Co-targeting ALK and EGFR parallel signaling in oral squamous cell carcinoma

Cetuximab chemotherapy resistance: Insight into the homeostatic evolution of head and neck cancer (Review)

The complex evolution of genetic alterations in cancer that occurs in vivo is a selective process involving numerous factors and mechanisms. Chemotherapeutic agents that prevent the growth and spread of cancer cells induce selective pressure, leading to rapid artificial selection of resistant subclones. This rapid evolution is possible because antineoplastic drugs promote alterations in tumor‑cell metabolism, thus creating a bottleneck event. The few resistant cells that survive in this new environment obtain differential reproductive success that enables them to pass down the newly selected resistant gene pool. The present review aims to summarize key findings of tumor evolution, epithelial‑mesenchymal transition and resistance to cetuximab therapy in head and neck squamous cell carcinoma.

Genome sequencing reveals molecular subgroups in oral epithelial dysplasia

This study aimed to analyze the molecular characteristics of oral epithelial dysplasia (OED), highlighting the pathways and variants of genes that are frequently mutated in oral squamous cell carcinoma (OSCC) and other cancers. Ten archival OED cases were retrieved for retrospective clinicopathological analysis and exome sequencing. Comparative genomic analysis was performed between high-grade dysplasia (HGD) and low-grade dysplasia (LGD), focusing on 57 well-known cancer genes, of which 10 were previously described as the most mutated in OSCC. HGD cases had significantly more variants; however, a similar mutational landscape to OSCC was observed in both groups. CASP8+FAT1/HRAS, TP53, and miscellaneous molecular signatures were also present. FAT1 is the gene that is most affected by pathogenic variants. Hierarchical divisive clustering showed division between the two groups: "HGD-like cluster" with 4HGD and 2LGD and "LGD-like cluster" with 4 LGD. MLL4 pathogenic variants were exclusively in the "LGD-like cluster". TP53 was affected in one case of HGD; however, its pathway was usually altered. We describe new insights into the genetic basis of epithelial malignant transformation by genomic analysis, highlighting those associated with FAT1 and TP53. Some LGDs presented a similar mutational landscape to HGD after cluster analysis. Perhaps molecular alterations have not yet been reflected in histomorphology. The relative risk of malignant transformation in this molecular subgroup should be addressed in future studies.

EGFR R521K Polymorphism Is Not a Major Determinant of Clinical Cetuximab Resistance in Head and Neck Cancer

Background: Head and neck squamous cell carcinomas (HNSCCs) are among the most abundant malignancies worldwide. Patients with recurrent/metastatic disease undergo combination chemotherapy containing cetuximab, the monoclonal antibody used against the epidermal growth factor receptor (EGFR). Cetuximab augments the effect of chemotherapy; however, a significant number of patients show therapy resistance. The mechanism of resistance is yet to be unveiled, although extracellular alterations of the receptor have been reported, and their role in cetuximab failure has been proposed. Aims: Here, we investigate possible effects of the multi-exon deletion variant (EGFRvIII), and the single nucleotide polymorphism EGFR R521K on cetuximab efficacy. Results: Our results show that in HNSCC patients, the EGFRvIII allele frequency is under 1%; therefore, it cannot lead to common resistance. EGFR R521K, present in 42% of the patients, is investigated in vitro in four HNSCC cell lines (two wild-type and two heterozygous for EGFR R521K). While no direct effect is found to be related to the EGFR status, cells harboring R521K show a reduced sensitivity in ADCC experiments and in vivo xenograft experiments. However, this preclinical difference is not reflected in the progression-free or overall survival of HNSCC patients. Furthermore, NK cell and macrophage presence in tumors is not related to EGFR R521K. Discussion: Our results suggest that EGFR R521K, unlike reported previously, is unable to cause cetuximab resistance in HNSCC patients; therefore, its screening before therapy selection is not justifiable.

Small molecule profiling to define synergistic EGFR inhibitor combinations in head and neck squamous cell carcinoma

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is a debilitating disease with poor survival. Although epidermal growth factor receptor (EGFR)-targeting antibody cetuximab improves survival in some settings, responses are limited suggesting that alternative approaches are needed.

METHODS

We performed a high throughput drug screen to identify EGFR inhibitor-based synergistic combinations of clinically advanced inhibitors in models resistant to EGFR inhibitor monotherapies, and then performed downstream validation experiments on prioritized synergistic combinations.

RESULTS

From our screen, we re-discovered known synergistic EGFR inhibitor combinations with FGFR or IGF-1R inhibitors that were broadly effective and also discovered novel synergistic combinations with XIAP inhibitor and DNMT inhibitors that were effective in only a subset of models.

CONCLUSIONS

Conceptually, our data identify novel synergistic combinations that warrant evaluation in future studies, and suggest that some combinations, although highly synergistic, will require parallel companion diagnostic development to be effectively advanced in patients.

Prognostic value of the PIK3CA, AKT, and PTEN mutations in oral squamous cell carcinoma: literature review

Over 260,000 (2013) new oral squamous cell carcinoma (OSCC) cases are reported annually worldwide. Despite development in OSCC management, the outcome is still unsatisfactory. Identification of new molecular markers may be of use in prevention, prognosis, and choice of an appropriate therapy. The intracellular molecular signalling pathway of phosphatidyl-inositol-3-kinase is involved in the process of cell growth, differentiation, migration, and survival. The main components of this pathway: PIK3CA (phosphatidylinositol-4,5-bisphosphate-3-kinase catalytic subunit α), PTEN (phosphatase and tensin homologue deleted on chromosome 10), and AKT (serine-threonine kinase) are potential objects of research when introducing new therapeutic agents. The aim of this paper is to evaluate the PIK3CA, PTEN, and AKT gene mutations as prognostic factors in OSCC and to describe their role in aggressive disease progression. This is crucial for oral cancer biology understanding and for indicating which direction new clinical treatments should take.

Integrated Molecular Profiling as an Approach to Identify PI3K Inhibitor Resistance Mechanisms

The identification of drug resistance pathways and approaches to target these pathways remains a significant and important challenge in cancer biology. Here, we address this challenge in the context of ongoing efforts to advance phosphatidylinositol 3-kinase (PI3K) inhibitors for the treatment of PI3K-aberrant cancers. While PI3K inhibitors have had tremendous success in some diseases, such as breast cancer, early clinical trials in other malignancies, such as head and neck squamous cell carcinoma (HNSCC), have not had the same level of success. Since HNSCC and other cancers display relatively high PI3K pathway alteration rates (>45%), these underwhelming results suggest that additional or unexpected factors may contribute to the lower response rates. Here, we highlight some of the emerging functional genomic and sequencing approaches being used to identify predictive biomarkers of PI3K inhibitor response using both cancer cell lines and clinical trial specimens. Importantly, these approaches have uncovered both innate genetic and adaptive mechanisms driving PI3K inhibitor resistance. In this chapter, we describe recent technological advances that have revolutionized our understanding of PI3K inhibitor resistance pathways in HNSCC and highlight how these and other approaches lay the groundwork to make significant strides in our understanding of molecular pharmacology in the cancer field.

Combined EGFR/ALK Expression Analysis in Laryngeal Squamous Cell Carcinoma

BACKGROUND/AIM

Epidermal growth factor receptor (EGFR) acts as an oncogene in malignancies. Our aim was to examine the role of combined EGFR/ anaplastic lymphoma kinase (ALK) expression as molecular markers in laryngeal squamous cell carcinoma (LSCC) patients.

MATERIALS AND METHODS

Fifty (n=50) tissue sections derived from twenty-five (n=25) primary LSCCs were analyzed by immunohistochemistry (IHC).

RESULTS

EGFR overexpression was observed in 17/25 (68%) cases. Concerning ALK, 23/25 (92%) demonstrated low expression. EGFR expression was associated with grade (p=0.049), whereas ALK expression was correlated with stage (p=0.048). ALK overexpression was detected at advanced-stage EGFR-positive cases. A biphasic EGFR protein expression pattern was observed in five (n=5) LSCC cases, whereas ALK expression was stable in all cases.

CONCLUSION

EGFR overexpression is frequently observed in LSCC combined with low ALK expression. LSCC patients with EGFR/ALK protein overexpression should be eligible for targeted therapeutic strategies.

The novel capsazepine analog, CIDD-99, significantly inhibits oral squamous cell carcinoma in vivo through a TRPV1-independent induction of ER stress, mitochondrial dysfunction, and apoptosis

BACKGROUND

Oral squamous cell carcinoma (OSCC) is a deadly disease with a mere 40% five-year survival rate for patients with advanced disease. Previously, we discovered that capsazepine (CPZ), a transient receptor potential channel, Vanilloid subtype 1 (TRPV1) antagonist, has significant anti-tumor effects against OSCC via a unique mechanism-of-action that is independent of TRPV1. Thus, we developed novel CPZ analogs with more potent anti-proliferative effects (CIDD-24, CIDD-99, and CIDD-111).

METHODS

Using OSCC xenograft models, we determined the efficacy of these analogs in vivo. TRPV1 interactions were evaluated using calcium imaging and a rat model of orofacial pain. Anti-cancer mechanism(s)-of-action were assessed by cell cycle analysis and mitochondrial depolarization assays.

RESULTS

CIDD-99 was the most potent analog demonstrating significant anti-tumor effects in vivo (P < 0.001). CIDD-24 was equipotent to the parent compound CPZ, but less potent than CIDD-99. CIDD-111 was the least efficacious analog. Calcium imaging studies confirmed that CIDD-99 neither activates nor inhibits TRPV1 confirming that TRPV1 activity is not involved in its anti-cancer effects. All analogs induced an S-phase block, dose-dependent mitochondrial depolarization, and apoptosis. Histological analyses revealed increased apoptosis and reduced cell proliferation in tumors treated with these analogs. Importantly, CIDD-99 had the most dramatic anti-tumor effects with 85% of tumors resolving leaving only minute traces of viable tissue. Additionally, CIDD-99 was non-noxious and demonstrated no observable adverse reactions CONCLUSION: This study describes a novel, highly efficacious, CPZ analog, CIDD-99, with dramatic anti-tumor effects against OSCC that may be efficacious as a lone therapy or in combination with standard therapies.

Novel polygodial analogs P3 and P27: Efficacious therapeutic agents disrupting mitochondrial function in oral squamous cell carcinoma

Polygodial, a drimane sesquiterpenoid dialdehyde isolated as a pungent component of the water pepper Persicaria hydropiper, exhibits antifeedant, antimicrobial, anti-inflammatory and anticancer effects. Polygodial also activates transient receptor potential vanilloid subtype 1 (TRPV1) channels. Previously, we described the synthesis of a C₁₂-Wittig derivative of polygodial, termed P3, with significant antiproliferative effects against multiple cancer types including oral squamous cell carcinoma (OSCC). In the present study, a more potent derivative, P27, with superior anti-proliferative effects in vitro and antitumor effects in Cal-27 derived xenografts is described. Polygodial, P3, and P27 all significantly decreased OSCC tumor growth, with P27 being equipotent with polygodial and P3 being the least efficacious. However, neither analog elicited the adverse effect observed with polygodial: Profound transient inflammation. Although P3 and P27 pharmacophores are based on polygodial, novel effects on OSCC cell cycle distribution were identified and shared anticancer effects that are independent of TRPV1 activity were observed. Polygodial elicits an S-phase block, whereas P3 and P27 lead to G₂/M phase arrest. Pretreatment of OSCC cells with the TRPV1 antagonist capsazepine does not affect the antiproliferative activity of P3 or P27, indicating that TRPV1 interactions do not regulate OSCC cell proliferation. Indeed, calcium imaging studies identified that the analogs neither activate nor antagonize TRPV1. Behavioral studies using a rat model for orofacial pain confirmed that these analogs fail to induce nocifensive responses, indicating that they are non-noxious in vivo. All compounds induced a significant concentration-dependent decrease in the mitochondrial transmembrane potential and corresponding apoptosis. Considering that P27 is equipotent to polygodial with no TRPV1-associated adverse effects, P27 may serve as an efficacious novel therapy for OSCC.

Induction of anaplastic lymphoma kinase (ALK) as a novel mechanism of EGFR inhibitor resistance in head and neck squamous cell carcinoma patient-derived models

Head and neck squamous cell carcinoma (HNSCC) currently only has one FDA-approved cancer intrinsic targeted therapy, the epidermal growth factor receptor (EGFR) inhibitor cetuximab, to which only approximately 10% of tumors are sensitive. In order to extend therapy options, we subjected patient-derived HNSCC cells to small-molecule inhibitor and siRNA screens, first, to find effective combination therapies with an EGFR inhibitor, and second, to determine a potential mechanistic basis for repurposing the FDA approved agents for HNSCC. The combinations of EGFR inhibitor with anaplastic lymphoma kinase (ALK) inhibitors demonstrated synergy at the highest ratio in our cohort, 4/8 HNSCC patients' derived tumor cells, and this corresponded with an effectiveness of siRNA targeting ALK combined with the EGFR inhibitor gefitinib. Co-targeting EGFR and ALK decreased HNSCC cell number and colony formation ability and increased annexin V staining. Because ALK expression is low and ALK fusions are infrequent in HNSCC, we hypothesized that gefitinib treatment could induce ALK expression. We show that ALK expression was induced in HNSCC patient-derived cells both in 2D and 3D patient-derived cell culture models, and in patient-derived xenografts in mice. Four different ALK inhibitors, including two (ceritinib and brigatinib) FDA approved for lung cancer, were effective in combination with gefitinib. Together, we identified induction of ALK by EGFR inhibitor as a novel mechanism potentially relevant to resistance to EGFR inhibitor, a high ratio of response of HNSCC patient-derived tumor cells to a combination of ALK and EGFR inhibitors, and applicability of repurposing ALK inhibitors to HNSCC that lack ALK aberrations.

Thymol inhibits oral squamous cell carcinoma growth via mitochondria-mediated apoptosis

BACKGROUND

Thymol is a transient receptor potential ankyrin subtype 1 channel, (TRPA1) agonist found in thyme and oregano. Thymol has antioxidant, anti-inflammatory, and antimicrobial properties; thus, thymol is added to many commercially available products including Listerine mouthwash. Thymol is also cytotoxic to HL-60 (acute promyelocytic leukemia) cells in vitro. Therefore, we evaluated the effects of thymol against oral squamous cell carcinoma (OSCC) and its anticancer mechanism-of-action.

METHODS

The antiproliferative effects of thymol in OSCC Cal27 cells were determined by MTS assays. Antitumor effects were evaluated in Cal27- and HeLa-derived mouse xenografts. Calcium imaging, mitochondrial transmembrane potential (ΔΨm) studies, and Western blot analysis of cleaved PARP (c-PARP) evaluated thymol's mechanism-of-action.

RESULTS

Thymol had significant, long-lasting antiproliferative effects in vitro. In vivo, thymol displayed significant antitumor effects in Cal27-derived tumors. Thymol's anticancer effects were confirmed in HeLa-derived xenografts demonstrating that thymol effects are not tumor-type specific. Calcium imaging verified calcium influx in Cal27 cells that were reversed with the TRPA1 antagonist, HC030031. However, no calcium influx was seen in HeLa cells indicating that TRP channels do not regulate thymol cytotoxicity. This was confirmed using cell viability assays in which pre-treatment with HC030031 had no effect on thymol cytotoxicity. Instead, ΔΨm studies revealed that thymol induces significant ΔΨm depolarization and apoptosis.

CONCLUSION

Our findings provide the first evidence of thymol's novel antitumor effects against OSCC in vivo, which do not rely on TRPA1 activity. Instead, we show that thymol induces mitochondrial dysfunction and apoptosis and may be efficacious against multiple cancers.

CD109 and squamous cell carcinoma

Squamous cell carcinoma (SCC) is well-known for its high rate of metastasis with poor prognosis. CD109 is a glycosylphosphatidylinositol-anchored cell-surface glycoprotein. Recently, CD109 emerges as a potential biomarker and a therapeutic target for SCCs. Accumulating studies have reported that CD109 is highly expressed in human SCCs of multiple organs, and may contribute to the progression of SCCs. In this review, we summarized the findings on expression pattern of CD109 in SCCs, and discussed the molecular mechanisms underlying the roles of CD109 in pathogenesis of SCCs.

EGFR and Cortactin: Markers for potential double target therapy in oral squamous cell carcinoma

Survival periods of patients following surgical therapy of oral squamous cell carcinoma (OSCC) have previously been demonstrated to decrease over recent decades. Epidermal growth factor receptor (EGFR) and Cortactin are molecular markers that are important in tumour progression and development, and interact within the EGF pathway. Although EGFR antibody therapy exists, sufficient efforts for increased survival are still lacking due to the present limited response rates. The aim of the present study was to examine the association between EGFR and Cortactin expression on survival rates of OSCC patients and to determine whether EGFR and Cortactin expression levels are associated with advanced tumor sizes and lymphnode-metastases. In total, 222 OSCC patients were included in the study. EGFR and Cortactin expression in tumor tissue was evaluated by immunohistochemistry. Cox regression was used for survival analysis. Categories were tested for associations by using cross tabs (Chi-square test). Groups were compared by the non-parametric Mann Whitney U-test. Probabilities of less than 0.05 were considered significant and significant expression of Cortactin was observed in Advanced Union Internationale Contre le Cancer stage (P=0.032), including advanced tumour stage (P=0.021) and lymph node metastasis (P=0.049). High Cortactin expression was significantly associated with poorer survival rates (P=0.037). Further Cortactin expression was not associated with extracapsular spread, however EGFR exhibited a significant association (P=0.034). Neither EGFR nor Cortactin expression was correlated to grading. EGFR and Cortactin co-expression was demonstrated to be significantly associated with poorer survival rates in OSCC patients, suggesting that identification of predictive biomarkers for adjuvant therapies are of primary concern in OSCC. In particular, efficient dual-target therapy may act as an appropriate therapy to improve survival time for patients at advanced OSCC tumor stages.

Inhibition of EGF-induced migration and invasion by sulfated polysaccharide of Sepiella maindroni ink via the suppression of EGFR/Akt/p38 MAPK/MMP-2 signaling pathway in KB cells

SIP-SII, the sulfated Sepiella maindroni ink polysaccharide (SIP), has been manifested to possess anti-tumor and anti-metastasis activity in vivo and in vitro. In the present study, we evaluated its inhibitory effect on the epidermal growth factor (EGF)-induced migration and invasion of human epidermoid carcinoma cell (KB cell line) as well as the related signaling pathways. The results of MTT assay indicated that SIP-SII inhibited the proliferation of KB cells in a concentration and time dependent manner. Notably, the attenuation of cell growth by SIP-SII was enlarged in the presence of EGF. The wound healing assay and transwell invasion assay were used to evaluate the effect of SIP-SII on the EGF-induced migration and invasion of KB cells and the results showed that SIP-SII markedly attenuated the EGF-induced migration and invasion. Besides, the EGF-induced matrix metalloproteinase-2 (MMP-2) expression was also suppressed by SIP-SII. However, SIP-SII showed no significant inhibition of the EGF-induced matrix metalloproteinase-9 (MMP-9) expression. Further research revealed that SIP-SII decreased the EGF-induced phosphorylation of epidermal growth factor receptor (EGFR), Akt and p38, but no significant suppression on EGF-induced phosphorylation of extracellular signal-regulated kinase 1 and 2 (Erk1/2) and c-Jun N-terminal kinases (JNK) by SIP-SII treatment was observed. The involvement of EGFR/Akt/p38 pathway was confirmed by evidence that SIP-SII would enlarge the inhibitory effect of the specific signal pathway inhibitors. These results indicate that SIP-SII has the potential to be used as the inhibitor of tumor metastasis especially for cancers characterized by over-activation of EGF/EGFR signaling.

DKK3 Overexpression Increases the Malignant Properties of Head and Neck Squamous Cell Carcinoma Cells

DKK3, a member of the dickkopf Wnt signaling pathway inhibitor family, is believed to be a tumor suppressor because of its reduced expression in cancer cells. However, our previous studies have revealed that DKK3 expression is predominantly observed in head and neck/oral squamous cell carcinoma (HNSCC/OSCC). Interestingly, HNSCC/OSCC patients with DKK3 expression showed a high rate of metastasis and poorer survival, and siRNA-mediated knockdown of DKK3 in HNSCC-derived cancer cell lines resulted in reduced cellular migration and invasion. From these data, it was hypothesized that DKK3 might exert an oncogenic function specific to HNSCC. In the present research, the DKK3 overexpression model was established, and its influences were investigated, together with molecular mechanism studies. The DKK3 expression profile in cancer cell lines was investigated, including HNSCC/OSCC, esophageal, gastric, colorectal, pancreatic, prostatic, and lung cancers. DKK3 overexpression was performed in HNSCC-derived cells by transfection of expression plasmid. The effects of DKK3 overexpression were assessed on cellular proliferation, migration, invasion, and in vivo tumor growth. The molecular mechanism of DKK3 overexpression was investigated by Western blotting and microarray analysis. DKK3 overexpression significantly elevated cellular proliferation, migration, and invasion, as well as increased mRNA expression of cyclin D1 and c-myc. However, reporter assays did not show TCF/LEF activation, suggesting that the increased malignant property of cancer cells was not driven by the Wnt/β-catenin pathway. For the investigation of the pathways/molecules in DKK3-mediated signals, the Western blot analyses revealed that phosphorylation of Akt (S473) and c-Jun (Ser63) was elevated. The application of a PI3K kinase inhibitor, LY294002, on HSC-3 DKK3 cells significantly decreased tumor cell proliferation, migration, and invasion. From these results, we demonstrated that DKK3 might contribute to cellular proliferation, invasion, migration, and tumor cell survival in HNSCC cells through a mechanism other than the canonical Wnt signaling pathway, which might be attributed to PI3K–Akt signaling.