VELHO, CASTRO JR, AND CHUNG 10. Maehama T, Dixon JE. The tumor suppressor, PTEN/MMAC1, dephosphorylates the lipid second messenger, phosphatidylinositol 3,4,5- trisphosphate. J Biol Chem. 1998;273: Agrawal N, Frederick MJ, Pickering CR, et al. Exome sequencing of head and neck squamous cell carcinoma reveals inactivating mutations in NOTCH1. Science. 2011;333: Stransky N, Egloff AM, Tward AD, et al. The mutational landscape of head and neck squamous cell carcinoma. Science. 2011;333: Seiwert TY, Zuo Z, Keck MK, et al. Integrative and comparative genomic analysis of HPV-positive and HPV-negative head and neck squamous cell carcinomas. Clin Cancer Res. 2015;21: Chung CH, Guthrie VB, Masica DL, et al. Genetic alterations in head and neck squamous cell carcinoma determined by cancer gene-targeted sequencing. Ann Oncol. Epub 2015 Feb Shao X, Tandon R, Samara G, et al. Mutational analysis of the PTEN gene in head and neck squamous cell carcinoma. Int J Cancer. 1998;77: Pedrero JM, Carracedo DG, Pinto CM, et al. Frequent genetic and biochemical alterations of the PI 3-K/AKT/PTEN pathway in head and neck squamous cell carcinoma. Int J Cancer. 2005;114: Lui VW, Hedberg ML, Li H, et al. Frequent mutation of the PI3K pathway in head and neck cancer defınes predictive biomarkers. Cancer Discov. 2013;3: Suda T, Hama T, Kondo S, et al. Copy number amplifıcation of the PIK3CA gene is associated with poor prognosis in non-lymph node metastatic head and neck squamous cell carcinoma. BMC Cancer. 2012;12: Iglesias-Bartolome R, Martin D, Gutkind JS. Exploiting the head and neck cancer oncogenome: widespread PI3K-mTOR pathway alterations and novel molecular targets. Cancer Discov. 2013;3: Sewell A, Brown B, Biktasova A, et al. Reverse-phase protein array profıling of oropharyngeal cancer and signifıcance of PIK3CA mutations in HPV-associated head and neck cancer. Clin Cancer Res. 2014;20: Schelhaas M, Shah B, Holzer M, et al. Entry of human papillomavirus type 16 by actin-dependent, clathrin- and lipid raft-independent endocytosis. PLoS Pathog. 2012;8:e Surviladze Z, Sterk RT, DeHaro SA, et al. Cellular entry of human papillomavirus type 16 involves activation of the phosphatidylinositol 3-kinase/Akt/mTOR pathway and inhibition of autophagy. J Virol. 2013;87: Slebos RJ, Yi Y, Ely K, et al. Gene expression differences associated with human papillomavirus status in head and neck squamous cell carcinoma. Clin Cancer Res. 2006;12: Maira SM, Stauffer F, Brueggen J, et al. Identifıcation and characterization of NVP-BEZ235, a new orally available dual phosphatidylinositol 3-kinase/mammalian target of rapamycin inhibitor with potent in vivo antitumor activity. Mol Cancer Ther. 2008;7: Jimeno A, Shirai K, Choi M, et al. 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. Ann Oncol. 2014:26: Hudes G, Carducci M, Tomczak P, et al. Temsirolimus, interferon alfa, or both for advanced renal-cell carcinoma. N Engl J Med. 2007;356: Motzer RJ, Escudier B, Oudard S, et al. Phase 3 trial of everolimus for metastatic renal cell carcinoma: fınal results and analysis of prognostic factors. Cancer. 2010;116: Franz DN, Belousova E, Sparagana S, et al. Everolimus for subependymal giant cell astrocytoma in patients with tuberous sclerosis complex: 2-year open-label extension of the randomised EXIST-1 study. Lancet Oncol. 2014;15: Yao JC, Shah MH, Ito T, et al. Everolimus for advanced pancreatic neuroendocrine tumors. N Engl J Med. 2011;364: Baselga J, Campone M, Piccart M, et al. Everolimus in postmenopausal hormone-receptor-positive advanced breast cancer. N Engl J Med. 2012; 366: Fury MG, Xiao H, Baxi SS, et al. A phase II trial of temsirolimus plus low-dose weekly carboplatin and paclitaxel for recurrent/metastatic HNSCC. J Clin Oncol. 2014;32:5s (suppl; abstr 6019). 32. Bauman JE, Arias-Pulido H, Lee S-J, et al. A phase II study of temsirolimus and erlotinib in patients with recurrent and/or metastatic, platinum-refractory head and neck squamous cell carcinoma. Oral Oncol. 2013;49: Altomare DA, Zhang L, Deng J, et al. GSK delays tumor onset and progression in genetically defıned mouse models expressing activated Akt. Clin Cancer Res. 2010;16: Amornphimoltham P, Leelahavanichkul K, Molinolo A, et al. Inhibition of mammalian target of rapamycin by rapamycin causes the regression of carcinogen-induced skin tumor lesions. Clin Cancer Res. 2008;14: Gwinn DM, Shackelford DB, Egan DF, et al. AMPK phosphorylation of raptor mediates a metabolic checkpoint. Mol Cell. 2008;30: Nathan CO, Amirghahari N, Rong X, et al. Mammalian target of rapamycin inhibitors as possible adjuvant therapy for microscopic residual disease in head and neck squamous cell cancer. Cancer Res. 2007;67: Kang H, Kiess A, Chung CH. Emerging biomarkers in head and neck cancer in the era of genomics. Nat Rev Clin Oncol. 2015;12: Hatakeyama H, Cheng H, Wirth P, et al. Regulation of heparin-binding EGF-like growth factor by mir-212 and acquired cetuximab-resistance in head and neck squamous cell carcinoma. PLoS One. 2010;5:e Wang Z, Martin D, Molinolo AA, et al. mtor co-targeting in cetuximab resistance in head and neck cancers harboring PIK3CA and RAS mutations. J Natl Cancer Inst. Epub 2014 Aug ASCO EDUCATIONAL BOOK asco.org/edbook