Early tumor progression associated with enhanced EGFR signaling with bortezomib, cetuximab, and radiotherapy for head and neck cancer

Myoglobin-loaded gadolinium nanotexaphyrins for oxygen synergy and imaging-guided radiosensitization therapy

Gadolinium (Gd3+)-coordinated texaphyrin (Gd-Tex) is a promising radiosensitizer that entered clinical trials, but temporarily fails largely due to insufficient radiosensitization efficacy. Little attention has been given to using nanovesicles to improve its efficacy. Herein, Gd-Tex is transformed into building blocks "Gd-Tex-lipids" to self-assemble nanovesicles called Gd-nanotexaphyrins (Gd-NTs), realizing high density packing of Gd-Tex in a single nanovesicle and achieving high Gd-Tex accumulation in tumors. To elucidate the impact of O2 concentration on Gd-Tex radiosensitization, myoglobin (Mb) is loaded into Gd-NTs (Mb@Gd-NTs), resulting in efficient relief of tumor hypoxia and significant enhancement of Gd-Tex radiosensitization, eventually inducing the obvious long-term antitumor immune memory to inhibit tumor recurrence. In addition to Gd3+, the versatile Mb@Gd-NTs can also chelate 177Lu3+ (Mb@177Lu/Gd-NTs), enabling SPECT/MRI dual-modality imaging for accurately monitoring drug delivery in real-time. This "one-for-all" nanoplatform with the capability of chelating various trivalent metal ions exhibits broad clinical application prospects in imaging-guided radiosensitization therapy.

Pharmacogenomic landscape of head and neck squamous cell carcinoma informs precision oncology therapy

Head and neck squamous cell carcinoma (HNSCC) is a common and frequently lethal cancer with few therapeutic options. In particular, there are few effective targeted therapies. Development of highly effective therapeutic strategies tailored to patients with HNSCC remains a pressing challenge. To address this, we present a pharmacogenomic study to facilitate precision treatments for patients with HNSCC. We established a large collection of 56 HNSCC patient-derived cells (PDCs), which recapitulated the molecular features of the original tumors. Pharmacological assessment of HNSCCs was conducted using a three-tiered high-throughput drug screening using 2248 compounds across these PDC models and an additional 18 immortalized cell lines. We integrated genomic, transcriptomic, and pharmacological analysis to predict biomarkers, gene-drug associations, and validated biomarkers. These results supported drug repurposing for multiple HNSCC subtypes, including the JAK2 inhibitor fedratinib, for low KRT18-expressing HNSCC cases, and the topoisomerase inhibitor mitoxantrone, for IL6R-activated HNSCC cases. Our results demonstrated concordance between susceptibility predictions from the PDCs and the matched patients' responses to standard clinical medication. Moreover, we identified and experimentally confirmed that high expression of ITGB1 elicited therapeutic resistance to docetaxel and high SOD1 expression conferred resistance to afatinib. We further validated ITGB1 as a predictive biomarker for the efficacy of docetaxel therapy in a phase 2 clinical trial. In summary, our study shows that this HNSCC cell resource, as well as the resulting pharmacogenomic profiles, is effective for biomarker discovery and for guiding precision oncology therapies in HNSCCs.

STAT3 pathway in cancers: Past, present, and future

Signal transducer and activator of transcription 3 (STAT3), a member of the STAT family, discovered in the cytoplasm of almost all types of mammalian cells, plays a significant role in biological functions. The duration of STAT3 activation in normal tissues is a transient event and is strictly regulated. However, in cancer tissues, STAT3 is activated in an aberrant manner and is induced by certain cytokines. The continuous activation of STAT3 regulates the expression of downstream proteins associated with the formation, progression, and metastasis of cancers. Thus, elucidating the mechanisms of STAT3 regulation and designing inhibitors targeting the STAT3 pathway are considered promising strategies for cancer treatment. This review aims to introduce the history, research advances, and prospects concerning the STAT3 pathway in cancer. We review the mechanisms of STAT3 pathway regulation and the consequent cancer hallmarks associated with tumor biology that are induced by the STAT3 pathway. Moreover, we summarize the emerging development of inhibitors that target the STAT3 pathway and novel drug delivery systems for delivering these inhibitors. The barriers against targeting the STAT3 pathway, the focus of future research on promising targets in the STAT3 pathway, and our perspective on the overall utility of STAT3 pathway inhibitors in cancer treatment are also discussed.

Proteasome inhibition by bortezomib parallels a reduction in head and neck cancer cells growth, and an increase in tumor-infiltrating immune cells

Head and neck cancer (HNC) has frequently an aggressive course for the development of resistance to standard chemotherapy. Thus, the use of innovative therapeutic drugs is being assessed. Bortezomib is a proteasome inhibitor with anticancer effects. In vitro antitumoral activity of Bortezomib was investigated employing human tongue (SCC-15, CAL-27), pharynx (FaDu), salivary gland (A-253) cancer cell lines and a murine cell line (SALTO-5) originated from a salivary gland adenocarcinoma arising in BALB-neuT male mice transgenic for the oncogene neu. Bortezomib inhibited cell proliferation, triggered apoptosis, modulated the expression and activation of pro-survival signaling transduction pathways proteins activated by ErbB receptors and inhibited proteasome activity in vitro. Intraperitoneal administration of Bortezomib delayed tumor growth of SALTO-5 cells transplanted in BALB-neuT mice, protracted mice survival and adjusted tumor microenvironment by increasing tumor-infiltrating immune cells (CD4⁺ and CD8⁺ T cells, B lymphocytes, macrophages, and Natural Killer cells) and by decreasing vessels density. In addition, Bortezomib modified the expression of proteasome structural subunits in transplanted SALTO-5 cells. Our findings further support the use of Bortezomib for the treatment of HNC and reveal its ineffectiveness in counteracting the activation of deregulated specific signaling pathways in HNC cell lines when resistance to proteasome inhibition is developed.

Regulation of NFκB Signalling by Ubiquitination: A Potential Therapeutic Target in Head and Neck Squamous Cell Carcinoma?

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide, with over 600,000 cases per year. The primary causes for HNSCC include smoking and alcohol consumption, with an increasing number of cases attributed to infection with Human Papillomavirus (HPV). The treatment options for HNSCC currently include surgery, radiotherapy, and/or platinum-based chemotherapeutics. Cetuximab (targeting EGFR) and Pembrolizumab (targeting PD-1) have been approved for advanced stage, recurrent, and/or metastatic HNSCC. Despite these advances, whilst HPV+ HNSCC has a 3-year overall survival (OS) rate of around 80%, the 3-year OS for HPV- HNSCC is still around 55%. Aberrant signal activation of transcription factor NFκB plays an important role in the pathogenesis and therapeutic resistance of HNSCC. As an important mediator of inflammatory signalling and the immune response to pathogens, the NFκB pathway is tightly regulated to prevent chronic inflammation, a key driver of tumorigenesis. Here, we discuss how NFκB signalling is regulated by the ubiquitin pathway and how this pathway is deregulated in HNSCC. Finally, we discuss the current strategies available to target the ubiquitin pathway and how this may offer a potential therapeutic benefit in HNSCC.

Manipulation of JAK/STAT Signalling by High-Risk HPVs: Potential Therapeutic Targets for HPV-Associated Malignancies

Human papillomaviruses (HPVs) are small, DNA viruses that cause around 5% of all cancers in humans, including almost all cervical cancer cases and a significant proportion of anogenital and oral cancers. The HPV oncoproteins E5, E6 and E7 manipulate cellular signalling pathways to evade the immune response and promote virus persistence. The Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) pathway has emerged as a key mediator in a wide range of important biological signalling pathways, including cell proliferation, cell survival and the immune response. While STAT1 and STAT2 primarily drive immune signalling initiated by interferons, STAT3 and STAT5 have widely been linked to the survival and proliferative potential of a number of cancers. As such, the inhibition of STAT3 and STAT5 may offer a therapeutic benefit in HPV-associated cancers. In this review, we will discuss how HPV manipulates JAK/STAT signalling to evade the immune system and promote cell proliferation, enabling viral persistence and driving cancer development. We also discuss approaches to inhibit the JAK/STAT pathway and how these could potentially be used in the treatment of HPV-associated disease.

Targeting Cullin-RING E3 Ligases for Radiosensitization: From NEDDylation Inhibition to PROTACs

As a dynamic regulator for short-lived protein degradation and turnover, the ubiquitin-proteasome system (UPS) plays important roles in various biological processes, including response to cellular stress, regulation of cell cycle progression, and carcinogenesis. Over the past decade, research on targeting the cullin-RING (really interesting new gene) E3 ligases (CRLs) in the UPS has gained great momentum with the entry of late-phase clinical trials of its novel inhibitors MLN4924 (pevonedistat) and TAS4464. Several preclinical studies have demonstrated the efficacy of MLN4924 as a radiosensitizer, mainly due to its unique cytotoxic properties, including induction of DNA damage response, cell cycle checkpoints dysregulation, and inhibition of NF-κB and mTOR pathways. Recently, the PROteolysis TArgeting Chimeras (PROTACs) technology was developed to recruit the target proteins for CRL-mediated polyubiquitination, overcoming the resistance that develops inevitably with traditional targeted therapies. First-in-class cell-permeable PROTACs against critical radioresistance conferring proteins, including the epidermal growth factor receptor (EGFR), androgen receptor (AR) and estrogen receptor (ER), cyclin-dependent kinases (CDKs), MAP kinase kinase 1 (MEK1), and MEK2, have emerged in the past 5 years. In this review article, we will summarize the most important research findings of targeting CRLs for radiosensitization.

Ubiquitin ligase SMURF2 enhances epidermal growth factor receptor stability and tyrosine-kinase inhibitor resistance

The discovery of activating epidermal growth factor receptor (EGFR) mutations spurred the use of EGFR tyrosine kinase inhibitors (TKIs), such as erlotinib, as the first-line treatment of lung cancers. We previously reported that differential degradation of TKI-sensitive (e.g. L858R) and resistant (T790M) EGFR mutants upon erlotinib treatment correlates with drug sensitivity. We also reported that SMAD ubiquitination regulatory factor 2 (SMURF2) ligase activity is important in stabilizing EGFR. However, the molecular mechanisms involved remain unclear. Here, using in vitro and in vivo ubiquitination assays, MS, and superresolution microscopy, we show SMURF2-EGFR functional interaction is important for EGFR stability and response to TKI. We demonstrate that L858R/T790M EGFR is preferentially stabilized by SMURF2-UBCH5 (an E3-E2)-mediated polyubiquitination. We identified four lysine residues as the sites of ubiquitination and showed that replacement of one of them with acetylation-mimicking glutamine increases the sensitivity of mutant EGFR to erlotinib-induced degradation. We show that SMURF2 extends membrane retention of EGF-bound EGFR, whereas SMURF2 knockdown increases receptor sorting to lysosomes. In lung cancer cell lines, SMURF2 overexpression increased EGFR levels, improving TKI tolerance, whereas SMURF2 knockdown decreased EGFR steady-state levels and sensitized lung cancer cells. Overall, we propose that SMURF2-mediated polyubiquitination of L858R/T790M EGFR competes with acetylation-mediated receptor internalization that correlates with enhanced receptor stability; therefore, disruption of the E3-E2 complex may be an attractive target to overcome TKI resistance.

Clinical Development of Molecular Targeted Therapy in Head and Neck Squamous Cell Carcinoma

A better understanding of cancer biology has led to the development of molecular targeted therapy, which has dramatically improved the outcome of some cancer patients, especially when a biomarker of efficacy has been used for patients' selection. In head and neck oncology, cetuximab that targets epidermal growth factor receptor is the only targeted therapy that demonstrated a survival benefit, both in the recurrent and in the locally advanced settings, yet without prior patients' selection. We herein review the clinical development of targeted therapy in head and neck squamous cell carcinoma in light of the molecular landscape and give insights in on how innovative clinical trial designs may speed up biomarker discovery and deployment of new molecular targeted therapies. Given the recent approval of immune checkpoint inhibitors targeting programmed cell death-1 in head and neck squamous cell carcinoma, it remains to be determined how targeted therapy will be incorporated into a global drug development strategy that will inevitably incorporate immunotherapy.

Targeting the unfolded protein response in head and neck and oral cavity cancers

Many FDA-approved anti-cancer therapies, targeted toward a wide array of molecular targets and signaling networks, have been demonstrated to activate the unfolded protein response (UPR). Despite a critical role for UPR signaling in the apoptotic execution of cancer cells by many of these compounds, the authors are currently unaware of any instance whereby a cancer drug was developed with the UPR as the intended target. With the essential role of the UPR as a driving force in the genesis and maintenance of the malignant phenotype, a great number of pre-clinical studies have surged into the medical literature describing the ability of dozens of compounds to induce UPR signaling in a myriad of cancer models. The focus of the current work is to review the literature and explore the role of the UPR as a mediator of chemotherapy-induced cell death in squamous cell carcinomas of the head and neck (HNSCC) and oral cavity (OCSCC), with an emphasis on preclinical studies.

In HPV-Positive HNSCC Cells, Functional Restoration of the p53/p21 Pathway by Proteasome Inhibitor Bortezomib Does Not Affect Radio- or Chemosensitivity

Human papillomavirus (HPV) associated squamous cell carcinomas of the head and neck region (HPV+ HNSCCs) harbor diverging biological features as compared to classical noxa-induced (HPV−) HNSCC. One striking difference between subtypes is that the tumor suppressor gene TP53 is usually not mutated in HPV+ HNSCCs. However, p53 is inhibited by viral oncoprotein E6, leading to premature proteasomal degradation. We asked whether bortezomib (BZM), a clinically approved inhibitor of the proteasome, can functionally restore p53 and investigated in how far this will result in an enhanced radio- or chemosensitivity of HPV+ HNSCC cell lines. For all four HPV+ cell lines tested, BZM led to functional restoration of p53 and transactivation of downstream protein p21. In HPV+ cells, BZM also restored the radiation-induced p53/p21 transactivation. Consistently, in HPV+ cells, a restored G1 arrest as well as enhanced apoptosis were seen when BZM was given prior to irradiation (IR) or cisplatin (CDDP). BZM alone reduced the clonogenic survival of both HPV− and HPV+ cells. However, if BZM was combined with IR or CDDP, BZM did not significantly enhance radio- or chemosensitivity of HPV+ or HPV− HNSCC cell lines.

Application of molecular targeted therapies in the treatment of head and neck squamous cell carcinoma

Despite the development of standard therapies, including surgery, radiotherapy and chemotherapy, survival rates for head and neck squamous cell carcinoma (HNSCC) have not changed significantly over the past three decades. Complete recovery is achieved in <50% of patients. The treatment of advanced HNSCC frequently requires multimodality therapy and involves significant toxicity. The promising, novel treatment option for patients with HNSCC is molecular-targeted therapies. The best known targeted therapies include: Epidermal growth factor receptor (EGFR) monoclonal antibodies (cetuximab, panitumumab, zalutumumab and nimotuzumab), EGFR tyrosine kinase inhibitors (gefitinib, erlotinib, lapatinib, afatinib and dacomitinib), vascular endothelial growth factor (VEGF) inhibitor (bevacizumab) or vascular endothelial growth factor receptor (VEGFR) inhibitors (sorafenib, sunitinib and vandetanib) and inhibitors of phosphatidylinositol 3-kinase/serine/threonine-specific protein kinase/mammalian target of rapamycin. There are also various inhibitors of other pathways and targets, which are promising and require evaluation in further studies.

Differential protein stability of EGFR mutants determines responsiveness to tyrosine kinase inhibitors

Non-small cell lung cancer (NSCLC) patients carrying specific EGFR kinase activating mutations (L858R, delE746-A750) respond well to tyrosine kinase inhibitors (TKIs). However, drug resistance develops within a year. In about 50% of such patients, acquired drug resistance is attributed to the enrichment of a constitutively active point mutation within the EGFR kinase domain (T790M). To date, differential drug-binding and altered ATP affinities by EGFR mutants have been shown to be responsible for differential TKI response. As it has been reported that EGFR stability plays a role in the survival of EGFR driven cancers, we hypothesized that differential TKI-induced receptor degradation between the sensitive L858R and delE746-A750 and the resistant T790M may also play a role in drug responsiveness. To explore this, we have utilized an EGFR-null CHO overexpression system as well as NSCLC cell lines expressing various EGFR mutants and determined the effects of erlotinib treatment. We found that erlotinib inhibits EGFR phosphorylation in both TKI sensitive and resistant cells, but the protein half-lives of L858R and delE746-A750 were significantly shorter than L858R/T790M. Third generation EGFR kinase inhibitor (AZD9291) inhibits the growth of L858R/T790M-EGFR driven cells and also induces EGFR degradation. Erlotinib treatment induced polyubiquitination and proteasomal degradation, primarily in a c-CBL-independent manner, in TKI sensitive L858R and delE746-A750 mutants when compared to the L858R/T790M mutant, which correlated with drug sensitivity. These data suggest an additional mechanism of TKI resistance, and we postulate that agents that degrade L858R/T790M-EGFR protein may overcome TKI resistance.

CCR 20th anniversary commentary: Preclinical study of proteasome inhibitor bortezomib in head and neck cancer

In a study published in the May 1, 2001, issue of Clinical Cancer Research, Sunwoo and colleagues provided evidence for proteasome inhibition of NF-κB and tumorigenesis, supporting early-phase clinical trials in solid malignancies of the upper aerodigestive tract. Subsequent clinical studies uncovered a dichotomy of responses in patients with hematopoietic and solid malignancies, and the mechanisms of resistance.

Unilateral Cervical Polyneuropathies following Concurrent Bortezomib, Cetuximab, and Radiotherapy for Head and Neck Cancer

We report a constellation of cervical polyneuropathies in a patient treated with concurrent bortezomib, cetuximab, and cisplatin alongside intensity modulated radiotherapy for carcinoma of the tonsil with neck metastasis. The described deficits include brachial plexopathy, cervical sensory neuropathy, and oculosympathetic, recurrent laryngeal, and phrenic nerve palsies within the ipsilateral radiation field. Radiation neuropathy involving the brachial plexus is typically associated with treatment of breast or lung cancer; however, increased awareness of this entity in the context of investigational agents with potential neuropathic effects in head and neck cancer has recently emerged. With this report, we highlight radiation neuropathy in the setting of investigational therapy for head and neck cancer, particularly since these sequelae may present years after therapy and entail significant and often irreversible morbidity.

EGFR-targeted mAb therapy modulates autophagy in head and neck squamous cell carcinoma through NLRX1-TUFM protein complex

EGFR-targeted therapy in head and neck squamous cell carcinoma (HNSCC) patients frequently results in tumor resistance to treatment. Autophagy is an emerging underlying resistance mechanism, however, the molecular autophagy machinery in HNSCC cells and potential biomarkers of patient response to EGFR-targeted therapy remain insufficiently characterized. Here we show that the EGFR blocking with cetuximab leads to varied autophagic responses, which modulate cancer cell susceptibility to EGFR inhibition. Inhibition of autophagy sensitizes HNSCC cells to EGFR blockade. Importantly, we identify a novel signaling hub centering on the NLRX1-TUFM protein complex, promoting autophagic flux. Defects in the expression of either NLRX1 or TUFM result in compromised autophagy when treated with EGFR inhibitors. As a previously undefined autophagy-promoting mechanism, we found that TUFM serves as a novel anchorage site, recruiting Beclin-1 to mitochondria, promoting its polyubiquitination, and interfering with its interaction with Rubicon. This protein complex is also essential for endoplasmic reticulum (ER) stress signaling induction, possibly as an additional mechanism to promote autophagy. Utilizing tumor specimens from a novel neoadjuvant clinical trial, we show that increased expression of the autophagy adaptor protein, SQSTM1/p62, is associated with poor response to cetuximab therapy. These findings expand our understanding of the components involved in HNSCC autophagy machinery that responds to EGFR inhibitors, and suggest potential combinatorial approaches to enhance its therapeutic efficacy.

The Efficacy of Synchronous Combination of Chemotherapy and EGFR TKIs for the First-Line Treatment of NSCLC: A Systematic Analysis

Background

The combination of chemotherapy and epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) currently has become the hotspot issue in the treatment of non-small lung cancer (NSCLC). This systematic review was conducted to compare the efficacy and safety of the synchronous combination of these two treatments with EGFR TKIs or chemotherapy alone in advanced NSCLC.

Methods

EMBASE, PubMed, the Central Registry of Controlled Trials in the Cochrane Library (CENTRAL), Chinese biomedical literature database (CNKI) and meeting summaries were searched. The Phase II/III randomized controlled trials were selected by which patients with advanced NSCLC were randomized to receive a combination of EGFR TKIs and chemotherapy by synchronous mode vs. EGFR TKIs or chemotherapy alone.

Results

A total of six randomized controlled trials (RCTs) including 4675 patients were enrolled in the systematic review. The meta-analysis demonstrated that the synchronous combination group of chemotherapy and EGFR TKIs did not reach satisfactory results; there was no significant difference in overall survival (OS), time to progression (TTP) and objective response rate (ORR), compared with monotherapy (OS: HR = 1.05, 95%CI = 0.98–1.12; TTP: HR = 0.94, 95%CI = 0.89–1.00; ORR: RR = 1.07, 95%CI = 0.98–1.17), and no significant difference in OS and progression-free survival (PFS), compared with EGFR TKIs alone (OS: HR = 1.10, 95% CI = 0.83–1.46; PFS: HR = 0.86, 95% CI = 0.67–1.10). The patients who received synchronous combined therapy presented with increased incidences of grade 3/4 anemia (RR = 1.40, 95% CI = 1.10–1.79) and rash (RR = 7.43, 95% CI = 4.56–12.09), compared with chemotherapy, grade 3/4 anemia (RR = 6.71, 95% CI = 1.25–35.93) and fatigue (RR = 9.60, 95% CI = 2.28–40.86) compared with EGFR TKI monotherapy.

Conclusions

The synchronous combination of chemotherapy and TKIs is not superior to chemotherapy or EGFR TKIs alone for the first-line treatment of NSCLC.

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.

The ubiquitin-proteasome system: opportunities for therapeutic intervention in solid tumors

The destruction of proteins via the ubiquitin-proteasome system is a multi-step, complex process involving polyubiquitination of substrate proteins, followed by proteolytic degradation by the macromolecular 26S proteasome complex. Inhibitors of the proteasome promote the accumulation of proteins that are deleterious to cell survival, and represent promising anti-cancer agents. In multiple myeloma and mantle cell lymphoma, treatment with the first-generation proteasome inhibitor, bortezomib, or the second-generation inhibitor, carfilzomib, has demonstrated significant therapeutic benefit in humans. This has prompted United States Food and Drug Administration (US FDA) approval of these agents and development of additional second-generation compounds with improved properties. There is considerable interest in extending the benefits of proteasome inhibitors to the treatment of solid tumor malignancies. Herein, we review progress that has been made in the preclinical development and clinical evaluation of different proteasome inhibitors in solid tumors. In addition, we describe several novel approaches that are currently being pursued for the treatment of solid tumors, including drug combinatorial strategies incorporating proteasome inhibitors and the targeting of components of the ubiquitin-proteasome system that are distinct from the 26S proteasome complex.

KRAS protein stability is regulated through SMURF2: UBCH5 complex-mediated β-TrCP1 degradation

Attempts to target mutant KRAS have been unsuccessful. Here, we report the identification of Smad ubiquitination regulatory factor 2 (SMURF2) and UBCH5 as a critical E3:E2 complex maintaining KRAS protein stability. Loss of SMURF2 either by small interfering RNA/short hairpin RNA (siRNA/shRNA) or by overexpression of a catalytically inactive mutant causes KRAS degradation, whereas overexpression of wild-type SMURF2 enhances KRAS stability. Importantly, mutant KRAS is more susceptible to SMURF2 loss where protein half-life decreases from >12 hours in control siRNA-treated cells to <3 hours on Smurf2 silencing, whereas only marginal differences were noted for wild-type protein. This loss of mutant KRAS could be rescued by overexpressing a siRNA-resistant wild-type SMURF2. Our data further show that SMURF2 monoubiquitinates UBCH5 at lysine 144 to form an active complex required for efficient degradation of a RAS-family E3, β-transducing repeat containing protein 1 (β-TrCP1). Conversely, β-TrCP1 is accumulated on SMURF2 loss, leading to increased KRAS degradation. Therefore, as expected, β-TrCP1 knockdown following Smurf2 siRNA treatment rescues mutant KRAS loss. Further, we identify two conserved proline (P) residues in UBCH5 critical for SMURF2 interaction; mutation of either of these P to alanine also destabilizes KRAS. As a proof of principle, we demonstrate that Smurf2 silencing reduces the clonogenic survival in vitro and prolongs tumor latency in vivo in cancer cells including mutant KRAS-driven tumors. Taken together, we show that SMURF2:UBCH5 complex is critical in maintaining KRAS protein stability and propose that targeting such complex may be a unique strategy to degrade mutant KRAS to kill cancer cells.

Efficacy of an EGFR-specific peptide against EGFR-dependent cancer cell lines and tumor xenografts

We have recently synthesized a peptide called Disruptin, which comprised the SVDNPHVC segment of the epidermal growth factor receptor (EGFR) that inhibits binding of heat shock protein 90 (Hsp90) to the EGFR and EGF-dependent EGFR dimerization to cause EGFR degradation. The effect is specific for EGFR versus other Hsp90 client proteins [Ahsan et al.: (2013). Destabilization of the epidermal growth factor receptor (EGFR) by a peptide that inhibits EGFR binding to heat shock protein 90 and receptor dimerization. J Biol Chem288, 26879-26886]. Here, we show that Disruptin decreases the clonogenicity of a variety of EGFR-dependent cancer cells in culture but not of EGFR-independent cancer or noncancerous cells. The selectivity of Disruptin toward EGFR-driven cancer cells is due to the high level of EGF stimulation of EGFR in EGFR-dependent tumor cells relative to normal cells. When administered by intraperitoneal injection into nude mice bearing EGFR-driven human tumor xenografts, Disruptin causes extensive degradation of EGFR in the tumor but not in adjacent host tissue. Disruptin markedly inhibits the growth of EGFR-driven tumors without producing the major toxicities caused by the Hsp90 inhibitor geldanamycin or by cisplatin. These findings provide proof of concept for development of a new Disruptin-like class of antitumor drugs that are directed specifically against EGFR-driven tumors.

Carfilzomib and oprozomib synergize with histone deacetylase inhibitors in head and neck squamous cell carcinoma models of acquired resistance to proteasome inhibitors

Acquired resistance to proteasome inhibitors represents a considerable impediment to their effective clinical application. Carfilzomib and its orally bioavailable structural analog oprozomib are second-generation, highly-selective, proteasome inhibitors. However, the mechanisms of acquired resistance to carfilzomib and oprozomib are incompletely understood, and effective strategies for overcoming this resistance are needed. Here, we developed models of acquired resistance to carfilzomib in two head and neck squamous cell carcinoma cell lines, UMSCC-1 and Cal33, through gradual exposure to increasing drug concentrations. The resistant lines R-UMSCC-1 and R-Cal33 demonstrated 205- and 64-fold resistance, respectively, relative to the parental lines. Similarly, a high level of cross-resistance to oprozomib, as well as paclitaxel, was observed, whereas only moderate resistance to bortezomib (8- to 29-fold), and low level resistance to cisplatin (1.5- to 5-fold) was seen. Synergistic induction of apoptosis signaling and cell death, and inhibition of colony formation followed co-treatment of acquired resistance models with carfilzomib and the histone deacetylase inhibitor (HDACi) vorinostat. Synergism was also seen with other combinations, including oprozomib plus vorinostat, or carfilzomib plus the HDACi entinostat. Synergism was accompanied by upregulation of proapoptotic Bik, and suppression of Bik attenuated the synergy. The acquired resistance models also exhibited elevated levels of MDR-1/P-gp. Inhibition of MDR-1/P-gp with reversin 121 partially overcame carfilzomib resistance in R-UMSCC-1 and R-Cal33 cells. Collectively, these studies indicate that combining carfilzomib or oprozomib with HDAC or MDR-1/P-gp inhibitors may be a useful strategy for overcoming acquired resistance to these proteasome inhibitors.

Emerging opportunities for the combination of molecularly targeted drugs with radiotherapy

Recent drug discovery developments in the field of small molecule targeted agents have led to much interest in combining these with radiotherapy. There are good preclinical data to suggest this approach worthy of investigation and in this review we discuss how this has translated into recent clinical trials. The outcome of clinical trials investigating radiotherapy/targeted drug combinations published in the last 5 years is discussed, as are trials in progress. The perceived future opportunities and challenges in the development of this exciting area are considered.

Survey of pre-inflammation cytokines levels in radiotherapy-induced-mucositis

Mucositis is a toxic side effect of anti-cancer treatments and is a major focus in cancer research. Pro-inflammatory cytokines have previously been implicated in the pathophysiology of chemotherapy-induced mucositis. The aim of this study was to detect a correlation between serum cytokine levels in head and neck (H and N) cancer patients receiving combined chemo-radiation therapy. Thirty patients with H and N epithelial cancer were recruited to this study. All patients received radiotherapy to the H and N region with doses ranging from 50-70 Gray (Gy). Chemotherapy with cisplatin, carboplatin, 5-fluorouracil and taxanes was given to high-risk patients, using standard chemotherapy protocols. Patients were evaluated for mucositis according to WHO common toxicity criteria and blood samples were drawn for inflammatory (IL-1 and TNF-a) and before and during treatment. The mucositis evaluation demonstrated mucositis grade IV in 33.3% of the patients after the 3rd treatment week. At the end of treatment, the number of patients with grade IV mucositis was less. IL-1 and TNF-alpha did not show any correlation with PEG tube installation. The level of cytokines measured before and during therapy showed decreased TNF-alpha especially after the third week of therapy. No relationship between IL-1 and TNF-alpha, level and mucositis grade was shown.

Characterization of the EGFR interactome reveals associated protein complex networks and intracellular receptor dynamics

Growth factor receptor mediated signaling is meanwhile recognized as a complex signaling network, which is initiated by recruiting specific patterns of adaptor proteins to the intracellular domain of epidermal growth factor receptor (EGFR). Approaches to globally identify EGFR-binding proteins are required to elucidate this network. We affinity-purified EGFR with its interacting proteins by coprecipitation from lysates of A431 cells. A total of 183 proteins were repeatedly detected in high-resolution MS measurements. For 15 of these, direct interactions with EGFR were listed in the iRefIndex interaction database, including Grb2, shc-1, SOS1 and 2, STAT 1 and 3, AP2, UBS3B, and ERRFI. The newly developed Cytoscape plugin ModuleGraph allowed retrieving and visualizing 93 well-described protein complexes that contained at least one of the proteins found to interact with EGFR in our experiments. Abundances of 14 proteins were modulated more than twofold upon EGFR activation whereof clathrin-associated adaptor complex AP-2 showed 4.6-fold enrichment. These proteins were further annotated with different cellular compartments. Finally, interactions of AP-2 proteins and the newly discovered interaction of CIP2A could be verified. In conclusion, a powerful technique is presented that allowed identification and quantitative assessment of the EGFR interactome to provide further insight into EGFR signaling.

Targeted therapies for squamous cell carcinoma of the head and neck: current knowledge and future directions

Despite progress in the therapeutic management of patients with squamous cell carcinoma of the head and neck (SCCHN), the mortality rate of patients presenting with advanced disease remains high. One approach to improve treatment efficacy is to add novel molecular targeted agents to the classical treatment regimens. Monoclonal antibodies targeting the epidermal growth factor receptor (EGFR) have shown clinical benefits in palliative and curative settings. However, only a minority of patients presenting with recurrent or metastatic (R/M) SCCHN have meaningful tumor regression with these agents and virtually all who do develop acquired tumor resistance after a few months of treatment. For these reasons, other inhibitors of EGFR or molecules that interfere with known molecular pathways activated in SCCHN are of considerable interest, either as single agents or in combination with other treatment modalities. In this review, we discuss the different molecular therapeutic approaches explored in SCCHN. We also briefly outline new trial designs that could be used to accelerate the investigation of emerging therapeutic agents in this disease.

Design and conduct of early-phase radiotherapy trials with targeted therapeutics: lessons from the PRAVO experience

New strategies to facilitate the improvement of physical and integrated biological optimization of high-precision treatment protocols are an important priority for modern radiation oncology. From a clinical perspective, as knowledge accumulates from molecular radiobiology, there is a complex and exciting opportunity to investigate novel approaches to rational patient treatment stratification based on actionable tumor targets, together with the appropriate design of next-generation early-phase radiotherapy trials utilizing targeted therapeutics, to formally evaluate relevant clinical and biomarker endpoints. A unique aspect in the development pathway of systemic agents with presumed radiosensitizing activity will also be the need for special attention on patient eligibility and the rigorous definition of radiation dose-volume relationships and potential dose-limiting toxicities. Based on recent experience from systematically investigating histone deacetylase inhibitors as radiosensitizing agents, from initial studies in preclinical tumor models through the conduct of a phase I clinical study to evaluate tumor activity of the targeted agent as well as patient safety and tumor response to the combined treatment modality, this communication will summarize principles relating to early clinical evaluation of combining radiotherapy and targeted therapeutics.

Cetuximab: its unique place in head and neck cancer treatment

Head and neck cancer is the sixth most common cancer worldwide. At present, globally about 650,000 new cases of squamous cell carcinoma of the head and neck (SCCHN) are diagnosed each year. The epidermal growth factor receptor (EGFR) is almost invariably expressed in SCCHN. Overexpression of the EGFR is a strong and independent unfavorable prognostic factor in SCCHN. Cetuximab is a chimeric monoclonal antibody, which binds with high affinity to the extracellular domain of the human EGFR, blocking ligand binding, resulting in inhibition of the receptor function. It also targets cytotoxic immune effector cells towards EGFR-expressing tumor cells (antibody dependent cell-mediated cytotoxicity). The addition of cetuximab to radiotherapy (RT) improves locoregional control and survival when compared to RT alone. The addition of cetuximab to platinum-based chemoradiation (CRT) is feasible but does not lead to an improved outcome. Cetuximab plus RT has never been compared prospectively to CRT, which therefore remains the standard treatment for patients with locoregionally advanced SCCHN for whom surgery is not considered the optimal treatment, provided they can tolerate CRT. The addition of cetuximab to platinum-based chemotherapy prolongs survival in patients with recurrent or metastatic SCCHN. The combination of a platinum-based regimen and cetuximab should be considered as the standard first line regimen for patients who can tolerate this treatment.

Aberrant IKKα and IKKβ cooperatively activate NF-κB and induce EGFR/AP1 signaling to promote survival and migration of head and neck cancer

The Inhibitor-κB Kinase-Nuclear Factor-κB (IKK-NF-κB) and Epidermal Growth Factor Receptor-Activator Protein-1 (EGFR-AP-1) pathways are often co-activated and promote malignant behavior, but the underlying basis for this relationship is unclear. Resistance to inhibitors of IKKβ or EGFR is observed in head and neck squamous cell carcinomas (HNSCC). Here, we reveal that both IKKα and β contribute to nuclear activation of canonical and alternate NF-κB/REL family transcription factors, and overexpression of signal components enhancing co-activation of the EGFR-AP1 pathway. We observed that IKKα and IKKβ exhibit increased protein expression, nuclear localization and phosphorylation in HNSCC tissues and cell lines. Individually, IKK activity varied amongst different cell lines, but overexpression of both IKKs induced the strongest NF-κB activation. Conversely, siRNA knockdown of both IKKs significantly decreased nuclear localization and phosphorylation of canonical RELA and IκBα, and alternative p52 and RELB subunits. Knockdown of both IKKs more effectively inhibited NF-κB activation, broadly modulated gene expression, and suppressed cell proliferation and migration. Global expression profiling revealed that NF-κB, cytokine, inflammatory response, and growth factor signaling are among the top pathways and networks regulated by IKKs. Importantly, IKKα and IKKβ together promoted the expression and activity of TGFα, EGFR, and AP1 transcription factors cJun, JunB, and Fra1. Knockdown of AP1 subunits individually decreased 8/15 (53%) of IKK-targeted genes sampled, and similarly inhibited cell proliferation and migration. Mutations of NF-κB and AP1 binding sites abolished or decreased IKK-induced IL-8 promoter activity. Compounds such as wedelactone with dual IKK inhibitory activity, and geldanomycins that block IKKα/β and EGFR pathways were more active than IKKβ-specific inhibitors in suppressing NF-κB activation and proliferation, and inducing cell death. We conclude that IKKα and IKKβ cooperatively activate NF-κB and EGFR/AP1 networks of signaling pathways, and contribute to the malignant phenotype and the intrinsic or acquired therapeutic resistance of HNSCC.

Wild-type EGFR is stabilized by direct interaction with HSP90 in cancer cells and tumors

The epidermal growth factor receptor (EGFR) has been targeted for inhibition using tyrosine kinase inhibitors and monoclonal antibodies, with improvement in outcome in subsets of patients with head and neck, lung, and colorectal carcinomas. We have previously found that EGFR stability plays a key role in cell survival after chemotherapy and radiotherapy. Heat shock protein 90 (HSP90) is known to stabilize mutant EGFR and ErbB2, but its role in cancers with wild-type (WT) WT-EGFR is unclear. In this report, we demonstrate that fully mature, membrane-bound WT-EGFR interacts with HSP90 independent of ErbB2. Further, the HSP90 inhibitors geldanamycin (GA) and AT13387 cause a decrease in WT-EGFR in cultured head and neck cancer cells. This decrease results from a significantly reduced half-life of WT-EGFR. WT-EGFR was also lost in head and neck xenograft specimens after treatment with AT13387 under conditions that inhibited tumor growth and prolonged survival of the mice. Our findings demonstrate that WT-EGFR is a client protein of HSP90 and that their interaction is critical for maintaining both the stability of the receptor as well as the growth of EGFR-dependent cancers. Furthermore, these findings support the search for specific agents that disrupt HSP90's ability to act as an EGFR chaperone.

The role of human papillomavirus in nongenital cancers

Human papillomavirus (HPV), one of the most common sexually transmitted diseases worldwide, has an established role in the pathogenesis of genital malignancies such as cervical cancer. The virus has also been implicated in the oncogenesis of nongenital cancers including head and neck malignancies (specifically oropharyngeal cancers) as well as anal cancer. There is less clarity regarding its role in lung and esophageal cancers. Worldwide, the incidence and prevalence of HPV-associated oropharyngeal cancer has been increasing over time. These patients have improved outcomes compared with those with HPV-negative oropharyngeal cancers, and there is continued interest in designing treatments specifically for this HPV-positive subgroup. Clinicians continue to gain an understanding of HPV in anal cancers and the risk factors associated with infection and progression to malignancy. This has potential implications for the eventual screening of high-risk groups. While HPV vaccination is currently approved for the prevention of cervical cancer, it also has potential in the prevention of all HPV-associated malignancies. In this review, current understanding of the role of HPV in nongenital cancers is discussed, as well as future implications for treatment and prevention.

Degradation of epidermal growth factor receptor mediates dasatinib-induced apoptosis in head and neck squamous cell carcinoma cells

Epidermal growth factor receptor (EGFR) is an important oncoprotein that promotes cell growth and proliferation. Dasatinib, a bcr-abl inhibitor, has been approved clinically for the treatment of chronic myeloid leukemia and demonstrated to be effective against solid tumors in vitro through Src inhibition. Here, we disclose that EGFR degradation mediated dasatinib-induced apoptosis in head and neck squamous cell carcinoma (HNSCC) cells. HNSCC cells, including Ca9-22, FaDu, HSC3, SAS, SCC-25, and UMSCC1, were treated with dasatinib, and cell viability, apoptosis, and underlying signal transduction were evaluated. Dasatinib exhibited differential sensitivities against HNSCC cells. Growth inhibition and apoptosis were correlated with its inhibition on Akt, Erk, and Bcl-2, irrespective of Src inhibition. Accordingly, we found that down-regulation of EGFR was a determinant of dasatinib sensitivity. Lysosome inhibitor reversed dasatinib-induced EGFR down-regulation, and c-cbl activity was increased by dasatinib, indicating that dasatinib-induced EGFR down-regulation might be through c-cbl-mediated lysosome degradation. Increased EGFR activation by ligand administration rescued cells from dasatinib-induced apoptosis, whereas inhibition of EGFR enhanced its apoptotic effect. Estrogen receptor α (ERα) was demonstrated to play a role in Bcl-2 expression, and dasatinib inhibited ERα at the pretranslational level. ERα was associated with EGFR in dasatinib-treated HNSCC cells. Furthermore, the xenograft model showed that dasatinib inhibited HSC3 tumor growth through in vivo down-regulation of EGFR and ERα. In conclusion, degradation of EGFR is a novel mechanism responsible for dasatinib-induced apoptosis in HNSCC cells.

Targeting C4-demethylating genes in the cholesterol pathway sensitizes cancer cells to EGF receptor inhibitors via increased EGF receptor degradation

Persistent signaling by the oncogenic EGF receptor (EGFR) is a major source of cancer resistance to EGFR targeting. We established that inactivation of 2 sterol biosynthesis pathway genes, SC4MOL (sterol C4-methyl oxidase-like) and its partner, NSDHL (NADP-dependent steroid dehydrogenase-like), sensitized tumor cells to EGFR inhibitors. Bioinformatics modeling of interactions for the sterol pathway genes in eukaryotes allowed us to hypothesize and then extensively validate an unexpected role for SC4MOL and NSDHL in controlling the signaling, vesicular trafficking, and degradation of EGFR and its dimerization partners, ERBB2 and ERBB3. Metabolic block upstream of SC4MOL with ketoconazole or CYP51A1 siRNA rescued cancer cell viability and EGFR degradation. Inactivation of SC4MOL markedly sensitized A431 xenografts to cetuximab, a therapeutic anti-EGFR antibody. Analysis of Nsdhl-deficient Bpa(1H/+) mice confirmed dramatic and selective loss of internalized platelet-derived growth factor receptor in fibroblasts, and reduced activation of EGFR and its effectors in regions of skin lacking NSDHL.

SIGNIFICANCE

This work identifies a critical role for SC4MOL and NSDHL in the regulation of EGFR signaling and endocytic trafficking and suggests novel strategies to increase the potency of EGFR antagonists in tumors.

Targeting C4-demethylating genes in the cholesterol pathway sensitizes cancer cells to EGF receptor inhibitors via increased EGF receptor degradation

Persistent signaling by the oncogenic EGF receptor (EGFR) is a major source of cancer resistance to EGFR targeting. We established that inactivation of 2 sterol biosynthesis pathway genes, SC4MOL (sterol C4-methyl oxidase-like) and its partner, NSDHL (NADP-dependent steroid dehydrogenase-like), sensitized tumor cells to EGFR inhibitors. Bioinformatics modeling of interactions for the sterol pathway genes in eukaryotes allowed us to hypothesize and then extensively validate an unexpected role for SC4MOL and NSDHL in controlling the signaling, vesicular trafficking, and degradation of EGFR and its dimerization partners, ERBB2 and ERBB3. Metabolic block upstream of SC4MOL with ketoconazole or CYP51A1 siRNA rescued cancer cell viability and EGFR degradation. Inactivation of SC4MOL markedly sensitized A431 xenografts to cetuximab, a therapeutic anti-EGFR antibody. Analysis of Nsdhl-deficient Bpa(1H/+) mice confirmed dramatic and selective loss of internalized platelet-derived growth factor receptor in fibroblasts, and reduced activation of EGFR and its effectors in regions of skin lacking NSDHL.

SIGNIFICANCE

This work identifies a critical role for SC4MOL and NSDHL in the regulation of EGFR signaling and endocytic trafficking and suggests novel strategies to increase the potency of EGFR antagonists in tumors.

Fighting cancer from different signalling pathways: Effects of the proteasome inhibitor Bortezomib in combination with the polo-like-kinase-1-inhibitor BI2536 in SCCHN

Inhibition of the proteasome with Bortezomib as well as inhibition of Polo-like-kinase-1 (PLK-1) has been shown to be effective in many solid tumour models and also in squamous cell carcinoma of the head and neck (SCCHN) cell lines. For the first time, we systematically examined the antitumour effect of Bortezomib in combination with BI2536 in SCCHN in an in vitro study. Dose escalation studies were performed with nine SCCHN cell lines using Bortezomib and BI2536 as single agent and combination treatments. Growth-inhibitory and pro-apoptotic effects were measured quantitatively using cytohistology and Human Apoptose Array kit. The combination of Bortezomib and BI2536 showed significant anti-proliferative and apoptotic activity in all SCCHN cell lines investigated (P=0.008) compared to both the untreated control group and Bortezomib alone. A combination treatment regime consisting of the proteasome inhibitor, Bortezomib, and the inhibitor of PLK-1, BI2536, leads to an enhanced anti-proliferative and apoptotic effect in SCCHN cell lines, compared to single agent treatment with Bortezomib alone.

Carfilzomib and ONX 0912 inhibit cell survival and tumor growth of head and neck cancer and their activities are enhanced by suppression of Mcl-1 or autophagy

PURPOSE

Carfilzomib is a selective, irreversible inhibitor of the chymotrypsin-like activity of the proteasome and is undergoing clinical evaluation in myeloma. ONX 0912 (oprozomib) is an orally bioavailable derivative. The activities of carfilzomib and ONX 0912 against solid tumor malignancies are less well understood. We investigated the impact and mechanisms of action of carfilzomib and ONX 0912 in preclinical models of head and neck squamous cell carcinoma (HNSCC).

EXPERIMENTAL DESIGN

The effects of carfilzomib and ONX 0912 on HNSCC cell survival and xenograft tumor growth were evaluated. The impact and mechanisms of both agents on apoptosis and autophagy induction were also investigated. The contribution of the unfolded protein response (UPR) to autophagy induction and the role of autophagy in attenuating HNSCC cell death were determined.

RESULTS

Carfilzomib and ONX 0912 potently induced apoptosis in HNSCC cell lines via upregulation of pro-apoptotic Bik. Upregulation of Mcl-1 by these agents served to dampen their efficacies. Carfilzomib and ONX 0912 also induced autophagy, mediated, in part, by activation of the UPR pathway involving upregulation of ATF4 transcription factor. Autophagy induction served a prosurvival role. Oral administration of ONX 0912 inhibited the growth of HNSCC xenograft tumors in a dose-dependent manner.

CONCLUSIONS

These results show that carfilzomib and ONX 0912 are potently active against HNSCC cells, and the activities of these agents can be enhanced via suppression of Mcl-1 or inhibition of autophagy. Oral ONX 0912 exhibits in vivo activity against HNSCC tumors and may represent a useful therapeutic agent for this malignancy.

Effect of erlotinib on epidermal growth factor receptor and downstream signaling in oral cavity squamous cell carcinoma

BACKGROUND

The purpose of this study was to determine if there are differences in biomarker modulation and epidermal growth factor receptor (EGFR) degradation between the tumor and the normal mucosa after treatment with an EGFR inhibitor, erlotinib, in head and neck cancer.

METHODS

Patients with primary oral cavity squamous cell cancers received a course of erlotinib, 150 mg every day for 7 days before surgical resection. Tumor and normal mucosa biopsies were obtained both pre-erlotinib and post-erlotinib. Changes in known markers of EGFR activity (phospho, AKT, STAT3) were measured by immunoblotting, whereas changes in tissue distribution were analyzed by immunohistochemical analysis.

RESULTS

Twelve patients were enrolled; 7 had evaluable paired tumors and normal mucosa biopsies pretreatment and posttreatment. Expression of EGFR was higher in tumors compared to the normal mucosa (p = .005). Erlotinib administration was associated with marked inhibition of phosphorylated epidermal growth factor receptor (pEGFR) and reduction in total EGFR protein (p = .004, p = .007) in tumors, whereas there was heterogeneity in EGFR inhibition in the normal mucosa (p = .10 [pEGFR], and p = .07 [EGFR]). Reduced levels of pSrc and pSTAT3 and enhanced p27 levels were noted in tumors after erlotinib. Cell culture studies confirmed that EGFR is degraded in tumor cells after prolonged treatment with erlotinib.

CONCLUSION

Our results show that EGFR inhibition by erlotinib led to a marked reduction in EGFR protein levels in patients. Differential effects of erlotinib on tumors compared to the normal mucosa suggest there may be individual patient heterogeneity. These preliminary data suggest EGFR degradation should be further analyzed as a potential biomarker in selecting patients likely to benefit from EGFR inhibitors.

Autophagic action of new targeting agents in head and neck oncology

The survival rates of patients with squamous cell carcinoma of the head and neck (HNSCC) have not improved significantly despite multi-modality therapy, including surgery, radiation therapy, and chemotherapy. Recently, molecular targeted agents have shown significant improvement in clinical outcomes; for example, in chronic myelogeneous leukemia with imatinib, breast cancer with trastuzumab, colon cancer with bevacizumab and cetuximab, and renal cell cancer with sorafenib and sunitinib. In HNSCC, the epidermal growth factor receptor antibody cetuximab has shown promising results in combination with radiation. Targeted agents including cetuximab induce stresses to activate prosurvival autophagy. Combining autophagy inhibitors with agents that induce autophagy as a prosurvival response may therefore increase their therapeutic efficacy. Whether autophagy contributes to the prosurvival response or to the antitumor effect of chemotherapeutic drugs is largely unknown. This review will discuss the possible role of autophagy as a novel target for anticancer therapy agents in HNSCC.

Phase II 2-arm trial of the proteasome inhibitor, PS-341 (bortezomib) in combination with irinotecan or PS-341 alone followed by the addition of irinotecan at time of progression in patients with locally recurrent or metastatic squamous cell carcinoma of the head and neck (E1304): a trial of the Eastern Cooperative Oncology Group

BACKGROUND

Constitutive activation of nuclear factor κB (NF-κB) is associated with poor prognosis. Irinotecan demonstrates single-agent activity in head and neck cancer but activates NF-κB, promoting cell survival and resistance. Bortezomib is a proteasome inhibitor that inactivates NF-κB.

PATIENTS AND METHODS

We performed a randomized phase II trial of bortezomib on days 1, 4, 8, and 11 and irinotecan on days 1 and 8 of each 21-day cycle or single-agent bortezomib on days 1, 4, 8, and 11 on a 21-day cycle. The addition of irinotecan to bortezomib was allowed in patients who progressed on bortezomib alone.

RESULTS

The response rate of bortezomib and irinotecan was 13%. One patient had a partial response to bortezomib alone (response rate 3%). No responses were seen in patients with addition of irinotecan at time of progression on bortezomib.

CONCLUSIONS

The bortezomib-based regimens evaluated in this study have minimal activity in recurrent or metastatic head and neck cancer.

Optimising the delivery of tubulin targeting agents through antibody conjugation

Despite their side effect profile, there currently remains a heavy reliance on traditional cytotoxics and particularly tubulin targeting agents in cancer chemotherapy. To address this concern, significant progress has been made in the selective delivery of drugs to the tumour site. This review will examine the published data in support of the hypothesis that forming antibody conjugates of tubulin targeting agents is an effective approach towards their more effective delivery to the tumour site. Particular emphasis will be placed on the diversity of concepts under investigation, the efficacy of resultant conjugates, evidence of decreased resistance and the side effect profiles of the conjugates.

New promising molecular targets in head and neck squamous cell carcinoma

PURPOSE OF REVIEW

Despite advances in multimodality therapy, the overall 5-year survival rate is 40-50% in patients with head and neck squamous cell carcinoma (HNSCC) and current multimodality approaches impart significant toxicities. This review highlights promising targets with the potential to improve clinical outcomes in HNSCC.

RECENT FINDINGS

In addition to mutagenic exposure to tobacco and alcohol as risk factors, recent studies have shown that human papillomavirus is one of the main causes of HNSCC and as such is being investigated as a therapeutic target. Furthermore, recent data generated from whole exome sequencing of HNSCC, new insights into the biology of DNA damage repair, and increased understanding of tumor hypoxia responses are pointing to new therapeutic possibilities for treating HNSCC.

SUMMARY

HNSCC is a heterogeneous disease. Improved treatment will require a rapid translation of basic science research, and the simultaneous development of novel therapeutics and corresponding biomarkers to guide their application.