Cancer Stem Cell Signaling during Repopulation in Head and Neck Cancer

Role of cancer stem cells in head-and-neck squamous cell carcinoma - A systematic review

Targeting cancer stem cell (CSC) subpopulation within the tumor remains an obstacle for specific therapy in head-and-neck squamous cell carcinoma (HNSCC). Few studies in the literature describe a panel of stem cell makers, however a distinct panel has not been put forth. This systematic review aims to enhance the knowledge of additional markers to accurately relate their expression to tumorigenesis, metastasis, and therapy resistance. Databases, including PubMed, Google Scholar, Ebsco, and Science Direct, were searched from 2010 to 2017 using various combinations of the following keywords: “Stem cell markers in HNSCC” and “chemoresistance and radioresistence in HNSCC.” Original experimental studies (both in vitro and in vivo) published in English considering stem cell markers in HNSCC, were considered and included. We excluded articles on tumors other than HNSCC, reviews, editorial letters, book chapters, opinions, and abstracts from the analyses. Forty-two articles were included, in which 13 types of stem cell markers were identified. The most commonly expressed CSC markers were CD44, aldehyde dehydrogenase, and CD133, which were responsible for tumorigenesis, self-renewal, and therapy resistance, whereas NANOG, SOX-2, and OCT-4 were involved in metastasis and invasion. Identification of an accurate panel of CSC markers is the need of the hour as nonspecificity of the current markers poses a problem. Further studies with a large sample size would help validate the role of these CSC markers in HNSCC. These CSC proteins can be developed as therapeutic targets for HNSCC therapy, making future treatment modality more specific and effective.

Mitogen-activated protein kinase-activated protein kinase-2 (MK2) and its role in cell survival, inflammatory signaling, and migration in promoting cancer

Cancer and the immune system share an intimate relationship. Chronic inflammation increases the risk of cancer occurrence and can also drive inflammatory mediators into the tumor microenvironment enhancing tumor growth and survival. The p38 MAPK pathway is activated both acutely and chronically by stress, inflammatory chemokines, chronic inflammatory conditions, and cancer. These properties have led to extensive efforts to find effective drugs targeting p38, which have been unsuccessful. The immediate downstream serine/threonine kinase and substrate of p38 MAPK, mitogen-activated-protein-kinase-activated-protein-kinase-2 (MK2) protects cells against stressors by regulating the DNA damage response, transcription, protein and messenger RNA stability, and motility. The phosphorylation of downstream substrates by MK2 increases inflammatory cytokine production, drives an immune response, and contributes to wound healing. By binding directly to p38 MAPK, MK2 is responsible for the export of p38 MAPK from the nucleus which gives MK2 properties that make it unique among the large number of p38 MAPK substrates. Many of the substrates of both p38 MAPK and MK2 are separated between the cytosol and nucleus and interfering with MK2 and altering this intracellular translocation has implications for the actions of both p38 MAPK and MK2. The inhibition of MK2 has shown promise in combination with both chemotherapy and radiotherapy as a method for controlling cancer growth and metastasis in a variety of cancers. Whereas the current data are encouraging the field requires the development of selective and well tolerated drugs to target MK2 and a better understanding of its effects for effective clinical use.

Tyrosine Kinase c-MET as Therapeutic Target for Radiosensitization of Head and Neck Squamous Cell Carcinomas

The receptor tyrosine kinase c-MET activates intracellular signaling and induces cell proliferation, epithelial-to-mesenchymal-transition and migration. Within the present study, we validated the prognostic value of c-MET in patients with head and neck squamous cell carcinoma (HNSCC) treated with radio(chemo)therapy using the Cancer Genome Atlas database and found an association of increased MET gene expression and protein phosphorylation with reduced disease-specific and progression-free survival. To investigate the role of c-MET-dependent radioresistance, c-MET-positive cells were purified from established HNSCC cell lines and a reduced radiosensitivity and enhanced sphere-forming potential, compared to the c-MET-depleted cell population, was found in two out of four analyzed cell lines pointing to regulatory heterogeneity. We showed that c-MET is dynamically regulated after irradiation in vitro and in vivo. Interestingly, no direct impact of c-MET on DNA damage repair was found. The therapeutic potential of eight c-MET targeting agents in combination with irradiation demonstrated variable response rates in six HNSCC cell lines. Amongst them, crizotinib, foretinib, and Pha665752 exhibited the strongest radiosensitizing effect. Kinase activity profiling showed an association of crizotinib resistance with compensatory PI3K/AKT and MAP kinase signaling. Overall, our results indicate that c-MET is conferring radioresistance in HNSCC through modulation of intracellular kinase signaling and stem-like features.

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.

Advancements in Cancer Stem Cell Isolation and Characterization

Occurrence of stem cells (CSCs) in cancer is well established in last two decades. These rare cells share several properties including presence of common surface markers, stem cell markers, chemo- and radio- resistance and are highly metastatic in nature; thus, considered as valuable prognostic and therapeutic targets in cancer. However, the studies related to CSCs pave number of issues due to rare cell population and difficulties in their isolation ascribed to common stem cell marker. Various techniques including flow cytometry, laser micro-dissection, fluorescent nanodiamonds and microfluidics are used for the isolation of these rare cells. In this review, we have included the advance strategies adopted for the isolation of CSCs using above mentioned techniques. Furthermore, CSCs are primarily found in the core of the solid tumors and their microenvironment plays an important role in maintenance, self-renewal, division and tumor development. Therefore, in vivo tracking and model development become obligatory for functional studies of CSCs. Fluorescence and bioluminescence tagging has been widely used for transplantation assay and lineage tracking experiments to improve our understanding towards CSCs behaviour in their niche. Techniques such as Magnetic resonance imaging (MRI) and Positron emission tomography (PET) have proved useful for tracking of endogenous CSCs which could be helpful in their identification in clinical settings.

Effect of c-Met and CD44v6 Expression in Resistance to Chemotherapy in Esophageal Squamous Cell Carcinoma

BACKGROUND

c-Met relies on CD44v6 for its activation and signaling in several cancer cell lines. However, the correlation of c-Met and CD44v6 expression and its biological significance in esophageal squamous cell carcinoma (ESCC) remains unknown.

METHODS

Expression of c-Met and CD44v6 was examined by immunohistochemistry (IHC) in 147 ESCC specimens. We analyzed the impact of c-Met and CD44v6 expression on clinicopathological parameters, including chemoresistance or prognosis in ESCC.

RESULTS

High expression of c-Met and CD44v6 in cancerous lesions was identified in 49.7% and 50.3% of all patients, respectively. The c-Met-high group comprised more advanced pT and pM stages than the c-Met-low group. In addition, more patients in the c-Met-high group received neoadjuvant chemotherapy (NACT) than the c-Met-low group (64.4% vs. 43.2%, P = 0.010). On the other hand, the CD44v6-high group was associated with more advanced pT/pN stages and a poorer clinical response to NACT (response rate 53.5% vs. 77.8%, P = 0.025) than the CD44v6-low group. Double-positive immunostaining of c-Met and CD44v6 was identified in 28.6% of all cases, and multivariate analysis of overall survival (OS) identified them (hazard ratio 1.79, 95% confidence interval 1.03-3.04, P = 0.038) as independent prognostic factors in addition to pN and pM stage.

CONCLUSIONS

c-Met/CD44v6 were associated with tumor progression or chemoresistance. Double-positive expression of c-Met and CD44v6 negatively impacted patient prognosis in ESCC, implying that c-Met and CD44v6 are candidates for targeted therapy in ESCC.

Combined CD44, c-MET, and EGFR expression in p16-positive and p16-negative head and neck squamous cell carcinomas

PURPOSE/OBJECTIVE(S)

To examine the association between CD44 and c-MET expression in relation to p16 and EGFR in patients with head and neck squamous cell carcinoma (HNSCC).

MATERIALS/METHODS

Immunohistochemical staining of CD44, p16, EGFR, and c-MET was performed on 105 locally advanced HNSCC patients treated with chemoradiation. CD44 expression was correlated with c-MET, EGFR, and p16, locoregional control (LRC), distant metastases (DM), disease-free survival (DFS) and overall survival (OS).

RESULTS

High CD44 expression was present in 33% of patients and was associated with non-oropharynx primaries (P < 0.001), high c-MET expression (P < 0.001), p16-negative (P < 0.001) and EGFR-positive tumors (P < 0.001). Fifty-seven percent of CD44 high expressing tumors had high c-MET expression compared to 21% of CD44 low expressing tumors (P < 0.001). High CD44 expression predicted for worse LRC (HR: 2.44; 95% CI: 1.16-5.13; P = 0.018), DFS (HR: 2.61; 95% CI: 1.46-4.67; P = 0.001), and OS (HR: 2.52; 95% CI: 1.30-4.92; P = 0.007) but not DM (P = 0.57) on univariate analysis. Patients with both high CD44 and c-MET expression had a poor prognosis with a 2-year DFS of 30% compared to 70% in the rest of the cohort (P = 0.003). On multivariable analysis, after adjusting for site, T-stage, smoking history, and EGFR status, high c-MET (P = 0.039) and negative p16 status (P = 0.034) predicted for worse DFS, while high CD44 expression did not (P = 0.43).

CONCLUSIONS

High CD44 expression is associated with high c-MET expression, p16-negative tumors, and EGFR-positive tumors. The combination of these markers predicts for poor prognosis in HNSCC patients treated with chemoradiation.