Mammalian Target of Rapamycin Inhibitors as Possible Adjuvant Therapy for Microscopic Residual Disease in Head and Neck Squamous Cell Cancer

A Kinome-Wide Synthetic Lethal CRISPR/Cas9 Screen Reveals That mTOR Inhibition Prevents Adaptive Resistance to CDK4/CDK6 Blockade in HNSCC

The comprehensive genomic analysis of the head and neck squamous cell carcinoma (HNSCC) oncogenome revealed the frequent loss of p16INK4A (CDKN2A) and amplification of cyclin D1 genes in most human papillomavirus-negative HNSCC lesions. However, cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors have shown modest effects in the clinic. The aberrant activation of the PI3K/mTOR pathway is highly prevalent in HNSCC, and recent clinical trials have shown promising clinical efficacy of mTOR inhibitors (mTORi) in the neoadjuvant and adjuvant settings but not in patients with advanced HNSCC. By implementing a kinome-wide CRISPR/Cas9 screen, we identified cell-cycle inhibition as a synthetic lethal target for mTORis. A combination of mTORi and palbociclib, a CDK4/6-specific inhibitor, showed strong synergism in HNSCC-derived cells in vitro and in vivo. Remarkably, we found that an adaptive increase in cyclin E1 (CCNE1) expression upon palbociclib treatment underlies the rapid acquired resistance to this CDK4/6 inhibitor. Mechanistically, mTORi inhibits the formation of eIF4G-CCNE1 mRNA complexes, with the consequent reduction in mRNA translation and CCNE1 protein expression. Our findings suggest that mTORi reverts the adaptive resistance to palbociclib. This provides a multimodal therapeutic option for HNSCC by cotargeting mTOR and CDK4/6, which in turn may halt the emergence of palbociclib resistance.

SIGNIFICANCE

A kinome-wide CRISPR/Cas9 screen identified cell-cycle inhibition as a synthetic lethal target of mTORis. A combination of mTORi and palbociclib, a CDK4/6-specific inhibitor, showed strong synergistic effects in HNSCC. Mechanistically, mTORis inhibited palbociclib-induced increase in CCNE1.

Establishment of head and neck squamous cell carcinoma mouse models for cetuximab resistance and sensitivity

Aim: Acquired resistance to the targeted agent cetuximab poses a significant challenge in finding effective anti-cancer treatments for head and neck squamous cell carcinoma (HNSCC). To accurately study novel combination treatments, suitable preclinical mouse models for cetuximab resistance are key yet currently limited. This study aimed to optimize an acquired cetuximab-resistant mouse model, with preservation of the innate immunity, ensuring intact antibody-dependent cellular cytotoxicity (ADCC) functionality. Methods: Cetuximab-sensitive and acquired-resistant HNSCC cell lines, generated in vitro, were subcutaneously engrafted in Rag2 knock-out (KO), BALB/c Nude and CB17 Scid mice with/without Matrigel or Geltrex. Once tumor growth was established, mice were intraperitoneally injected twice a week with cetuximab for a maximum of 3 weeks. In addition, immunohistochemistry was used to evaluate the tumor and its microenvironment. Results: Despite several adjustments in cell number, cell lines and the addition of Matrigel, Rag2 KO and BALB/C Nude mice proved to be unsuitable for xenografting our HNSCC cell lines. Durable tumor growth of resistant SC263-R cells could be induced in CB17 Scid mice. However, these cells had lost their resistance phenotype in vivo. Immunohistochemistry revealed a high infiltration of macrophages in cetuximab-treated SC263-R tumors. FaDu-S and FaDu-R cells successfully engrafted into CB17 Scid mice and maintained their sensitivity/resistance to cetuximab. Conclusion: We have established in vivo HNSCC mouse models with intact ADCC functionality for cetuximab resistance and sensitivity using the FaDu-R and FaDu-S cell lines, respectively. These models serve as valuable tools for investigating cetuximab resistance mechanisms and exploring novel drug combination strategies.

Everolimus downregulates STAT3/HIF-1α/VEGF pathway to inhibit angiogenesis and lymphangiogenesis in TP53 mutant head and neck squamous cell carcinoma (HNSCC)

TP53 mutant head and neck squamous cell carcinoma (HNSCC) patients exhibit poor clinical outcomes with 50-60% recurrence rates in advanced stage patients. In a recent phase II clinical trial, adjuvant therapy with everolimus (mTOR inhibitor) significantly increased 2-year progression-free survival in p53 mutated patients. TP53-driven mTOR activation in solid malignancies causes upregulation of HIF-1α and its target, downstream effector VEGF, by activating STAT3 cell signaling pathway. Here, we investigated the effects of everolimus on the STAT3/HIF-1α/VEGF pathway in TP53 mutant cell lines and xenograft models. Treatment with everolimus significantly inhibited cell growth in vitro and effectively reduced the growth of TP53 mutant xenografts in a minimal residual disease (MRD) model in nude mice. Everolimus treatment was associated with significant downregulation of STAT3/HIF-1α/VEGF pathway in both models. Further, treatment with everolimus was associated with attenuation in tumor angiogenesis and lymphangiogenesis as indicated by decreased microvessel density of vascular and lymphatic vessels in HN31 and FaDu xenografts. Everolimus downregulated the STAT3/HIF-1α/VEGF pathway to inhibit growth and in vitro tube formation of HMEC-1 (endothelial) and HMEC-1A (lymphatic endothelial) cell lines. Our studies demonstrated that everolimus inhibits the growth of TP53 mutant tumors by inhibiting angiogenesis and lymphangiogenesis through the downregulation of STAT3/HIF-1α/VEGF signaling.

A Randomized Multi-institutional Phase II Trial of Everolimus as Adjuvant Therapy in Patients with Locally Advanced Squamous Cell Cancer of the Head and Neck

PURPOSE

Investigate whether adjuvant everolimus, an mTOR inhibitor, improves progression-free survival (PFS) in advanced-stage head and neck squamous cell carcinoma (HNSCC) and provide outcomes related to correlative biological factors associated with disease control.

PATIENTS AND METHODS

This was a prospective, randomized, double-blind phase II trial of patients with advanced-stage HNSCC from 13 institutions who were confirmed disease-free post-definitive therapy and enrolled between December 2010 and March 2015. Patients received adjuvant everolimus or placebo daily (10 mg, oral) for a maximum of 1 year. p16 IHC as a surrogate marker for human papillomavirus infection and whole-exome sequencing were performed. Cox proportional hazard models estimated hazard rates. Log-rank tests evaluated differences in survival. The primary endpoint was PFS. Secondary endpoints and objectives included overall survival (OS) and toxicity assessment.

RESULTS

52 patients [median (range) age, 58 (37-76) years; 43 men (83%), 9 women (17%)] were randomized to placebo (n = 24) or everolimus (n = 28). PFS favored everolimus, but was not significant [log-rank P = 0.093; HR = 0.44; 95% confidence interval (CI), 0.17-1.17]. There was no difference in OS (P = 0.29; HR = 0.57; 95% CI, 0.20-16.2). Everolimus resulted in significant improvement in PFS for p16-negative patients (n = 31; P = 0.031; HR = 0.26; 95% CI, 0.07-0.97), although subgroup analysis showed no difference for p16-positive patients (n = 21; P = 0.93). Further, PFS was significantly higher in TP53-mutated (TP53mut) patients treated with everolimus compared with placebo (log-rank P = 0.027; HR = 0.24; 95% CI, 0.06-0.95). No treatment difference was seen in patients with TP53 wild-type tumors (P = 0.79).

CONCLUSIONS

p16-negative and TP53mut patients may benefit from adjuvant treatment with everolimus.

Rapalogs induce non-apoptotic, autophagy-dependent cell death in HPV-negative TP53 mutant head and neck squamous cell carcinoma

TP53 is the most frequently mutated gene in head and neck squamous cell carcinoma (HNSCC). Patients with HPV-negative TP53 mutant HNSCC have the worst prognosis, necessitating additional agents for treatment. Since mutant p53 causes sustained activation of the PI3K/AKT/mTOR signaling pathway, we investigated the effect of rapalogs RAD001 and CCI-779 on HPV-negative mutTP53 HNSCC cell lines and xenografts. Rapalogs significantly reduced cell viability and colony formation. Interestingly, rapalogs-induced autophagy with no effect on apoptosis. Pretreatment with autophagy inhibitors, 3-methyladenine (3-MA) and ULK-101 rescued the cell viability by inhibiting rapalog-induced autophagy, suggesting that both RAD001 and CCI-779 induce non-apoptotic autophagy-dependent cell death (ADCD). Moreover, rapalogs upregulated the levels of ULK1 and pULK1 S555 with concomitant downregulation of the mTORC1 pathway. However, pretreatment of cells with rapalogs prevented the ULK-101-mediated inhibition of ULK1 to sustained autophagy, suggesting that rapalogs induce ADCD through the activation of ULK1. To further translate our in vitro studies, we investigated the effect of RAD001 in HPV-negative mutTP53 (HN31 and FaDu) tumor cell xenograft model in nude mice. Mice treated with RAD001 exhibited a significant tumor volume reduction without induction of apoptosis, and with a concomitant increase in autophagy. Further, treatment with RAD001 was associated with a considerable increase in pULK1 S555 and ULK1 levels through the inhibition of mTORC1. 3-MA reversed the effect of RAD001 on FaDu tumor growth suggesting that RAD001 promotes ACDC in HPV-negative mutTP53 xenograft. This is the first report demonstrating that rapalogs promote non-apoptotic ADCD in HPV-negative mutTP53 HNSCC via the ULK1 pathway. Further studies are required to establish the promising role of rapalogs in preventing the regrowth of HPV-negative mutTP53 HNSCC.

Control of the eIF4E activity: structural insights and pharmacological implications

The central role of eukaryotic translation initiation factor 4E (eIF4E) in controlling mRNA translation has been clearly assessed in the last decades. eIF4E function is essential for numerous physiological processes, such as protein synthesis, cellular growth and differentiation; dysregulation of its activity has been linked to ageing, cancer onset and progression and neurodevelopmental disorders, such as autism spectrum disorder (ASD) and Fragile X Syndrome (FXS). The interaction between eIF4E and the eukaryotic initiation factor 4G (eIF4G) is crucial for the assembly of the translational machinery, the initial step of mRNA translation. A well-characterized group of proteins, named 4E-binding proteins (4E-BPs), inhibits the eIF4E–eIF4G interaction by competing for the same binding site on the eIF4E surface. 4E-BPs and eIF4G share a single canonical motif for the interaction with a conserved hydrophobic patch of eIF4E. However, a second non-canonical and not conserved binding motif was recently detected for eIF4G and several 4E-BPs. Here, we review the structural features of the interaction between eIF4E and its molecular partners eIF4G and 4E-BPs, focusing on the implications of the recent structural and biochemical evidence for the development of new therapeutic strategies. The design of novel eIF4E-targeting molecules that inhibit translation might provide new avenues for the treatment of several conditions.

The PI3K/Akt/mTORC signaling axis in head and neck squamous cell carcinoma: Possibilities for therapeutic interventions either as single agents or in combination with conventional therapies

The latest advances in the sequencing methods in head and neck squamous cell carcinoma (HNSCC) tissues have revolutionized our understanding of the disease by taking off the veil from the most frequent genetic alterations in the components of the oncogenic pathways. Among all the identified alterations, aberrancies in the genes attributed to the phosphoinositide 3-kinases (PI3K) axis have attracted special attention as they were altered in more than 90% of the tissues isolated from HNSCC patients. In fact, the association between these aberrancies and the increased risk of cancer metastasis suggested this axis as an "Achilles Heel" of HNSCC, which may be therapeutically targeted. The results of the clinical trials investigating the therapeutic potential of the inhibitors targeting the components of the PI3K axis in the treatment of HNSCC patients, either alone or in a combined-modal strategy, opened a new chapter in the treatment strategy of this malignancy. The present study aimed to review the importance of the PI3K axis in the pathogenesis of HNSCC and also provide a piece of information about the breakthroughs and challenges of PI3K inhibitors in the therapeutic strategies of the disease.

mTOR inhibitor use in head and neck squamous cell carcinoma: A meta-analysis on survival, tumor response, and toxicity

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) has been rising in incidence primarily related to HPV-associated oropharyngeal cancers. Novel molecular therapeutics are evolving with the mTOR pathway as a new target. Previous studies have shown variable outcomes with relatively low toxicity. This study reports the tumor response, survivability, and toxicity of mTOR inhibitors (mTORi) in HNSCC. Despite expanding research on this pathway, there remains controversy around mTORi use for treatment of HNSCC.

MATERIALS AND METHODS

Studies were included if: (a) Used mTORi alone or in combination with other treatment modalities in HNSCC. (b) Site of cancer included were one of the following: nasopharyngeal, oral cavity, oropharynx, hypopharynx or larynx. (c) All stages of cancer and treatment stage (neoadjuvant, adjuvant, and palliative) were included. The rate of adverse events (AEs), tumor response, progression free survival, and overall survival were meta-analyzed.

RESULTS

From 1299 publications only 11 studies met inclusion criteria with a combined 232 total patients treated. Two studies used mTORi neoadjuvantly, five adjuvantly, and four in palliative/unresectable/metastatic setting. Monotherapeutic mTORi resulted in stabilization of disease (52.5%), but partial response was the most common response when mTORi were combined with chemotherapy and/or radiation (CRT) (48.1%). Survival rate was the highest in the mTORi combined with CRT. Hyperglycemia of any grade was the most commonly reported toxicity while grade 3 or less AEs were the most common grade of toxicity.

CONCLUSION

The use of mTORi as monotherapy in HNSCC has thus far not yielded significant tumor response, however, in combination with other agents, an improved partial tumor response is evident that may or may not be associated with the addition of mTORi. Although adverse events were common, grade 4/5 AEs were uncommon. Further prospective, randomized clinical trials are necessary to confirm the direct roles of these agents in HNSCC tumor response.

LEVEL OF EVIDENCE

2a.

Targeting cellular metabolism to reduce head and neck cancer growth

Head and neck squamous cell carcinoma (HNSCC) presents a major public health concern because of delayed diagnosis and poor prognosis. Malignant cells often reprogram their metabolism in order to promote their survival and proliferation. Aberrant glutaminase 1 (GLS1) expression enables malignant cells to undergo increased glutaminolysis and utilization of glutamine as an alternative nutrient. In this study, we found a significantly elevated GLS1 expression in HNSCC, and patients with high expression levels of GLS1 experienced shorter disease-free periods after therapy. We hypothesized that the GLS1 selective inhibitor, bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl)ethyl sulfide (BPTES), which curtails cells' glutamine consumption, may inhibit HNSCC cell growth. Our results support the idea that BPTES inhibits HNSCC growth by inducing apoptosis and cell cycle arrest. Considering that metformin can reduce glucose consumption, we speculated that metformin would enhance the anti-neoplasia effect of BPTES by suppressing malignant cells' glucose utilization. The combination of both compounds exhibited an additive inhibitory effect on cancer cell survival and proliferation. All of our data suggest that GLS1 is a promising therapeutic target for HNSCC treatment. Combining BPTES with metformin might achieve improved anti-cancer effects in HNSSC, which sheds light on using novel therapeutic strategies by dually targeting cellular metabolism.

Targeting phosphoinositide 3-kinase (PI3K) in head and neck squamous cell carcinoma (HNSCC)

The landscape of head and neck squamous cell carcinoma (HNSCC) has been changing rapidly due to growing proportion of HPV-related disease and development of new therapeutic agents. At the same time, there has been a constant need for individually tailored treatment based on genetic biomarkers in order to optimize patient survival and alleviate treatment-related toxicities. In this regard, aberrations of PI3K pathway have important clinical implications in the treatment of HNSCC. They frequently constitute ‘gain of function’ mutations which trigger oncogenesis, and PI3K mutations can also lead to emergence of drug resistance after treatment with EGFR inhibitors. In this article, we review PI3K pathway as a target of treatment for HNSCC and summarize PI3K/mTOR inhibitors that are currently under clinical trials. In light of recent advancement of immune checkpoint inhibitors, consideration of PI3K inhibitors as potential immune modulators is also suggested.

A phase II study of temsirolimus added to low-dose weekly carboplatin and paclitaxel for patients with recurrent and/or metastatic (R/M) head and neck squamous cell carcinoma (HNSCC)

Background

Activating events along the PI3K/mTOR pathway are common in head and neck squamous cell carcinomas (HNSCC), and preclinical studies suggest additive or synergistic effects when combining mTORC1 inhibitors with carboplatin and paclitaxel chemotherapy.

Patients and methods

In this single-institution phase II study, the combination of temsirolimus 25 mg, carboplatin AUC 1.5, and paclitaxel 80 mg/m2 administered on days 1 and 8 of a 21-day cycle was evaluated in 36 patients with recurrent and/or metastatic (R/M) HNSCC. The primary end point was objective response rate after two cycles of treatment. Secondary end points include the safety and tolerability profile and overall survival. Correlative studies with exome mutational analysis were performed in pre-treatment biopsy samples from 21 patients.

Results

Fifteen (41.7%) patients had an objective response, which were all partial responses, and 19 (52.3%) patients had stable disease as best response. The two patients who were designated as 'non-responders' were removed from study prior to two cycles of treatment, but are included in the efficacy and safety analyses. The median duration on study was 5.3 months and the median progression-free survival and overall survival were 5.9 months (95% confidence interval, 4.8-7.1) and 12.8 months (95% confidence interval, 9.8-15.8), respectively. The most common grade 3 and 4 adverse events were hematologic toxicities. Three (3.8%) patients developed neutropenic fever on study. Three of four patients with PIK3CA mutations experienced tumor regressions, and responses were also seen in patients with other genetic alterations in the PI3K/mTOR pathway.

Conclusion

The combination of temsirolimus with low-dose weekly carboplatin and paclitaxel appears to have meaningful clinical efficacy in the treatment of R/M HNSCC. This regimen has a relatively high response rate compared to other treatments evaluated in R/M HNSCC, and potential associations with genetic alterations in the PI3K/mTOR pathway should be further explored.

Precision Therapy of Head and Neck Squamous Cell Carcinoma

Precision medicine is an approach to disease prevention and treatment that takes into account genetic variability and environmental and lifestyle influences that are unique to each patient. It facilitates stratification of patient populations that vary in their susceptibility to disease and response to therapy. Shared databases and the implementation of new technology systems designed to advance the integration of this information will enable health care providers to more accurately predict and customize prevention and treatment strategies for patients. Although precision medicine has had a limited impact in most areas of medicine, it has been shown to be an increasingly successful approach to cancer therapy. Despite early promising results targeting aberrant signaling pathways or inhibitors designed to block tumor-driven processes such as angiogenesis, limited success emphasizes the need to discover new biomarkers and treatment targets that are more reliable in predicting response to therapy and result in better health outcomes. Recent successes in the use of immunity-inducing antibodies have stimulated increased interest in the use of precision immunotherapy of head and neck squamous cell carcinoma. Using next-generation sequencing, the precise profiling of tumor-infiltrating lymphocytes has great promise to identify hypoimmunogenic cancer that would benefit from a rationally designed combinatorial approach. Continued interrogation of tumors will reveal new actionable targets with increasing therapeutic efficacy and fulfill the promise of precision therapy of head and neck cancer.

A Phase I Trial of the IGF-1R Antibody Ganitumab (AMG 479) in Combination with Everolimus (RAD001) and Panitumumab in Patients with Advanced Cancer

PURPOSE

This study evaluated the maximum tolerated dose or recommended phase II dose (RPTD) and safety and tolerability of the ganitumab and everolimus doublet regimen followed by the ganitumab, everolimus, and panitumumab triplet regimen.

MATERIALS AND METHODS

This was a standard 3 + 3 dose escalation trial. Doublet therapy consisted of ganitumab at 12 mg/kg every 2 weeks; doses of everolimus were adjusted according to dose-limiting toxicities (DLTs). Panitumumab at 4.8 mg/kg every 2 weeks was added to the RPTD of ganitumab and everolimus. DLTs were assessed in cycle 1; toxicity evaluation was closely monitored throughout treatment. Treatment continued until disease progression or undesirable toxicity. Pretreatment and on-treatment skin biopsies were collected to assess insulin-like growth factor 1 receptor and mammalian target of rapamycin (mTOR) target modulation.

RESULTS

Forty-three subjects were enrolled. In the doublet regimen, two DLTs were observed in cohort 1, no DLTs in cohort -1, and one in cohort -1B. The triplet combination was discontinued because of unacceptable toxicity. Common adverse events were thrombocytopenia/neutropenia, skin rash, mucositis, fatigue, and hyperglycemia. In the doublet regimen, two patients with refractory non-small cell lung cancer (NSCLC) achieved prolonged complete responses ranging from 18 to >60 months; one treatment-naïve patient with chondrosarcoma achieved prolonged stable disease >24 months. In dermal granulation tissue, the insulin-like growth factor receptor and mTOR pathways were potently and specifically inhibited by ganitumab and everolimus, respectively.

CONCLUSION

The triplet regimen of ganitumab, everolimus, and panitumumab was associated with unacceptable toxicity. However, the doublet of ganitumab at 12 mg/kg every 2 weeks and everolimus five times weekly had an acceptable safety profile and demonstrated notable clinical activity in patients with refractory NSCLC and sarcoma.

IMPLICATIONS FOR PRACTICE

This trial evaluated the maximum tolerated dose or recommended phase II dose and safety and tolerability of the ganitumab and everolimus doublet regimen followed by the ganitumab, everolimus, and panitumumab triplet regimen. Although the triplet regimen of ganitumab, everolimus, and panitumumab was associated with unacceptable toxicity, the doublet of ganitumab at 12 mg/kg every 2 weeks and everolimus at five times weekly had an acceptable safety profile and demonstrated notable clinical activity in patients with refractory non-small cell lung cancer and sarcoma.

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.

mTOR inhibition as an adjuvant therapy in a metastatic model of HPV+ HNSCC

Effective treatments for recurrent/metastatic human papillomavirus-positive (HPV+) head and neck squamous cell cancer (HNSCC) are limited. To aid treatment development, we characterized a novel murine model of recurrent/metastatic HPV+ HNSCC. Further analysis of the parental tumor cell line and its four recurrent/metastatic derivatives led to preclinical testing of an effective treatment option for this otherwise fatal disease. Reverse phase protein arrays identified key signaling cascades in the parental and recurrent/metastatic cell lines. While protein expression profiles differed among the recurrent/metastatic cell lines, activated proteins associated with the mTOR signaling cascade were a commonality. Based on these data, mTOR inhibition was evaluated as an adjuvant treatment for recurrent/metastatic disease. mTOR activity and treatment response were assessed in vitro by western blot, Seahorse, proliferation, clonogenic, and migration assays. Standard-of-care cisplatin/radiation therapy (CRT) versus CRT/rapamycin were compared in vivo. Low-dose rapamycin inhibited mTOR signaling, decreasing proliferation (43%) and migration (62%) while it enhanced CRT-induced cytotoxicity (3.3 fold) in clonogenic assays. Furthermore, rapamycin re-sensitized CRT-resistant, metastatic tumors to treatment in vivo, improving long-term cures (0-30% improved to 78-100%, depending on the recurrent/metastatic cell line) and limiting lymph node metastasis (32%) and lung metastatic burden (30 fold). Studies using immune compromised mice suggested rapamycin's effect on metastasis is independent of the adaptive immune response. These data suggest a role of mTOR activation in HPV+ HNSCC recurrent/metastatic disease and that adjuvant mTOR inhibition may enhance treatment of resistant, metastatic cell populations at the primary site and limit distant metastasis.

Genomics and advances towards precision medicine for head and neck squamous cell carcinoma

Objective

To provide a review of emerging knowledge from genomics and related basic science, preclinical, and clinical precision medicine studies in head and neck squamous cell carcinoma (HNSCC).

Data Sources

The Cancer Genome Atlas Network (TCGA) publications, PubMed‐based literature review, and ClinicalTrials.gov.

Review Methods

TCGA publications, PubMed, and ClinicalTrials.gov were queried for genomics and related basic science, preclinical, and developmental clinical precision medicine studies in HNSCC.

Results

TCGA reported comprehensive genomic analyses of 279 HNSCC, defining the landscape and frequency of chromosomal copy number alterations, mutations, and expressed genes that contribute to pathogenesis, prognosis, and resistance to therapy. This provides a road map for basic science and preclinical studies to identify key pathways in cancer and cells of the tumor microenvironment affected by these alterations, and candidate targets for new small molecule and biologic therapies.

Conclusion

Recurrent chromosomal abnormalities, mutations, and expression of genes affecting HNSCC subsets are associated with differences in prognosis, and define molecules, pathways, and deregulated immune responses as candidates for therapy. Activity of molecularly targeted agents appears to be enhanced by rational combinations of these agents and standard therapies targeting the complex alterations that affect multiple pathways and mechanisms in HNSCC.

Level of Evidence

NA.

mTOR, metabolism, and the immune response in HPV-positive head and neck squamous cell cancer

Extensive preclinical studies have identified mammalian target of rapamycin (mTOR) activation as a frequent molecular signature underlying head and neck squamous cell carcinoma (HNSCC), including the distinct clinical subtype that is human papillomavirus (HPV) related, and have demonstrated the potential therapeutic utility of mTOR inhibitors in the treatment of these cancers. Numerous clinical studies have begun to evaluate this potential, however few have selected for and fewer have focused specifically on HPV-related disease. While HPV-positive (HPV+) HNSCC patients have a generally favorable prognosis, the overall number of patients who suffer failed treatment, recurrent disease, metastasis, and death is increasing due to the rapidly increasing incidence of HPV-related cancers. In this review, we discuss the rationale for proposing the adjuvant use of mTOR inhibition in the treatment of HPV+ HNSCC, highlighting the interplay of virally activated mTOR signaling, cellular metabolism, and the anti-tumor immune response.

Targeting the PI3K Pathway in Head and Neck Squamous Cell Carcinoma

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.

Targeting translation: eIF4E as an emerging anticancer drug target

The translation initiation factor eIF4E mediates a rate-limiting process that drives selective translation of many oncongenic proteins such as cyclin D1, survivin and VEGF, thereby contributing to tumour growth, metastasis and therapy resistance. As an essential regulatory hub in cancer signalling network, many oncogenic signalling pathways appear to converge on eIF4E. Therefore, targeting eIF4E-mediated cap-dependent translation is considered a promising anticancer strategy. This paper reviews the strategies that can be used to target eIF4E, highlighting agents that target eIF4E activity at each distinct level.

Assessment of antitumor activity and acute peripheral neuropathy of 1,2-diaminocyclohexane platinum (II)-incorporating micelles (NC-4016)

Oxaliplatin, a third-generation platinum compound incorporating oxalate and 1,2-diaminocyclohexane platinum, has been widely used in chemotherapy regimens for the treatment of metastatic colorectal cancer. Because of its wide spectrum of antitumor activity, oxaliplatin has been applied for the treatment of other carcinomas. However, the antitumor activity of single-agent oxaliplatin is insufficient. To increase its antitumor effects, polymeric micellar nanoparticles incorporating 1,2-diaminocyclohexane platinum (NC-4016) have been developed. The present study was designed to evaluate the efficacy of NC-4016 and its association with peripheral neuropathy, which is a primary dose-limiting factor in oxaliplatin therapy. The in vitro antitumor activity of NC-4016 was investigated using human carcinoma cell lines. To investigate the antitumor effects of NC-4016 in vivo, nude mice bearing the human carcinoma cell line KB were administered NC-4016 or oxaliplatin. The in vitro growth-inhibiting effect of NC-4016 was significantly weaker than that of oxaliplatin. However, the antitumor efficacy of NC-4016 was superior to that of oxaliplatin in vivo. Moreover, we compared the severity of peripheral neuropathy induced by oxaliplatin and NC-4016 in a rat model. Oxaliplatin, NC-4016, or 5% glucose (control) were administered by a single tail vein injection. In the oxaliplatin-treated rats, neither mechanical nor heat allodynia was observed during the experimental period, whereas cold hyperalgesia/allodynia was observed from day 1 to 7. Conversely, cold hyperalgesia/allodynia was not observed in the NC-4016-treated rats. The present study demonstrated that the antitumor efficacy of NC-4016 was superior to that of oxaliplatin in a mouse model of human carcinoma cell line KB. In addition, NC-4016-treated rats did not develop acute cold hypersensitivity, which is frequently experienced by patients after oxaliplatin administration.

The dual PI3K/mTOR inhibitor PKI-587 enhances sensitivity to cetuximab in EGFR-resistant human head and neck cancer models

BACKGROUND

Cetuximab is the only targeted agent approved for the treatment of head and neck squamous cell carcinomas (HNSCC), but low response rates and disease progression are frequently reported. As the phosphoinositide 3-kinase (PI3K) and the mammalian target of rapamycin (mTOR) pathways have an important role in the pathogenesis of HNSCC, we investigated their involvement in cetuximab resistance.

METHODS

Different human squamous cancer cell lines sensitive or resistant to cetuximab were tested for the dual PI3K/mTOR inhibitor PF-05212384 (PKI-587), alone and in combination, both in vitro and in vivo.

RESULTS

Treatment with PKI-587 enhances sensitivity to cetuximab in vitro, even in the condition of epidermal growth factor receptor (EGFR) resistance. The combination of the two drugs inhibits cells survival, impairs the activation of signalling pathways and induces apoptosis. Interestingly, although significant inhibition of proliferation is observed in all cell lines treated with PKI-587 in combination with cetuximab, activation of apoptosis is evident in sensitive but not in resistant cell lines, in which autophagy is pre-eminent. In nude mice xenografted with resistant Kyse30 cells, the combined treatment significantly reduces tumour growth and prolongs mice survival.

CONCLUSIONS

Phosphoinositide 3-kinase/mammalian target of rapamycin inhibition has an important role in the rescue of cetuximab resistance. Different mechanisms of cell death are induced by combined treatment depending on basal anti-EGFR responsiveness.

Clinical application of genetics to guide prevention and treatment of oral diseases

Dental care costs in the United States exceed $100 billion annually. Personalized medicine efforts in dentistry are driven by potentially compelling clinical utility and cost-effectiveness prospects in the major diseases of periodontitis, caries, and oral cancers. This review discusses progress and challenges identifying genetic markers and showing clinical utility in dentistry. Genome-wide association studies (GWAS) of chronic periodontitis (CP) identified no significant variants, but CDKN2BAS variants on chromosome 9 were significantly associated with aggressive periodontitis. Stratifying patients by interleukin (IL)-1 gene variants, smoking and diabetes differentiated CP prevention outcomes. Dental caries' GWAS identified significant signals in LYZL2, AJAp1, and KPNA4; and efforts are ongoing to identify genetic factors for multiple caries phenotypes. Trials of molecularly targeted therapies are in progress for oral, head, and neck squamous cell carcinomas (OHNSCC) and results have been promising but limited in their effectiveness. Current opportunities and challenges for molecular targeting for OHNSCC are discussed.

A phase 1 study of everolimus + weekly cisplatin + intensity modulated radiation therapy in head-and-neck cancer

PURPOSE

Elevated expression of eukaryotic protein synthesis initiation factor 4E (eIF4E) in histologically cancer-free margins of resected head and neck squamous cell carcinomas (HNSCCs) is mediated by mammalian target of rapamycin complex 1 (mTORC1) and has been associated with increased risk of disease recurrence. Preclinically, inhibition of mTORC1 with everolimus sensitizes cancer cells to cisplatin and radiation.

METHODS AND MATERIALS

This was single-institution phase 1 study to establish the maximum tolerated dose of daily everolimus given with fixed dose cisplatin (30 mg/m(2) weekly × 6) and concurrent intensity modulated radiation therapy for patients with locally and/or regionally advanced head-and-neck cancer. The study had a standard 3 + 3 dose-escalation design.

RESULTS

Tumor primary sites were oral cavity (4), salivary gland (4), oropharynx (2), nasopharynx (1), scalp (1), and neck node with occult primary (1). In 4 of 4 cases in which resected HNSCC surgical pathology specimens were available for immunohistochemistry, elevated expression of eIF4E was observed in the cancer-free margins. The most common grade ≥3 treatment-related adverse event was lymphopenia (92%), and dose-limiting toxicities (DLTs) were mucositis (n=2) and failure to thrive (n=1). With a median follow up of 19.4 months, 2 patients have experienced recurrent disease. The maximum tolerated dose was everolimus 5 mg/day.

CONCLUSIONS

Head-and-neck cancer patients tolerated everolimus at therapeutic doses (5 mg/day) given with weekly cisplatin and intensity modulated radiation therapy. The regimen merits further evaluation, especially among patients who are status post resection of HNSCCs that harbor mTORC1-mediated activation of eIF4E in histologically negative surgical margins.

Impact of apigenin and kaempferol on human head and neck squamous cell carcinoma

OBJECTIVE

Apigenin and kaempferol are plant flavonoids with reported chemopreventive activities. This study aimed to determine the effect of apigenin and kaempferol on cell viability in cultured cells derived from the pharynx (FaDu cell line), an oral cavity carcinoma (PCI-13 cell line), and a metastatic lymph node (PCI-15B cell line) and in explanted FaDu cells.

STUDY DESIGN

The in vitro viability of FaDu, PCI-13, and PCI-15B cells treated with apigenin and kaempferol was determined. Tumor growth of FaDu explants was evaluated in athymic mice that were gavaged with either apigenin or kaempferol.

RESULTS

Although apigenin and kaempferol treatment decreased viability of cells in vitro, cell-type-dependent differences in responsiveness were observed. In vivo apigenin treatment significantly increased the tumor size of FaDu explants. Results obtained using kaempferol were similar.

CONCLUSIONS

The in vitro decrease in FaDu cell viability by apigenin and kaempferol was not observed in in vivo tumor explants using the conditions described in this study.

Identification and validation of a multigene predictor of recurrence in primary laryngeal cancer

Purpose

Local recurrence is the major manifestation of treatment failure in patients with operable laryngeal carcinoma. Established clinicopathological factors cannot sufficiently predict patients that are likely to recur after treatment. Additional tools are therefore required to accurately identify patients at high risk for recurrence. This study attempts to identify and independently validate gene expression models, prognostic of disease-free survival (DFS) in operable laryngeal cancer.

Materials and Methods

Using Affymetrix U133A Genechips, we profiled fresh-frozen tumor tissues from 66 patients with laryngeal cancer treated locally with surgery. We applied Cox regression proportional hazards modeling to identify multigene predictors of recurrence. Gene models were then validated in two independent cohorts of 54 and 187 patients (fresh-frozen and formalin-fixed tissue validation sets, respectively).

Results

We focused on genes univariately associated with DFS (p<0.01) in the training set. Among several models comprising different numbers of genes, a 30-probe set model demonstrated optimal performance in both the training (log-rank, p<0.001) and 1^st validation (p = 0.010) sets. Specifically, in the 1^st validation set, median DFS as predicted by the 30-probe set model, was 34 and 80 months for high- and low-risk patients, respectively. Hazard ratio (HR) for recurrence in the high-risk group was 3.87 (95% CI 1.28–11.73, Wald's p = 0.017). Testing the expression of selected genes from the above model in the 2^nd validation set, with qPCR, revealed significant associations of single markers, such as ACE2, FLOT1 and PRKD1, with patient DFS. High PRKD1 remained an unfavorable prognostic marker upon multivariate analysis (HR = 2.00, 95% CI 1.28–3.14, p = 0.002) along with positive nodal status.

Conclusions

We have established and validated gene models that can successfully stratify patients with laryngeal cancer, based on their risk for recurrence. It seems worthy to prospectively validate PRKD1 expression as a laryngeal cancer prognostic marker, for routine clinical applications.

Mechanistic target of rapamycin small interfering RNA and rapamycin synergistically inhibit tumour growth in a mouse xenograft model of human oesophageal carcinoma

OBJECTIVES

To investigate the effect of mechanistic target of rapamycin (mTOR)-specific small interfering RNA (siRNA) and rapamycin on tumour size and levels of hypoxia inducible factor 1α(HIF-1α), vascular endothelial growth factor (VEGF) and mTOR proteins, and mTOR mRNA, in a mouse xenograft model of human oesophageal carcinoma.

METHODS

Tumours were induced in BALB/c nude mice using the human oesophageal squamous cell carcinoma cell line, EC1, injected subcutaneously. Animals were divided into four treatment groups (n = 5 per group) after 7 days: control (phosphate buffered saline, daily intraperitoneal [i.p.] injection); 50 μg/kg rapamycin, daily i.p. injection; 3 μg/kg mTOR siRNA, daily i.p. injection; combined mTOR siRNA and rapamycin, daily i.p. injections. Tumour volume was measured 21 days after xenograft. Levels of mTOR, VEGF and HIF-1α were assessed via immunohistochemistry and in situ hybridization.

RESULTS

mTOR siRNA and/or rapamycin significantly decreased tumour volume and levels of HIF-1α, VEGF and mTOR protein, and mTOR mRNA. Combination treatment was significantly more effective than either treatment alone.

CONCLUSIONS

mTOR siRNA and/or rapamycin inhibited the growth of oesophageal carcinoma in vivo. This may represent a novel and effective treatment strategy for oesophageal carcinoma.

PI3K/mTOR inhibitor PF-04691502 antitumor activity is enhanced with induction of wild-type TP53 in human xenograft and murine knockout models of head and neck cancer

PURPOSE

Phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway activation is often associated with altered expression or mutations of PIK3CA, TP53/p73, PTEN, and TGF-β receptors (TGFBR) in head and neck squamous cell carcinomas (HNSCC). However, little is known about how these alterations affect response to PI3K/mTOR-targeted agents.

EXPERIMENTAL DESIGN

In this preclinical study, PI3K/Akt/mTOR signaling was characterized in nine HNSCC (UM-SCC) cell lines and human oral keratinocytes. We investigated the molecular and anticancer effects of dual PI3K/mTOR inhibitor PF-04691502(PF-502) in UM-SCC expressing PIK3CA with decreased wild-type TP53, mutant TP53-/+ mutantTGFBR2, and in HNSCC of a conditional Pten/Tgfbr1 double knockout mouse model displaying PI3K/Akt/mTOR activation.

RESULTS

UM-SCC showed increased PIK3CA expression and Akt/mTOR activation, and PF-502 inhibited PI3K/mTORC1/2 targets. In human HNSCC expressing PIK3CA and decreased wtTP53 and p73, PF-502 reciprocally enhanced TP53/p73 expression and growth inhibition, which was partially reversible by p53 inhibitor pifithrin-α. Most UM-SCC with wtTP53 exhibited a lower IC50 than those with mtTP53 status. PF-502 blocked growth in G0-G1 and increased apoptotic sub-G0 DNA. PF-502 suppressed tumorigenesis and showed combinatorial activity with radiation in a wild-type TP53 UM-SCC xenograft model. PF-502 also significantly delayed HNSCC tumorigenesis and prolonged survival of Pten/Tgfbr1-deficient mice. Significant inhibition of p-Akt, p-4EBP1, p-S6, and Ki67, as well as increased p53 and TUNEL were observed in tumor specimens.

CONCLUSIONS

PI3K-mTOR inhibition can enhance TP53/p73 expression and significantly inhibit tumor growth alone or when combined with radiation in HNSCC with wild-type TP53. PIK3CA, TP53/p73, PTEN, and TGF-β alterations are potential modifiers of response and merit investigation in future clinical trials with PI3K-mTOR inhibitors.

Inactivation of the mTORC1-eukaryotic translation initiation factor 4E pathway alters stress granule formation

Stress granules (SG) are cytoplasmic multimeric RNA bodies that form under stress conditions known to inhibit cap-dependent translation. SG contain translation initiation factors, RNA binding proteins, and signaling molecules. SG are known to inhibit apoptotic pathways, thus contributing to chemo- and radioresistance in tumor cells. However, whether stress granule formation involves oncogenic signaling pathways is currently unknown. Here, we report a novel role of the mTORC1-eukaryotic translation initiation factor 4E (eIF4E) pathway, a key regulator of cap-dependent translation initiation of oncogenic factors, in SG formation. mTORC1 specifically drives the eIF4E-mediated formation of SG through the phosphorylation of 4E-BP1, a key factor known to inhibit formation of the mTORC1-dependent eIF4E-eIF4GI interactions. Disrupting formation of SG by inactivation of mTOR with its specific inhibitor pp242 or by depletion of eIF4E or eIF4GI blocks the SG-associated antiapoptotic p21 pathway. Finally, pp242 sensitizes cancer cells to death in vitro and inhibits the growth of chemoresistant tumors in vivo. This work therefore highlights a novel role of the oncogenic mTORC1-eIF4E pathway, namely, the promotion of formation of antiapoptotic SG.

mTOR Pathway and mTOR Inhibitors in Head and Neck Cancer

Head and neck cancer is the sixth most common type of Cancer worldwide. Since conventional treatment regimens are nonselective and are associated with systemic toxicities, intense investigations focus on molecular targeted therapy with high selectivity and low adverse effects. mTOR signaling pathway has been found to be activated in head and neck cancer, making it attractive for targeted therapy. In addition, expression levels of mTOR and downstream targets eIF4E, 4EBP1, S6K1, and S6 are potential diagnostic and prognostic biomarkers for head and neck cancer. mTOR inhibitors, such as rapamycin and its derivatives temsirolimus and everolimus, exhibit inhibitory effects on head and neck cancer in both in vitro cell line model and in vivo xenograft model. A large number of clinical trials have been initiated to evaluate the therapeutic effects of mTOR inhibitors on patients with head and neck cancer. mTOR inhibitor has potential as a single therapeutic agent or in combination with radiation, chemotherapeutic agents, or other targeted therapeutic agents to obtain synergistic repression on head and neck cancer.

18F-fluorodeoxythymidine micro-positron-emission tomography versus 18F-fluorodeoxyglucose micro-positron-emission tomography for in vivo minimal residual disease imaging

OBJECTIVES/HYPOTHESIS

The early detection of persistent/recurrent disease of head and neck squamous cell carcinoma (HNSCC) after treatment can be challenging. The currently used radioisotope (18)F-fluorodeoxyglucose (FDG) is a nonspecific tracer for cancer cells as it detects all metabolically active cells including inflammation. (18)F-fluorodeoxythymidine (FLT) is a radioactive tracer for rapidly proliferating cells, and therefore is more specific for detecting cancer. Our aim was to compare FLT and FDG microPET (positron-emission tomography) to the gold standard in vivo bioluminescence imaging for serial assessment of neoplastic growth in a minimal residual disease in vivo model.

STUDY DESIGN

Prospective outcomes research.

METHODS

In order to mimic the postsurgical environment of HNSCC patients FaDu cells transfected with a luciferase-expressing retrovirus were inoculated into the skin flap of Balb/c nu/nu mice. Three days later before tumors formed, mice were randomized into (18)F-FLT or (18) F-FDG groups, and microPET imaging was performed on days 3, 6, 10, 18, and 24 after tumor cell inoculation.

RESULTS

(18)F-FLT detected tumors as early as day 3 even before tumors were palpable, whereas (18)F-FDG only detected palpable tumors. The average overall normalized radioactivity in the FLT group was significantly higher than the FDG group (P = .025).

CONCLUSIONS

(18)F-FLT identified tumor cells before tumors were palpable and can potentially be used for early detection of persistence/recurrence of HNSCC. In addition, this radioisotope can be used to monitor adjuvant therapy with novel targeted therapeutics in preclinical models of persistent disease.

mTOR inhibition prevents epithelial stem cell senescence and protects from radiation-induced mucositis

The integrity of the epidermis and mucosal epithelia is highly dependent on resident self-renewing stem cells, which makes them vulnerable to physical and chemical insults compromising the repopulating capacity of the epithelial stem cell compartment. This is frequently the case in cancer patients receiving radiation or chemotherapy, many of whom develop mucositis, a debilitating condition involving painful and deep mucosal ulcerations. Here, we show that inhibiting the mammalian target of rapamycin (mTOR) with rapamycin increases the clonogenic capacity of primary human oral keratinocytes and their resident self-renewing cells by preventing stem cell senescence. This protective effect of rapamycin is mediated by the increase in expression of mitochondrial superoxide dismutase (MnSOD), and the consequent inhibition of ROS formation and oxidative stress. mTOR inhibition also protects from the loss of proliferative basal epithelial stem cells upon ionizing radiation in vivo, thereby preserving the integrity of the oral mucosa and protecting from radiation-induced mucositis.

Differential expression of organic cation transporter OCT-3 in oral premalignant and malignant lesions: potential implications in the antineoplastic effects of metformin

BACKGROUND

Recent evidence indicates that metformin, a biguanide used as first-line treatment for type 2 diabetes, prevents the conversion of carcinogen-induced oral dysplasias into head and neck squamous cell carcinomas (HNSCC), most likely by inhibiting mammalian target of rapamycin complex 1 (mTORC1) oncogenic signaling. Whether metformin acts directly at the primary tumor site or indirectly by modulating hormonal secretion from extratumoral organs remains unknown. As organic cation transporters (OCT) belonging to the solute carrier 22A gene family, including OCT-1, OCT-2, and OCT-3, mediate metformin uptake and activity, it is critical to define what role they play in the antineoplastic activity of metformin.

METHODS

Immunohistochemical and immunoblotting techniques were used in normal, dysplastic and HNSCC tissues, and HNSCC cell lines, respectively, to determine OCTs expression levels.

RESULTS

We report that only OCT-3 was highly expressed in a number of HNSCC cell lines, oral epithelial dysplasias, and well to moderately differentiated HNSCC. Indeed, inhibition of OCT-3 expression and activity in HNSCC cells prevented metformin-induced AMP-activated protein kinase activation and mTORC1 pathway inhibition. Moreover, in oral dysplasias, high OCT-3 expression localized to epithelial compartments where mTORC1 signaling was also upregulated suggestive of a potential local effect of metformin.

CONCLUSIONS

The concept of using metformin as a chemopreventive agent to control head and neck carcinogenesis is promising. Further work is warranted to elucidate largely unexplored mechanisms of metformin uptake and pharmacologic action that may ultimately influence the selection of the most suitable patients who can benefit from metformin in head and neck cancer chemoprevention.

Chemopreventive and chemotherapeutic actions of mTOR inhibitor in genetically defined head and neck squamous cell carcinoma mouse model

PURPOSE

To assess the efficacy of rapamycin treatment in chemoprevention and chemotherapy of tumorigenesis in a genetically defined mouse model of head and neck squamous cell carcinoma (HNSCC).

EXPERIMENTAL DESIGN

Knockdown of Tgfbr1 and/or Pten using siRNA-mediated RNA interference was carried out in human HNSCC cell lines to analyze molecular changes in the mTOR pathway. Tgfbr1(flox/flox); Pten(flox/flox); K14-CreER(tam) mice were treated with oral gavage of tamoxifen for the conditional deletion of Tgfbr1 and Pten in oral mucosa, resulting in HNSCC. Tgfbr1 and Pten conditonal deletion (2cKO) mice were treated with rapamycin before or after the onset of HNSCC, and the efficacy of this treatment was assessed by determining tumor burden, longevity, and molecular analysis of the mTOR pathway. Molecular changes observed in human HNSCC cell lines and 2cKO mice were compared to identify key alterations in the mTOR pathway.

RESULTS

Knockdown of Tgfbr1 and/or Pten in human HNSCC cell lines resulted in activation of mTOR activity complex 1 and increased levels of survivin. Furthermore, we observed similar changes in HNSCC of the 2cKO mouse. In the human HNSCC tissue array, a loss of Tgfbr1 expression correlated with increased survivin levels. Chemopreventive rapamycin treatment significantly delayed the onset of the HNSCC tumors and prolonged survival in 2cKO mice. In addition, we also found that rapamycin had a therapeutic effect on squamous cell carcinomas in these mice. In 2cKO HNSCC tongue tumors, rapamycin treatment induced apoptosis, inhibited cell proliferation and phosphorylation of Akt and S6, and decreased survivin expression.

CONCLUSIONS

These findings indicate that tumorigenesis in 2cKO HNSCC is associated with activation of the Akt/mTOR/survivin pathway, and inhibition of this pathway by rapamycin treatment successfully ameliorates the onset and progression of tumorigenesis.

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.

Inhibition of chondrosarcoma growth by mTOR inhibitor in an in vivo syngeneic rat model

Background

Chondrosarcomas are the second most frequent primary malignant type of bone tumor. No effective systemic treatment has been identified in advanced or adjuvant phases for chondrosarcoma. The aim of the present study was to determine the antitumor effects of doxorubicin and everolimus, an mTOR inhibitor on chondrosarcoma progression.

Methods and Findings

Doxorubin and/or everolimus were tested in vivo as single agent or in combination in the rat orthotopic Schwarm chondrosarcoma model, in macroscopic phase, as well as with microscopic residual disease. Response to everolimus and/or doxorubicin was evaluated using chondrosarcoma volume evolution (MRI). Histological response was evaluated with % of tumor necrosis, tumor proliferation index, metabolism quantification analysis between the treated and control groups. Statistical analyses were performed using chi square, Fishers exact test. Doxorubicin single agent has no effect of tumor growth as compared to no treatment; conversely, everolimus single agent significantly inhibited tumor progression in macroscopic tumors with no synergistic additive effect with doxorubicin. Everolimus inhibited chondrosarcoma proliferation as evaluated by Ki67 expression did not induce the apoptosis of tumor cells; everolimus reduced Glut1 and 4EBP1 expression. Importantly when given in rats with microscopic residual diseases, in a pseudo neoadjuvant setting, following R1 resection of the implanted tumor, everolimus significantly delayed or prevented tumor recurrence.

Conclusions

MTOR inhibitor everolimus blocks cell proliferation, Glut1 expression and HIF1a expression, and prevents in vivo chondrosarcoma tumor progression in both macroscopic and in adjuvant phase post R1 resection. Taken together, our preclinical data indicate that mTOR inhibitor may be effective as a single agent in treating chondrosarcoma patients. A clinical trial evaluating mTOr inhibitor as neo-adjuvant and adjuvant therapy in chondrosarcoma patients is being constructed.

A phase I study of temsirolimus plus carboplatin plus paclitaxel for patients with recurrent or metastatic (R/M) head and neck squamous cell cancer (HNSCC)

PURPOSE

The mammalian target of rapamycin complex 1 (mTORC1) is aberrantly activated in many head and neck squamous cell carcinomas (HNSCCs). This phase I study combines the mTORC1 inhibitor temsirolimus with carboplatin and paclitaxel.

METHODS

This was a single institution phase I study for patients with R/M HNSCC with a standard 3 + 3 design. Three doses of temsirolimus were planned: 15, 20, and 25 mg. Due to excessive toxicity with the original study regimen, the protocol was amended to carboplatin AUC 1.5, paclitaxel 80 mg/m(2), and temsirolimus (according to dose escalation plan), all on days 1 and 8 of a 21-day cycle.

RESULTS

18 patients (14 male, 4 female) enrolled, with median age 56 years (range 33-78). The most common toxicities were anemia, leukopenia, thrombocytopenia, and hyperglycemia. Among all patients treated, the confirmed objective partial response (cPR) rate was 22 %. DLT was not exceeded among 6 patients treated at dose level 3 of the revised protocol, and 4 of 6 subjects treated at this dose level had cPRs.

CONCLUSION

The phase II recommended regimen is temsirolimus 25 mg, carboplatin AUC 1.5, and paclitaxel 80 mg/m(2), all on days 1 and 8 of a 21-day cycle. A phase II study of this regimen in R/M HNSCC is ongoing.

Role of phosphatidylinositol-3-kinase pathway in head and neck squamous cell carcinoma

Activation of the phosphatidylinositol-3-kinase (PI3K) pathway is one of the most frequently observed molecular alterations in many human malignancies, including head and neck squamous cell carcinoma (HNSCC). A growing body of evidence demonstrates the prime importance of the PI3K pathway at each stage of tumorigenesis, that is, tumor initiation, progression, recurrence, and metastasis. Expectedly, targeting the PI3K pathway yields some promising results in both preclinical studies and clinical trials for certain cancer patients. However, there are still many questions that need to be answered, given the complexity of this pathway and the existence of its multiple feedback loops and interactions with other signaling pathways. In this paper, we will summarize recent advances in the understanding of the PI3K pathway role in human malignancies, with an emphasis on HNSCC, and discuss the clinical applications and future direction of this field.

Metformin prevents the development of oral squamous cell carcinomas from carcinogen-induced premalignant lesions

Head and neck squamous cell carcinoma (HNSCC) is a major public health concern. The recent identification of the mTOR complex 1 (mTORC1) signaling pathway as a highly prevalent molecular signature underlying HNSCC pathogenesis has provided the foundation to search for novel therapeutic approaches to prevent and treat HNSCC. Here, we asked whether metformin, the most widely used medication for the treatment of type II diabetes, which acts in part by stimulating the AMP-activated protein kinase (AMPK) signaling pathway thereby reducing mTORC1 activity, may lower the risk of HNSCC development. Indeed, we show that metformin reduces the growth of HNSCC cells and diminishes their mTORC1 activity by both AMPK-dependent and -independent mechanisms. We also optimized an oral-specific carcinogenesis mouse model that results in the accumulation of multiple oral premalignant lesions at the end of the carcinogen exposure, some of which then spontaneously progress into HNSCC. Using this mouse model, we observed that metformin specifically inhibits mTORC1 in the basal proliferating epithelial layer of oral premalignant lesions. Remarkably, metformin prevented the development of HNSCC by reducing significantly the size and number of carcinogen-induced oral tumoral lesions and by preventing their spontaneous conversion to squamous cell carcinomas. Collectively, our data underscore the potential clinical benefits of using metformin as a targeted chemopreventive agent in the control of HNSCC development and progression.

Novel targeted therapies in head and neck cancer

INTRODUCTION

Molecularly targeted therapy, with the potential for increased selectivity and fewer adverse effects, hold promise in the treatment of HNSCC.

AREAS COVERED

Targeted agents for HNSCC expected to improve the effectiveness of current therapy including HER family, Src-family kinase, cell cycle, MET, AKT, HDAC, PARP, COX inhibitors and antiangiogenesis.

EXPERT OPINION

Epidermal growth factor receptor inhibitors are established in HNSCC and the need now is to find biomarkers for sensitivity to better select patients. Moreover, other pathway inhibitors hold significant promise and are being tested in clinical trials. Angiogenesis inhibition is likely to yield only modest efficacy alone but may augment existing standards. Lastly, one clinical arena where targeted therapies may find secure purchase is in the adjuvant or prevention setting where minimal or preneoplastic disease can be affected by inhibition of a single or few targets.

Inhibitors of mTOR overcome drug resistance from topoisomerase II inhibitors in solid tumors

The present study was performed to investigate the possible role of mTOR inhibitors in restoring chemosensitivity to adriamycin/cisplatin and elucidate the underlying mechanism. Combining adriamycin/cisplatin with torisel synergistically inhibited the cell proliferation in human oropharyngeal carcinoma cell line KB and its multidrug-resistant subclone KB/7D. Combining adriamycin and torisel inhibited the phosphorylation of 4EBP-1 and p70S6K, the proteins involved in mTOR pathway, increased expression of γH2AX indicative of DNA damage, triggered cell cycle arrest at G2/M and apoptosis. We conclude that chromatin decondensation by DNA damage provided an easy access for torisel to block the translation of proteins essential for DNA repair thereby restoring the chemosensitivity.

Mammalian target of rapamycin expression and laryngeal squamous cell carcinoma prognosis: novel preliminary evidence

AIMS

The mammalian target of rapamycin (mTOR) has a key role in regulating cancer cell proliferation, apoptosis, cell migration, and angiogenesis. The aim of this study was to assess the relationships between mTOR and clinicopathological and prognostic parameters in laryngeal squamous cell carcinoma (SCC).

METHODS AND RESULTS

Mammalian target of rapamycin expression was determined in 103 consecutive operable laryngeal SCCs. Among the mTOR-positive cases, the locoregional recurrence rate was higher (P=0.048) and the disease-free survival (DFS) rate was shorter (P=0.031) in patients with mTOR expression >50.7%. In the N(0) subgroup, the disease recurrence rate was higher (P=0.034) and the DFS was shorter (P=0.009) in patients with mTOR expression >50.7%. In mTOR-positive patients, multivariate analysis showed that N stage (P=0.0001) and mTOR status (P=0.042) were independent indicators of a poor prognosis.

CONCLUSIONS

mTOR appeared to be a significant predictor of DFS in univariate and multivariate models. mTOR expression in laryngeal SCC may be useful for the detection of patients at higher risk for recurrence, and N(0) patients at higher risk for early locoregional recurrence who might benefit from more aggressive therapy. The role of mTOR inhibitors in multimodality or multitarget strategies against laryngeal SCC warrants investigation.

Decreased lymphangiogenesis and lymph node metastasis by mTOR inhibition in head and neck cancer

Despite our improved understanding of cancer, the 5-year survival rate for head and neck squamous cell carcinomas (HNSCC) patients remains relatively unchanged at 50% for the past three decades. HNSCCs often metastasize to locoregional lymph nodes, and lymph node involvement represents one of the most important prognostic factors of poor clinical outcome. Among the multiple dysregulated molecular mechanism in HNSCCs, emerging basic, preclinical, and clinical findings support the importance of the mTOR signaling route in HNSCC progression. Indeed, we observed here that the activation of mTOR is a widespread event in clinical specimens of HNSCCs invading locoregional lymph nodes. We developed an orthotopic model of HNSCC consisting of the implantation of HNSCC cells into the tongues of immunocompromised mice. These orthotopic tumors spontaneously metastasize to the cervical lymph nodes, where the presence of HNSCC cells can be revealed by histologic and immunohistochemical evaluation. Both primary and metastatic experimental HNSCC lesions exhibited elevated mTOR activity. The ability to monitor and quantitate lymph node invasion in this model system enabled us to explore whether the blockade of mTOR could impact HNSCC metastasis. We found that inhibition of mTOR with rapamycin and the rapalog RAD001 diminished lymphangiogenesis in the primary tumors and prevented the dissemination of HNSCC cancer cells to the cervical lymph nodes, thereby prolonging animal survival. These findings may provide a rationale for the future clinical evaluation of mTOR inhibitors, including rapamycin and its analogues, as part of a molecular-targeted metastasis preventive strategy for the treatment of patients with HNSCC.

Efficacy and comparative effectiveness of sirolimus as an anticancer drug

OBJECTIVES/HYPOTHESIS

To evaluate antitumor efficacy of the generic mammalian target of rapamycin (mTOR) inhibitor sirolimus in preclinical animal models of head and neck squamous cell carcinoma (HNSCC) and compare its effects with those of the patented analogue temsirolimus.

STUDY DESIGN

In vivo study.

METHODS

To develop xenograft established tumor model (ETM) of HNSCC, FaDu cells were injected subcutaneously into nude mice. When tumors reached 50 to 60 mm(3), mice were randomized into five groups and treated daily intraperitoneally with sirolimus at various doses for 5 days per week for 3 weeks. Tumor volumes were measured. The results were compared with historical data on temsirolimus effects. In the minimal residual disease (MRD) model, surgical wounds were created and FaDu cells implanted. After 72 hours, animals were randomized into two groups and were injected intraperitoneally with 0 or 5 mg/kg sirolimus for 5 days per week for 30 days.

RESULTS

In the ETM, sirolimus significantly inhibited tumor growth (P < .01), although there was no overall significant difference in tumor growth inhibition between sirolimus and temsirolimus. In the MRD model, sirolimus significantly suppressed growth of tumors (P < .001) and improved survival compared with controls (P < .01). There was a significant decrease in pS6 expression, indicating mTOR inhibition.

CONCLUSIONS

In this study, we demonstrate that the generic mTOR inhibitor sirolimus shows potent antitumor activity in HNSCC and produces comparable effects to the patent drug temsirolimus. Sirolimus has the potential of serving as an economic and comparative targeted agent to temsirolimus in the treatment of HNSCC.

Mammalian target of rapamycin and head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC), a significant cause of cancer deaths worldwide, has multiple stepwise malignant evolutions. Mammalian target of rapamycin (mTOR) plays a critical role in tumor development, invasion, metastasis and angiogenesis that impact local recurrence and survival. mTOR can also act as a biomarker for personalized adjuvant therapy. In in vivo and in vitro studies, mTOR inhibitor suppresses tumor growth and sensitizes HNSCC to radiation, cytotoxic agents and epidermoid growth factor receptor inhibitors. We have reviewed the pathogenesis of HNSCC, mTOR pathway, mTOR inhibitor and the role of mTOR in HNSCC.

Rapamycin inhibits anal carcinogenesis in two preclinical animal models

The incidence of anal cancer is increasing especially among HIV-infected persons in the HAART era. Treatment of this cancer is based upon traditional chemoradiotherapeutic approaches, which are associated with high morbidity and of limited effectiveness for patients with high-grade disease. The mammalian target of rapamycin (mTOR) pathway has been implicated in several human cancers, and is being investigated as a potential therapeutic target. In archival human anal cancers, we observed mTOR pathway activation. To assess response of anal cancer to mTOR inhibition, we utilized two newly developed mouse models, one in which anal cancers are induced to arise in HPV16 transgenic mice and the second a human anal cancer xenograft model. Using the transgenic mouse model, we assessed the preventative effect of rapamycin on neoplastic disease. We saw significant changes in the overall incidence of tumors, and tumor growth rate was also reduced. Using both the transgenic mouse and human anal xenograft mouse models, we studied the therapeutic effect of rapamycin on preexisting anal cancer. Rapamycin was found to significantly slow, if not stop, the growth of both mouse and human anal cancers. As has been seen in other cancers, rapamycin treatment led to an activation of the MAPK pathway. These results provide us cause to pursue further the evaluation of rapamycin as a therapeutic agent in the control of anal cancer.