Implications For Carcinogenesis Research Articles

Understanding the Molecular Activity of Alkaline Sphingomyelinase (NPP7) by Computer Modeling

The enzymes in the nucleotide pyrophosphatase/phosphodiesterase (NPP) family have various substrates such as nucleotides, phospholipids, and sphingolipids. The substrate specificity in relation to their structures is largely unknown because no mammalian NPP complex has been crystallized. NPP7, also called alkaline sphingomyelinase (alk-SMase), is a NPP family member that may have important implications in carcinogenesis and cholesterol absorption. The sequence of NPP7 is 36% similar to that of the closest NPP member, but NPP7 has no activity against nucleotides. In this work, we predict the three-dimensional structure of NPP7 by homology modeling using a recently crystallized NPP from bacteria. Using the model, we studied the substrate specificity of the enzyme by docking. The model generated explains the functional changes in previous mutagenesis studies and rationalizes the structural basis for the lack of activity toward nucleotides. An effort to shift the substrate specificity from sphingomyelin (SM) to nucleotide was not successful but revealed a site-directed mutation that increased activity toward SM. In conclusion, this is the first study to predict the structure of a mammalian NPP and its substrate specificity by molecular modeling. The information may be helpful in understanding the functional differences of NPP members.

Subsite-specific differences of estrogen receptor beta expression in the normal colonic epithelium: implications for carcinogenesis and colorectal cancer epidemiology

This study aimed at investigating whether a differential estrogen receptor beta (ER-beta) expression between the colonic subsites could correspond to a modification in proliferation, apoptosis, and adhesion of the normal colonocytes. ER-beta, Ki-67, Bcl-2, and E-cadherin expressions were investigated immunohistochemically, in normal epithelium biopsies from the ascending and the descending colon of 53 individuals, who underwent colonoscopy for the investigation of anemia and in whom no local pathology was identified. ER-beta immunoreactivity has been shown to be stronger at the superficial epithelium than the crypts' base, the difference being important only for the ascending colon. In addition, ER-beta expression was higher in the superficial epithelium of the ascending colon than that of the descending colon. The variations of ER-beta expression did not correspond to the alterations in Ki-67, Bcl-2, and E-cadherin expression. A subsite-specific variation of ER-beta expression has been shown in the normal colonic epithelium. This modulation of ER-beta might account for some well established specificities of colorectal cancer epidemiology like the right-sided predominance of the neoplasm in women and its gradual shift to more proximal sites over time.

Abstract 1473: Fra-2 and JunB are overexpressed in precancerous bile ducts and primary/transplanted hamster cholangiocarcinomas with a strong positive correlation

Abstract The transciption factor complex AP-1 plays important roles in cell proliferation, differentiation and apoptosis of which dysregulation is closely associated with cancer development. Fra-2 and JunB, components of AP-1 family proteins, had been found overexpressed in certain of tumors, suggesting their possible implication in carcinogenesis. In the present study, we investigated differential expression patterns of those two AP-1family proteins during hamster cholangiocarcinogenesis and aggressive transplanted cholangiocarcinomas (ChCs). First, we prepared appropriate liver tissue samples with precancerous lesions and ChCs from hamster ChC model as well as normal liver. The transplanted ChCs were produced by syngenic transplantation of the primary ChCs. We then performed immunohistochemistry (IHC) for Fra-2 and JunB using ABC methods. The typical nuclear staining for Fra-2 and JunB was determined as positive immunoreactivity and the ratio of positive cells was evaluated by counting 800-3000 cells, followed by statistical analysis. The correlation of Fra-2 and JunB expression was analyzed by scattergram. Our IHC indicated significantly increased frequency of Fra-2 and JunB positive cells according to the tumor progression, i.e., respectively in the early dysplatic bile ducts (10∼20%) and late dysplastic bile ducts (40∼50%), primary ChC (40∼60%) and transplanted ChC (higher than 70% positivity), while normal and simple hyperplastic bile duct epithelia were negative or indicated very low labeling index for both Fra-2 and JunB (under 1% positivity). The expression of Fra-2 and JunB showed a strong correlation (r=0.93) and the immunoreactive cells for Fra-2 and JunB were mainly localized in the invading areas adjacent to normal surrounding tissue. In summary, we found in the present study the followings 1) Expression of Fra-2 and JunB progressively increased as bile duct cells become carcinogenic, 2) Fra-2 and JunB have a high correlation in the expression patterns in the biliary cell populations including cancers, 3) In the transplanted biliary cancers, overexpression of Fra-2 and JunB (especially JunB) were localized in the neoplastic cells which are very aggressive to invade into adjacent normal tissue. Based on our results, Fra-2 and JunB could play significant roles in cholangiocarcinogenesis, possibly by collaboratively participating in dysplastic changes and acquisition of tumorigenicity of candidate bile duct cells for ChC. Also, those two AP-1 family proteins could contribute to invasiveness of biliary cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1473.

Abstract 173: Frequent concomitant epigenetic silencing of the SFRPs and SOX1, Wnt/β-catenin regulators, in human hepatocellular carcinoma

Abstract Oncogenic activation of the Wnt/β-catenin signaling pathway is common in hepatocellular carcinoma (HCC). The secreted frizzled-related proteins (SFRPs) function as negative regulators of Wnt signaling and have important implications for carcinogenesis. Recently, we have shown that SFRPs are frequently downregulated through promoter hypermethylation in HCC cell lines and clinical HCC tissues. Furthermore, we have demonstrated that restoration of SFRPs could attenuate Wnt signaling in HCC cells with β-catenin point mutation, decrease abnormal accumulation of free β-catenin in the nucleus, and then suppress cell growth. Sox1 encodes a transcription factor involved in the regulation of embryonic development and cell fate determination. Structurally related to TCF/LEFs, several members of the Sox family, including Sox17, Sox3, Sox7, and Sox9, have also been implicated in repressing β-catenin activity by a mechanism that is not well understood. In this study, we found that the Sox1 was severely down-regulated by quantitative reverse transcription polymerase chain reaction (QRT-PCR). Next, we employed bisulfite modification and methylation-specific PCR (MS-PCR) to analyze the feature of Sox1 promoter methylation in the HCC cell lines and found that the majority of the tested cell lines exhibited hypermethylation. Meanwhile, we also examined sixty primary HCC surgical samples and adjacent nonturmorous liver tissues from Taiwan Liver Cancer Network (TLCN). These results showed that aberrant promoter methylation of SOX1 were found in 32 of 60 HCCs (53.3%), in 13 of 50 cirrhotic livers (26%), and in one of 30 normal control tissues (3.3%). Concomitantly, SFRPs was epigenetically inactivated in HCC cell lines and most of all the tumors with methylated SOX1. A significant correlation between the methylation of both genes was found (p >0.05). Furthermore, overexpression of SOX-1 in HCC cells could suppress TCF-dependent transcriptional activity and suppress colony formation. Taken together, our data suggest that SOX1 is a negative modulator of Wnt/β-catenin signaling, and that SOX1 silencing due to promoter hypermethylation is an early event during tumorigenesis and may contribute to aberrant activation of Wnt signaling in HCC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 173.

Arecoline arrests cells at prometaphase by deregulating mitotic spindle assembly and spindle assembly checkpoint: Implication for carcinogenesis

One apparent feature of cancerous cells is genomic instability, which may include various types of chromosomal aberrations, such as translocation, aneuploidy, and the presence of micronuclei inside the cells. Mutagenic factors that promote the emergence of genomic instability are recognized as risk factors for the development of human malignancies. In Asia, betel quid (BQ) chewing is one of such risk factors for oral cancer. Areca nut is an essential constitute of BQ and is declared as a group I carcinogen by the International Agency for Research on Cancer. However, the molecular and cellular mechanisms regarding the carcinogenicity of areca nut are not fully explored. Here we reported that arecoline, a major alkaloid of areca nut, could arrest cells at prometaphase with large amounts of misaligned chromosomes. This prometaphase arrest was evidenced by condensed chromosome pattern, increased histone H3 phosphorylation, and accumulation of mitotic proteins, including aurora A and cyclin B(1). To investigate the molecular mechanisms accounting for arecoline-induced prometaphase arrest, we found that arecoline could stabilize mitotic spindle assembly, which led to distorted organization of mitotic spindles, misalignment of chromosomes, and up-regulation of spindle assembly checkpoint (SAC) genes. The SAC proteins BubR1 and Mps1 were differentially modified between the cells treated with arecoline and nocodazole. This together with aurora A overexpression suggested that SAC might be partly suppressed by arecoline. As a result, the arecoline-exposed cells might produce progeny that contained various chromosomal aberrations and exhibited genomic instability.

Genetic alterations in a telomerase-immortalized human esophageal epithelial cell line: Implications for carcinogenesis

Ectopic expression of viral oncoproteins disrupts cellular functions and limits the value of many existing immortalization models as models for carcinogenesis, especially for cancers without definitive viral etiology. Our newly established telomerase-immortalized human esophageal epithelial cell line, NE2-hTERT, retained nearly-diploid and non-tumorigenic characteristics, but exhibited genetic and genomic alterations commonly found in esophageal cancer, including progressive loss of the p16 INK4a alleles, upregulation of anti-apoptotic proteins, epithelial-mesenchymal transition, whole-chromosome 7 gain and duplicated 5q arm. Our data also revealed a novel positive regulation of p16 INK4a on cyclin D1. These findings probably represent early crucial events and mechanisms in esophageal carcinogenesis.

Emerging role of radiation induced bystander effects: Cell communications and carcinogenesis

Ionizing radiation is an invaluable diagnostic and treatment tool used in various clinical applications. On the other hand, radiation is a known cytotoxic with a potential DNA damaging and carcinogenic effects. However, the biological effects of low and high linear energy transfer (LET) radiations are considerably more complex than previously thought. In the past decade, evidence has mounted for a novel biological phenomenon termed as "bystander effect" (BE), wherein directly irradiated cells transmit damaging signals to non-irradiated cells thereby inducing a response similar to that of irradiated cells. BE can also be induced in various cells irrespective of the type of radiation, and the BE may be more damaging in the longer term than direct radiation exposure. BE is mediated either through gap-junctions or via soluble factors released by irradiated cells. DNA damage response mechanisms represent a vital line of defense against exogenous and endogenous damage caused by radiation and promote two distinct outcomes: survival and the maintenance of genomic stability. The latter is critical for cancer avoidance. Therefore, efforts to understand and modulate the bystander responses will provide new approaches to cancer therapy and prevention. This review overviews the emerging role of BE of low and high LET radiations on the genomic instability of bystander cells and its possible implications for carcinogenesis.

Elevated expression of semaphorin 5A in human gastric cancer and its implication in carcinogenesis

Aims Semaphorin 5A, a member of semaphorin family, was originally identified as axonal guidance factor functioning during neuronal development. Here, we investigated semaphorin 5A expression in gastric cancer and explored its roles in gastric carcinogenesis. Main methods The expression of semaphorin 5A was examined by reverse transcription-polymerase chain reaction (RT-PCR) analysis in six gastric cancer cell lines and detected by real-time RT-PCR and Western blotting in 30 pairs of primary gastric cancer and normal gastric mucosa tissues. RNA interference (RNAi) technique was used to generate a semaphorin 5A-silenced stable cell line. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and anchorage-independent growth as well as flow cytometry assays were conducted to examine the effect of siRNA–semaphorin 5A on gastric cancer cell growth, proliferation and apoptosis. Key findings Semaphorin 5A was expressed in all human gastric cancer lines and the expression of semaphorin 5A was significantly higher in cancer tissues than that in normal mucosa tissues. siRNA-mediated semaphorin 5A knockdown significantly suppressed the proliferation and anchorage-independent growth, and induced the apoptosis of gastric cancer cell line SGC7901. Significance The present study suggests that overexpression of semaphorin 5A may contribute to gastric carcinogenesis, which reveals a novel expression and function of semaphorin 5A outside the nervous system and adds more weight to our knowledge of semaphorin 5A.

The Links between Transcription, β-catenin/JNK Signaling, and Carcinogenesis

Interactions between transcription and signaling are fundamentally important for understanding both the structure and function of genetic pathways and their role in diseases such as cancer. The finding that beta-catenin/TCF4 and JNK/c-Jun cooperate has important implications in carcinogenesis. Previously, we found that binding of c-Jun and beta-catenin/TCF4 to the c-jun promoter is dependent upon JNK activity, thus one role for this complex is to contribute to the repression and/or activation of genes that may mediate cell maintenance, proliferation, differentiation, and death, whereas deregulation of these signals may contribute to carcinogenesis. Here we address the functional links reported between activated beta-catenin/JNK signaling pathways, their component genes, and their common targets, and discuss how alterations in the properties of these genes lead to the development of cancer.

Significant association between EGFR-mutated lung adenocarcinoma and past illness from gastric cancer or uterine myoma: Its implication in carcinogenesis

The present study investigated the potential difference between EGFR-mutated lung adenocarcinoma (ADC) and KRAS-mutated ADC in relation to past illness and family history. Among the 153 tumors examined, 33 (21.6%) were EGFR-mutated, and 22 (14.4%) were KRAS-mutated. The EGFR-mutated cases showed a significantly higher prevalence of past illness involving the gastric cancer in males (EGFR 3/8 (37.5%), KRAS 0/13 (0.0%), no mutation (NONE) 1/57 (1.8%); Fisher's exact test, P = 0.0064) or uterine myoma in females (EGFR 8/25 (32.0%), KRAS 0/9 (0.0%), NONE 3/41 (7.3%); Fisher's exact test, P = 0.0139). No association between the mutations and family history was found. The EGFR-mutated ADC is therefore likely to develop through a distinct carcinogenetic pathway from the others, but genetic backgrounds seemed unlikely to be determinant predisposing to the EGFR-mutated ADC.

Breast cancer and aneusomy 17: implications for carcinogenesis and therapeutic response

Abnormalities of chromosome 17, recognised over two decades ago to be important in tumorigenesis, often occur in breast cancer. Changes of specific loci on chromosome 17 including ERBB2 amplification, P53 loss, BRCA1 loss, and TOP2A amplification or deletion are known to have important roles in breast-cancer pathophysiology. Numerical aberrations of chromosome 17 are linked to breast-cancer initiation and progression, and possibly to treatment response. However, the clinical importance of chromosome 17 anomalies, in particular the effect on ERBB2 protein expression, is unknown. Reports are conflicting regarding the association of copy gain of chromosome 17 (polysomy 17) with strong ERBB2 protein expression in the absence of true ERBB2 gene amplification. Copy-number anomalies in chromosome 17 seem to be common in tumours that show discrepant ERBB2 expression and in tumours with discordant ERBB2-protein and ERBB2 gene copy number measurements. The mechanisms of ERBB2 dosage changes-gene amplification versus chromosome gain and loss-probably differ in primary and metastatic disease; however, a correction for chromosome 17 copy-number is necessary to completely distinguish between these mechanisms. A better understanding of how polysomy 17 affects gene-copy number and protein expression will help to select patients who will respond to therapies targeting ERBB2 and other protein products of chromosome 17 loci.

SFRP1 and SFRP2 suppress the transformation and invasion abilities of cervical cancer cells through Wnt signal pathway

Objectives Aberrant activation of the Wnt/β-catenin signaling pathway is common in human cancers, including cervical cancer. The secreted frizzled-related proteins (SFRPs) function as Wnt antagonists and play important implications in carcinogenesis. Recently, we have shown that SFRP1 and SFRP2 are frequently downregulated through promoter hypermethylation. However, the function of SFRP1 and SFRP2 in cervical cancer remains unclear. Methods To improve our understanding of the role of SFRP1 and SFRP2 in cervical cancer cells, we use overexpression or shRNA approach in cervical cancer cell lines. Results Restoration of the expression of SFRP1 and SFRP2 attenuated Wnt signaling in CaSki cells, decreased abnormal accumulation of free β-catenin in the nucleus, and suppressed cancer cell growth. In addition, different statuses of β-catenin accumulation in the cytoplasm of CaSki or HeLa3rd cells were observed, suggesting that different Wnt pathways are executed. Furthermore, we demonstrated that SFRP1 and SFRP2 enhance the expression of the epithelial marker E-cadherin, through inhibition of the expression of SLUG, TWIST and SNAIL, three transcription factors involved in the epithelial mesenchymal transition (EMT) program. Finally, in a xenograft animal model, we showed that SFRP1 suppresses tumorigenicity of cancer cells in vivo. Conclusions Taken together, these data strongly suggest that epigenetic silencing of SFRP genes leads to oncogenic activation of the Wnt pathway and contributes to cervical cancer progression through the EMT program.

Pontin and Reptin, Two Related ATPases with Multiple Roles in Cancer

Studies in model organisms or cultured human cells suggest potential implications in carcinogenesis for the AAA+ ATPases Pontin and Reptin. Both proteins are associated with several chromatin-remodeling complexes and have many functions including transcriptional regulation, DNA damage repair, and telomerase activity. They also interact with major oncogenic actors such as beta-catenin and c-myc and regulate their oncogenic function. We only now begin to get insight into the role of Pontin and Reptin in human cancers.

Eosinophils and mast cells in chronic gastritis: possible implications in carcinogenesis

Eosinophils and mast cells participate in the immune response against Helicobacter pylori, but their involvement in the gastric precancerous process is unclear. This study aimed to estimate eosinophil and mast cell density in antral mucosa in subjects from 2 Colombian populations with contrasting gastric cancer risks. Gastric mucosa biopsies were collected from 117 adult males (72 from a high-risk area and 45 from a low-risk area). A histopathology score was used to quantify severity of the lesions. Quantitation of eosinophils in hematoxylin-eosin-stained sections and mast cells in immunostained sections for CD117/c-Kit was performed. Helicobacter pylori infection and genotyping were assessed in Steiner stain and polymerase chain reaction, respectively. Logistic regression models and semiparametric cubic smoothing splines were used for analysis of the results. Eosinophil density was significantly higher in subjects from the low-risk area as compared with subjects from the high-risk area. In both populations, eosinophil density increased with the histopathology score in the progression of lesions from normal morphology to multifocal atrophic gastritis. Intestinal metaplasia and dysplasia specimens showed further increase in eosinophil density in the high-risk area but an abrupt decrease in the low-risk area. Mast cell density increased in parallel to the histopathology score in both populations. Our results suggest that eosinophils play a dual role in chronic gastritis. In the low-risk area, elevated eosinophil density represents a T helper 2-biased response that may down-regulate the effects of proinflammatory cytokines preventing cancer development. In contrast, in the high-risk area, eosinophils might promote a T helper 1-type response leading to progression of precancerous lesions.

The regulated assembly of a PKCɛ complex controls the completion of cytokinesis

The cell cycle is exquisitely controlled by multiple sequential regulatory inputs to ensure fidelity. Here we demonstrate that the final step in division, the physical separation of daughter cells, is controlled by a member of the PKC gene superfamily. Specifically, we have identified three phosphorylation sites within PKCepsilon that control its association with 14-3-3. These phosphorylations are executed by p38 MAP kinase (Ser 350), GSK3 (Ser 346) and PKC itself (Ser 368). Integration of these signals is essential during mitosis because mutations that prevent phosphorylation of PKCepsilon and/or PKCepsilon binding to 14-3-3 also cause defects in the completion of cytokinesis. Using chemical genetic and dominant-negative approaches it is shown that selective inhibition of PKCepsilon halts cells at the final stages of separation. This arrest is associated with persistent RhoA activation at the midbody and a delay in actomyosin ring dissociation. This study therefore identifies a new regulatory mechanism that controls exit from cytokinesis, which has implications for carcinogenesis.

Increased expression of Nlp, a potential oncogene in ovarian cancer, and its implication in carcinogenesis

Objective Nlp (Ninein-like protein), a novel centrosome protein involved in microtubule nucleation, has been studied extensively in our laboratory, and its overexpression has been found in some human tumors. To understand the role of Nlp in human ovarian cancer development, we studied the correlation of Nlp expression with clinicopathological parameters and survival in epithelial ovarian cancer, and the impact of Nlp overexpression on ovarian cancer cells. Methods Nlp expression in normal, borderline, benign and malignant epithelial ovarian tissues was examined by immunohistochemistry. The correlation between Nlp expression and tumor grade, FIGO stage and histological type was also evaluated. Survival was calculated using Kaplan–Meier estimates. Cell proliferation and apoptosis were assayed after stable transfection of pEGFP-C3-Nlp or empty vector in human ovarian cancer cell line SKOV3. Results Nlp was positive in 1 of 10 (10%) normal ovarian tissues, 5 of 34 (14.7%) benign tumors, 9 of 26 (34.6%) borderline tumors and 73 of 131 (56.0%) ovarian tumors. Nlp immunoreactivity intensity significantly correlated with tumor grade, but not with FIGO stage or histological type. Kaplan–Meier curves showed that Nlp overexpression was marginally associated with decreased overall survival. Overexpression of Nlp enhanced proliferation and inhibited apoptosis induced by paclitaxel in the SKOV3 cell line. Conclusions Overexpression of Nlp in ovarian tumors raises the possibility that Nlp may play a role in ovarian carcinogenesis.

Macro-environment of breast carcinoma: frequent genetic alterations in the normal appearing skins of patients with breast cancer

Genetic abnormalities in microenvironmental tissues with subsequent alterations of reciprocal interactions between epithelial and mesenchymal cells play a key role in the breast carcinogenesis. Although a few reports have demonstrated abnormal fibroblastic functions in normal-appearing fibroblasts taken from the skins of breast cancer patients, the genetic basis of this phenomenon and its implication for carcinogenesis are unexplored. We analyzed 12 mastectomy specimens showing invasive ductal carcinomas. In each case, morphologically normal epidermis and dermis, carcinoma, normal stroma close to carcinoma, and stroma at a distant from carcinoma were microdissected. Metastatic-free lymphatic tissues from lymph nodes served as a control. Using PCR, DNA extracts were examined with 11 microsatellite markers known for a high frequency of allelic imbalances in breast cancer. Losses of heterozygosity and/or microsatellite instability were detected in 83% of the skin samples occurring either concurrently with or independently from the cancerous tissues. In 80% of these cases at least one microsatellite marker displayed loss of heterozygosity or microsatellite instability in the skin, which was absent in carcinoma. A total of 41% of samples showed alterations of certain loci observed exclusively in the carcinoma but not in the skin compartments. Our study suggests that breast cancer is not just a localized genetic disorder, but rather part of a larger field of genetic alterations/instabilities affecting multiple cell populations in the organ with various cellular elements, ultimately contributing to the manifestation of the more ‘localized' carcinoma. These data indicate that more global assessment of tumor micro- and macro-environment is crucial for our understanding of breast carcinogenesis.

Arsenic-induced changes in the gene expression of lung epithelial L2 cells: implications in carcinogenesis

BackgroundArsenic is a carcinogen that is known to induce cell transformation and tumor formation. Although studies have been performed to examine the modulation of signaling molecules caused by arsenic exposure, the molecular mechanisms by which arsenic causes cancer are still unclear. We hypothesized that arsenic alters gene expression leading to carcinogenesis in the lung.ResultsIn this study, we examined global gene expression in response to 0.75 μM arsenic treatment for 1–7 days in a rat lung epithelial cell line (L2) using an in-house 10 k rat DNA microarray. One hundred thirty one genes were identified using the one-class statistical analysis of microarray (SAM) test. Of them, 33 genes had a fold change of ≥ 2 between at least two time points. These genes were then clustered into 5 groups using K-means cluster analysis based on their expression patterns. Seven selected genes, all associated with cancer, were confirmed by real-time PCR. These genes have functions directly or indirectly related to metabolism, glycolysis, cell proliferation and differentiation, and regulation of transcription.ConclusionOur findings provide important insight for the future studies of arsenic-mediated lung cancer.

Upregulated ATM Gene Expression and Activated DNA Crosslink-Induced Damage Response Checkpoint in Fanconi Anemia: Implications for Carcinogenesis

Fanconi anemia (FA) predisposes to hematopoietic failure, birth defects, leukemia, and squamous cell carcinoma of the head and neck (HNSCC) and cervix. The FA/BRCA pathway includes 8 members of a core complex and 5 downstream gene products closely linked with BRCA1 or BRCA2. Precancerous lesions are believed to trigger the DNA damage response (DDR), and we focused on the DDR in FA and its putative role as a checkpoint barrier to cancer. In primary fibroblasts with mutations in the core complex FANCA protein, we discovered that basal expression and phosphorylation of ATM (ataxia telangiectasia mutated) and p53 induced by irradiation (IR) or mitomycin C (MMC) were upregulated. This heightened response appeared to be due to increased basal levels of ATM in cultured FANCA-mutant cells, highlighting the new observation that ATM can be regulated at the transcriptional level in addition to its well-established activation by autophosphorylation. Functional analysis of this response using gamma-H2AX foci as markers of DNA double-stranded breaks (DSBs) demonstrated abnormal persistence of only MMC- and not IR-induced foci. Thus, we describe a processing defect that leads to general DDR upregulation but specific persistence of DNA crosslinker-induced damage response foci. Underscoring the significance of these findings, we found resistance to DNA crosslinker-induced cell cycle arrest and apoptosis in a TP53-mutant, patient-derived HNSCC cell line, whereas a lymphoblastoid cell line derived from this same individual was not mutated at TP53 and retained DNA crosslinker sensitivity. Our results suggest that cancer in FA may arise from selection for cells that escape from a chronically activated DDR checkpoint.

Panmasala Chewing Induces Deterioration in Oral Health and Its Implications in Carcinogenesis

ABSTRACTPanmasala containing tobacco was introduced in the Indian market during the 1970s. Panmasala consists of areca nut (betel nut), catechu, lime, cardamom, spices, and unspecified flavoring agents, etc., with tobacco locally known as gutkha or without tobacco (Plain or sada), and consumed abundantly in India and also other parts of the world, predominantly in South East Asian countries. Available studies demonstrate that the habits of chewing panmasala gutkha or plain by students and adolesescents are on the increase, which may lead to deterioration of oral health and other organ systems. Based on the experimental as well as clinical studies available on panmasala as well as on different components of panmasala, this review suggests that it has the potential in causation of various oral diseases such as Oral Sub Mucosis Fibrosis (OSMF) and leucoplakia which may lead to oral cancer. Studies reviewed on these chewing mixtures also reveal that it is likely to be carcinogenic, as tobacco and areca nut have carcinogenic potential and both have encompassing addictive potential leading to dependence on chewing mixture containing areca nut and tobacco. These mixtures might not only lead to cancer but may also affect other organs of the body, including oral hard tissues in the form of dental attrition and sensitivity. There is a need to consider the potential health hazards associated with the habits of these products, especially oral cancer. More research is needed to find out early changes which could be reversible and also intervention measures through education to desist people in indulging in such habits.