Cancer radioresistance is characterized by a differential lipid droplet content along the cell cycle

BACKGROUND

Cancer radiation treatments have seen substantial advancements, yet the biomolecular mechanisms underlying cancer cell radioresistance continue to elude full understanding. The effectiveness of radiation on cancer is hindered by various factors, such as oxygen concentrations within tumors, cells' ability to repair DNA damage and metabolic changes. Moreover, the initial and radiation-induced cell cycle profiles can significantly influence radiotherapy responses as radiation sensitivity fluctuates across different cell cycle stages. Given this evidence and our prior studies establishing a correlation between cancer radiation resistance and an increased number of cytoplasmic Lipid Droplets (LDs), we investigated if LD accumulation was modulated along the cell cycle and if this correlated with differential radioresistance in lung and bladder cell lines.

RESULTS

Our findings identified the S phase as the most radioresistant cell cycle phase being characterized by an increase in LDs. Analysis of the expression of perilipin genes (a family of proteins involved in the LD structure and functions) throughout the cell cycle also uncovered a unique gene cell cycle pattern.

CONCLUSIONS

In summary, although these results require further molecular studies about the mechanisms of radioresistance, the findings presented here are the first evidence that LD accumulation could participate in cancer cells' ability to better survive X-Ray radiation when cells are in the S phase. LDs can represent new players in the radioresistance processes associated with cancer metabolism. This could open new therapeutic avenues in which the use of LD-interfering drugs might enhance cancer sensitivity to radiation.

Radio-resistance of hypoxic tumors: exploring the effects of oxygen and x-ray radiation on non-small lung cancer cell lines

BACKGROUND

Solid tumors are often riddled with hypoxic areas, which develops as a result of high proliferation. Cancer cells willingly adapt and thrive in hypoxia by activating complex changes which contributes to survival and enhanced resistance to treatments, such as photon radiation. Photon radiation primarily relies on oxygen for the production of reactive oxygen species to induce DNA damage. The present in-vitro study aimed at investigating the biochemical responses of hypoxic non-small cell lung cancer (NSCLC) cells, particularly the effects on the DNA damage repair systems contributing to more radioresistant phenotypes and their pro- and anti-oxidant potential, within the first 24 h post-IR.

METHODS

NSCLC cell lines (H460, A549, Calu-1) were irradiated using varying X-ray doses under normoxia (21% O₂) and hypoxia (0.1% O₂). The overall cell survival was assessed by clonogenic assays. The extent of irradiation (IR)-induced DNA damage was evaluated by analyzing γ-H2AX foci induction and the altered expression of repair genes involved in non-homologous end joining and homologous recombination pathways. Moreover, cell-altered responses were investigated, including the nuclear and cytosolic hydrogen peroxide (H₂O₂) production, as well as the associated anti-oxidant potential, in particular some components related to the glutathione system.

RESULTS

Analysis of clonogenic survival revealed an enhanced radioresistance of the hypoxic NSCLC cells associated with reduced DNA damage and a downregulation of DNA repair genes. Moreover, nuclear H₂O₂ levels were IR-induced in a dose-dependent manner only under normoxia, and directly correlated with the DNA double-strand breaks. However, the observed nuclear H₂O₂ reduction in hypoxia appeared to be unaffected by IR, thus highlighting a possible reason for the enhanced radioresistance of the hypoxic NSCLC cells. The cellular antioxidant capacity was upregulated by IR in both oxygen conditions most likely helping to counteract the radiation effect on the cytosolic H₂O₂.

CONCLUSIONS

In conclusion, our data provide insight into the adaptive behavior of radiation-resistant hypoxic NSCLC cells, in particular their DNA repair and oxidative stress responses, which could contribute to lower DNA damage and higher cell survival rates following X-ray exposure. These findings may therefore help to identify potential targets for improving cancer treatment outcomes.

Modulating Nucleus Oxygen Concentration by Altering Intramembrane Cholesterol Levels: Creating Hypoxic Nucleus in Oxic Conditions

We propose a novel mechanism by which cancer cells can modulate the oxygen concentration within the nucleus, potentially creating low nuclear oxygen conditions without the need of an hypoxic micro-environment and suited for allowing cancer cells to resist chemo- and radio-therapy. The cells ability to alter intra-cellular oxygen conditions depends on the amount of cholesterol present within the cellular membranes, where high levels of cholesterol can yield rigid membranes that slow oxygen diffusion. The proposed mechanism centers on the competition between (1) the diffusion of oxygen within the cell and across cellular membranes that replenishes any consumed oxygen and (2) the consumption of oxygen in the mitochondria, peroxisomes, endoplasmic reticulum (ER), etc. The novelty of our work centers around the assumption that the cholesterol content of a membrane can affect the oxygen diffusion across the membrane, reducing the cell ability to replenish the oxygen consumed within the cell. For these conditions, the effective diffusion rate of oxygen becomes of the same order as the oxygen consumption rate, allowing the cell to reduce the oxygen concentration of the nucleus, with implications to the Warburg Effect. The cellular and nucleus oxygen content is indirectly evaluated experimentally for bladder (T24) cancer cells and during the cell cycle, where the cells are initially synchronized using hydroxeaurea (HU) at the late G1-phase/early S-phase. The analysis of cellular and nucleus oxygen concentration during cell cycle is performed via (i) RT-qPCR gene analysis of hypoxia inducible transcription factors (HIF) and prolyl hydroxylases (PHD) and (ii) radiation clonogenic assay every 2 h, after release from synchronization. The HIF/PHD genes allowed us to correlate cellular oxygen with oxygen concentration in the nucleus that is obtained from the cells radiation response, where the amount DNA damage due to radiation is directly related to the amount of oxygen present in the nucleus. We demonstrate that during the S-phase cells can become hypoxic in the late S-phase/early G2-phase and therefore the radiation resistance increases 2- to 3-fold.

Lipid Droplet Biosynthesis Impairment through DGAT2 Inhibition Sensitizes MCF7 Breast Cancer Cells to Radiation

Breast cancer is the most frequent cancer in women worldwide and late diagnosis often adversely affects the prognosis of the disease. Radiotherapy is commonly used to treat breast cancer, reducing the risk of recurrence after surgery. However, the eradication of radioresistant cancer cells, including cancer stem cells, remains the main challenge of radiotherapy. Recently, lipid droplets (LDs) have been proposed as functional markers of cancer stem cells, also being involved in increased cell tumorigenicity. LD biogenesis is a multistep process requiring various enzymes, including Diacylglycerol acyltransferase 2 (DGAT2). In this context, we evaluated the effect of PF-06424439, a selective DGAT2 inhibitor, on MCF7 breast cancer cells exposed to X-rays. Our results demonstrated that 72 h of PF-06424439 treatment reduced LD content and inhibited cell migration, without affecting cell proliferation. Interestingly, PF-06424439 pre-treatment followed by radiation was able to enhance radiosensitivity of MCF7 cells. In addition, the combined treatment negatively interfered with lipid metabolism-related genes, as well as with EMT gene expression, and modulated the expression of typical markers associated with the CSC-like phenotype. These findings suggest that PF-06424439 pre-treatment coupled to X-ray exposure might potentiate breast cancer cell radiosensitivity and potentially improve the radiotherapy effectiveness.

Lipid droplets and ferritin heavy chain: a devilish liaison in human cancer cell radioresistance

Although much progress has been made in cancer treatment, the molecular mechanisms underlying cancer radioresistance (RR) as well as the biological signatures of radioresistant cancer cells still need to be clarified. In this regard, we discovered that breast, bladder, lung, neuroglioma, and prostate 6 Gy X-ray resistant cancer cells were characterized by an increase of lipid droplet (LD) number and that the cells containing highest LDs showed the highest clonogenic potential after irradiation. Moreover, we observed that LD content was tightly connected with the iron metabolism and in particular with the presence of the ferritin heavy chain (FTH1). In fact, breast and lung cancer cells silenced for the FTH1 gene showed a reduction in the LD numbers and, by consequence, became radiosensitive. FTH1 overexpression as well as iron-chelating treatment by Deferoxamine were able to restore the LD amount and RR. Overall, these results provide evidence of a novel mechanism behind RR in which LDs and FTH1 are tightly connected to each other, a synergistic effect that might be worth deeply investigating in order to make cancer cells more radiosensitive and improve the efficacy of radiation treatments.

Does FLASH deplete oxygen? Experimental evaluation for photons, protons, and carbon ions

PURPOSE

To investigate experimentally, if FLASH irradiation depletes oxygen within water for different radiation types such as photons, protons, and carbon ions.

METHODS

This study presents measurements of the oxygen consumption in sealed, 3D-printed water phantoms during irradiation with x-rays, protons, and carbon ions at varying dose rates up to 340 Gy/s. The oxygen measurement was performed using an optical sensor allowing for noninvasive measurements.

RESULTS

Oxygen consumption in water only depends on dose, dose rate, and linear energy transfer (LET) of the irradiation. The total amount of oxygen depleted per 10 Gy was found to be 0.04% atm - 0.18% atm for 225 kV photons, 0.04% atm - 0.25% atm for 224 MeV protons, and 0.09% atm - 0.17% atm for carbon ions. Consumption depends on dose rate by an inverse power law and saturates for higher dose rates because of self-interactions of radicals. Higher dose rates yield lower oxygen consumption. No total depletion of oxygen was found for clinical doses.

CONCLUSIONS

FLASH irradiation does consume oxygen, but not enough to deplete all the oxygen present. For higher dose rates, less oxygen was consumed than at standard radiotherapy dose rates. No total depletion was found for any of the analyzed radiation types for 10 Gy dose delivery using FLASH.

A Novel Analysis Method for Evaluating the Interplay of Oxygen and Ionizing Radiation at the Gene Level

Whilst the impact of hypoxia and ionizing radiations on gene expression is well-understood, the interplay of these two effects is not. To better investigate this aspect at the gene level human bladder, brain, lung and prostate cancer cell lines were irradiated with photons (6 Gy, 6 MV LINAC) in hypoxic and normoxic conditions and prepared for the whole genome analysis at 72 h post-irradiation. The analysis was performed on the obtained 20,000 genes per cell line using PCA and hierarchical cluster algorithms to extract the most dominant genes altered by radiation and hypoxia. With the help of the introduced novel radiation-in-hypoxia and oxygen-impact profiles, it was possible to overcome cell line specific gene regulation patterns. Based on that, 37 genes were found to be consistently regulated over all studied cell lines. All DNA-repair related genes were down-regulated after irradiation, independently of the oxygen state. Cell cycle-dependent genes showed up-regulation consistent with an observed change in cell population in the S and G2/M phases of the cell cycle after irradiation. Genes behaving oppositely in their regulation behavior when changing the oxygen concentration and being irradiated, were immunoresponse and inflammation related genes. The novel analysis method, and by consequence, the results presented here have shown how it is important to consider the two effects together (oxygen and radiation) when analyzing gene response upon cancer radiation treatment. This approach might help to unrevel new gene patterns responsible for cancer radioresistance in patients.

Iron and copper complexes with antioxidant activity as inhibitors of the metastatic potential of glioma cells

Iron and copper complexes with antioxidant activity able to inhibit tumor metastasis by inhibiting epithelial-mesenchymal transition in glioma cells.

Treatment (trx) patterns of angiogenesis inhibitors in patients (pts) with metastatic renal cell carcinoma (mRCC) in Ireland

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Background: This study evaluated rates of trx modifications and reasons for these changes among pts treated with angiogenesis inhibitors in Irish clinical practice.

Methods: Data from medical records were retrospectively reviewed at 3 large oncology centers in Ireland for mRCC pts who were ≥ 18 years and received sunitinib (SU) (n=54), sorafenib (n=9), bevacizumab (n=6), or temsirolimus (n=7) as first-line trx from 1/1/2005 to 8/31/2010. Proportions of pts with trx discontinuation (d/c), interruption, or dose change, and reasons for modifications and time to modifications were determined.

Results: Due to small sample sizes in other groups, only results for SU are summarized. 1.9% of pts had prior cytokine therapy. Median first-line trx duration for SU was 8.7 months (mo), while median progression-free survival was 13.8 mo. 87% of patients treated with first-line SU experienced adverse events (AEs); 18.5% experienced grade 3/4 AEs. AEs led to trx modifications in 42.6% of pts. 94.4% of pts started trx on 50 mg QD 4/2 dosing; 33.3% of them were dose reduced to 37.5 mg QD 4/2 with median time to reduction 2.7 mo. Among pts who discontinued trx, 31.6% discontinued within 18 weeks (w) (15.8% within 0-6 w, 7.9% in 7-12 w, and 7.9% in 13-18 w). Among pts who discontinued trx within 18 w, 66.7% discontinued due to AEs.

Conclusions: Over three-quarters of SU pts experienced trx modifications, more than half due to AEs. About 24% of txt discontinuations occurred within the first two cycles. This real-world practice study suggests that treatment tolerability is a challenge for physicians in the clinical care of mRCC pts.

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Attitudes and perceptions regarding skin cancer and sun protection behaviour in an Irish population

BACKGROUND

Although people seem to be well educated on the harmful effects of the sun, they continue to intentionally expose themselves without adequate protection.

AIMS

To ascertain baseline knowledge regarding skin cancer and review the sun protection behaviours in an Irish population and the effect of doctor-based education on these behaviours.

METHODS

Two hundred participants were recruited for a questionnaire-based study on their perceptions regarding skin cancer and their sun protection behaviour. They were divided into two groups, with one group receiving doctor-based education following the initial survey, and a follow-up questionnaire was carried out within 3 months.

RESULTS

Ninety per cent of participants knew that sun exposure was the major risk factor for skin cancer, and 95% knew that sun beds were not a safe way to tan. Despite this, < 20% used regular sunscreen, and 30% had used or were currently using sun beds in order to tan.

CONCLUSION

Our study indicated that although the participants' knowledge of skin cancer and risk of sun exposure is high, their sun-protective attitudes were not influenced by education in the clinical setting.

Computational methods for comparison of large genomic and proteomic datasets reveal protein markers of metastatic cancer

Large-scale genomic and proteomic analysis has provided a wealth of information on biologically relevant systems, and the ability to analyze this information is crucial to uncovering important biological relationships. However, it has proven difficult to compare large datasets from different sources due to different gene and protein identifiers assigned by individual laboratories and database systems. Here, we describe the design of a fully automated blast program (BlastPro) that facilitates rapid comparison of large protein-protein, nucleotide--nucleotide, or nucleotide--protein datasets from numerous, independent studies. Using this system, we compared several published genomic and proteomic databases for proteins that are upregulated in highly motile, metastatic tumor cells. Analysis of five independent studies comprised of greater than 1 x 10(6) genomic sequences and greater than 1,000 proteins revealed that the cytoskeletal-associated protein alpha-actinin is increased at both the mRNA and protein level in metastatic breast, prostate, and skin cancer cells. Interestingly, spatial analysis of alpha-actinin expression revealed that it is amplified 8-fold in the leading pseudopodium compared to the cell body compartment of migrating cells. These findings indicate that amplification of alpha-actinin and its localization to the leading pseudopodium are potential biomarkers of cancer progression to a more metastatic phenotype. Together, our results demonstrate that the BlastPro system can be used to compare large genomic and proteomic datasets to reveal important biological relationships including those associated with cancer progression.

Troglitazone improves ovulation and hirsutism in the polycystic ovary syndrome: a multicenter, double blind, placebo-controlled trial

We hypothesized that the administration of troglitazone, an insulin-sensitizing agent of the thiazolidinedione class, would improve the ovulatory dysfunction, hirsutism, hyperandrogenemia, and hyperinsulinemia of polycystic ovary syndrome (PCOS) patients. Four hundred and ten premenopausal women with PCOS in a multicenter, double blind trial were randomly assigned to 44 weeks of treatment with placebo (PBO) or troglitazone [150 mg/day (TGZ-150), 300 mg/day (TGZ-300), or 600 mg/day (TGZ-600)]. We compared changes in ovulatory function (by monitoring the urinary level of pregnanediol-3-glucuronide daily), hirsutism (by a modified Ferriman-Gallwey scoring method), hormonal levels (total and free testosterone, androstenedione, sex hormone-binding globulin, LH, FSH, and the LH/FSH ratio), and measures of glycemic parameters (fasting levels of glucose, insulin, hemoglobin A(1c), and the glucose and insulin areas under the curve during an oral glucose challenge) among study groups. Of the 410 patients recruited, 305 (74.4%) met evaluability criteria and were included in the analyses. The patients' baseline characteristics were similar across all treatment arms. Ovulatory rates were significantly greater for patients receiving TGZ-300 and TGZ-600 than for those receiving PBO (0.42 and 0.58 vs. 0.32; P < 0.05 and 0.0001, respectively). Of PCOS patients treated with TGZ-600, 57% ovulated over 50% of the time compared with 12% of placebo-treated patients. There was a significant decrease in the Ferriman-Gallwey score with TGZ-600 compared with PBO (0.22 +/- 0.53 vs. -2.21 +/- 0.49; P < 0.05, respectively). Free testosterone decreased and sex hormone-binding globulin increased in a dose-related fashion with troglitazone treatment, and all three troglitazone treatment groups were significantly different from placebo. Nearly all glycemic parameters showed dose-related decreases with troglitazone treatment. The total number and severity of adverse events (including elevations in liver enzymes) and the proportion of patients withdrawn from the study due to the development of adverse effects were similar between treatment groups. Troglitazone improves the ovulatory dysfunction, hirsutism, hyperandrogenemia, and insulin resistance of PCOS in a dose-related fashion, with a minimum of adverse effects.

Coexistence of cognitive impairment and depression in geriatric outpatients

The authors diagnosed depression in 20 (23%) of 88 cognitively impaired geriatric outpatients. Three (20%) of these patients had depression only, and 17 (85%) had depression superimposed on an underlying dementia. The rate of coexisting depression decreased significantly with greater severity of the cognitive impairment: 9 (33%) of 27 mildly impaired patients were depressed, compared with 8 (23%) of 35 moderately impaired and 3 (12%) of 26 severely impaired patients. There was a nonsignificant trend for cognitively impaired women to be more likely to be depressed than for similarly impaired men. The authors conclude that although depression must be differentiated from dementia, it is equally important to consider the possibility that the diagnoses coexist.

Five-year experience of a community outreach program for the elderly

The authors report on more than 2,000 impaired elderly people who were referred to a geriatric outreach program during its first 5 years of operation. These patients were referred by a wide variety of professionals and private citizens, who were usually concerned about the person's ability to care for himself or herself or about psychiatric symptoms. The most common diagnosis was dementing illness (21% of the patients), followed by depression (13%). Intervention usually involved making appropriate plans based on an accurate diagnosis, often including coordinating the services of other agencies. A follow-up of 100 patients showed that most of the patients who were still living had maintained their independence.