The association of breast cancer patients survival and prior menopausal hormone therapy in women with type 2 diabetes.

We investigated the association of prediagnostic use of menopausal hormone therapy (MHT) with breast cancer survival among women with type 2 diabetes (T2D). The study cohort was identified from a Finnish nationwide diabetes database, and consisted of women with T2D, who were diagnosed with breast cancer between 2000 and 2011 (n = 3189). The patients were classified according to their previous MHT use: systemic MHT, local MHT, and no history of any MHT. The cumulative mortality from breast cancer, cardiovascular diseases, and other causes in three MHT groups was described by the Aalen-Johansen estimator. The cause-specific mortality rates were analyzed by Cox models, and adjusted hazard ratios (HRs) were estimated for the use of MHT. The breast cancer mortality appeared to be lower among systemic MHT users (HR 0.49, 95% Cl 0.36-0.67) compared with non-users of MHT. The mortality from cardiovascular diseases and from other causes of death was found to be lower among systemic MHT users, (HR 0.49, 95% Cl 0.32-0.74), and (HR 0.51, 95% Cl 0.35-0.76), respectively. In conclusion, prediagnostic systemic MHT use is associated with reduced breast cancer, cardiovascular, and other causes of mortality in women with T2D.

The Association of Metformin, Other Antidiabetic Medications, and Statins With the Prognosis of Colon Cancer in Patients With Type 2 Diabetes: A Retrospective Cohort Study.

BACKGROUND: Use of metformin and statins have been associated with improved prognosis of colon cancer (CC) in patients with type 2 diabetes (T2D). We examined the survival from CC in relation to the use of metformin, other oral antidiabetic medications (ADM), insulin, and statins in T2D patients. MATERIALS AND METHODS: A cohort (n = 2252) of persons with pre-existing T2D diagnosed with incident CC between 1998 and 2011 was identified from several Finnish registers. Cox models were fitted for cause-specific mortality rates to obtain adjusted estimates of the hazard ratios (HR) with 95% confidence intervals (CI) in relation to use of ADM and statins before the CC diagnosis. Cox models were also fitted for mortality in relation to post-diagnostic use of the medications treating these as time-dependent exposures, and starting follow-up 1 year after the CC diagnosis. RESULTS: Pre- and post-diagnostic metformin use was weakly associated with the risk of CC-related death (HR .75; 95% CI .58-.99, and HR .78; 95% CI .54-1.14, respectively) compared to the use of other oral ADMs. Pre- and post-diagnostic statin use predicted a reduced risk of CC-related death (HR .83; 95% CI .71- .98, and HR .69; 95% CI .54-.89, respectively). CONCLUSION: Additional evidence was found for use of statins being associated with an improved survival from CC in patients with pre-existing T2D, but for metformin use the evidence was weaker.

The Association of Metformin, Other Antidiabetic Medications and Statins on the Prognosis of Rectal Cancer in Patients with Type 2 Diabetes: A Retrospective Cohort Study.

Metformin and statin use have been associated with an improved prognosis for colorectal cancer in persons with type 2 diabetes (T2D). Data regarding rectal cancer (RC) have been inconclusive; therefore, we investigated the issue with high-quality data and a robust study design. We identified 1271 eligible patients with T2D and incident RC between 1998 and 2011 from the Diabetes in Finland (FinDM) database. Cox models were fitted for cause-specific mortality rates to obtain adjusted estimates of the hazard ratios (HR) with 95% confidence intervals (CI) in relation to use of antidiabetic medication (ADM) and statins before the RC diagnosis and for post-diagnostic use in a time-dependent exposure manner. No sufficient evidence was found for either pre- or post-diagnostic metformin use and RC mortality (HR 0.96, 95% CI 0.67-1.38, and 0.70, 95% CI 0.45-1.10, respectively) when compared to other oral ADMs. Both pre- and post-diagnostic statin use appeared to be inversely associated with mortality from RC (HR 0.77 95% CI 0.63-0.94, and 0.57, 95% CI 0.42-0.78, respectively). Our study was inconclusive as to the association of metformin use with the prognosis of RC, but statin use was found to predict reduced mortality, both from RC and from other causes of death in persons with T2D.

Total or partial tonsillar resection (tonsillectomy or tonsillotomy) to change the quality of life for adults with recurrent or chronic tonsillitis: study protocol for a randomised controlled trial.

BACKGROUND: Tonsillar surgery has been used for decades to treat recurrent and chronic tonsillitis in adults. Recurrent and chronic tonsillitis result in disturbing symptoms, treatment costs, sick leave, and impaired quality of life (QoL). Theoretically, removing all or part of the altered pathological palatal lymphoid tissue alleviates the symptoms and enhances the QoL. Whether this is true with total or partial tonsillar resection (tonsillectomy (TE) and tonsillotomy (TT), respectively) has not been reported in a randomised trial yet. METHODS: We conduct a multicentre, partly blinded, randomised, 6-month, parallel-group clinical study including 285 adult participants referred to surgical treatment for chronic or recurrent tonsillitis. The participants will either have TE, TT or watchful waiting (WW). The primary outcome will be the difference between the mean disease-specific Tonsillectomy Outcome Inventory-14 (QoL questionnaire) scores at 6 months. Comparison is made firstly between the combined TE+TT and WW groups (superiority analysis), and secondly between the TE and TT groups (non-inferiority analysis). DISCUSSION: This study will add significant new information to the effects and harms of TE and TT procedures in the treatment of adults with chronic or recurrent tonsillitis. TRIAL REGISTRATION: ClinicalTrials.gov: NCT04657549.

Association of antidiabetic medication and statins with survival from ductal and lobular breast carcinoma in women with type 2 diabetes.

We investigated the survival of female patients with pre-existing type 2 diabetes (T2D) diagnosed with invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) of breast, in relation to the use of metformin, other antidiabetic medication (ADM) and statins. The study cohort consisted of 3,165 women (2,604 with IDC and 561 with ILC). The cumulative mortality from breast cancer (BC) and from other causes was calculated using the Aalen-Johansen estimator. The cause-specific mortality rates were analysed by Cox models, and adjusted hazard ratios (HRs) were estimated for the use of different medications. No evidence of an association of metformin use with BC mortality was observed in either IDC (HR 0.92, 95% confidence interval [CI] 0.64-1.31) or ILC (HR 0.68, 95% CI 0.32-1.46) patients, when compared to other oral ADMs. The mortality from other causes was found to be lower amongst the IDC patients using metformin (HR 0.64, 95% CI 0.45-0.89), but amongst ILC patients the evidence was inconclusive (HR 1.22, 95% CI 0.64-2.32). Statin use was consistently associated with reduced mortality from BC in IDC patients (HR 0.77, 95% CI 0.62-0.96) and ILC patients (HR 0.59, 95% CI 0.37-0.96), and also mortality from other causes in IDC patients (HR 0.81, 95% CI 0.67-0.96) and in ILC patients (HR 0.66, 95% CI 0.43-1.01). We found no sufficient evidence for the possible effects of metformin and statins on the prognosis of BC being different in the two histological subtypes.

Association of Metformin, Other Antidiabetic Medications, and Statins With Incidence of Colon Cancer in Patients With Type 2 Diabetes.

BACKGROUND: Metformin and statins may have anticancer effects, with plausible cellular mechanisms. However, the association of these agents with the risk of colorectal cancer is unclear. PATIENTS AND METHODS: This was a retrospective cohort study on a large population (N = 316,317) of patients with type 2 diabetes. Data were obtained from the Diabetes in Finland database (FinDM). In a full cohort analysis, hazard ratios (HRs) with their 95% confidence intervals (CIs) for ever use versus never use were estimated using a multiple Poisson regression model. A nested case-control design within the cohort was used to examine the association of colon cancer (CC) with the defined daily dose of medication. The data were analyzed by conditional logistic regression. The analyses were adjusted for the patient's age, sex, and duration of diabetes. RESULTS: In total, 1351 CC cases were diagnosed during 1996-2011. The results revealed insufficient evidence for an association between metformin (HR, 1.01; 95% CI, 0.90-1.14), other oral antidiabetic medications (HR, 1.05; 95% CI, 0.93-1.19), insulin (HR, 1.02; 95% CI, 0.86-1.22), or statins (HR, 0.94; 95% CI, 0.84-1.05) and the incidence of CC in the full cohort analysis. The results from the case-control study were similar, with no consistent trend in the incidence of CC according to the cumulative dose of metformin or the other studied medications. CONCLUSION: This study found insufficient evidence for an association between metformin, insulin, other oral type 2 diabetes medications, or statins and the incidence of CC.

Survival after breast cancer in women with type 2 diabetes using antidiabetic medication and statins: a retrospective cohort study.

Background: We assessed survival of breast cancer in women with type 2 diabetes (T2D) treated with metformin, other types of antidiabetic medication (ADM) and statins.Materials and Methods: The study cohort consisted of women with T2D and diagnosed with breast cancer in Finland in 1998─2011. Mortality rates from breast cancer and other causes were analysed by Cox models, and adjusted hazard ratios (HRs) with 95% confidence intervals (Cls) were estimated in relation to the use of different types of medication.Results: The final cohort consisted of 3,533 women. No clear evidence was found for breast cancer mortality being different in metformin users (HR 0.86, 95% Cl 0.63-1.17), but their other-cause mortality appeared to be lower (HR 0.73, 95% Cl 0.55-0.97) in comparison with women using other types of oral ADM. Other-cause mortality was higher among insulin users (HR 1.45, 95% Cl 1.16-1.80) compared with users of other oral ADMs, other than metformin. Prediagnostic statin use was observed to be associated with decreased mortality from both breast cancer (HR 0.76, 95% Cl 0.63-0.92) and other causes (HR 0.75, 95% Cl 0.64-0.87).Conclusions: We did not find any association between ADM use and disease-specific mortality among women with T2D diagnosed with breast cancer. However, interestingly, prediagnostic statin use was observed to predict reduced mortality from breast cancer and other causes. We hypothesise that treating treatment practices of T2D or hypercholesterolaemia of breast cancer patients might affect overall prognosis of women diagnosed with breast cancer and T2D.

Association of antidiabetic medication and statins with breast cancer incidence in women with type 2 diabetes.

PURPOSE: To address the possible association between the use of metformin, other forms of antidiabetic medication (ADM) and statins with the incidence of breast cancer in women with type 2 diabetes (T2D). METHODS: Data were collected from a Finnish nationwide diabetes database (FinDM). The study cohort consisted of women diagnosed with T2D in 1996-2011 in Finland. In full-cohort analysis, Poisson regression was used to estimate hazard ratios (HRs) in relation to use of metformin, insulin, other forms of oral ADM and statins. In nested case-control analysis, up to 20 controls were matched for age and duration of diabetes to each case of breast cancer. Conditional logistic regression was used to estimate HRs in relation to medication use and cumulative use of different forms of ADM, and statins. RESULTS: 2300 women were diagnosed with breast cancer during follow-up. No difference in breast cancer incidence was observed between metformin users [HR 1.02, 95% confidence interval (CI) 0.93-1.11] or statin users (HR 0.97, 95% CI 0.89-1.05) compared with non-users. In nested case-control analysis the results were similar. Use of insulin (HR 1.18, 95% CI 1.03-1.36) was associated with a slightly increased incidence of breast cancer. CONCLUSIONS: No evidence of an association between the use of metformin or statins and the incidence of breast cancer in women with T2D was found. Among insulin users, a slightly higher incidence of breast cancer was observed.

Diverse age-incidence patterns of atopic sensitization in an unselected Finnish population up to 12 years.

BACKGROUND: The temporal sequence in which allergic sensitization to different allergens emerges is not well characterized at the level of general population. OBJECTIVE: We describe the incidence patterns of atopic sensitization to different allergens from birth up to 12 years of age in an unselected Finnish population. METHODS: The study population comprised all children born between 2001 and 2006 identified from the nationwide population register as residents of the province of South Karelia, Finland (n = 5564). The results of allergy tests (22,380 results from skin prick tests, immunoglobulin E [IgE] antibodies, and open food challenges [OFCs], performed in 1827 children) were collected from patient records of all the health care units in the area. RESULTS: The incidence rates of positive results for food and animal allergens as well as positive OFCs for cow's milk showed prominent peaks at 5 months of age. Positive results for pollen allergens started to emerge after 1.5 years of age. The 12-year cumulative incidence of sensitization to food, animal, pollen, and any allergens was 12%, 8%, 10%, and 18%, respectively. The cumulative incidence of sensitization to house dust mites was 1% and to molds or latex less than 1%. Firstborn boys had the highest, and those who were not firstborn girls and children born in rural municipalities had the lowest early incidence of sensitization to inhalation allergens. CONCLUSION: In the unselected population, the atopic sensitization against food and animal allergens began before 6 months of age and was followed by sensitization to pollen allergens before 2 years of age. Primary prevention of sensitization to food and inhalation allergens should therefore occur in early infancy.

Estimating multilevel regional variation in excess mortality of cancer patients using integrated nested Laplace approximation.

Models of excess mortality with random effects were used to estimate regional variation in relative or net survival of cancer patients. Statistical inference for these models based on the Markov chain Monte Carlo (MCMC) methods is computationally intensive and, therefore, not feasible for routine analyses of cancer register data. This study assessed the performance of the integrated nested Laplace approximation (INLA) in monitoring regional variation in cancer survival. Poisson regression model of excess mortality including both spatially correlated and unstructured random effects was fitted to the data of patients diagnosed with ovarian and breast cancer in Finland during 1955-2014 with follow up from 1960 through 2014 by using the period approach with five-year calendar time windows. We estimated standard deviations associated with variation (i) between hospital districts and (ii) between municipalities within hospital districts. Posterior estimates based on the INLA approach were compared to those based on the MCMC simulation. The estimates of the variation parameters were similar between the two approaches. Variation within hospital districts dominated in the total variation between municipalities. In 2000-2014, the proportion of the average variation within hospital districts was 68% (95% posterior interval: 35%-93%) and 82% (60%-98%) out of the total variation in ovarian and breast cancer, respectively. In the estimation of regional variation, the INLA approach was accurate, fast, and easy to implement by using the R-INLA package.

Thermospermine Synthase (ACL5) and Diamine Oxidase (DAO) Expression Is Needed for Zygotic Embryogenesis and Vascular Development in Scots Pine.

Unlike in flowering plants, the detailed roles of the enzymes in the polyamine (PA) pathway in conifers are poorly known. We explored the sequence conservation of the PA biosynthetic genes and diamine oxidase (DAO) in conifers and flowering plants to reveal the potential functional diversification of the enzymes between the plant lineages. The expression of the genes showing different selective constraints was studied in Scots pine zygotic embryogenesis and early seedling development. We found that the arginine decarboxylase pathway is strongly preferred in putrescine production in the Scots pine as well as generally in conifers and that the reduced use of ornithine decarboxylase (ODC) has led to relaxed purifying selection in ODC genes. Thermospermine synthase (ACL5) genes evolve under strong purifying selection in conifers and the DAO gene is also highly conserved in pines. In developing Scots pine seeds, the expression of both ACL5 and DAO increased as embryogenesis proceeded. Strong ACL5 expression was present in the procambial cells of the embryo and in the megagametophyte cells destined to die via morphologically necrotic cell death. Thus, the high sequence conservation of ACL5 genes in conifers may indicate the necessity of ACL5 for both embryogenesis and vascular development. Moreover, the result suggests the involvement of ACL5 in morphologically necrotic cell death and supports the view of the genetic regulation of necrosis in Scots pine embryogenesis and in plant development. DAO transcripts were located close to the cell walls and between the walls of adjacent cells in Scots pine zygotic embryos and in the roots of young seedlings. We propose that DAO, in addition to the role in Put oxidation for providing H2O2 during the cell-wall structural processes, may also participate in cell-to-cell communication at the mRNA level. To conclude, our findings indicate that the PA pathway of Scots pines possesses several special functional characteristics which differ from those of flowering plants.

Antidiabetic Medication, Statins and the Risk and Prognosis of Non-endometrioid Endometrial Cancer in Women with Type 2 Diabetes.

AIM: To determine the incidence and prognosis of non-endometrioid endometrial cancer (EC) in relation to the use of metformin, other antidiabetic medication (ADM) and statins in patients with type 2 diabetes (T2D). MATERIALS AND METHODS: In order to analyze the incidence and prognosis of non-endometrioid EC, two cohorts were obtained from a nationwide diabetes database (FinDM); 57 non-endometrioid ECs were observed in a cohort of 92,366 women with newly-diagnosed T2D during the follow-up (1996 to 2011) to assess the incidence, and a retrospective cohort of 105 women with T2D diagnosed with non-endometrioid EC (1998 to 2011) was used to estimate cumulative mortality from EC and other causes of death. Hazard ratios (HRs) with 95% confidence intervals (CIs) for EC incidence were estimated in the full-cohort analysis and in the nested case-control analysis, matched for age and duration of T2D. Cumulative mortality was estimated by using the Aalen-Johansen estimator. Cause-specific mortality rates were analyzed by using Cox models regarding the pre-diagnostic use of different forms of ADM and statins. RESULTS: In the nested case-control analysis, the use of metformin was not associated with the risk of non-endometrioid EC (HR=1.09, 95% CI=0.59-2.00), whereas statin use was associated with a lower risk (HR=0.47, 95% CI=0.26-0.84). The results from the full-cohort analysis supported these findings. Mortality from non-endometrioid EC was not different between users of metformin and other types of oral ADM (HR=1.56, 95% CI=0.40-6.07) but was observed to be lower in statin users (HR=0.41, 95% CI=0.20-0.82). CONCLUSION: Our findings were inconclusive regarding the association of metformin with the risk and prognosis of non-endometrioid EC. However, statin use was associated with a lower incidence and mortality from this disease.

Prognosis of ovarian cancer in women with type 2 diabetes using metformin and other forms of antidiabetic medication or statins: a retrospective cohort study.

BACKGROUND: Ovarian cancer is one of the most lethal cancers and women with type 2 diabetes (T2D) have even poorer survival from it. We assessed the prognosis of ovarian cancer in women with type 2 diabetes treated with metformin, other forms of antidiabetic medication, or statins. METHODS: Study cohort consisted of women with T2D diagnosed with ovarian cancer in Finland 1998-2011. They were identified from a nationwide diabetes database (FinDM), being linked to several national registers. Patients were grouped according to their medication in the three years preceding ovarian cancer diagnosis. The Aalen-Johansen estimator was used to describe cumulative mortality from ovarian cancer and from other causes in different medication groups. Mortality rates were analysed by Cox models, and adjusted hazard ratios (HR) with 95% confidence intervals (95% CIs) were estimated in relation to the use of different forms of medication. Main outcome measures were death from ovarian cancer and death from other causes. RESULTS: During the accrual period 421 newly diagnosed ovarian cancers were identified in the FinDM database. No evidence was found for any differences in mortality from ovarian cancer or other causes between different antidiabetic medication groups. Pre-diagnostic use of statins was observed to be associated with decreased mortality from ovarian cancer compared with no such use (HR 0.72, 95% CI 0.56-0.93). CONCLUSIONS: Our findings are inconclusive as regards the association between metformin and ovarian cancer survival. However, some evidence was found for improved prognosis of ovarian cancer with pre-diagnostic statin use, requiring cautious interpretation, though.

Cause-specific mortality in patients with head and neck cancer: Long-term follow-up of a population-based cohort from 1986 to 2012 accounting for competing risks.

OBJECTIVES: Recent recommendations for treating head and neck cancer (HNC) patients favor an individualized approach. Expected long-term survival - together with short-term survival - after diagnosis is the primary focus in assessing the treatment modality and follow-up scheme. "Disease-specific" survival up to five years is often used for measuring the prognosis and for assessing treatment methods. However, especially long-term survival is strongly affected by competing causes of death among HNC patients. MATERIALS AND METHODS: The long-term prognosis of patients with HNC in terms of mortality from both cancer and competing causes was analyzed according to recent methodological guidelines by examining cumulative incidence functions and models for cause-specific hazards and sub-distribution hazards in a population based cohort of 220 patients treated in a tertiary care center in Northern Finland. RESULTS: In addition to well-known tumor-related factors, mortality from HNC was associated with older age. The mortality from other causes of death was strongly dependent on age and Charlson's Comorbidity Index, but less on gender. When demonstrating the importance of individualized approach in simulated patients, the mortality was highly variable across patients with similar cancer status, but with different comorbidities or age. CONCLUSION: The overall survival pattern of HNC patients depends not only on their cancer characteristics, but also varies greatly according to their age and comorbidities. Our findings support the need for individualized treatment and follow-up protocols, and active management of comorbid diseases. Appropriate methods for analyzing competing risks should be used when presenting survival estimates of cancer patients.

Prognostic biomarkers for oral tongue squamous cell carcinoma: a systematic review and meta-analysis.

BACKGROUND: Identifying informative prognostic biomarkers for oral tongue squamous cell carcinoma (OTSCC) is of great importance in order to better predict tumour behaviour and to guide treatment planning. Here, we summarise existing evidence regarding immunohistochemical prognostic biomarkers for OTSCC. METHODS: A systematic search of the literature was performed using the databases of Scopus, Ovid Medline, Web of Science and Cochrane Library. All studies which had investigated the prognostic significance of immunohistochemical biomarkers in OTSCC during the period from 1985 to 2015 were retrieved. For the five most often evaluated biomarkers a random-effects meta-analysis on overall survival was performed, including those studies that provided the necessary statistical results. RESULTS: A total of 174 studies conducted during the last three decades were found, and in these 184 biomarkers were evaluated for the prognostication of OTSCC. The five biomarkers most frequently assessed were p53, Ki-67, p16, VEGFs and cyclin D1. In the meta-analyses, the most promising results of the prognostic power for OTSCC were obtained for cyclin D1. For studies of VEGF A and C the results were equivocal, but the pooled analysis of VEGF A separately showed it to be a useful prognosticator for OTSCC. There was no sufficient evidence to support p53, Ki-67 and p16 as prognostic biomarkers for OTSCC. Limitations in the quality of the published studies (e.g., small cohorts, lack of compliance with REMARK guidelines) are widespread. CONCLUSIONS: Numerous biomarkers have been presented as useful prognosticators for OTSCC, but the quality of the conduct and reporting of original studies is overall unsatisfactory which does not allow reliable conclusions. The value of two biomarkers (VEGF-A and cyclin D1) should be validated in a multicentre study setting following REMARK guidelines.

Antidiabetic medication, statins and the risk of endometrioid endometrial cancer in patients with type 2 diabetes.

OBJECTIVE: To gain further evidence of an association between the incidence of endometrial cancer (EC) and the use of metformin, other antidiabetic medication (ADM) and statins in women with type 2 diabetes (T2D). METHODS: A retrospective cohort of 92,366 women with newly diagnosed T2D was obtained from a diabetes register (FinDM). 590 endometrioid ECs were observed during the follow-up time. Poisson regression was utilized to estimate the hazard ratios (HRs) with 95% confidence intervals (95% CIs) of the endometrioid EC in relation to the use of metformin, other oral ADM, insulin and statins. Nested case-control analyses were performed, where up to 20 controls were matched for age and duration of DM for each EC case. The HRs were estimated by conditional logistic regression for never/ever and cumulative use of different forms of ADM and statins. RESULTS: In the case-control analyses the use of metformin (HR 1.24, 95% CI 1.02-1.51) and other oral ADM (HR 1.25, 95% CI 1.04-1.50) was associated with an increased incidence of endometrioid EC compared to no ADM use. No difference was observed between metformin users and those using other oral ADMs. The use of statins was inversely related to the incidence of endometrioid EC (HR 0.78, 95% CI 0.65-0.94). Results from the full cohort analysis supported this finding. CONCLUSIONS: In our study the use of metformin or other oral forms of ADM was not associated with a lowered risk of endometrioid EC in women with T2D. Instead statins were observed to be inversely associated with endometrioid EC in this population.

Competing risks analysis of cause-specific mortality in patients with oral squamous cell carcinoma.

BACKGROUND: Survival studies on head and neck cancers are frequently reported with inadequate account for competing causes of death. Realistic descriptions and predictions of postdiagnosis mortality should be based on proper competing risks methodology. METHODS: Prognosis of patients with oral squamous cell carcinoma (OSCC) in terms of mortality from OSCC and from other causes, respectively, was analyzed according to recent methodological recommendations using cumulative incidence functions and models for cause-specific hazards and subdistribution hazards in 306 patients treated in a tertiary care center in Northern Finland. RESULTS: More coherent and informative descriptions and predictions of mortality by cause were obtained with state-of-the-art statistical methods for competing risks than using the prevalent but questionable practice to graph "disease-specific survival." CONCLUSION: From the patients' perspective, proper competing risks analysis offers more relevant prognostic scenarios than naïve analyses of "disease-specific survival"; therefore, it should be used in prognostic studies of head and neck cancers. © 2016 Wiley Periodicals, Head Neck 39: 56-62, 2017.

Dual targeted poplar ferredoxin NADP(+) oxidoreductase interacts with hemoglobin 1.

Previous reports have connected non-symbiotic and truncated hemoglobins (Hbs) to metabolism of nitric oxide (NO), an important signalling molecule involved in wood formation. We have studied the capability of poplar (Populus tremula × tremuloides) Hbs PttHb1 and PttTrHb proteins alone or with a flavin-protein reductase to relieve NO cytotoxicity in living cells. Complementation tests in a Hb-deficient, NO-sensitive yeast (Saccharomyces cerevisiae) Δyhb1 mutant showed that neither PttHb1 nor PttTrHb alone protected cells against NO. To study the ability of Hbs to interact with a reductase, ferredoxin NADP(+) oxidoreductase PtthFNR was characterized by sequencing and proteomics. To date, by far the greatest number of the known dual-targeted plant proteins are directed to chloroplasts and mitochondria. We discovered a novel variant of hFNR that lacks the plastid presequence and resides in cytosol. The coexpression of PttHb1 and PtthFNR partially restored NO resistance of the yeast Δyhb1 mutant, whereas PttTrHb coexpressed with PtthFNR failed to rescue growth. YFP fusion proteins confirmed the interaction between PttHb1 and PtthFNR in plant cells. The structural modelling results indicate that PttHb1 and PtthFNR are able to interact as NO dioxygenase. This is the first report on dual targeting of central plant enzyme FNR to plastids and cytosol.