Dual blockade of PI3K and MEK in combination with radiation in head and neck cancer

Mutant HRas Signaling and Rationale for Use of Farnesyltransferase Inhibitors in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinomas (HNSCCs) are often associated with poor outcomes, due at least in part to the limited number of treatment options available for those patients who develop recurrent and/or metastatic disease (R/M HNSCC). Even with the recent validation and approval of immunotherapies in the first-line setting for these patients, the need for the development of new and alternative precision medicine strategies with survival benefit is clear. Oncogenic alterations in the HRAS (Harvey rat sarcoma virus) proto-oncogene are seen in approximately 4-8% of R/M HNSCC tumors. Recently, several preclinical and clinical advancements have been made in the implementation of small-molecule inhibitors that block post-translational farnesylation of HRas, thereby abrogating its downstream oncogenic activity. In this review, we focus on the biology of wild-type and mutant HRas signaling in HNSCC, and rationale for use and outcomes of farnesyltransferase inhibitors in patients with HRAS-mutant tumors.

Pharmacological PI3K inhibition in head and neck squamous cell carcinoma: A systematic review

BACKGROUND

This systematic review aimed to investigate the in vitro and in vivo effects of phosphatidylinositol-3-kinase (PI3K) inhibitors on head and neck squamous cell carcinoma (HNSCC). Considering the role of PI3K and its downstream effectors in cell proliferation, invasion, and survival, it is reasonable to expect that treatment with PI3K inhibitors could control HNSCC onset and progression. Thus, the research question for our review was whether pharmacological inhibition of PI3K affects HNSCC progression.

METHODS

In vitro and in vivo studies were selected from six databases. We collected data regarding cell viability, apoptosis, and the regulation of protein expression levels from in vitro studies. For the in vivo studies, we analyzed the reduction in tumor size or gene and protein expression.

RESULTS

The included studies showed reduced cell proliferation and apoptosis after treatment with PI3K inhibitors. PI3K inhibitors in combination with other drugs had an enhanced anticancer effects compared to those of single-drug treatments.

CONCLUSIONS

The results support the potential of PI3K inhibitors as candidates for clinical trials in HNSCC.

Functional proteomics of patient derived head and neck squamous cell carcinoma cells reveal novel applications of trametinib

In this study, we report a differential response of mitogen-activated protein kinase–kinase (MEK) inhibitor trametinib in 20 head and neck squamous cell carcinoma (HNSCC) patients’ tumor-derived cell cultures. Relatively sensitive and resistant cases to trametinib were identified using high throughput metabolic assays and validated in extended dose response studies in vitro. High throughput metabolic assays exploring combination therapies with trametinib were subjected to synergy models and maximal synergistic dose analyses. These yielded several candidates, including axtinib, GDC-0032, GSK-690693, and SGX-523. The combination regimen of trametinib and AXL/MET/VEGFR inhibitor glesatinib showed initial efficacy both in vitro and in vivo (92% reduction in tumor volume). Sensitivity was validated in vivo in a patient-derived xenograft (PDX) model in which trametinib as a single agent effected reduction in tumor volume up to 72%. Reverse Phase Protein Arrays (RPPA) demonstrated differentially expressed proteins and phosphoproteins upon trametinib treatment. Furthermore, resistant cell lines showed a compensatory mechanism via increases in MAPK and non-MAPK pathway proteins that may represent targets for future combination regimens. Intrinsic-targeted options have potential to address paucity of medical treatment options for HNSCC cancer patients, enhance response to extrinsic targeted agents, and/or reduce morbidity as neoadjuvant to surgical treatments.

Lost in application: Measuring hypoxia for radiotherapy optimisation

The history of radiotherapy is intertwined with research on hypoxia. There is level 1a evidence that giving hypoxia-targeting treatments with radiotherapy improves locoregional control and survival without compromising late side-effects. Despite coming in and out of vogue over decades, there is now an established role for hypoxia in driving molecular alterations promoting tumour progression and metastases. While tumour genomic complexity and immune profiling offer promise, there is a stronger evidence base for personalising radiotherapy based on hypoxia status. Despite this, there is only one phase III trial targeting hypoxia modification with full transcriptomic data available. There are no biomarkers in routine use for patients undergoing radiotherapy to aid management decisions, and a roadmap is needed to ensure consistency and provide a benchmark for progression to application. Gene expression signatures address past limitations of hypoxia biomarkers and could progress biologically optimised radiotherapy. Here, we review recent developments in generating hypoxia gene expression signatures and highlight progress addressing the challenges that must be overcome to pave the way for their clinical application.

Inhibition of PI3K Isoform p110γ Increases Both Anti-Tumor and Immunosuppressive Responses to Aggressive Murine Head and Neck Squamous Cell Carcinoma with Low Immunogenicity

Simple Summary

Poorly immunogenic head and neck squamous carcinomas (HNSCC) remain difficult to treat due to poor response rates to immunotherapy. Inhibition of the PI3K catalytic subunit p110γ, which is expressed in leukocytes and some HNSCCs, has shown promise in treating HNSCC; with clinical trials underway to gauge its effectiveness. However, the effect of PI3K p110γ inhibition on the host immune system in poorly immunogenic HNSCC has not been fully described. In this study, our group characterized the immune response to poorly immunogenic HNSCC in the absence of PI3K p110γ using an orthotopic mouse model with the MOC2 cell line. We found that mice lacking p110γ did not demonstrate significantly different tumor growth or metastasis, though we observed substantial elevation in both anti-tumor and immunosuppressive activity at the primary tumor site. Our results indicate that PI3K p110γ inhibition may potentially enhance anti-tumor immunity against poorly immunogenic HNSCC if administered with checkpoint inhibitors.

Abstract

HNSCC is the sixth most common cancer, with around 650,000 new cases yearly. Gain of function mutations in the PI3K pathway are common in HNSCC, and inhibition of the PI3K p110γ subunit has shown promise in HNSCC treatment. However, given that PI3K p110γ plays an important role in myeloid and lymphoid immune cell function, it is essential to understand how PI3K p110γ inhibition affects the anti-tumor immune response independent of tumor cells. To elucidate PI3K p110γ function in HNSCC, we employed an orthotopic mouse model using poorly immunogenic and aggressive cell line MOC2 on Pik3cg^−/− mice. We observed that wild-type and Pik3cg^−/− mice displayed similar rates of HNSCC tumor growth and metastasis after 20 days following tumor injection. T-cell infiltration and intrinsic T-cell responses to MOC2 oral tumors were comparable between wild-type and Pik3cg^−/− mice. Interestingly, the immune response of tumor-bearing Pik3cg^−/− mice was marked by increased anti-tumor cytotoxic molecules (IFN-γ, IL-17)) by T-cells and immune checkpoint marker (PD-L1, PD-1) expression by myeloid cells and T-cells compared to tumor-bearing wild-type mice. Taken together, our findings demonstrate that inhibition of PI3K p110γ modulates tumor-associated immune cells, which likely potentiates HNSCC treatment when used in combination with selective checkpoint inhibitors.

Dacomitinib and gedatolisib in combination with fractionated radiation in head and neck cancer

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We evaluated radiation with dual EGFR and PI3K targeting in head and neck cancer.

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Dacomitinib, showed an inverse correlation between growth inhibition and EGFR expression.

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Gedatolisib was effective in each cell line. Neither drug caused radiosensitization in vitro.

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Gedatolisib was relatively ineffective in vivo in combination with dacomitinib and/or radiation.

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Dacomitinib was highly effective alone and in combination with radiation and/or gedatolisib.

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Immunoblotting studies in vivo mirrored the effects seen with growth delay.

Background and purpose

There has been little success targeting individual genes in combination with radiation in head and neck cancer. In this study we investigated whether targeting two key pathways simultaneously might be more effective.

Materials and methods

We studied the effect of combining dacomitinib (pan-HER, irreversible inhibitor) and gedatolisib (dual PI3K/MTOR inhibitor) with radiation in well characterized, low passage xenograft models of HNSCC in vitro and in vivo.

Results

Dacomitinib showed differential growth inhibition in vitro that correlated to EGFR expression whilst gedatolisib was effective in both cell lines. Neither agent radiosensitized the cell lines in vitro. In vivo studies demonstrated that dacomitinib was an effective agent alone and in combination with radiation whilst the addition of gedatolisib did not enhance the effect of these two modalities despite inhibiting phosphorylation of key genes in the PI3K/MTOR pathway.

Conclusions

Our results showed that combining two drugs with radiation provided no added benefit compared to the single most active drug. Dacomitinib deserves more investigation as a radiation sensitizing agent in HNSCC.

The influence of PI3K inhibition on the radiotherapy response of head and neck cancer cells

Radiotherapy has a central role in the treatment of head and neck squamous cell carcinoma (HNSCC). Activation of the PI3K/AKT/mTOR pathway can decrease the efficiency of radiotherapy via the promotion of cell survival and DNA repair. Here, the influence of PI3K pathway inhibition on radiotherapy response was investigated. Two PI3K inhibitors were investigated and both BKM120 and GDC0980 effectively inhibited cellular and clonogenic growth in 6 HNSCC cells, both HPV-positive as well as HPV-negative. Despite targeted inhibition of the pathway and slight increase in DNA damage, PI3K inhibition did not show significant radiosensitization. Currently only one clinical trial is assessing the effectiveness of combining BKM120 with RT in HNSCC (NCT02113878) of which the results are eagerly awaited.

Improving the Efficacy of Tumor Radiosensitization Through Combined Molecular Targeting

Chemoradiation, either alone or in combination with surgery or induction chemotherapy, is the current standard of care for most locally advanced solid tumors. Though chemoradiation is usually performed at the maximum tolerated doses of both chemotherapy and radiation, current cure rates are not satisfactory for many tumor entities, since tumor heterogeneity and plasticity result in chemo- and radioresistance. Advances in the understanding of tumor biology, a rapidly growing number of molecular targeting agents and novel technologies enabling the in-depth characterization of individual tumors, have fuelled the hope of entering an era of precision oncology, where each tumor will be treated according to its individual characteristics and weaknesses. At present though, molecular targeting approaches in combination with radiotherapy or chemoradiation have not yet proven to be beneficial over standard chemoradiation treatment in the clinical setting. A promising approach to improve efficacy is the combined usage of two targeting agents in order to inhibit backup pathways or achieve a more complete pathway inhibition. Here we review preclinical attempts to utilize such dual targeting strategies for future tumor radiosensitization.

Alterations and molecular targeting of the GSK-3 regulator, PI3K, in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is a highly morbid, genetically unstable disease derived from the mucoepithelium of the upper aerodigestive tract. Recent characterization of this disease has implicated the PI3K-Akt-mTOR pathway as one of the most frequently dysregulated pathways. As such, there are several classes of PI3K inhibitors currently undergoing clinical trials. In this article, we review the PI3K pathway, mutations of this pathway in HNSCC, drugs that target PI3K, the impact of these agents on the PI3K and GSK-3 signaling axes, ongoing clinical trials evaluating PI3K inhibitors, and the challenges of using these drugs in the clinic. This article is part of a Special Issue entitled: GSK-3 and related kinases in cancer, neurological and other disorders edited by James McCubrey, Agnieszka Gizak and Dariusz Rakus.

Prognostic significance of MTOR expression in HPV positive and negative head and neck cancers treated by chemoradiation

BACKGROUND

The mechanistic target of rapamycin (MTOR) plays a key role in regulating cell growth and metabolism and is commonly overexpressed in head and neck cancer (HNSCC). This study investigated the association of MTOR with clinical outcome in human papilloma virus (HPV) positive and negative HNSCC patients treated by chemoradiation.

METHODS

A tissue microarray (TMA) consisting of cores from 109 HNSCC patients treated by definitive chemoradiation was constructed and stained with antibodies against p16 and MTOR and expression correlated with clinicopathological features and clinical outcome.

RESULTS

MTOR varied widely between tumor cores and was not associated with HPV status or clinicopathological features. There was a positive correlation with pre-treatment FDG uptake. (P = .01). In HPV negative patients, MTOR predicted for shorter locoregional control (P = .02), diseases free survival (P = .02), and overall survival (P = .04). MTOR expression was not associated with outcome in HPV positive patients.

CONCLUSIONS

Prognostic significance of MTOR expression depends on HPV status.