Somatic, gain-of-function mutations in ras genes were the first specific genetic alterations identified in human cancer about 3 decades ago. Studies during the last quarter century have characterized the Ras proteins as essential components of signaling networks controlling cellular proliferation, differentiation, or survival. The oncogenic mutations of the H-ras, N-ras, or K-ras genes frequently found in human tumors are known to throw off balance the normal outcome of those signaling pathways, thus leading to tumor development. Oncogenic mutations in a number of other upstream or downstream components of Ras signaling pathways (including membrane RTKs or cytosolic kinases) have been detected more recently in association with a variety of cancers. Interestingly, the oncogenic Ras mutations and the mutations in other components of Ras/MAPK signaling pathways appear to be mutually exclusive events in most tumors, indicating that deregulation of Ras-dependent signaling is the essential requirement for tumorigenesis. In contrast to sporadic tumors, separate studies have identified germline mutations in Ras and various other components of Ras signaling pathways that occur in specific association with a number of different familial, developmental syndromes frequently sharing common phenotypic cardiofaciocutaneous features. Finally, even without being a causative force, defective Ras signaling has been cited as a contributing factor to many other human illnesses, including diabetes and immunological and inflammatory disorders. We aim this review at summarizing and updating current knowledge on the contribution of Ras mutations and altered Ras signaling to development of various tumoral and nontumoral pathologies.

/pdf/ras-in-cancer-and-developmental-diseases-575bykpvjv.pdf

Ras in cancer and developmental diseases.

The greater incidence of hypertension and coronary artery disease in men and postmenopausal women compared with premenopausal women has been related, in part, to gender differences in vascular tone and possible vascular protective effects of the female sex hormones estrogen and progesterone. However, vascular effects of the male sex hormone testosterone have also been suggested. Estrogen, progesterone, and testosterone receptors have been identified in blood vessels of human and other mammals and have been localized in the plasmalemma, cytosol, and nuclear compartments of various vascular cells, including the endothelium and the smooth muscle. The interaction of sex hormones with cytosolic/nuclear receptors triggers long-term genomic effects that could stimulate endothelial cell growth while inhibiting smooth muscle proliferation. Activation of plasmalemmal sex hormone receptors may trigger acute nongenomic responses that could stimulate endothelium-dependent mechanisms of vascular relaxation such as the nitric oxide-cGMP, prostacyclin-cAMP, and hyperpolarization pathways. Additional endothelium-independent effects of sex hormones may involve inhibition of the signaling mechanisms of vascular smooth muscle contraction such as intracellular Ca2+ concentration and protein kinase C. The sex hormone-induced stimulation of the endothelium-dependent mechanisms of vascular relaxation and inhibition of the mechanisms of vascular smooth muscle contraction may contribute to the gender differences in vascular tone and may represent potential beneficial vascular effects of hormone replacement therapy during natural and surgically induced deficiencies of gonadal hormones.

Gender, Sex Hormones, and Vascular Tone

The exact function of HBx during HBV replication and its influence in HBV-associated hepatocellular carcinoma are still undefined, but common themes are emerging. Most studies agree that, if not absolutely essential for HBV infections, HBx at the very least plays a critical role in viral replication. HBx functions in the cytoplasm to activate various signaling pathways, many of which are controlled by modulation of cytosolic calcium. A number of groups have now demonstrated that HBx activities somehow involve modulation of cytosolic calcium, although the exact molecular mechanism is undefined. In the nucleus, HBx can regulate transcription through a direct interaction with different transcription factors and, in some cases, enhance their binding to specific transcription elements. Clearly, HBx can influence apoptotic and cell cycle regulatory pathways, but the exact consequences of these activities of HBx are likely affected by the cell types in which the studies have been conducted. In this regard, it is interesting to note that much of the seeming confusion or controversy regarding HBx activities is likely the result of the different assays performed, and the findings of different studies may ultimately be more compatible than expected. In most experiments, HBx activities have been analyzed based on the end product of what are long and complex pathways. For example, transcriptional reporter readout, apoptotic assays, cell cycle regulation, and mutagenic studies are judged based on an analysis of the final product of a given pathway without considering common effectors. HBx may initiate overlapping and very similar effectors in all the studies conducted, but the consequence of this will likely vary depending on the specific cellular phenotype and the assay involved. Moreover, the frequency or longevity of this stimulus may vary depending on the amount of HBx present, which in turn influences the results. Fluctuations in the frequency or longevity of a HBx-induced stimulus, such as calcium signaling, can have a dramatic influence on the final effect on a cell (reviewed in reference 19). Equally interesting is the possibility that HBx has different consequences for hepatocyte physiology as HBV-infected cells are targeted by the immune system or as hepatocytes in which HBx is expressed undergo transformation and progression to HCC. Both these processes are dynamic, and it is likely that cellular physiology is consequently altered. The demonstration that different signaling pathways can be activated based on the differentiation state of hepatocytes derived from the same parental cell line and suggestions that the cellular status of p53, p21, and p27 can affect HBx-dependent regulation of cell cycle control supports the notion that the consequence of HBx expression may change as hepatocytes become transformed (2, 62, 93). It remains to be determined whether similar results will be observed in the context of an authentic HBV infection. Such observations will add to the complexity of identifying and understanding the precise molecular mechanism of HBx activities during viral replication. However, there is the exciting possibility that the end product of HBx activities may change as the cell responds to the infection. Finally, studies of HBx activities during HBV replication should help clarify the many properties that have been ascribed to HBx expression, including those that are required for viral replication and those that may influence cellular transformation.

https://jvi.asm.org/content/jvi/78/23/12725.full.pdf

The Enigmatic X Gene of Hepatitis B Virus

Molecular bases for the development of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC).

The authors present sexual dimorphism at the molecular, cellular and tissue level and suggest that it contributes to differences in disease onset, susceptibility, prevalence and treatment responses in hypertension and cardiovascular disease. Several factors that confer relative cardioprotection in women are discussed, including biological age, sex hormones, sex chromosome complement and lifestyle. Although intrinsic mechanisms that regulate arterial blood pressure (BP) are similar in men and women, marked variations exist at the molecular, cellular and tissue levels. These physiological disparities between the sexes likely contribute to differences in disease onset, susceptibility, prevalence and treatment responses. Key systems that are important in the development of hypertension and cardiovascular disease (CVD), including the sympathetic nervous system, the renin–angiotensin–aldosterone system and the immune system, are differentially activated in males and females. Biological age also contributes to sexual dimorphism, as premenopausal women experience a higher degree of cardioprotection than men of similar age. Furthermore, sex hormones such as oestrogen and testosterone as well as sex chromosome complement likely contribute to sex differences in BP and CVD. At the cellular level, differences in cell senescence pathways may contribute to increased longevity in women and may also limit organ damage caused by hypertension. In addition, many lifestyle and environmental factors — such as smoking, alcohol consumption and diet — may influence BP and CVD in a sex-specific manner. Evidence suggests that cardioprotection in women is lost under conditions of obesity and type 2 diabetes mellitus. Treatment strategies for hypertension and CVD that are tailored according to sex could lead to improved outcomes for affected patients.

Sex-specific differences in hypertension and associated cardiovascular disease

https://www.gastrojournal.org/article/S0016-5085(96)00225-9/pdf

Effect of hepatocyte proliferation and cellular DNA synthesis on hepatitis B virus replication

The insulin-like growth factor axis, which has been shown to protect cells from apoptosis, plays an essential role in normal cell physiology and in cancer development. The family of insulin-like growth factor binding proteins (IGFBPs) has been shown to have a diverse spectrum of functions in cell growth, death, motility, and tissue remodeling. Among the six IGFBP family members, IGFBP-5 has recently been shown to play an important role in the biology of breast cancer, especially in breast cancer metastasis; however, the exact mechanisms of action remain obscure and sometimes paradoxical. An in-depth understanding of IGFBP-5 would shed light on its potential role as a target for breast cancer therapeutics.

/pdf/multifunctional-roles-of-insulin-like-growth-factor-binding-1ww7xl693u.pdf

Multifunctional roles of insulin-like growth factor binding protein 5 in breast cancer

Objective: In this study the role of 17β-estradiol (E2) in the regulation of endothelin-1 (ET-1) mRNA expression and secretion was investigated in cultured human umbilical vein endothelial cells (HUVECs). Methods: Endothelial cells were either deprived of or treated with 17β-estradiol (10−9, 10−7 M) for 48 h. After the incubation, the effect of E2 on ET-1 gene expression was evaluated by Northern blot analysis. ET-1 release into the media was measured by radioimmunoassay after 6 h of incubation under basal conditions and upon stimulation with thrombin (4 U/ml). In addition, the cyclic guanosine 5′-monophosphate (cGMP) content of cells was assayed by immunoassay. In order to exclude the role of nitric oxide (NO) in E2-induced effects on endothelin-1 gene expression and secretion, nitric oxide synthase (NOS) inhibitor, N -nitro l-arginine methyl ester (1 mM) (l-NAME) was added to the media of some cultures. Results: Incubation of HUVECs with 10−9 and 10−7 M E2 for 48 h resulted in a 30 and 47% inhibition of ET-1 mRNA expression, respectively. Incubation with E2 also decreased the basal and thrombin-stimulated ET-1 release while increasing the cGMP content of cells significantly. NOS inhibitor l-NAME increased the release of ET-1 from E2-incubated cells but did not alter the ET-1 release from hormone-deprived cells. However, ET-1 secretion of E2-treated cells were significantly less than the deprived ones. Northern blot analyses also demonstrated that inhibition of NOS only partly attenuated the effect of E2 on ET-1 gene expression. In the presence of l-NAME, treatment with 10−7 M E2 caused a 12% decrease in ET-1 gene expression. Conclusion: The results demonstrate that E2 may play both direct and indirect role in regulation of ET-1 gene expression and production in human endothelial cells. E2-induced increase in NO but decrease in ET-1 production may partly explain the mechanism of the protective effects of the hormone on the cardiovascular system.

17β-Estradiol modulates endothelin-1 expression and release in human endothelial cells

Breast cancer (BCa) is the most common cancer and the second cause of death among women. Phosphoinositide 3-kinase (PI3K) signaling pathway has a crucial role in the cellular processes such as cell survival, growth, division, and motility. Moreover, oncogenic mutations in the PI3K pathway generally involve the activation phosphatidylinositol-4,5-bisphosphate 3-kinase-catalytic subunit alpha (PIK3CA) mutation which has been identified in numerous BCa subtypes. In this review, correlations between PIK3CA mutations and their clinicopathological parameters on BCa will be described. It is reported that PIK3CA mutations which have been localized mostly on exon 9 and 20 hot spots are detected 25-40 % in BCa. This relatively high frequency can offer an advantage for choosing the best treatment options for BCa. PIK3CA mutations may be used as biomarkers and have been major focus of drug development in cancer with the first clinical trials of PI3K pathway inhibitors currently in progress. Screening of PIK3CA gene mutations might be useful genetic tests for targeted therapeutics or diagnosis. Increasing data about PIK3CA mutations and its clinical correlations with BCa will help to introduce new clinical applications in the near future.

Mutation distributions and clinical correlations of PIK3CA gene mutations in breast cancer.

BACKGROUND AND AIMS Genetic alterations of p53, K-ras and DCC genes have a pivotal role in the colorectal cancer progression. The aim of this study was to clarify the association between K-ras mutations, p53 aberrations and DCC loss of heterozygosity (LOH), with the patient outcome and tumor characteristics in 43 stage I-II colorectal cancer patients. METHODS Mutations in exons 5-8 of the p53 gene and codon 12 and/or 13 of the K-ras gene were assayed by PCR-SSCP and then confirmed by DNA sequencing. DCC LOH was studied by PCR-RFLP, while p53 immunohistochemistry was also made. RESULTS Mutations of the p53 gene were found in 14 (32.5%) tumors. Five (12%) cases showed mutation of the K-ras gene. Nuclear staining of p53 was found in 22 (51 %) cases. DCC LOH was found in 5 (12%) cases. Cases with guanine to thymine substitution that occurred in K-ras codon 12 and DCC LOH were found to be more aggressive than other cases with codon 12 mutations or DCC wild-type phenotype. Many tumors with p53 over-expression were localized on the left side of the colon (p=0.005). The stage of the tumor was higher in patients who died during the follow-up period, when compared to the ones who have survived. CONCLUSIONS Although none of these genetic alterations showed a significant prognostic value, specific mutation of K-ras gene and DCC LOH phenotype might have a predictive prognostic implication in colorectal cancer. Furthermore, different etiopathogenetic mechanisms might be involved in the tumorigenesis of the left and right colon.

Ayşe Özer

Papers

Effect of hepatocyte proliferation and cellular DNA synthesis on hepatitis B virus replication

Multifunctional roles of insulin-like growth factor binding protein 5 in breast cancer

17β-Estradiol modulates endothelin-1 expression and release in human endothelial cells

Mutation distributions and clinical correlations of PIK3CA gene mutations in breast cancer.

Clinical significance of p53, K-ras and DCC gene alterations in the stage I-II colorectal cancers.