EGFR-PI3K-AKT-mTOR signaling in head and neck squamous cell carcinomas: attractive targets for molecular-oriented therapy

Integrated Genomic and Functional microRNA Analysis Identifies miR-30-5p as a Tumor Suppressor and Potential Therapeutic Nanomedicine in Head and Neck Cancer

PURPOSE

To identify deregulated and inhibitory miRNAs and generate novel mimics for replacement nanomedicine for head and neck squamous cell carcinomas (HNSCC).

EXPERIMENTAL DESIGN

We integrated miRNA and mRNA expression, copy number variation, and DNA methylation results from The Cancer Genome Atlas (TCGA), with a functional genome-wide screen.

RESULTS

We reveal that the miR-30 family is commonly repressed, and all 5 members sharing these seed sequence similarly inhibit HNSCC proliferation in vitro. We uncover a previously unrecognized inverse relationship with overexpression of a network of important predicted target mRNAs deregulated in HNSCC, that includes key molecules involved in proliferation (EGFR, MET, IGF1R, IRS1, E2F7), differentiation (WNT7B, FZD2), adhesion, and invasion (ITGA6, SERPINE1). Reexpression of the most differentially repressed family member, miR-30a-5p, suppressed this mRNA program, selected signaling proteins and pathways, and inhibited cell proliferation, migration, and invasion in vitro. Furthermore, a novel miR-30a-5p mimic formulated into a targeted nanomedicine significantly inhibited HNSCC xenograft tumor growth and target growth receptors EGFR and MET in vivo. Significantly decreased miR-30a/e family expression was related to DNA promoter hypermethylation and/or copy loss in TCGA data, and clinically with decreased disease-specific survival in a validation dataset. Strikingly, decreased miR-30e-5p distinguished oropharyngeal HNSCC with poor prognosis in TCGA (P = 0.002) and validation (P = 0.007) datasets, identifying a novel candidate biomarker and target for this HNSCC subset.

CONCLUSIONS

We identify the miR-30 family as an important regulator of signal networks and tumor suppressor in a subset of HNSCC patients, which may benefit from miRNA replacement nanomedicine therapy.

MicroRNA expression correlates with disease recurrence and overall survival in oral squamous cell carcinoma

OBJECTIVES

Locoregional disease recurrence and metastatic events are the leading causes of death and the most important prognostic factors in patients with head and neck squamous cell carcinoma (HNSCC). A major goal of oncology is the identification of clinical and molecular parameters to evaluate the individual risk of recurrence. MicroRNAs (miRNAs) have been shown to correlate well with tumor size and differentiation. Therefore, they are candidate biomarkers for estimating clinical outcomes.

MATERIALS AND METHODS

In this study, the expression levels of distinct miRNAs extracted from formalin-fixed, paraffin-embedded (FFPE) samples of oral squamous cell carcinoma were compared.

RESULTS

Statistical analysis revealed significant correlations between distinct miRNAs and disease recurrence (miR-99*, miR-194*; p < 0.05) and overall survival (miR-99*; p < 0.05). The results were then validated via data from The Cancer Genome Atlas (TCGA).

CONCLUSIONS

Our data show that miR-99* and miR-194* can possibly serve as biomarkers for clinical outcome in HNSCC. These findings may help to identify high-risk patients, who could profit from a more individualized treatment and follow-up.

Ginsenoside Rd Inhibits the Metastasis of Colorectal Cancer via Epidermal Growth Factor Receptor Signaling Axis

Ginsenoside Rd is a saponin from ginseng and has been reported to have various biological activities. However, the effect of ginsenoside Rd on the metastasis of colorectal cancer (CRC) remains unknown. Here, we found that ginsenoside Rd decreased the colony-forming ability, migration, invasion, and wound-healing abilities of CRC cells, although it did not affect cell proliferation. In addition, using an inverse-docking assay, we found that ginsenoside Rd bound to epidermal growth factor receptor (EGFR) with a high binding affinity, inducing the downregulation of stemness- and epithelial-mesenchymal transition-related genes; these were partially rescued by either exogenous EGF treatment or ectopic expression of SOX2. Furthermore, ginsenoside Rd significantly decreased the number and size of tumor metastasis nodules in the livers, lungs, and kidneys of mouse model of metastasis. © 2018 IUBMB Life, 71(5):601-610, 2019.

A prognostic mRNA expression signature of four 16q24.3 genes in radio(chemo)therapy-treated head and neck squamous cell carcinoma (HNSCC)

Previously, we have shown that copy number gain of the chromosomal band 16q24.3 is associated with impaired clinical outcome of radiotherapy‐treated head and neck squamous cell carcinoma (HNSCC) patients. We set out to identify a prognostic mRNA signature from genes located on 16q24.3 in radio(chemo)therapy‐treated HNSCC patients of the TCGA (The Cancer Genome Atlas, n = 99) cohort. We applied stepwise forward selection using expression data of 41 16q24.3 genes. The resulting optimal Cox‐proportional hazards regression model included the genes APRT, CENPBD1, CHMP1A, and GALNS. Afterward, the prognostic value of the classifier was confirmed in an independent cohort of HNSCC patients treated by adjuvant radio(chemo)therapy (LMU‐KKG cohort). The signature significantly differentiated high‐ and low‐risk patients with regard to overall survival (HR = 2.01, 95% CI 1.10–3.70; P = 0.02125), recurrence‐free survival (HR = 1.84, 95% CI 1.01–3.34; P = 0.04206), and locoregional recurrence‐free survival (HR = 1.87, 95% CI 1.03–3.40; P = 0.03641). The functional impact of the four signature genes was investigated after reconstruction of a gene association network from transcriptome data of the TCGA HNSCC cohort using a partial correlation approach. Subsequent pathway enrichment analysis of the network neighborhood (first and second) of the signature genes suggests involvement of HNSCC‐associated signaling pathways such as apoptosis, cell cycle, cell adhesion, EGFR, JAK‐STAT, and mTOR. Furthermore, a detailed analysis of the first neighborhood revealed a cluster of co‐expressed genes located on chromosome 16q, substantiating the impact of 16q24.3 alterations in poor clinical outcome of HNSCC. The reported gene expression signature represents a prognostic marker in HNSCC patients following postoperative radio(chemo)therapy.

C6 ceramide motivates the anticancer sensibility induced by PKC412 in preclinical head and neck squamous cell carcinoma models

The purpose of this study was to evaluate the anti-head and neck squamous cell carcinoma (anti-HNSCC) cell activity by C6 ceramide and multikinase inhibitor PKC412. Experiments were performed on HNSCC cell lines (SQ20B and SCC-9) and primary human oral carcinoma cells. Results showed that PKC412 inhibited HNSCC cell proliferation without provoking apoptosis activation. Cotreatment of C6 ceramide significantly augmented PKC412-induced lethality in HNSCC cells. PKC412 decreased Akt-mammalian target of rapamycin (mTOR) activation in HNSCC cells, facilitated with cotreatment of C6 ceramide. In contrast, exogenous expression of a constitutively active Akt restored Akt-mTOR activation and attenuated lethality by the cotreatment. We propose that Mcl-1 is a primary resistance factor of PKC412. The cytotoxicity of PKC412 in HNSCC cells was potentiated with Mcl-1 short hairpin RNA knockdown, but was attenuated with Mcl-1 overexpression. Intriguingly, C6 ceramide downregulated Mcl-1 in HNSCC cells. In vivo, PKC412 oral administration inhibited SQ20B xenograft tumor growth in severe combined immunodeficient mice. The antitumor activity of PKC412 was further sensitized with coadministration of liposomal C6 ceramide. Together, we suggest that PKC412 could be further studied as a promising anti-HNSCC strategy, alone or in combination with C6 ceramide.

Follistatin supplementation during in vitro embryo culture improves developmental competence of bovine embryos produced using sex-sorted semen

Using sex-sorted semen to produce offspring of desired sex is associated with reduced developmental competence in vitro and lower fertility rates in vivo. The objectives of the present study were to investigate the effects of exogenous follistatin supplementation on the developmental competence of bovine embryos produced with sex-sorted semen and possible link between TGF-β regulated pathways and embryotrophic actions of follistatin. Effects of follistatin on expression of cell lineage markers (CDX2 and Nanog) and downstream targets of SMAD signaling (CTGF, ID1, ID2 and ID3) and AKT phosphorylation were investigated. Follistatin was supplemented during the initial 72 h of embryo culture. Exogenous follistatin restored the in vitro developmental competence of embryos produced with sex-sorted semen to the levels of control embryos produced with unsorted semen, and comparable results were obtained using sorted semen from three different bulls. The mRNA abundance for SMAD signaling downstream target genes, CTGF (SMAD 2/3 pathway) and ID2 (SMAD 1/5 pathway), was lower in blastocysts produced using sex-sorted versus unsorted semen, but mRNA levels for CDX2, NANOG, ID1 and ID3 were similar in both groups. Follistatin supplementation restored CTGF and ID2 mRNA in blastocysts produced using sex-sorted semen to levels of control embryos. Moreover, levels of phosphorylated (p)AKT (Ser-473 and Thr-308) were similar in embryos derived from sex-sorted and unsorted semen, but follistatin treatment increased pAKT levels in both groups. Taken together, results demonstrated that follistatin improves in vitro development of embryos produced with sex-sorted semen and such effects are associated with enhanced indices of SMAD signaling.

Dopamine Receptor Subtypes Differentially Regulate Autophagy

Some dopamine receptor subtypes were reported to participate in autophagy regulation, but their exact functions and mechanisms are still unclear. Here we found that dopamine receptors D2 and D3 (D2-like family) are positive regulators of autophagy, while dopamine receptors D1 and D5 (D1-like family) are negative regulators. Furthermore, dopamine and ammonia, the two reported endogenous ligands of dopamine receptors, both can induce dopamine receptor internalization and degradation. In addition, we found that AKT (protein kinase B)-mTOR (mechanistic target of rapamycin) and AMPK (AMP-activated protein kinase) pathways are involved in DRD3 (dopamine receptor D3) regulated autophagy. Moreover, autophagy machinery perturbation inhibited DRD3 degradation and increased DRD3 oligomer. Therefore, our study investigated the functions and mechanisms of dopamine receptors in autophagy regulation, which not only provides insights into better understanding of some dopamine receptor-related neurodegeneration diseases, but also sheds light on their potential treatment in combination with autophagy or mTOR pathway modulations.

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

Background and purpose

In this study we have combined fractionated radiation treatment (RT) with two molecular targeted agents active against key deregulated signaling pathways in head and neck cancer.

Materials and methods

We used two molecularly characterized, low passage HNSCC cell lines of differing biological characteristics to study the effects of binimetinib and buparlisib in combination with radiation in vitro and in vivo.

Results

Buparlisib was active against both cell lines in vitro whereas binimetinib was more toxic to UT-SCC-14. Neither agent modified radiation sensitivity in vitro. Buparlisib significantly inhibited growth of UT-SSC-15 alone or in combination with RT but was ineffective in UT-SCC-14. Binimetinib did cause a significant delay with RT in UT-SCC-14 and it significantly reduced growth of the UT-SCC-15 tumors both alone and with RT. The tri-modality treatment was not as effective as RT with a single effective agent.

Conclusions

No significant benefit was gained by the combined use of the two agents with RT even though each was efficacious when used alone.

Milk fat globule membrane protein promotes C2C12 cell proliferation through the PI3K/Akt signaling pathway

Milk fat globule membrane (MFGM) protein is known to have several health benefits, including an anti-sarcopenia effect; however, its mechanism is unclear. The aim of this study was to investigate the potential mechanism of action of the MFGM protein. The MFGM protein was extracted and separated into 4 fractions, and Fraction 2 (57% of total MFGM) demonstrated the greatest effect on C₂C₁₂ cell proliferation. Milk fat globule-EGF factor 8 (MFG-E8) accounted for 82.35% of the MFGM protein. The effects of whole Fraction 2 (100μg/mL, 200μg/mL and 300μg/mL) on cell proliferation and morphology were measured. Using qRT-PCR or a Western blot assay, several regulatory factors, e.g., PI3K P85α, p-pI3K p85α (Tyr 508), Akt, p-Akt (Ser 473), mTOR and p-mTOR (Ser 2448), were measured in cells incubated with 200μg/mL of Fraction 2 with or without wortmannin. The results demonstrated that Fraction 2 induced C₂C₁₂ cell proliferation in a dose-dependent manner, upregulated the mRNA expression of mTOR and p70S6K, and activated PI3K, Akt, mTOR and P70S6K phosphorylation; however, Fraction 2 inhibited FOXO3a and 4E-BP. The results demonstrate that the MFGM protein, predominantly MFG-E8, promotes cell proliferation through the PI3K/Akt/mTOR signaling pathway. This study elucidated the molecular mechanism of the MFGM protein, primarily MFG-E8, in promoting C₂C₁₂ cell proliferation via the PI3K/Akt/mTOR/P70S6K signal pathway.

Predictive value of EGFR-PI3K-pAKT-mTOR-pS6 pathway in sinonasal squamous cell carcinomas

BACKGROUND AND OBJECTIVES

We have previously indicated that EGFR has a role in carcinogenesis in a subgroup of sinonasal squamous cell carcinomas (SNSCC). In addition, EGFR activates 2 of the most important intracellular signalling pathways: PI3K/pAKT/mTOR/pS6 and MAP pathway kinases. The objective of this study was to evaluate the involvement of the EGFR/PI3K/pAKT/mTOR/pS6 pathway and its relationship with clinical-pathological parameters and follow-up of sinonasal squamous cell carcinoma.

MATERIAL AND METHODS

The immunohistochemical expression of different components of the PI3K/AKT/mTOR/pS6 pathway and its relationship with various clinical-pathological parameters was studied in a series of 54 patients with SNSCC.

RESULTS

Loss of PTEN expression was observed in 33/54 cases (61%) and pAKT, mTOR and pS6 pre-expression was observed in 19/54 cases (35%), 8/54 cases (15%), and 47/54 cases (87%), respectively. Loss of PTEN expression was related to intracranial invasion and development of regional metastases (p=0.005). Overexpression of pS6 was associated with a decrease in survival (p=0.008), presence of local recurrences (p=0.055), and worsening of overall prognosis (p=0.007). No significant relationships were observed between pAKT and mTOR expression and the clinicopathological parameters studied.

CONCLUSIONS

Alterations in the expression of EGFR/PI3K/pAKT/mTOR/pS6 pathway components are common in a subgroup of SNSCC. This study reveals that the absence of pS6 overexpression is associated with better clinical outcomes. Therefore, pS6 expression could be considered as an unfavourable prognostic marker.

MiR-128 reverses the gefitinib resistance of the lung cancer stem cells by inhibiting the c-met/PI3K/AKT pathway

Gefitinib is a first line anti-tumor drug used for the treatment of patients with non-small cell lung cancer (NSCLC) harboring EGFR mutations. However, the drug resistance to gefitinib limits its clinical application. Here, we observed the CSCs of PC9 are obviously resistant to gefitinib compared with the non-CSCs. Furthermore, we found the gefitinib failed to suppress the PI3K/AKT pathway in the PC9-CSCs. Mechanically, we showed significant down-regulation of miR-128 in the PC9-CSCs compared with the non-CSCs. Overexpression of miR-128 significantly increased the sensitivity of PC9-CSCs to gefitinib-induced apoptosis. In addition, the gene of c-met was proved to be directly inhibited by miR-128. Enforced expression of c-met could "rescue" the miR-128 promoted apoptosis and cleavage of caspases in PC9-CSCs treated with gefitinib. Thus, these results indicate that the miR-128/c-met pathway enhances the gefitinib sensitivity of the lung cancer stem cells by suppressing the PI3K/AKT pathway.

Toward the use of precision medicine for the treatment of head and neck squamous cell carcinoma

Precision medicine is a new strategy that aims at preventing and treating human diseases by focusing on individual variations in people's genes, environment and lifestyle. Precision medicine has been used for cancer diagnosis and treatment and shows evident clinical efficacy. Rapid developments in molecular biology, genetics and sequencing technologies, as well as computational technology, has enabled the establishment of "big data", such as the Human Genome Project, which provides a basis for precision medicine. Head and neck squamous cell carcinoma (HNSCC) is an aggressive cancer with a high incidence rate and low survival rate. Current therapies are often aggressive and carry considerable side effects. Much research now indicates that precision medicine can be used for HNSCC and may achieve improved results. From this perspective, we present an overview of the current status, potential strategies, and challenges of precision medicine in HNSCC. We focus on targeted therapy based on cell the surface signaling receptors epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF) and human epidermal growth factor receptor-2 (HER2), and on the PI3K/AKT/mTOR, JAK/STAT3 and RAS/RAF/MEK/ERK cellular signaling pathways. Gene therapy for the treatment of HNSCC is also discussed.

ON 01910.Na (rigosertib) inhibits PI3K/Akt pathway and activates oxidative stress signals in head and neck cancer cell lines

Squamous cell carcinoma of the head and neck (HNSCC) is characterized by high morbidity and mortality. Treatment failure, drug resistance and chemoradiation toxicity have necessitated the development of alternative treatment strategies. Styryl benzyl sulfones, a family of novel small molecule inhibitors, are being evaluated as anti-neoplastic agents in multiple clinical trials. The activity of these compounds has been well characterized in several preclinical tumor studies, but their activity has yet to be fully examined in HNSCC. We tested ON 01910.Na (rigosertib), a styryl benzyl sulfone in late-stage development, in HNSCC preclinical models. Rigosertib induced cytotoxicity in both HPV(+) and HPV(−) HNSCC cells in a dose-dependent manner. Characterization of the underlying molecular mechanism indicated that rigosertib induced inhibition of the PI3K/Akt/mTOR pathway, induced oxidative stress resulting in increased generation of reactive oxygen species (ROS), and activated extracellular signal-regulated kinases (ERK1/2) and c-Jun NH2-terminal kinase (JNK). Increased phosphorylation and cytoplasmic translocation of ATF-2 were also observed following rigosertib treatment. These changes in cell signaling led us to consider combining rigosertib with HNSCC standard-of-care therapies, such as cisplatin and radiation. Our study highlights the promising preclinical activity of rigosertib in HNSCC irrespective of HPV status and provides a molecular basis for rigosertib in combination with standard of care agents for HNSCC.

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.

A positive feedback loop involving EGFR/Akt/mTORC1 and IKK/NF-kB regulates head and neck squamous cell carcinoma proliferation

The overexpression or mutation of epidermal growth factor receptor (EGFR) has been associated with a number of cancers, including head and neck squamous cell carcinoma (HNSCC). Increasing evidence indicates that both the phosphatidylinositol-3-kinase (PI3K)-Akt-mammalian target of Rapamycin (mTOR) and the nuclear factor-kappa B (NF-κB) are constitutively active and contribute to aggressive HNSCC downstream of EGFR. However, whether these two oncogenic signaling pathways exhibit molecular and functional crosstalk in HNSCC is unclear. Our results now reveal that mTORC1, not mTORC2, contributes to NF-κB activation downstream of EGFR/PI3K/Akt signaling. Mechanistically, mTORC1 enhances the inhibitor of nuclear factor kappa-B kinase (IKK) activity to accelerate NF-κB signaling. Concomitantly, activated NF-κB/IKK up-regulates EGFR expression through positive feedback regulation. Blockage of NF-κB/IKK activity by the novel IKKβ specific inhibitor, CmpdA, leads to significant inhibition of cell proliferation and induction of apoptosis. CmpdA also sensitizes intrinsic cisplatin-resistant HNSCC cells to cisplatin treatment. Our findings reveal a new mechanism by which EGFR/PI3K/Akt/mTOR signaling promotes head and neck cancer progression and underscores the need for developing a therapeutic strategy for targeting IKK/NF-κB either as a single agent or in combination with cisplatin in head and neck cancer.

Apoptosis in human liver carcinoma caused by gold nanoparticles in combination with carvedilol is mediated via modulation of MAPK/Akt/mTOR pathway and EGFR/FAAD proteins

In cancers, apoptosis signaling pathways and cell survival and growth pathways responsible for resistance to conventional treatments, such as Pi3K/Akt/mTOR and mitogen-activated protein kinase (MAPK) become dysregulated. Recently, alternative treatments to promote tumor cell death have become important. The present study reports on the antitumor and cytoprotective action of gold nanoparticles (GNPs) and carvedilol in combination and in isolated application. Apoptosis was analyzed by FITC/propidium iodide staining flow cytometry; caspase-3, caspase-8, Bcl-2 and MAPK/ERK activity by immunofluorescence microscopy; gene expression of proteins related to cell death as Akt, mTOR, EGFR, MDR1, survivin, FADD and Apaf, by the real-time PCR; and western blot analysis for MAPK/ERK, Akt and mTOR. Oxidative stress evaluation was performed by reduced glutathione (GSH) and malondialdehyde (MDA) levels. Intracellular GNPs targets were identified by transmission electron microscopy. After exposure to a combination of GNPs (6.25 µg/ml) and carvedilol (3 µM), death as promoted by apoptosis was detected using flow cytometry, for expression of pro-apoptotic proteins FADD, caspase-3, caspase-8 and sub-regulation of anti-apoptotic MAPK/ERK, Akt, mTOR, EGFR and MDR1 resistance. Non-tumor cell cytoprotection with GSH elevation and MDA reduction levels was detected. GNPs were identified within the cell near to the nucleus when combined with carvedilol. The combination of GNP and carvedilol promoted downregulation of anti-apoptotic and drug resistance genes, over-regulation of pro-apoptotic proteins in tumor cells, as well as cytoprotection of non-tumor cells with reduction of apoptosis and oxidative stress.

Targeting the PI3K/AKT/mTOR signaling pathway as an effectively radiosensitizing strategy for treating human oral squamous cell carcinoma in vitro and in vivo

Radiation therapy (RT) is the current standard adjuvant approach for oral squamous cell carcinoma (OSCC) patients. Radioresistance is a major contributor to radiotherapy failure. In this study, we used patient-derived cells and a radiation-resistant cell line in vitro and in vivo for two purposes: evaluate the anti-tumor effects and understand the mechanisms in the dual PI3K/mTOR signaling pathway regulation of radiosensitization. Our findings indicate that in OML1-R cells, the radioresistance phenotype is associated with activation of the PI3K/AKT/mTOR signaling pathway. Compared to a combination of PI3K or mTOR inhibitors and radiation, dual blockade of the PI3K and mTOR kinases significantly improved radiation efficacy in oral cancer and patient-derived OSCC cells. Dual PI3K/mTOR inhibition enhanced the effect of radiation by inhibiting AKT/mTOR signaling pathways and caused G1 phase arrest, which is associated with downregulation of cyclin D1/CDK4 activity, leading to growth inhibition. In nude mice xenografted with radioresistant OML1-R cells, the combined treatment was also more effective than RT alone in reducing tumor growth. This treatment was also demonstrated to be dependent on the inhibition of protein kinase-dependent S6 kinase pathway and eIF4E-mediated cap-dependent translation. These findings indicate that activation of the PI3K/AKT/mTOR signaling pathway has a role in radioresistance of OSCC. We determined that a PI3K/mTOR inhibitor combined with radiation exhibits synergistic inhibition of the AKT/mTOR axis and induces cell cycle arrest. Our results show the therapeutic potential of drugs targeting the PI3K/AKT/mTOR signaling pathway should be new candidate drugs for radiosensitization in radiotherapy.

GSK1059615 kills head and neck squamous cell carcinoma cells possibly via activating mitochondrial programmed necrosis pathway

This study tested the anti-head and neck squamous cell carcinoma (HNSCC) cell activity by GSK1059615, a novel PI3K and mTOR dual inhibitor. GSK1059615 inhibited survival and proliferation of established (SCC-9, SQ20B and A253 lines) and primary human HNSCC cells. GSK1059615 blocked PI3K-AKT-mTOR activation in HNSCC cells. Intriguingly, GSK1059615 treatment in HNSCC cells failed to provoke apoptosis, but induced programmed necrosis. The latter was tested by mitochondria depolarization, ANT-1-cyclophilin-D mitochondrial association and lactate dehydrogenase (LDH) release. Reversely, mPTP blockers (sanglifehrin A, cyclosporin A and bongkrekic acid) or cyclophilin-D shRNA dramatically alleviated GSK1059615-induced SCC-9 cell death. Further studies demonstrated that GSK1059615 i.p. injection suppressed SCC-9 tumor growth in nude mice, which was compromised with co-administration with cyclosporin A. Thus, targeting PI3K-AKT-mTOR pathway by GSK1059615 possibly provokes programmed necrosis pathway to kill HNSCC cells.

Effect of the histone deacetylase inhibitor resminostat on head and neck squamous cell carcinoma cell lines

BACKGROUND

Carcinogenesis is determined by various epigenetic events, such as histone deacetylation. The purpose of this study was to investigate the effect of the new histone deacetylase inhibitor resminostat on head and neck squamous cell carcinoma (HNSCC) cell lines.

METHODS

The cytotoxicity of resminostat and cisplatin on HNSCC cell lines SCC25, CAL27, and FaDu was determined using CCK-8 cell proliferation assay and combination index analysis. Cells were irradiated with 2 to 8 Gray. Apoptosis was measured using flow cytometry and expression of Mcl-1, p-AKT, and survivin was investigated.

RESULTS

Treatment with resminostat showed a decrease of cell proliferation of HNSCC cell lines. In addition, a synergistic effect with cisplatin as well as with radiation treatment could be observed. Induction of cell death and dose-dependent downregulation of survivin was evident in all cell lines.

CONCLUSION

Resminostat is a promising treatment of HNSCC because of its antiproliferative, chemosensitizing, and radiosensitizing effects. © 2017 Wiley Periodicals, Inc. Head Neck 39: 900-907, 2017.

Inhibition of Bcl-2 potentiates AZD-2014-induced anti-head and neck squamous cell carcinoma cell activity

Mammalian target of rapamycin (mTOR) is a therapeutic target for head and neck squamous cell carcinoma (HNSCC). Here, we evaluated the activity of AZD-2014, a potent mTOR complex 1/2 (mTORC1/2) dual inhibitor, against HNSCC cells. We showed that AZD-2014 blocked mTORC1/2 activation in established and primary human HNSCC cells, where it was anti-proliferative and pro-apoptotic. Yet, AZD-2014 was non-cytotoxic to the human oral epithelial cells with low basal mTORC1/2 activation. In an effect to identify possible AZD-2014 resistance factors, we showed that the anti-apoptosis protein Bcl-2 was upregulated in AZD-2014-resistant SQ20B HNSCC cells. Inhibition of Bcl-2 by ABT-737 (a known Bcl-2 inhibitor) or Bcl-2 shRNA dramatically potentiated AZD-2014 lethality against HNSCC cells. On the other hand, exogenous overexpression of Bcl-2 largely attenuated AZD-2014's activity against HNSCC cells. For the in vivo studies, we showed that oral gavage of AZD-2014 suppressed SQ20B xenograft growth in severe combined immunodeficient (SCID) mice. It also significantly improved mice survival. Importantly, AZD-2014's anti-HNSCC activity in vivo was potentiated with co-administration of ABT-737. The preclinical results of this study suggest that AZD-2014 could be further tested as a valuable anti-HNSCC agent, either alone or in combination with Bcl-2 inhibitors.

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.

Boehmenan, a lignan from the Chinese medicinal plant Clematis armandii, induces apoptosis in lung cancer cells through modulation of EGF-dependent pathways

BACKGROUND

Epidermal growth factor receptor (EGFR) is an effective molecular target for cancer treatment. Boehmenan, a lignan from the dried stems of Clematis armandii, exhibited the potent cytotoxic effects against many cancer cell lines in previous studies. However, the effects and underlying mechanism of boehmenan on non-small cell lung cancer (NSCLC) remains unclear.

PURPOSE

The present study was designed to determine the in vitro anti-cancer properties and underlying molecular mechanisms of boehmenan on A549 NSCLC cells.

STUDY DESIGN/METHODS

Cellular viability and chemoattractive properties of macrophages were investigated by using MTT and transwell migration assay, respectively. Mitochondrial membrane potential (ΔΨm), apoptotic ratio, and cell cycle were measured by flow cytometry. Protein expression was visualized by Western blot using specific antibodies.

RESULTS

Boehmenan concentration-dependently suppressed proliferation and induced G1 phase arrest in A549 NSCLC cells, which were accompanied by reduction of migration, colony formation and increase of apoptosis in A549 cells. In addition, boehmenan treatment markedly modulated apoptosis-related protein (p53, p21, cleaved caspase 3, and cleaved PARP) and cyclin D1 expression and induced ΔΨm collapse in a concentration dependent manner. Furthermore, boehmenan concentration-dependently inhibited EGF-induced activation of EGFR and its downstream signaling molecules, including MEK, Akt, ERK1/2, and STAT3.

CONCLUSION

Taken together, our results suggested that boehmenan-mediated anti-tumor property was mediated by modulation of mitochondria and EGFR signaling pathway in A549 NSCLC cells.

EGFR Activation Leads to Cell Death Independent of PI3K/AKT/mTOR in an AD293 Cell Line

The Epidermal Growth Factor Receptor (EGFR) and its mutations contribute in various ways to tumorigenesis and biology of human cancers. They are associated with tumor proliferation, progression, drug resistance and the process of apoptosis. There are also reports that overexpression and activation of wild-type EGFR may lead to cell apoptosis. To study this phenomenon, we overexpressed in an AD293 cell line two most frequently observed forms of the EGFR receptor: wild-type and the constitutively active mutant–EGFR variant III (EGFRvIII). Then, we compared the effect of EGF stimulation on cell viability and downstream EGFR signaling. AD293 cells overexpressing wild-type EGFR, despite a significant proliferation increase in serum supplemented medium, underwent apoptosis after EGF stimulation in serum free conditions. EGFRvIII expressing cells, however, were unaffected by either serum starvation or EGF treatment. The effect of EGF was completely neutralized by tyrosine kinase inhibitors (TKIs), indicating the specificity of this observation. Moreover, apoptosis was not prevented by inhibiting EGFR downstream proteins (PI3K, AKT and mTOR). Here we showed another EGFR function, dependent on environmental factors, which could be employed in therapy and drug design. We also proposed a new tool for EGFR inhibitor analysis.

Gene-expression profiles in lung adenocarcinomas related to chronic wood smoke or tobacco exposure

BACKGROUND

Tobacco-smoke is the major etiological factor related to lung cancer. However, other important factor is chronic wood smoke exposure (WSE). Approximately 30 % of lung cancer patients in Mexico have a history of WSE, and present different clinical, pathological and molecular characteristics compared to tobacco related lung cancer, including differences in mutational profiles. There are several molecular alterations identified in WSE associated lung cancer, however most studies have focused on the analysis of changes in several pathogenesis related proteins.

METHODS

Our group evaluated gene expression profiles of primary lung adenocarcinoma, from patients with history of WSE or tobacco exposure. Differential expression between these two groups were studied through gene expression microarrays.

RESULTS

Results of the gene expression profiling revealed 57 statistically significant genes (p < 0.01). The associated biological functional pathways included: lipid metabolism, biochemistry of small molecules, molecular transport, cell morphology, function and maintenance. A highlight of our analysis is that three of the main functional networks represent 37 differentially expressed genes out of the 57 found. These hubs are related with ubiquitin C, GABA(A) receptor-associated like protein; and the PI3K/AKT and MEK/ERK signaling pathways.

CONCLUSION

Our results reflect the intrinsic biology that sustains the development of adenocarcinoma related to WSE and show that there is a different gene expression profile of WSE associated lung adenocarcinoma compared to tobacco exposure, suggesting that they arise through different carcinogenic mechanisms, which may explain the clinical and mutation profile divergences between both lung adenocarcinomas.

PTPRG suppresses tumor growth and invasion via inhibition of Akt signaling in nasopharyngeal carcinoma

Protein Tyrosine Phosphatase, Receptor Type G (PTPRG) was identified as a candidate tumor suppressor gene in nasopharyngeal carcinoma (NPC). PTPRG induces significant in vivo tumor suppression in NPC. We identified EGFR as a PTPRG potential interacting partner and examined this interaction. Dephosphorylation of EGFR at EGFR-Y1068 and -Y1086 sites inactivated the PI3K/Akt signaling cascade and subsequent down-regulation of downstream pro-angiogenic and -invasive proteins (VEGF, IL6, and IL8) and suppressed tumor cell proliferation, angiogenesis, and invasion. The effect of Akt inhibition in NPC cells was further validated by Akt knockdown experiments in the PTPRG-down-regulated NPC cell lines. Our results suggested that inhibition of Akt in NPC cells induces tumor suppression at both the in vitro and in vivo levels, and also importantly, in vivo metastasis. In conclusion, we confirmed the vital role of PTPRG in inhibiting Akt signaling with the resultant suppression of in vivo tumorigenesis and metastasis.

Targeting IκB Kinase β/NF-κB Signaling in Human Prostate Cancer by a Novel IκB Kinase β Inhibitor CmpdA

NF-κB plays an important role in many types of cancer, including prostate cancer, but the role of the upstream kinase of NF-κB, IKKβ, in prostate cancer has neither been fully documented nor are there any effective IKKβ inhibitors used in clinical settings. Here, we have shown that IKKβ activity is mediated by multiple kinases including IKKα in human prostate cancer cell lines that express activated IKKβ. IHC analysis (IHC) of human prostate cancer tissue microarrays (TMA) demonstrates that phosphorylation of IKKα/β within its activation loop gradually increases in low to higher stage tumors as compared with normal tissue. The expression of cell proliferation and survival markers (Ki-67, Survivin) and epithelial-to-mesenchymal transition (EMT) markers (Slug, Snail), as well as cancer stem cell (CSC)-related transcription factors (Nanog, Sox2, Oct-4), also increase in parallel among the respective TMA samples analyzed. IKKβ, but not NF-κB, is found to regulate Nanog, which, in turn, modulates the levels of Oct4, Sox2, Snail, and Slug, indicating an essential role of IKKβ in regulating CSCs and EMT. The novel IKKβ inhibitor CmpdA inhibits constitutively activated IKKβ/NF-κB signaling, leading to induction of apoptosis and inhibition of proliferation, migration, and stemness in these cells. CmpdA also significantly inhibits tumor growth in xenografts without causing apparent in vivo toxicity. Furthermore, CmpdA and docetaxel act synergistically to inhibit proliferation of prostate cancer cells. These results indicate that IKKβ plays a pivotal role in prostate cancer, and targeting IKKβ, including in combination with docetaxel, may be a potentially useful strategy for treating advanced prostate cancer. Mol Cancer Ther; 15(7); 1504-14. ©2016 AACR.

Could the PI3K canonical pathway be a common link between chronic inflammatory conditions and oral carcinogenesis?

The association between chronic inflammatory disorders and oral carcinogenesis has been both a source of interest and contention. Based upon its central importance in oral carcinogenesis, the finding that the PI3k/Akt/mTOR pathway is activated in oral lichen planus, chronic graft-versus-host disease, and chronic oral candidiasis suggests that it may provide a link between benign and malignant oral conditions. Here, we discuss a possible mechanistic rationale that addresses the activation of this important signaling pathway and its downstream events, while correlating it with the carcinogenic potential of chronic oral disorders.

MicroRNA-365a-3p promotes tumor growth and metastasis in laryngeal squamous cell carcinoma

MicroRNAs (miRNAs) are increasingly recognized as oncogenes or tumor suppressors in laryngeal squamous cell carcinoma (LSCC). In this study, we analyzed the roles of miR-365a-3p, miR-143-5p, and miR-494-3p in LSCC using Annexin V/propidium iodide double staining and flow cyto-metry, along with a Transwell migration and invasion assay. The results showed that miR-365a-3p inhibitor significantly facilitated cell apoptosis and suppressed cell cycle progression, migration, and invasion in Hep-2 cells. However, miR-143-5p and miR-494-3p had no such influences. We then investigated the role of miR-365a-3p in LSCC in vivo and found that miR-365a-3p inhibitor suppressed LSCC xenograft tumor growth and metastasis in xenograft mouse models. Moreover, miR-365a-3p inhibitor significantly decreased the expression of p-AKT (Ser473), which indicated that miR-365a-3p can mediate PI3K/AKT signaling pathway transduction via p-AKT (Ser473) in LSCC. The data suggest that miR-365a-3p may act as an oncomiR and may promote growth and metastasis in LSCC via the PI3K/AKT signaling pathway, and thus miR‑365a-3p may be a potential therapeutic target for treatment of LSCC.

Dysregulation of splicing proteins in head and neck squamous cell carcinoma

Signaling plays an important role in regulating all cellular pathways. Altered signaling is one of the hallmarks of cancers. Phosphoproteomics enables interrogation of kinase mediated signaling pathways in biological systems. In cancers, this approach can be utilized to identify aberrantly activated pathways that potentially drive proliferation and tumorigenesis. To identify signaling alterations in head and neck squamous cell carcinoma (HNSCC), we carried out proteomic and phosphoproteomic analysis of HNSCC cell lines using a combination of tandem mass tag (TMT) labeling approach and titanium dioxide-based enrichment. We identified 4,920 phosphosites corresponding to 2,212 proteins in six HNSCC cell lines compared to a normal oral cell line. Our data indicated significant enrichment of proteins associated with splicing. We observed hyperphosphorylation of SRSF protein kinase 2 (SRPK2) and its downstream substrates in HNSCC cell lines. SRPK2 is a splicing kinase, known to phosphorylate serine/arginine (SR) rich domain proteins and regulate splicing process in eukaryotes. Although genome-wide studies have reported the contribution of alternative splicing events of several genes in the progression of cancer, the involvement of splicing kinases in HNSCC is not known. In this study, we studied the role of SRPK2 in HNSCC. Inhibition of SRPK2 resulted in significant decrease in colony forming and invasive ability in a panel of HNSCC cell lines. Our results indicate that phosphorylation of SRPK2 plays a crucial role in the regulation of splicing process in HNSCC and that splicing kinases can be developed as a new class of therapeutic target in HNSCC.

An Ultra-Deep Targeted Sequencing Gene Panel Improves the Prognostic Stratification of Patients With Advanced Oral Cavity Squamous Cell Carcinoma

An improved prognostic stratification of patients with oral cavity squamous cell carcinoma (OSCC) and pathologically positive (pN+) nodes is urgently needed. Here, we sought to examine whether an ultra-deep targeted sequencing (UDT-Seq) gene panel may improve the prognostic stratification in this patient group.A mutation-based signature affecting 10 genes (including genetic mutations in 6 oncogenes and 4 tumor suppressor genes) was devised to predict disease-free survival (DFS) in 345 primary tumor specimens obtained from pN+ OSCC patients. Of the 345 patients, 144 were extracapsular spread (ECS)-negative and 201 were ECS-positive. The 5-year locoregional control, distant metastases, disease-free, disease-specific, and overall survival (OS) rates served as outcome measures.The UDT-Seq panel was an independent risk factor (RF) for 5-year locoregional control (P = 0.0067), distant metastases (P = 0.0001), DFS (P < 0.0001), disease-specific survival (DSS, P < 0.0001), and OS (P = 0.0003) in pN+ OSCC patients. The presence of ECS and pT3-4 disease were also independent RFs for DFS, DSS, and OS. A prognostic scoring system was formulated by summing up the significant covariates (UDT-Seq, ECS, pT3-4) separately for each survival endpoint. The presence of a positive UDT-Seq panel (n = 77) significantly improved risk stratification for all the survival endpoints as compared with traditional AJCC staging (P < 0.0001). Among ECS-negative patients, those with a UDT-Seq-positive panel (n = 31) had significantly worse DFS (P = 0.0005) and DSS (P = 0.0002). Among ECS-positive patients, those with a UDT-Seq-positive panel (n = 46) also had significantly worse DFS (P = 0.0032) and DSS (P = 0.0098).Our UDT-Seq gene panel consisting of clinically actionable genes was significantly associated with patient outcomes and provided better prognostic stratification than traditional AJCC staging. It was also able to predict prognosis in OSCC patients regardless of ECS presence.

mTOR pathway protein immunoexpression as a prognostic factor for survival in head and neck cancer patients: a systematic review and meta-analysis

BACKGROUND

Several mTOR pathway proteins are involved in the regulation of cellular anabolism, growth, proliferation, and survival. Activated proteins in the mTOR pathway are deregulated in multiple types of cancers and could influence prognosis. However, it is unclear whether deregulation of mTOR pathway proteins serves a prognostic role in patients with head and neck cancer (HNC). Furthermore, proteins in the mTOR pathway may be important targets for anticancer therapy. The aim of this study was to summarize existing cohort studies to determine whether immunoexpression of mTOR pathway proteins are important prognostic factors for survival in patients with HNC.

MATERIALS AND METHODS

A systematic review was performed using the Cochrane, Lilacs, PubMed, ScienceDirect, Scopus, and Web of Science databases (up to 23 January 2015). A meta-analysis was conducted to measure the frequency of protein expression in head and neck cancer patient samples and the prognostic value of mTOR pathway proteins for overall survival (OS) and disease-free survival (DFS).

RESULTS

Twelve studies were included in our final analysis. The meta-analysis revealed that the frequency of overall expression of mTOR pathway proteins was 74.42% (CI: 63.3 to 84.0, P < 0.001, n = 2016 samples). The survival meta-analysis showed a pooled hazard ratio for OS and DFS of 1.44 (95% confidence interval [95% CI] 1.14-1.73) and 1.18 (95% CI 0.71-1.64), respectively.

CONCLUSION

This systematic review and meta-analysis support evidence that mTOR pathway proteins can be used as predictive markers for survival in patients with HNC because their expression was significantly associated with poor OS and short DFS.

The preclinical evaluation of the dual mTORC1/2 inhibitor INK-128 as a potential anti-colorectal cancer agent

The colorectal cancer is the leading contributor of cancer-related mortality. Mammalian target of rapamycin (mTOR), existing in 2 complexes (mTORC1/2), is frequently dysregulated and constitutively activated in colorectal cancers. It represents an important drug target. Here we found that INK-128, the novel ATP-competitive kinase inhibitor of mTOR, blocked both mTORC1 and mTORC2 activation in colorectal cancer cells (both primary and transformed cells). The immunoprecipitation results showed that the assembly of mTORC1 (mTOR-Raptor association) and mTORC2 (mTOR-Rictor-Sin1 association) was also disrupted by INK-128. INK-128 inhibited colorectal cancer cell growth and survival, and induced both apoptotic and non-apoptotic cancer cell death. Further, INK-128 showed no effect on Erk/MAPK activation, while MEK/Erk inhibition by MEK-162 enhanced INK-128-induced cytotoxicity in colorectal cancer cells. Meanwhile, INK-128 downregulated Fascin1 (FSCN1)/E-Cadherin expressions and inhibited HT-29 cell in vitro migration. In vivo, daily INK-128 oral administration inhibited HT-29 xenograft growth in mice, which was further enhanced by MEK-162 administration. Finally, we found that INK-128 sensitized 5-fluorouracil-(5-FU)-mediated anti-HT-29 activity in vivo and in vitro. Thus, our preclinical studies strongly suggest that INK-128 might be investigated for colorectal cancer treatment in clinical trials.

Significance of NF-κB activation in immortalization of nasopharyngeal epithelial cells

NF-κB is a key regulator of inflammatory response and is frequently activated in human cancer including the undifferentiated nasopharyngeal carcinoma (NPC), which is common in Southern China including Hong Kong. Activation of NF-κB is common in NPC and may contribute to NPC development. The role of NF-κB activation in immortalization of nasopharyngeal epithelial (NPE) cells, which may represent an early event in NPC pathogenesis, is unknown. Examination of NF-κB activation in immortalization of NPE cells is of particular interest as the site of NPC is often heavily infiltrated with inflammatory cellular components. We found that constitutive activation of NF-κB signaling is a common phenotype in telomerase-immortalized NPE cell lines. Our results suggest that NF-κB activation promotes the growth of telomerase-immortalized NPE cells, and suppression of NF-κB activity inhibits their proliferation. Furthermore, we observed upregulation of c-Myc, IL-6 and Bmi-1 in our immortalized NPE cells. Inhibition of NF-κB downregulated expression of c-Myc, IL-6 and Bmi-1, suggesting that they are downstream events of NF-κB activation in immortalized NPE cells. We further delineated that EGFR/MEK/ERK/IKK/mTORC1 is the key upstream pathway of NF-κB activation in immortalized NPE cells. Elucidation of events underlying immortalization of NPE cells may provide insights into early events in pathogenesis of NPC. The identification of NF-κB activation and elucidation of its activation mechanism in immortalized NPE cells may reveal novel therapeutic targets for treatment and prevention of NPC.

Models for Predicting Stage in Head and Neck Squamous Cell Carcinoma Using Proteomic and Transcriptomic Data

Late diagnosis is one of the reasons that head and neck squamous cell carcinoma (HNSCC) patients experience relative five-year survival rates ranging from 40%-66%. The molecular-level differences between early and advanced stage HNSCC may provide insight into therapeutic targets and strategies. Previous bioinformatics studies have shown mixed or limited results in identifying gene and protein markers and in developing models for discriminating between early and advanced stage HNSCC. Thus, we have investigated models for HNSCC stage prediction using RNAseq and reverse phase protein array data from The Cancer Genome Atlas and The Cancer Proteome Atlas. We systematically assessed individual and ensemble binary classifiers, using filter and wrapper feature selection methods, to develop several well-performing models. In particular, integrated models harnessing both data types consistently resulted in better performance. This study identifies informative protein and gene feature sets which may increase understanding of HNSCC progression.

Selective inhibition of EGFR downstream signaling reverses the irradiation-enhanced migration of HNSCC cells

Irradiation, which is one of the standard therapies used to treat squamous cell carcinoma of the head and neck (HNSCC), has been linked to enhanced tumor migration in carcinomas. In this study, we demonstrated that irradiation induced the phosphorylation of AKT, p38 MAPK and ERK. The combined activation of these pathways caused inactivation of GSK3β kinase, resulting in enhanced tumor cell migration. Here, we describe that the exclusive and specific inhibition of just one of the aforementioned key signaling molecules is sufficient to restore GSK3β activity and to reduce radiation-induced migration in HNSCC. These data indicate that pharmacological inhibition of pathways targeting GSK3β could decrease radiation-induced cell migration in HNSCC and thus potentially reduce metastasis and locoregional recurrence in patients.

Impact of Short-term 1,25-Dihydroxyvitamin D3 on the Chemopreventive Efficacy of Erlotinib against Oral Cancer

Activation of the epidermal growth factor receptor (EGFR) pathway is an early event in head and neck carcinogenesis. As a result, targeting EGFR for chemoprevention of head and neck squamous cell carcinomas (HNSCC) has received considerable attention. In the present study, we examined the impact of 1,25(OH)2D3, the active metabolite of the nutritional supplement vitamin D on the chemopreventive efficacy of the EGFR inhibitor, erlotinib, against HNSCC. Experimental studies were conducted in patient-derived xenografts (PDX) and the 4-nitroquinoline-1-oxide (4NQO) carcinogen-induced model of HNSCC. Short-term treatment (4 weeks) of PDX-bearing mice with 1,25(OH)2D3 and erlotinib resulted in significant inhibition of tumor growth. Noninvasive MRI enabled longitudinal monitoring of disease progression in the 4NQO model with 100% of control animals showing evidence of neoplastic lesions by 24 weeks. Among the experimental groups, animals treated with the combination regimen showed the greatest reduction in tumor incidence and volume (P < 0.05). Combination treatment was well tolerated and was not associated with any significant change in body weight. Histopathologic assessment revealed a significant reduction in the degree of dysplasia with combination treatment. Immunoblot analysis of whole tongue extracts showed downregulation of phospho-EGFR and phospho-Akt with the combination regimen. These results highlight the potential of 1,25(OH)2D3 to augment the efficacy of erlotinib against HNSCC. Further optimization of schedule and sequence of this combination regimen along with investigation into the activity of less calcemic analogues or dietary vitamin D is essential to fully realize the potential of this approach.

Emerging drugs for head and neck cancer

INTRODUCTION

Despite improvements in treatment, survival rates of head and neck squamous cell carcinoma (HNSCC) are stagnant. The existing chemotherapeutic agents are non-selective and associated with toxicities. Combinations of the only the US FDA-approved epidermal growth factor receptor (EGFR)-targeted agent, cetuximab, with chemotherapy or radiation improves overall survival. However, the response rates to cetuximab are modest. Thus, there is an urgent need for new agents that can be safely integrated into current treatment regimens to improve outcome.

AREAS COVERED

Current EGFR-targeted drugs under clinical development include mAbs and tyrosine kinase inhibitors. The modest efficacy of these drugs implicates intrinsic or acquired resistance. Novel molecular agents inhibiting alternative targets to overcome anti-EGFR resistance in HNSCC are under investigation. Gene therapy and immunotherapy are also promising strategies to improve efficacy and reduce toxicity.

EXPERT OPINION

To date, only six drugs have been FDA-approved for the treatment of head and neck cancer. Cetuximab is the only approved molecular targeting agent for HNSCC and despite ubiquitous expression of EGFR in HNSCC tumors, clinical responses are limited. Genetic and epigenetic characterization of HNSCC tumors, coupled with improved preclinical models, should facilitate the development of more effective drugs.

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.

Radiation Enhancement of Head and Neck Squamous Cell Carcinoma by the Dual PI3K/mTOR Inhibitor PF-05212384

PURPOSE

Radiation remains a mainstay for the treatment of nonmetastatic head and neck squamous cell carcinoma (HNSCC), a malignancy characterized by a high rate of PI3K/mTOR signaling axis activation. We investigated the ATP-competitive dual PI3K/mTOR inhibitor, PF-05212384, as a radiosensitizer in preclinical HNSCC models.

EXPERIMENTAL DESIGN

Extent of radiation enhancement of two HNSCC cell lines (UMSCC1-wtP53 and UMSCC46-mtP53) and normal human fibroblast (1522) was assessed by in vitro clonogenic assay with appropriate target inhibition verified by immunoblotting. Radiation-induced DNA damage repair was evaluated by γH2AX Western blots with the mechanism of DNA double-strand break repair abrogation investigated by cell cycle analysis, immunoblotting, and RT-PCR. PF-05212384 efficacy in vivo was assessed by UMSCC1 xenograft tumor regrowth delay, xenograft lysate immunoblotting, and tissue section immunohistochemistry.

RESULTS

PF-05212384 effectively inhibited PI3K and mTOR, resulting in significant radiosensitization of exponentially growing and plateau-phase cells with 24-hour treatment following irradiation, and variable radiation enhancement with 24-hour treatment before irradiation. Tumor cells radiosensitized to a greater extent than normal human fibroblasts. Postirradiation PF-05212384 treatment delays γH2AX foci resolution. PF-05212384 24-hour exposure resulted in an evident G1-S phase block in p53-competent cells. Fractionated radiation plus i.v. PF-05212384 synergistically delayed nude mice bearing UMSCC1 xenograft regrowth, with potential drug efficacy biomarkers identified, including pS6, pAkt, p4EBP1, and Ki67.

CONCLUSIONS

Taken together, our results of significant radiosensitization both in vitro and in vivo validate the PI3K/mTOR axis as a radiation modification target and PF-05212384 as a potential clinical radiation modifier of nonmetastatic HNSCC.

Radioresistance in head and neck squamous cell carcinoma: Biological bases and therapeutic implications

Head and neck squamous cell carcinoma (HNSCC) is strongly associated with alcohol and tobacco consumption. Lately, the incidence of human papillomavirus (HPV)-related tumors has shown a significant increase, and HPV-related tumors show distinctive features if compared with the HPV-negative counterpart. Locally advanced HNSCC can be treated with concomitant chemoradiotherapy, but early recurrences sometimes occur. Relapses are often related to an intrinsic radioresistance of the tumors. Alterations in intracellular pathways, primarily involved in cell proliferation, apoptosis, and DNA repair, can lead to radioresistance. Preclinical and clinical evidence highlighted that 3 main pathways, including the epidermal growth factor receptor (EGFR), the phosphotidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR), and the p53 signaling cascades, play a crucial role in radioresistance development. A future approach may consist in the association of radiotherapy (RT) and selective inhibition of the key pathways involved in radioresistance. Phase I, II, and III clinical trials are currently testing these novel treatment strategies.

Targeting the PI3K/AKT/mTOR pathway in squamous cell carcinoma of the head and neck

Despite recent advances in novel therapies, the prognosis for patients with squamous cell carcinoma of the head and neck (SCCHN) remains poor. Progress in understanding the biology of cancer has led to the development of personalized therapy targeted at blocking defective signaling pathways of cancer cells. These drugs aim to act selectively to reduce the adverse effects associated with systemic therapy. Cetuximab (Erbitux®), an anti-epidermal growth factor receptor gene (EGFR)-targeted agent, is the only approved targeted therapy for patients with SCCHN. However, resistance to EGFR therapy remains a major obstacle to achieving a positive clinical outcome with cetuximab. Other therapies that offer better clinical outcomes in patients with advanced SCCHN are urgently needed. The phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin pathway, which is downstream of EGFR, has also been implicated in SCCHN development and progression, and therefore, targeting this pathway offers another rational treatment approach. This review discusses the potential role of PI3K pathway inhibitors in the treatment of patients with advanced SCCHN, both alone and in combination with other therapies.