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Homeobox genes are master regulators of morphogenesis and differentiation by acting at the top of genetic hierarchies and their deregulation is associated with a variety of human diseases. They usually contain a highly conserved sequence that codes for the homeodomain of the protein, a specialized motif with three α helices and an N-terminal arm that aids in DNA binding. However, one homeodomain protein, HOPX, is unique among its family members in that it lacks the capacity to bind DNA and instead functions by interacting with transcriptional regulators. HOPX plays crucial roles in organogenesis and is expressed in both embryonic and adult stem cells. Loss of HOPX expression is common in cancer, where it functions primarily as a tumor suppressor gene. In this review, we describe the function of HOPX in development and discuss its role in carcinogenesis.

Simple Summary Oral cancer is one of the most frequent malignancies in the world, with a poor prognosis. The absence of accurate biomarkers for predicting oral cancer progression is the primary cause of treatment failures. Multiple studies have shown that cancer stem cells play a critical role in tumor growth and chemo resistance. We uncovered, for the first time, the importance of combinatorial expression of stem cell related molecules CXCR-4 and CD-133 as possible biomarkers to predict poor prognosis of oral squamous cell carcinoma. The findings will aid in the identification of high-risk cases in order to provide appropriate therapy. Abstract The activation of the SDF-1/CXCR-4 pathway is crucial for the invasion and metastasis of oral cancer cells. The CXCR-4 positive cells possess stem cell characteristics and express the cancer stem cell marker, CD133, in tumors of colon and pancreas. Despite several studies, the co-expression of CXCR-4 and CD133 and its significance is still largely unknown in oral cancer. Therefore, we aimed to investigate the impact of CXCR-4 and CD133 double positivity in the prognosis of oral cancer. The significance of PKC-δ, one of the key signaling molecules that regulates CXCR-4, was also analyzed. Immunohistochemistry and double immunofluorescence was used to investigate the co-localization of CXCR-4, PKC-δ and CD133 in the human tissues and cell lines of oral squamous cell carcinoma. The expression of CXCR-4, PKC-δ and CD133 were found to be higher in poorly differentiated and lymph node metastasis-positive cases. Interestingly, CXCR-4 positive cells showed positive staining for PKC-δ and CD133 in oral cancer tissue and cell lines. Moreover, CXCR-4+/CD133+ and CXCR-4+/PKC-δ+ double positive cases have the worst survival. We discovered, for the first time, that patients with expression of both CXCR-4 and CD133 have a lower survival rate, and CXCR-4+/CD133+, as well as CXCR-4+/PKC-δ+ double positivity, can be utilized to predict poor prognosis. CXCR-4, PKC-δ and CD133 might regulate aggressiveness and invasion of oral cancer cells.

Esophageal adenocarcinoma (EAC) has one of the fastest rising incidence rates in the U.S. and many other Western countries. One of the unique risk factors for EAC is gastroesophageal reflux disease (GERD), a chronic digestive condition in which acidic contents from the stomach, frequently mixed with duodenal bile, enter the esophagus resulting in esophageal tissue injury. At the cellular level, progression to EAC is underlined by continuous DNA damage caused by reflux and chronic inflammatory factors that increase the mutation rate and promote genomic instability. Despite recent successes in cancer diagnostics and treatment, EAC remains a poorly treatable disease. Recent research has shed new light on molecular alterations underlying progression to EAC and revealed novel treatment options. This review focuses on the genetic and molecular studies of EAC. The molecular changes that occur during the transformation of normal Barrett's esophagus to esophageal adenocarcinoma are also discussed.

In the present study, we have investigated the prognostic value of known stem cell-associated molecules such as Oct4, CD44 and c-Myc in patients with oral SCC who had received post-surgery radio- and/or chemotherapy. Immunohistochemistry was performed to analyse the expression of Oct4, CD44 and c-Myc in 87 tumour tissues, and the expression profile obtained was correlated with clinicopathological parameters of the patients with oral cancer. Tumourigenic potential of these molecules was also evaluated by in vivo studies. Our results showed significant correlation of Oct4 (OS, p = 0.003; DFS, p = 0.001) and c-Myc (OS, p = 0.01; DFS, p = 0.03) with overall survival and disease-free survival independently. Furthermore, all the three markers in combinations of two markers each, i.e. Oct4 + CD44 (OS, p = 0.003; DFS, p = 0.001), Oct4 + c-Myc (OS, p = 0.0001; DFS, p = 0.0001), CD44 + c-Myc (OS, p = 0.008; DFS, p = 0.02) and in combinations of three markers each, i.e. Oct4 + CD44 + c-Myc (OS, p = 0.0001; DFS, p = 0.0001) also significantly correlated with overall survival and disease-free survival. Univariate and multivariate analyses further established the independent prognostic value of Oct4. Oct4-, CD44- and c-Myc-enriched populations independently induced sarcomatoid carcinomas whereas primary keratinocytes developed poorly differentiated carcinomas in immunodeficient mice. Oct4 and c-Myc independently as well as in combination with CD44 might be useful for the prediction of local recurrence and poor survival of patients with oral cancer which is the novel finding of this study. Oct4, c-Myc and CD44 can be used to predict local recurrence and the outcome of treatment in oral cancer patients. In addition, these molecules may find use as molecular targets for effective therapy.

Gastroesophageal reflux disease (GERD) is the strongest known risk factor for esophageal adenocarcinoma. In the center of tumorigenic events caused by GERD is repeated damage of esophageal tissues by the refluxate. In this study, we focused on a genotoxic aspect of exposure of esophageal cells to acidic bile reflux (BA/A). Analyzing cells generated from patients with Barrett’s esophagus and human esophageal specimens, we found that BA/A cause significant DNA damage that is mediated by reactive-oxygen species. ROS originate from mitochondria and NADPH oxidases. We specifically identified NOX1 and NOX2 enzymes to be responsible for ROS generation. Inhibition of NOX2 and NOX1 with siRNA or chemical inhibitors significantly suppresses ROS production and DNA damage induced by BA/A. Mechanistically, our data showed that exposure of esophageal cells to acidic bile salts induces phosphorylation of the p47phox subunit of NOX2 and its translocation to the cellular membrane. This process is mediated by protein kinase C, which is activated by BA/A. Taken together, our studies suggest that inhibition of ROS induced by reflux can be a useful strategy for preventing DNA damage and decreasing the risk of tumorigenic transformation caused by GERD.

Head and neck squamous cell carcinoma (HNSCC) is generalized term that encompasses a diverse group of cancers that includes tumours of the oral cavity (OSCC), oropharynx (OPSCC) and nasopharynx (NPC). Genetic alterations that are common to all HNSCC types are likely to be important for squamous carcinogenesis. In this study, we have investigated the role of the homeodomain-only homeobox gene, HOPX, in the pathogenesis of HNSCC. We show that HOPX mRNA levels are reduced in OSCC and NPC cell lines and tissues and there is a general reduction of HOPX protein expression in these tumours and OPSCCs. HOPX promoter methylation was observed in a subset of HNSCCs and was associated with a worse overall survival in HPV negative tumours. RNAseq analysis of OSCC cells transfected with HOPX revealed a widespread deregulation of the transcription of genes related to epithelial homeostasis and ectopic over-expression of HOPX in OSCC and NPC cells inhibited cell proliferation, plating efficiency and migration, and enhanced sensitivity to UVA-induced apoptosis. Our results demonstrate that HOPX functions as a tumour suppressor in HNSCC and suggest a central role for HOPX in suppressing epithelial carcinogenesis.

Background The homeodomain only protein, HOPX (also known as HOP, NECC1, LAGY or OB1) was initially identified as a gene essential for cardiac development. HOPX is unusual because although it forms a classical homeodomain fold it lacks DNA-binding capacity due to the absence of several key residues known to mediate critical contacts with DNA that are conserved among other homeodomain proteins. The aim of this study is to investigate the expression pattern and role of HOPX in head and neck cancer. Methods Immunohistochemistry, Reverse Transcriptase-PCR and QPCR were performed to study the expression pattern of HOPX in head and neck carcinoma tissues and cell line. In addition, MTT, Transwell migration, Annexin V/PI staining for apoptosis and colony forming assay have been used to investigate the effect of forced HOPX expression in head and neck carcinoma cells. Results HOPX expression is markedly reduced in head and neck carcinoma tissues and cell line when compared with normal epithelial cells. Interestingly, forced expression of HOPX reduces plating efficiency, migration and sensitizes carcinoma cell to UV induced apoptosis. Conclusion Our results demonstrate that the loss of HOPX leads to more aggressive phenotype and insists the need to investigate the precise role of HOPX in homeostasis and tumor progressive for therapeutic implication.