N. Gopalakrishna Iyer

Mutational landscapes of tongue carcinoma reveal recurrent mutations in genes of therapeutic and prognostic relevance

BackgroundCarcinoma of the oral tongue (OTSCC) is the most common malignancy of the oral cavity, characterized by frequent recurrence and poor survival. The last three decades has witnessed a change in the OTSCC epidemiological profile, with increasing incidence in younger patients, females and never-smokers. Here, we sought to characterize the OTSCC genomic landscape and to determine factors that may delineate the genetic basis of this disease, inform prognosis and identify targets for therapeutic intervention.MethodsSeventy-eight cases were subjected to whole-exome (n = 18) and targeted deep sequencing (n = 60).ResultsWhile the most common mutation was in TP53, the OTSCC genetic landscape differed from previously described cohorts of patients with head and neck tumors: OTSCCs demonstrated frequent mutations in DST and RNF213, while alterations in CDKN2A and NOTCH1 were significantly less frequent. Despite a lack of previously reported NOTCH1 mutations, integrated analysis showed enrichments of alterations affecting Notch signaling in OTSCC. Importantly, these Notch pathway alterations were prognostic on multivariate analyses. A high proportion of OTSCCs also presented with alterations in drug targetable and chromatin remodeling genes. Patients harboring mutations in actionable pathways were more likely to succumb from recurrent disease compared with those who did not, suggesting that the former should be considered for treatment with targeted compounds in future trials.ConclusionsOur study defines the Asian OTSCC mutational landscape, highlighting the key role of Notch signaling in oral tongue tumorigenesis. We also observed somatic mutations in multiple therapeutically relevant genes, which may represent candidate drug targets in this highly lethal tumor type.

Outcomes following parotidectomy for metastatic squamous cell carcinoma with microscopic residual disease: Implications for facial nerve preservation

Metastatic cutaneous squamous cell carcinoma (SCC) of the parotid is an aggressive disease, requiring combined modality treatment of surgery and adjuvant radiotherapy to achieve cure. This study aims to determine whether facial nerve preservation followed by radiotherapy is a reasonable option in patients with microscopic residual disease involving the facial nerve.

Role of pretreatment 18FDG‐PET/CT in surgical decision‐making for head and neck cancers

Despite widespread use, the utility of pretreatment positron emission tomography/computed tomography (PET/CT) remains undefined. In this study, we aim to determine its accuracy in nodal disease.

Prognostic significance of lymph node density in squamous cell carcinoma of the tongue

The prognostic significance of lymph node density in oral squamous cell carcinoma (OSCC) has been well recognized. However, its use in a specific subsite of the tongue has not been evaluated. The purpose of this study was to determine the prognostic significance of lymph node density in tongue squamous cell carcinoma (SCC).

Changing epidemiology of oral squamous cell carcinoma of the tongue: A global study

There are reports about the changing epidemiology of tongue squamous cell carcinoma (SCC), with recent reports indicating an increasing incidence in young women.

An eleven gene molecular signature for extra-capsular spread in oral squamous cell carcinoma serves as a prognosticator of outcome in patients without nodal metastases.

OBJECTIVES Extracapsular spread (ECS) is an important prognostic factor for oral squamous cell carcinoma (OSCC) and is used to guide management. In this study, we aimed to identify an expression profile signature for ECS in node-positive OSCC using data derived from two different sources: a cohort of OSCC patients from our institution (National Cancer Centre Singapore) and The Cancer Genome Atlas (TCGA) head and neck squamous cell carcinoma (HNSCC) cohort. We also sought to determine if this signature could serve as a prognostic factor in node negative cancers. MATERIALS AND METHODS Patients with a histological diagnosis of OSCC were identified from an institutional database and fresh tumor samples were retrieved. RNA was extracted and gene expression profiling was performed using the Affymetrix GeneChip Human Genome U133 Plus 2.0 microarray platform. RNA sequence data and corresponding clinical data for the TCGA HNSCC cohort were downloaded from the TCGA Data Portal. All data analyses were conducted using R package and SPSS. RESULTS We identified an 11 gene signature (GGH, MTFR1, CDKN3, PSRC1, SMIM3, CA9, IRX4, CPA3, ZSCAN16, CBX7 and ZFP3) which was robust in segregating tumors by ECS status. In node negative patients, patients harboring this ECS signature had a significantly worse overall survival (p=0.04). CONCLUSIONS An eleven gene signature for ECS was derived. Our results also suggest that this signature is prognostic in a separate subset of patients with no nodal metastasis Further validation of this signature on other datasets and immunohistochemical studies are required to establish utility of this signature in stratifying early stage OSCC patients.

Internal mammary artery perforator flap for head and neck reconstruction.

Background:  The internal mammary artery perforator (IMAP) flap is a useful modification of the classic deltopectoral flap that has a number of important roles in head and neck reconstruction.

Targeting Cancer Stem Cell Plasticity Through Modulation of Epidermal Growth Factor and Insulin-Like Growth Factor Receptor Signaling in Head and Neck Squamous Cell Cancer

Emerging data suggest that cancer stem cells (CSCs) exist in equilibrium with differentiated cells and that stochastic transitions between these states can account for tumor heterogeneity and drug resistance. The aim of this study was to establish an in vitro system that recapitulates stem cell plasticity in head and neck squamous cell cancers (HNSCCs) and identify the factors that play a role in the maintenance and repopulation of CSCs. Tumor spheres were established using patient‐derived cell lines via anchorage‐independent cell culture techniques. These tumor spheres were found to have higher aldehyde dehydrogenase (ALD) cell fractions and increased expression of Kruppel‐like factor 4, SRY (sex determining region Y)‐box 2, and Nanog and were resistant to γ‐radiation, 5‐fluorouracil, cisplatin, and etoposide treatment compared with monolayer culture cells. Monolayer cultures were subject to single cell cloning to generate clones with high and low ALD fractions. ALDHigh clones showed higher expression of stem cell and epithelial‐mesenchymal transition markers compared with ALDLow clones. ALD fractions, representing stem cell fractions, fluctuated with serial passaging, equilibrating at a level specific to each cell line, and could be augmented by the addition of epidermal growth factor (EGF) and/or insulin. ALDHigh clones showed increased EGF receptor (EGFR) and insulin‐like growth factor‐1 receptor (IGF‐1R) phosphorylation, with increased activation of downstream pathways compared with ALDLow clones. Importantly, blocking these pathways using specific inhibitors against EGFR and IGF‐1R reduced stem cell fractions drastically. Taken together, these results show that HNSCC CSCs exhibit plasticity, with the maintenance of the stem cell fraction dependent on the EGFR and IGF‐1R pathways and potentially amenable to targeted therapeutics.

Reviewing the genetic alterations in high-risk cutaneous squamous cell carcinoma: A search for prognostic markers and therapeutic targets

Cutaneous squamous cell carcinoma (SCC) is second only in incidence to basal cell carcinoma (BCC), effecting up to 500 000 people in the United States annually. Metastasis to regional lymph nodes occurs in approximately 5% of cases and imparts significant morbidity. Standard treatment in this group involves a combination of surgery and adjuvant radiation. Currently, there are no clinically useful biomarkers of metastatic potential in primary cutaneous SCC and histological predictors can be unreliable. The high level of mutational burden in normal UV‐exposed skin has hampered the search for novel drivers of invasive disease, and indeed metastatic potential. This review outlines the clinical problems in high‐risk and metastatic cutaneous SCCs, reviews the known genetic events and molecular mechanisms in high‐risk primary cutaneous SCC and metastasis, and identifies avenues for further investigation and potential therapy.

Microarray profiling shows distinct differences between primary tumors and commonly used preclinical models in hepatocellular carcinoma

BackgroundDespite advances in therapeutics, outcomes for hepatocellular carcinoma (HCC) remain poor and there is an urgent need for efficacious systemic therapy. Unfortunately, drugs that are successful in preclinical studies often fail in the clinical setting, and we hypothesize that this is due to functional differences between primary tumors and commonly used preclinical models. In this study, we attempt to answer this question by comparing tumor morphology and gene expression profiles between primary tumors, xenografts and HCC cell lines.MethodsHep G2 cell lines and tumor cells from patient tumor explants were subcutaneously (ectopically) injected into the flank and orthotopically into liver parenchyma of Mus Musculus SCID mice. The mice were euthanized after two weeks. RNA was extracted from the tumors, and gene expression profiling was performed using the Gene Chip Human Genome U133 Plus 2.0. Principal component analyses (PCA) and construction of dendrograms were conducted using Partek genomics suite.ResultsPCA showed that the commonly used HepG2 cell line model and its xenograft counterparts were vastly different from all fresh primary tumors. Expression profiles of primary tumors were also significantly divergent from their counterpart patient-derived xenograft (PDX) models, regardless of the site of implantation. Xenografts from the same primary tumors were more likely to cluster together regardless of site of implantation, although heat maps showed distinct differences in gene expression profiles between orthotopic and ectopic models.ConclusionsThe data presented here challenges the utility of routinely used preclinical models. Models using HepG2 were vastly different from primary tumors and PDXs, suggesting that this is not clinically representative. Surprisingly, site of implantation (orthotopic versus ectopic) resulted in limited impact on gene expression profiles, and in both scenarios xenografts differed significantly from the original primary tumors, challenging the long-held notion that orthotopic PDX model is the gold standard preclinical model for HCC.