p53 apoptotic response to DNA damage dependent on bcl2 but not bax in head and neck squamous cell carcinoma lines

Yttrium Oxide nanoparticles induce cytotoxicity, genotoxicity, apoptosis, and ferroptosis in the human triple-negative breast cancer MDA-MB-231 cells

BACKGROUND

Triple-negative breast cancer (TNBC) is a lethal mammary carcinoma subtype that affects females and is associated with a worse prognosis. Chemotherapy is the only conventional therapy available for patients with TNBC due to the lack of therapeutic targets. Yttrium oxide (Y2O3) is a rare earth metal oxide, whose nanoparticle (NPs) formulations are used in various applications, including biological imaging, the material sciences, and the chemical synthesis of inorganic chemicals. However, the biological activity of Y2O3-NPs against TNBC cells has not been fully explored. The current study was conducted to assess Y2O3-NPs' anticancer activity against the human TNBC MDA-MB-231 cell line.

METHODS

Transmission electron microscopy (TEM), X-ray diffraction, Zeta potential, and dynamic light scattering (DLS) were used to characterize the Y2O3-NPs. SRB cell viability, reactive oxygen species (ROS) measurement, single-cell gel electrophoresis (comet assay), qPCR, flow cytometry, and Western blot were employed to assess the anticancer activity of the Y2O3-NPs.

RESULTS

Our results indicate favorable physiochemical properties of Y2O3-NPs (with approximately average size 14 nm, Zeta Potential about - 53.2 mV, and polydispersity index = 0.630). Y2O3-NPs showed a potent cytotoxic effect against MDA-MB-231 cells, with IC50 values of 74.4 µg/mL, without cytotoxic effect on the normal retina REP1 and human dermal fibroblast HDF cell lines. Further, treatment of MDA-MB-231 cells with IC50 Y2O3-NPs resulted in increased oxidative stress, accumulation of intracellular ROS levels, and induced DNA damage assessed by Comet assay. Upon Y2O3-NPs treatment, a significant increase in the early and late phases of apoptosis was revealed in MDA-MB-231 cells. qPCR results showed that Y2O3-NPs significantly upregulated the pro-apoptotic genes CASP3 and CASP8 as well as ferroptosis-related gene heme oxygenase-1 (HO-1), whereas the anti-apoptotic gene BCL2 was significantly downregulated.

CONCLUSION

This study suggests that Y2O3-NPs are safe on normal REP1 and HDF cells and exhibited a potent selective cytotoxic effect against the TNBC MDA-MB-231 cells through increasing levels of ROS generation with subsequent DNA damage, and induction of apoptosis and ferroptosis.

The multifunction of HSP70 in cancer: Guardian or traitor to the survival of tumor cells and the next potential therapeutic target

Heat shock protein 70 (HSP70) is a highly conserved protein composed of nucleotide-binding domains (NBD) and C-terminal substrate binding domain (SBD) that can function as a "molecular chaperone". HSP70 was discovered to directly or indirectly play a regulatory role in both internal and external apoptosis pathways. Studies have shown that HSP70 can not only promote tumor progression, enhance tumor cell resistance and inhibit anticancer effects but also induce an anticancer response by activating immune cells. In addition, chemotherapy, radiotherapy and immunotherapy for cancer may be affected by HSP70, which has shown promising potential as an anticancer drug. In this review, we summarized the molecular structure and mechanism of HSP70 and discussed the dual effects of HSP70 on tumor cells and the possibility and potential methods of using HSP70 as a target to treat cancer.

Chalcones: Promising therapeutic agents targeting key players and signaling pathways regulating the hallmarks of cancer

The need for innovative anticancer treatments with high effectiveness and low toxicity is urgent due to the development of malignancies that are resistant to chemotherapeutic agents and the poor specificity of existing anticancer treatments. Chalcones are 1,3-diaryl-2-propen-1-ones, which are the precursors for flavonoids and isoflavonoids. Chalcones are readily available from a wide range of natural resources and consist of very basic chemical scaffolds. Because the ease with which the synthesis it allows for the production of several chalcone derivatives. Various in-vitro and in-vivo studies indicate that naturally occurring and synthetic chalcone derivatives exhibit promising biological activities against cancer hallmarks such as proliferation, angiogenesis, invasion, metastasis, inflammation, stemness, and regulation of cancer epigenetics. According to their structure and functional groups, chalcones derivatives and their hybrid compounds exert a broad range of biological activities through targeting key elements and signaling molecules relevant to cancer progression. This review will provide valuable insights into the latest updates of chalcone groups as anticancer agents and extensively discuss their underlying molecular mechanisms of action.

[1,2,4] Triazolo [3,4-a]isoquinoline chalcone derivative exhibits anticancer activity via induction of oxidative stress, DNA damage, and apoptosis in Ehrlich solid carcinoma-bearing mice

Despite the advances made in cancer therapeutics, their adverse effects remain a major concern, putting safer therapeutic options in high demand. Since chalcones, a group of flavonoids and isoflavonoids, act as promising anticancer agents, we aimed to evaluate the in vivo anticancer activity of a synthetic isoquinoline chalcone (CHE) in a mice model with Ehrlich solid carcinoma. Our in vivo pilot experiments revealed that the maximum tolerated body weight-adjusted CHE dose was 428 mg/kg. Female BALB/c mice were inoculated with Ehrlich ascites carcinoma cells and randomly assigned to three different CHE doses administered intraperitoneally (IP; 107, 214, and 321 mg/kg) twice a week for two consecutive weeks. A group injected with doxorubicin (DOX; 4 mg/kg IP) was used as a positive control. We found that in CHE-treated groups: (1) tumor weight was significantly decreased; (2) the total antioxidant concentration was substantially depleted in tumor tissues, resulting in elevated oxidative stress and DNA damage evidenced through DNA fragmentation and comet assays; (3) pro-apoptotic genes p53 and Bax, assessed via qPCR, were significantly upregulated. Interestingly, CHE treatment reduced immunohistochemical staining of the proliferative marker ki67, whereas BAX was increased. Notably, histopathological examination indicated that unlike DOX, CHE treatment had minimal toxicity on the liver and kidney. In conclusion, CHE exerts antitumor activity via induction of oxidative stress and DNA damage that lead to apoptosis, making CHE a promising candidate for solid tumor therapy.

Hsp70 in cancer: A double agent in the battle between survival and death

The heat shock protein (Hsps) superfamily, also known as molecular chaperones, are highly conserved and present in all living organisms and play vital roles in protein fate. The HspA1A (Hsp70-1), called Hsp70 in this review, is expressed at low or undetectable levels in most unstressed normal cells, but numerous studies have shown that diverse types of tumor cells express Hsp70 at the plasma membrane that leads to resistance to programmed cell death and tumor progression. Hsp70 is released into the extracellular milieu in three forms including free soluble, complexed with cancer antigenic peptides, and exosome forms. Therefore, it seems to be a promising therapeutic target in human malignancies. However, a great number of studies have indicated that both intracellular and extracellular Hsp70 have a dual function. A line of evidence presented that intracellular Hsp70 has a cytoprotective function via suppression of apoptosis and lysosomal cell death (LCD) as well as that extracellular Hsp70 can promote tumorigenesis and angiogenesis. Other evidence showed intracellular Hsp70 can promote apoptosis and membrane-associated/extracellular Hsp70 can elicit antitumor innate and adaptive immune responses. Given the contradictory functions, as a "double agent," could Hsp70 be a promising tool in the future of targeted cancer therapies? To answer this question, in this review, we will discuss the functions of Hsp70 in cancers besides inhibition and stimulation strategies for targeting Hsp70 along with their challenges.

Assessment of acyl-CoA cholesterol acyltransferase (ACAT-1) role in ovarian cancer progression-An in vitro study

Abnormal accumulation of acyl-CoA cholesterol acyltransferase-1 (ACAT-1) mediated cholesterol ester has been shown to contribute to cancer progression in various cancers including leukemia, glioma, breast, pancreatic and prostate cancers. However, the significance of ACAT-1 and cholesterol esters (CE) is relatively understudied in ovarian cancer. In this in vitro study, we assessed the expression and contribution of ACAT-1 in ovarian cancer progression. We observed a significant increase in the expression of ACAT-1 and CE levels in a panel of ovarian cancer cell lines (OC-314, SKOV-3 and IGROV-1) compared to primary ovarian epithelial cells (normal controls). To confirm the tumor promoting capacity of ACAT-1, we inhibited ACAT-1 expression and activity by treating our cell lines with an ACAT inhibitor, avasimibe, or by stable transfection with ACAT-1 specific short hairpin RNA (shRNA). We observed significant suppression of cell proliferation, migration and invasion in ACAT-1 knockdown ovarian cancer cell lines compared to their respective controls (cell lines transfected with scrambled shRNA). ACAT-1 inhibition enhanced apoptosis with a concurrent increase in caspases 3/7 activity and decreased mitochondrial membrane potential. Increased generation of reactive oxygen species (ROS) coupled with increased expression of p53 may be the mechanism(s) underlying pro-apoptotic action of ACAT-1 inhibition. Additionally, ACAT-1 inhibited ovarian cancer cell lines displayed enhanced chemosensitivity to cisplatin treatment. These results suggest ACAT-1 may be a potential new target for the treatment of ovarian cancer.

Detection of p53 and Bcl-2 expression in cutaneous hemangioma through the quantum dot technique

Hemangioma is one of the most common types of infantile vascular benign tumor. The aim of the present study was to investigate the role of B-cell lymphoma 2 (Bcl-2) and tumor protein p53 (p53) in the proliferation and apoptosis of hemangioma cells. A total of 38 paraffin-embedded hemangioma specimens (16 males and 22 females) and another 5 paraffin-embedded healthy surrounding tissue samples, collected between January 2007 and December 2010, were obtained from the Department of Pathology at Renmin Hospital of Wuhan University (Wuhan, China). Immunohistochemistry, hematoxylin and eosin staining, and quantum dot double staining were used to detect the expression of proliferating cell nuclear antigen (PCNA), Bcl-2 and p53 in hemangioma and healthy surrounding skin tissue samples. All hemangioma specimens were classified into proliferative or the involuting stage hemangioma according to Mulliken's criteria and their expression of PCNA. The results of the quantum dot double staining were analyzed using a multi-spectral imaging system. One-way analysis of the variance and the Student-Newman-Keuls q test were performed to statistically analyze the data. There were 24 cases of proliferative stage and 14 cases of involuting stage hemangioma among the specimens. Immunohistochemical analysis results indicated a high expression of Bcl-2 and p53 in proliferative stage hemangioma tissue samples, and low expression in involuting stage hemangioma and healthy tissue samples. Statistical analysis of the results from quantum dot double staining demonstrated that the expression of Bcl-2 and p53 in proliferative hemangioma was significantly increased compared with that in involuting stage specimens (P<0.05) and healthy tissue samples (P<0.05). No significant difference in Bcl-2 and p53 expression was identified between the involuting hemangioma and healthy surrounding tissue samples. The higher expression of Bcl-2 and p53 in proliferative hemangioma suggests that Bcl-2 may cause an imbalance between endothelial cell proliferation and apoptosis through the inhibition of endothelial cell apoptosis. Furthermore, p53 may promote the proliferation of endothelial cells in proliferative hemangioma.

Knocking down of p53 triggers apoptosis and autophagy, concomitantly with inhibition of migration on SSC-4 oral squamous carcinoma cells

Oral squamous cell carcinoma (OSCC) is a malignancy with elevated prevalence and somber prognosis due to the fact that most of the patients are diagnosed at an advanced stage. p53 has a crucial role in proliferation and apoptosis during the occurrence and development of numerous malignant tumors. The impact of mutated p53 on the development and progression of OSCC is unclear and might have therapeutic implications. Using an in vitro RNA interference experiment, we have evaluated the impact of p53 knockdown on cell viability, apoptosis, migration, and gene expression for key genes involved in apoptosis and angiogenesis. We observed that inhibiting the expression of p53 decreased the proliferation ability and induced apoptosis/autophagy in SSC-4 cells. Moreover, we observed that this has decreased migration and has blocked the expression of VEGF. In conclusion, our research provides a proof that a direct connection between p53 knockdown and OSCC cell death can be established, therefore opening new potential directions in OSCC molecular therapeutics and management.

Targeting Hsp70: A possible therapy for cancer

In all organisms, heat-shock proteins (HSPs) provide an ancient defense system. These proteins act as molecular chaperones by assisting proper folding and refolding of misfolded proteins and aid in the elimination of old and damaged cells. HSPs include Hsp100, Hsp90, Hsp70, Hsp40, and small HSPs. Through its substrate-binding domains, Hsp70 interacts with wide spectrum of molecules, ranging from unfolded to natively folded and aggregated proteins, and provides cytoprotective role against various cellular stresses. Under pathophysiological conditions, the high expression of Hsp70 allows cells to survive with lethal injuries. Increased Hsp70, by interacting at several points on apoptotic signaling pathways, leads to inhibition of apoptosis. Elevated expression of Hsp70 in cancer cells may be responsible for tumorigenesis and for tumor progression by providing resistance to chemotherapy. In contrast, inhibition or knockdown of Hsp70 reduces the size of tumors and can cause their complete regression. Moreover, extracellular Hsp70 acts as an immunogen that participates in cross presentation of MHC-I molecules. The goals of this review are to examine the roles of Hsp70 in cancer and to present strategies targeting Hsp70 in the development of cancer therapeutics.

Scutellariae radixInduces Apoptosis in Chemoresistant SCC-25 Human Tongue Squamous Carcinoma Cells

Scutellariae radix is one of the most widely used anticancer herbal medicines in several Asian countries, including Korea, Japan, and China. Squamous cell carcinoma (SCC) is one of the most common head and neck carcinomas, which is highly invasive and metastatic, and can potentially develop chemoresistance. Therefore, new effective treatment methods are urgently needed. We determined the effects of Scutellariae radix on SCC-25 cells using the WST-1 assay, F-actin staining, flow cytometry analysis, immunofluorescence staining, and western blot analysis. Scutellariae radix treatment inhibited SCC-25 cell growth in a dose- and time-dependent manner, but it did not inhibit HaCaT (human keratinocyte) cell growth. Changes in cell morphology and disruption of filamentous (F)-actin organization were observed. Scutellariae radix-induced apoptosis as indicated by the translocation of cytochrome c and apoptosis-inducing factor (AIF) into the nucleus and cytosol. Scutellariae radix-induced an increase in cells with sub-G1 DNA content, and increased Bax, cleaved caspase-3, caspase-7, caspase-9, DNA fragmentation factor 45 (DFF 45), and poly(ADP-ribose) polymerase-1 (PARP-1) expression levels. Furthermore, increased expression of phosphorylated mitogen-activated protein kinase (MAPK)-related proteins was detected. The antitumor effect of Scutellariae radix was due to decreased cell proliferation, changes in cell morphology, and the activation of caspase and MAPK pathways. Taken together, the findings of this study highlight the anticancer activity of Scutellariae radix in chemoresistant SCC-25 oral squamous carcinoma cells.

Protective effects of [6]-paradol on histological lesions and immunohistochemical gene expression in DMBA induced hamster buccal pouch carcinogenesis

BACKGROUND

The search for naturally occurring agents in routinely consumed foods that may inhibit cancer development is of high priority. [6]-Paradol is a pungent phenolic bioactive component from ginger with well- documented health promoting antioxidant, antimutagenic, antigenotoxic and anti-inflammatory properties. However, anticarcinogenic effects have yet to be fully explored. The objectives of the present study were therefore to assess protective effects against 7,12-dimethylbenz(a)anthracene (DMBA) induced buccal pouch carcinogenesis in male golden Syrian hamsters.

METHODS

Oral squamous cell carcinomas developed in the left buccal pouch of hamsters on painting with 0.5% of DMBA, three times in a week. To assess the apoptotic associated gene expressing potential of [6]-paradol, it was orally administered to DMBA treated hamsters on alternate days from DMBA painting for 14 weeks.

RESULTS

We observed 100% tumor formation with marked levels of neoplastic changes and altered the expression of apoptotic associated gene (p53, bcl-2, caspase-3 and TNF-α) was observed in the DMBA alone painted hamsters as compared to control hamsters. Oral administration of [6]-paradol at a dose of 30 mg/kg b.wt to DMBA treated animals on alternative days for 14 weeks significantly reduced the neoplastic changes and improved the status of apoptosis associated gene expression.

CONCLUSION

These observations confirmed that [6]-paradol acts as a tumor suppressing agent against DMBA induced oral carcinogenesis. We also conclude that [6]-paradol also effectively enhances apoptosis- associated gene expression in DMBA treated animals.

5-AED enhances survival of irradiated mice in a G-CSF-dependent manner, stimulates innate immune cell function, reduces radiation-induced DNA damage and induces genes that modulate cell cycle progression and apoptosis

The steroid androst-5-ene-3ß,17ß-diol (5-androstenediol, 5-AED) elevates circulating granulocytes and platelets in animals and humans, and enhances survival during the acute radiation syndrome (ARS) in mice and non-human primates. 5-AED promotes survival of irradiated human hematopoietic progenitors in vitro through induction of Nuclear Factor-κB (NFκB)-dependent Granulocyte Colony-Stimulating Factor (G-CSF) expression, and causes elevations of circulating G-CSF and interleukin-6 (IL-6). However, the in vivo cellular and molecular effects of 5-AED are not well understood. The aim of this study was to investigate the mechanisms of action of 5-AED administered subcutaneously (s.c.) to mice 24 h before total body γ- or X-irradiation (TBI). We used neutralizing antibodies, flow cytometric functional assays of circulating innate immune cells, analysis of expression of genes related to cell cycle progression, DNA repair and apoptosis, and assessment of DNA strand breaks with halo-comet assays. Neutralization experiments indicated endogenous G-CSF but not IL-6 was involved in survival enhancement by 5-AED. In keeping with known effects of G-CSF on the innate immune system, s.c. 5-AED stimulated phagocytosis in circulating granulocytes and oxidative burst in monocytes. 5-AED induced expression of both bax and bcl-2 in irradiated animals. Cdkn1a and ddb1, but not gadd45a expression, were upregulated by 5-AED in irradiated mice. S.c. 5-AED administration caused decreased DNA strand breaks in splenocytes from irradiated mice. Our results suggest 5-AED survival enhancement is G-CSF-dependent, and that it stimulates innate immune cell function and reduces radiation-induced DNA damage via induction of genes that modulate cell cycle progression and apoptosis.

The chemoadjuvant potential of grape seed procyanidins on p53-related cell death in oral cancer cells

BACKGROUND

To clarify the efficacy of grape seed procyanidin (GSP) on antiproliferative effects related to p53 functional status of oral squamous cell carcinoma (OSCC) for its chemoadjuvant potential.

METHODS

We used GSP to investigate SCC-25 cells with wild-type p53 gene and OEC-M1 cells with mutant p53 gene for the assessment of antiproliferative effects including cell viability, cell cycle, apoptosis, migration and invasion potential, and alterations of associated oncoproteins involved in cellular and molecular events.

RESULTS

The findings suggest that GSP on OEC-M1 cells leads to cell cycle arrest by increasing the expression of p21(Cip1) /p27(Kip1) protein without functioning mitochondria-mediated apoptosis, whereas GSP on SCC-25 cells inhibits cell proliferation via both G1-phase arrest and mitochondria-mediated apoptosis in a dose-dependent manner as a result of alterations of Bcl-2. GSP also inhibits the migration and invasion of both cells, which are associated with the suppression of matrix metalloproteinases (MMPs), MMP-2 and MMP-9.

CONCLUSION

Antiproliferative effectiveness of GSP is closely associated with the p53 status of OSCC cells. GSP displays chemoadjuvant potential via cell cycle blockage and apoptotic induction. Our findings clearly suggest that GSP may play a role as a novel chemopreventive or therapeutic agent for OSCC.

Overexpression of the human ubiquitin E3 ligase CUL4A alleviates hypoxia-reoxygenation injury in pheochromocytoma (PC12) cells

The ubiquitin E3 ligase CUL4A plays important roles in diverse cellular processes including carcinogenesis and proliferation. It has been reported that the expression of CUL4A can be induced by hypoxic-ischemic injury. However, the effect of elevated expression of CUL4A on hypoxia-reoxygenation injury is currently unclear. In this study, human CUL4A (hCUL4A) was expressed in rat pheochromocytoma (PC12) cells using adenoviral vector-mediated gene transfer, and the effects of hCUL4A expression on hypoxia-reoxygenation injury were investigated. In PC12 cells subjected to hypoxia and reoxygenation, we found that hCUL4A suppresses apoptosis and DNA damage by regulating apoptosis-related proteins and cell cycle regulators (Bcl-2, caspase-3, p53 and p27); consequently, hCUL4A promotes cell survival. Taken together, our results reveal the beneficial effects of hCUL4A in PC12 cells upon hypoxia-reoxygenation injury.

The labdane diterpene sclareol (labd-14-ene-8, 13-diol) induces apoptosis in human tumor cell lines and suppression of tumor growth in vivo via a p53-independent mechanism of action

The labdane diterpene sclareol has demonstrated significant cytotoxicity against human tumor cell lines and human colon cancer xenografts. Therefore, there is need to elucidate the mode of action of this compound as very little information is known for the anticancer activity of sclareol and other labdane diterpenes, in general. COMPARE analysis of GI(50) values for a number of human cancer cell lines was initially implicated in an effort to assign a putative mechanism of action to the compound. Sclareol-induced cell cycle arrest and apoptosis were assessed by flow cytometry and Western blot analyses. Finally, the anticancer ability of sclareol in vivo was assessed by using human colon cancer xenograft/mouse models. Sclareol arrested in vitro the growth of p53-deficient (HCT116(p53-/-)) human colon cancer cells and subsequently induced apoptosis by activating both caspases-8 and -9. Intraperitoneal administration of liposome-encapsulated sclareol at the maximum tolerated dose induced a marked growth suppression of HCT116(p53-/-) tumors established as xenografts in immunodeficient NOD/SCID mice. In conclusion, we demonstrate herein that sclareol kills human tumor cells by inducing arrest at the G(1)-phase of the cell cycle followed by apoptosis that involves activation of caspases-8, -9 and -3 via a p53-independent mechanism. These findings suggest that liposome-encapsulated sclareol possesses chemotherapeutic potential for the treatment of colorectal and other types of human cancer regardless of the p53-status.

Pseudomonas aeruginosa exotoxin A reduces chemoresistance of oral squamous carcinoma cell via inhibition of heat shock proteins 70 (HSP70)

PURPOSE

Oral squamous carcinoma (OSCC) cells exhibit resistance to chemotherapeutic agent-mediated apoptosis in the late stage of malignancy. Increased levels of heat shock proteins 70 (HSP70) in cancer cells are known to confer resistance to apoptosis. Since recent advances in the understanding of bacterial toxins have produced new strategies for the treatment of cancers, we investigated the effect of Pseudomonas aeruginosa exotoxin A (PEA) on HSP70 expression and induction of apoptosis in chemoresistant OSCC cell line (YD-9).

MATERIALS AND METHODS

The apoptotic effect of PEA on chemoresistant YD-9 cells was confirmed by MTT, Hoechst and TUNEL stains, DNA electrophoresis, and Western blot analysis.

RESULTS

While YD-9 cells showed high resistance to chemotherapeutic agents such as etoposide and 5-fluorouraci (5-FU), HSP70 antisense oligonucelotides sensitized chemoresistant YD-9 cells to etoposide and 5-FU. On the other hand, PEA significantly decreased the viability of YD-9 cells by deteriorating the HSP70-relating protecting system through inhibition of HSP70 expression and inducing apoptosis in YD-9 cells. Apoptotic manifestations were evidenced by changes in nuclear morphology, generation of DNA fragmentation, and activation of caspases. While p53, p21, and E2F-1 were upregulated, cdk2 and cyclin B were downregulated by PEA treatment, suggesting that PEA caused cell cycle arrest at the G2/M checkpoint.

CONCLUSION

Therefore, these results indicate that PEA reduced the chemoresistance through inhibition of HSP70 expression and also induced apoptosis in chemoresistant YD-9 cells.

Biological Differences between Fibroblasts Derived from Peripheral and Central Areas of Keloid Tissues

BACKGROUND

Clinical observations indicate that the bulging and reddish peripheral areas of keloids are more elevated than their central areas. Moreover, the peripheral areas of keloids undergo aggressive growth and invasion into normal skin, beyond the boundaries of the initial wound. The aim of this study was to investigate the biological differences between peripheral and central keloid areas.

METHODS

Six patients suffering from keloids on the anterior chest were selected for this study. Fibroblasts were harvested from both central and peripheral keloid areas. Cell cycle distribution and apoptosis induction were analyzed by flow cytometry and with an antibody to Fas. The expression of apoptosis-related proteins (Fas, Bcl-2, and p53) was measured by flow cytometry.

RESULTS

Fibroblasts derived from both central and peripheral parts of keloids displayed significant resistance to Fas-mediated apoptosis. Analysis of cell cycle distribution indicated that approximately 60 percent of fibroblasts derived from the peripheral parts of keloids were in the proliferative periods of the cell cycle (G2 and S phase). However, the majority of fibroblasts derived from keloid centers were in G0 or G1 phase. Fas and Bcl-2 expression did not differ significantly between the two groups, but p53 expression was much higher in fibroblasts derived from central parts than from peripheral parts.

CONCLUSION

It is suggested that differences in cell cycle distribution and p53 protein expression may account for the different growth characteristics of keloid peripheries and centers.

Loss of p53 expression correlates with metastatic phenotype and transcriptional profile in a new mouse model of head and neck cancer

Squamous cell carcinoma of the head and neck (HNSCC) is the sixth most frequent cancer worldwide. Because HNSCC is largely acquired by environmental carcinogen exposure rather than through germ line mutations, there are no known familial forms of the disease in humans nor are there inbred rodent strains prone to spontaneous head and neck tumors. Transgenic animals with inactivation of tumor suppressor genes commonly mutated in human cases of HNSCC provide attractive models for studying the pathogenesis of head and neck cancer. p53 is the most frequently inactivated tumor suppressor gene in HNSCC. We used a chemical induction protocol in mice heterozygous for the p53 gene to evaluate how p53 inactivation contributed to head and neck carcinogenesis the mouse model. Metastatic squamous cell carcinomas developed in 100% of animals. Histopathologically, the tumors ranged from well to poorly differentiated and showed many molecular features of human HNSCC. Mice carrying only one p53 allele developed tumors with significantly reduced latency compared with wild-type controls (average, 18 versus 22 weeks). Metastatic cancer cells showed complete loss of p53 expression when compared with primary tumors. Transcriptional profiling showed not only distinct genetic differences between primary and metastatic tumors, but also when cancers from heterozygous null and wild-type animals were compared. Our results provide novel insights into the molecular genetics of tumor progression in head and neck cancer.