Involvement of PPARγ in the antitumoral action of cannabinoids on hepatocellular carcinoma

Cannabinoids exert antiproliferative effects in a wide range of tumoral cells, including hepatocellular carcinoma (HCC) cells. In this study, we examined whether the PPARγ-activated pathway contributed to the antitumor effect of two cannabinoids, Δ9-tetrahydrocannabinol (THC) and JWH-015, against HepG2 and HUH-7 HCC cells. Both cannabinoids increased the activity and intracellular level of PPARγ mRNA and protein, which was abolished by the PPARγ inhibitor GW9662. Moreover, genetic ablation with small interfering RNA (siRNA), as well as pharmacological inhibition of PPARγ decreased the cannabinoid-induced cell death and apoptosis. Likewise, GW9662 totally blocked the antitumoral action of cannabinoids in xenograft-induced HCC tumors in mice. In addition, PPARγ knockdown with siRNA caused accumulation of the autophagy markers LC3-II and p62, suggesting that PPARγ is necessary for the autophagy flux promoted by cannabinoids. Interestingly, downregulation of the endoplasmic reticulum stress-related protein tribbles homolog 3 (TRIB3) markedly reduced PPARγ expression and induced p62 accumulation, which was counteracted by overexpression of PPARγ in TRIB3-knocked down cells. Taken together, we demonstrate for the first time that the antiproliferative action of the cannabinoids THC and JWH-015 on HCC, in vitro and in vivo, are modulated by upregulation of PPARγ-dependent pathways.     

Is there a real risk of radiation-induced breast cancer for postmenopausal women?

The risk of radiation-induced breast cancer decreases with increasing age at exposure. Thus, for calculating the individual risk for a patient undergoing mammography, age-related risk coefficients need to be used. In this report, the results of epidemiological studies on risks of radiation-induced breast cancer are reviewed indicating that the available data do not show the risk to be enhanced for women exposed at the age of 55 years or older. This lack of evidence is reflected by the fact that the risk coefficients recommended by national and international advisory bodies differ by a factor of 10 or more for age at exposure of 50–60 years or older. A hypothesis is proposed indicating that the risk of radiation-induced breast cancer might decrease considerably at the time of menopause. The hypothesis is based on the following line of arguments: (1) evidence has accumulated from molecular genetic studies indicating that the development of colorectal cancer requires a cascade of subsequent mutations consisting of at least seven genetic events. (2) For colorectal cancer, the annual rates of incidence and mortality increase with age to the power of 5–6. Thus, the number of mutation steps (minus 1) is approximately reflected by the power of age dependence. (3) For western populations, the incidence and mortality of breast cancer up to the age of about 50 years increase with age to the power of about 6, indicating that a similar number of genetic events might be involved in development of breast cancer as has been identified for colorectal cancer. (4) For women aged 50 years or older, breast cancer occurs at an annual rate that is about proportional to age or age squared. This may mean that after menopause, the processes in the multistep mutation cascade leading to breast cancer are slowed down by a factor of about 4 or more. (5) The constant relative risk model of radiation carcinogenesis implies for solid cancers that radiation acts by inducing additional mutations in the earlier steps of the multistep cascade. It is suggested that the break-point in the age-specific annual rate of breast cancer incidence at menopause is associated with a corresponding drop in radiation sensitivity with respect to induction of breast cancer. Received: 8 January 2001 / Accepted: 20 March 2001     

Identification of miR-200a as a novel suppressor of connexin 43?in breast cancer cells

Both miRNAs (miRs) and connexin 43 (Cx43) were important regulators of the metastasis of breast cancer, whereas the miRs regulating Cx43 expression in breast cancer cells were still obscure. In the present study, we scanned and found miR-1, miR-206, miR-200a, miR-381, miR-23a/b and miR-186 were functional suppressors of human Cx43 mRNA and protein expression. Specially, we demonstrated that only miR-200a could directly target the 3′-untranslated region (3′-UTR) of human Cx43 gene. Functionally, overexpression of Cx43 in MCF cells potentiated the migration activity, whereas additional miR-200a treatment notably prevented this effect. Finally, we demonstrated that decreased levels of miR-200a and elevated expression of Cx43 in the metastatic breast cancer tissues compared with the primary ones. Thus, we are the first to identify miR-200a as a novel and direct suppressor of human Cx43, indicating that miR200a/Cx43 axis might be a useful diagnostic and therapeutic target of metastatic breast cancer.     

Simultaneous dual targeting of Par-4 and G6PD: a promising new approach in cancer therapy? Quintessence of a literature review on survival requirements of tumor cells

The aim of this hypothesis is to propose a new approach in targeted therapy of cancer: The simultaneous, dual targeting of two single molecules, Par-4 and G6PD, rather than inhibition of full-length signaling pathways. Rationale: Targeted inhibition of especially two survival signaling pathways (PI3K/AKT/mTOR and MAPK/ERK) is frequently tried, however, a major breakthrough has not yet been reported. Inhibition of complete pathways naturally goes along with a variety of dose-limiting side effects thus contributing to poor efficacy of the administered drugs. This essay offers a synopsis of relevant studies to support the above mentioned idea—targeting of two single molecules which either are crucial for tumor growth and cancer-cell-survival: on one side, Par-4-activation selectively triggers apoptosis of tumor cells thus reversing their characteristic feature—immortality. On the other side inhibition of G6PD breaks the energy supply of tumor cells, weakens their defence against oxidative stress and thereby enhances the sensitivity of tumor cells to oxidative agents (e.g. chemotherapy). Advantage of the proposed dual Par-4/G6PD-therapy is good tolerability and—especially when administered along with conventional therapy—less frequent emergence of resistance.     

The synthesis and anticancer effects of a range of natural and unnatural hop β-acids on breast cancer cells

The β-acids derived from hops (Humulus lupulus L.) are polyphenols classified as lupulones. As part of our on-going interest in the pharmacognosy of these natural products we were keen to investigate the anticancer activity of lupulone 1 as well as individual lupulone congeners. To achieve this we undertook the synthesis of natural as well as unnatural lupulone derivatives and evaluated them for their anticancer activity against the breast cancer cell lines MCF-7 and MDA-MB-231.The results of our investigations revealed that all of the novel unnatural lupulone derivatives that were synthesised were found to be more toxic to MDA-MB-231 cell lines at 72 h than the parent lupulone 1 itself (except for the α-substituent R¹ was CH₃). Further investigations confirmed that the novel lupulone derivatives were very efficient at killing cancer cells by apoptosis but appear to do so in a time-dependant process. This outcome may be of great significance as MDA-MB-231 cell lines are characterised by an aggressive phenotype with a propensity to invade other tissue, to form metastases as well as an ability to become insensitive to chemotherapeutic agents.     

Lack of association between stretch-activated and volume-activated Cl⁻ currents in hepatocellular carcinoma cells

Stretch-activated chloride currents (I(Cl,SA) ) have been considered to be a component of volume-activated chloride currents (I(Cl,vol) ) for some time. This is due to a similarity in biophysical and pharmacological properties that involve a membrane curvature-induced mechanism and rearrangement of the cytoskeleton induced by cell swelling or membrane stretch. In the present study, we demonstrated that current density, along with the time taken from the activation of currents to the peak, were significantly different between the two currents, in highly metastatic human hepatocellular carcinoma cells. In addition, the activation of I(Cl,vol) or I(Cl,SA), induced maximally by hypotonic solutions or membrane stretch, respectively, did not affect the following activation of the other one. Moreover, neither inhibition of I(Cl,vol) by sh-ClC-3 transfection, nor functional blocking of I(Cl,vol) by intracellular dialysis of anti-ClC-3 antibody had an effect on the activation and properties of I(Cl,SA). Collectively, our results suggest that I(Cl,SA) is different from I(Cl,vol) in activation mechanism and/or in molecular entity responsible for formation of the currents. ClC-3 is involved in the activation of I(Cl,vol), but not of I(Cl,SA).     

Cytohistologic correlation of cirrhosis and hepatocellular carcinoma. Pitfall in diagnosis?

OBJECTIVE: To compare the diagnostic criteria for cirrhosis and hepatocellular carcinoma (HCC) noted on liver fine needle aspirates (FNAs) and their corresponding liver needle core biopsies (NCBs). STUDY DESIGN: We reviewed FNA slides from 15 cases of cirrhosis and 6 cases of HCC and their corresponding NCBs. We compared a variety of specific nonarchitectural criteria, including small cell dysplasia (SCD) and large cell dysplasia (LCD), for distinguishing cirrhosis from HCC. RESULTS: FNA smears diagnostically correlated with NCBs. The cytologic criterion with the greatest correlation in predicting HCC on FNA was SCD. This was not noted in all the core biopsies, probably due to sampling error. LCD was seen more frequently in cirrhosis than HCC on both cytology and histology and therefore was not a criterion useful in establishing a diagnosis of malignancy. The remaining cytologic criteria had good correlations but did not aid in diagnosing HCC. CONCLUSION: FNA has good cytohistologic correlation with NCB for both cirrhosis and HCC. There is an association of SCD with HCC; however, LCD is not a reliable "precancerous" change as it is commonly seen in cirrhosis and HCC. Therefore, the presence of SCD on FNA should be reported and is an indication for close clinical follow-up to exclude HCC.     

Combined anti-tumor effects of IFN-α and sorafenib on hepatocellular carcinoma in vitro and in vivo

Hepatocellular carcinoma (HCC) is among the most common and aggressive cancers worldwide, and novel therapeutic strategies are urgently required to improve clinical outcome. Interferon-alpha (IFN-α) and sorafenib are widely used as anti-tumor agents against various malignancies. In this study, we investigated the combined effects of IFN-α and sorafenib against HCC. We demonstrated that the combination therapy synergistically suppressed HCC cellular viability, arrested cell cycle propagation and induced apoptosis in HCC cells. Further research revealed that IFN-α and sorafenib collaboratively regulated the expression levels of cell cycle-related proteins Cyclin A and Cyclin B as well as the pro-survival Bcl-2 family proteins Mcl-1, Bcl-2 and Bcl-X(L). Moreover, sorafenib inhibited IFN-α induced oncogenic signaling of STAT3, AKT and ERK but not the activation of the tumor suppressor STAT1. Xenograft experiments also confirmed the combined effects of IFN-α and sorafenib on tumor growth inhibition and apoptosis induction in vivo. In conclusion, these results provide rationale for the clinical application of IFN-α and sorafenib combination therapy in HCC treatment.     

Heritability of cellular radiosensitivity: a marker of low-penetrance predisposition genes in breast cancer?

Many inherited cancer-prone conditions show an elevated sensitivity to the induction of chromosome damage in cells exposed to ionizing radiation, indicative of defects in the processing of DNA damage. We earlier found that 40% of patients with breast cancer and 5%-10% of controls showed evidence of enhanced chromosomal radiosensitivity and that this sensitivity was not age related. We suggested that this could be a marker of cancer-predisposing genes of low penetrance. To further test this hypothesis, we have studied the heritability of radiosensitivity in families of patients with breast cancer. Of 37 first-degree relatives of 16 sensitive patients, 23 (62%) were themselves sensitive, compared with 1 (7%) of 15 first-degree relatives of four patients with normal responses. The distribution of radiosensitivities among the family members showed a trimodal distribution, suggesting the presence of a limited number of major genes determining radiosensitivity. Segregation analysis of 95 family members showed clear evidence of heritability of radiosensitivity, with a single major gene accounting for 82% of the variance between family members. The two alleles combine in an additive (codominant) manner, giving complete heterozygote expression. A better fit was obtained to a model that includes a second, rarer gene with a similar, additive effect on radiosensitivity, but the data are clearly consistent with a range of models. Novel genes involved in predisposition to breast cancer can now be sought through linkage studies using this quantitative trait.     

RNA-binding protein Dnd1 inhibits epithelial–mesenchymal transition and cancer stem cell-related traits on hepatocellular carcinoma cells

Objectives

To investigate the roles of Dead end 1 (Dnd1) in modulating cancer stem cell-related traits of hepatocellular carcinoma (HCC).

Results

Dead end (Dnd1) inhibited spheroid formation, suppressed the expression of stemness-related genes, and increased sensitivity to sorafenib in HCC cells. Mechanistically, Dnd1 could bind to 3′-UTR of LATS2, the key kinase of Hippo pathway, thus elevating LATS2 mRNA stability and its expression, subsequently leading to phosphorylation of YAP and its cytoplasmic retention. As a result, epithelial–mesenchymal transition (EMT) was weakened and therefore the generation of HCC stem cell properties was suppressed.

Conclusions

Dnd1 functions as a tumor suppressor by prohibiting CSC-like characteristics via activating Hippo pathway in HCC cells. Dnd1 could thus be a novel therapeutic target for HCC patients.

     

LOH-proficient embryonic stem cells: a model of cancer progenitor cells?

Cancers are thought to originate in stem cells through the accumulation of multiple mutations. Some of these mutations result in a loss of heterozygosity (LOH). A recent report demonstrates that exposure of mouse embryonic stem cells to nontoxic amounts of mutagens triggers a marked increase in the frequency of LOH. Thus, mutagen induction of LOH in embryonic stem cells suggests a new pathway to account for the multiple homozygous mutations in human tumors. This induction could mimic early mutagenic events that generate cancers in human tissue stem cells.     

Down-regulation of ζ-chain expression in T cells: a biomarker of prognosis in cancer?

The chain is a 16-kDa molecule associated with the T-cell receptor (TCR)-CD3 complex in T lymphocytes and FcRIII in CD3^–CD56⁺CD16⁺ natural killer (NK cells). The chain functions as a transmembrane signaling molecule in lymphocytes. Expression of was found to be decreased in CD4⁺ and CD8⁺ T lymphocytes isolated from the tumor site or from the peripheral circulation of patients with cancer. A quantitative flow cytometry–based assay for -chain expression allows for reproducible serial evaluations of disease- or therapy-associated changes in expression of this signaling molecule in phenotypically defined subsets of immune cells. Semiquantitative evaluation of expression in paraffin-embedded tissue specimens can link it to the conventional markers of prognosis or survival. Several distinct mechanisms may be responsible for decreased/absent in T cells of patients with cancer. Monitoring for expression is useful for assessing immune competence in these patients and for following changes in immune competence during anticancer therapies. Correlations made between clinical findings, pathologic results, and expression in immune cells suggest that low/absent is predictive of poor prognosis and survival in patients with cancer. Thus, is emerging as a clinically relevant signaling molecule, which also seems to predict a favorable response to biologic therapies and could be helpful in a selection of patients for immunotherapy trials. Validation studies have yet to be performed for this putative immunologic biomarker. Its consistent use for monitoring under standardized conditions of cancer patients treated with biotherapies may help in confirming a role for as a correlate of prognosis or survival.This article forms part of the Symposium in Writing Tumor escape from the immune response, published in Vol. 53.     

Synchronous bilateral breast cancer patients submitted to conservative treatment and brachytherapy – The experience of a service

Introduction

The incidence of breast carcinoma (BC) has increased in the last years. Between 2 and 12% of patients diagnosed with BC will develop bilateral breast carcinoma (BBC). The treatment of these carcinomas is more aggressive than unilateral BC.