Feasibility and Safety of Implementing Volumetric Arc Therapy (VMAT) for Pediatric Craniospinal Irradiation in a Low-Middle-Income Region: The Nigerian Experience.

Purpose: Volumetric modulated arc therapy (VMAT) is a relatively new treatment technique in sub-Saharan Africa. Although craniospinal irradiation (CSI) in the pediatric population has been practiced in Nigeria for many years, the use of VMAT to deliver this treatment is previously undocumented. We reviewed the first set of patients to undergo CSI at a cancer center in Nigeria, detailing the treatment technique, the progress experienced, dose statistics achieved, treatment toxicities, and cancer outcomes to date. Methods and Materials: This was a prospective case series of 5 children with histologically diagnosed cancers requiring CSI whose parents consented to the study. They were recruited at evaluation and followed through the process of their therapy. Toxicity was monitored at weekly review appointments using the Common Terminology Criteria for Adverse Events version 5.0. Follow-up of the children will continue in the long-term effects clinic. Results: Five patients with a median age of 6 were recruited. Diagnoses were intracranial germ cell tumor (n = 2), medulloblastoma (n = 1), pineoblastoma (n = 1), and ependymoma (n = 1). For all patients, a dose of 36.0 Gy in 1.8 Gy daily fractions was prescribed to the entire neuraxis. A subsequent boost of 18 Gy (n = 4) to 19.8 Gy (n = 1) in 10 daily fractions to the primary tumor bed (n = 2) and posterior fossa (n = 2) was delivered. Four patients had chemotherapy before, during, or after radiation therapy. No patient experienced grade 3 or greater toxicity. Conclusions: Our results indicate great progress has been made in the delivery of CSI in Nigeria, demonstrating tolerable acute side effects using VMAT. This series suggests the feasibility of implementing VMAT technology in low- or middle-income countries. Additional follow-up will be needed to determine whether survival rates and chronic toxicity rates are similar to those reported in the literature.

The Landscape of Pediatric Radiation Oncology in Nigeria.

Radiation therapy (RT) is an essential part of the multidisciplinary treatment of pediatric cancer. Over the past five decades, significant advances have been made in the delivery of RT, with better dose delivery to disease targets while minimizing exposure to nearby organs at risk. These advances have led to improved treatment outcomes, increased survival, and reduced treatment-related toxicities. Advanced treatment techniques, however, require significant investment in infrastructural and personnel resources. This review documents what is currently available regarding expertise and infrastructure for pediatric radiation oncology practice in Nigeria. It was performed to serve as a foundation for the creation and design of tailored solutions (initiatives and policies) to increase pediatric radiation availability, accessibility, and equity in Nigeria and ultimately improve pediatric cancer treatment outcomes in the region.

Examining Cancer Patients' Perceptions of the Impact of COVID-19 on Teleoncology: Findings From 15 Nigerian Outpatient Cancer Clinics.

PURPOSE: To examine cancer patients' perspectives on the impact of COVID-19 on teleoncology in Nigeria. METHODS: Data from a multicenter survey conducted at 15 outpatient clinics to 1,097 patients with cancer from April and July 2020 were analyzed. The study outcome was telemedicine, defined as patients who reported their routine follow-up visits were converted to virtual visits because of COVID-19 (coded yes/no). Covariates included patient age, ethnicity, marital status, income, cancer treatment, service disruption, and cancer diagnosis/type. Stata/SE.v.17 (StataCorp, College Station, TX) was used to perform chi-square and logistic regression analyses. P values ≤ .05 were considered statistically significant. RESULTS: The majority of the 1,097 patients with cancer were female (65.7%) and age 55 years and older (35.0%). Because of COVID-19, 12.6% of patients' routine follow-ups were converted to virtual visits. More patients who canceled/postponed surgery (17.7% v 7.5%; P ≤ .001), radiotherapy (16.9% v 5.3%; P ≤ .001), and chemotherapy (22.8% v 8.5%; P ≤ .001), injection chemotherapy (20.6% v 8.7%; P ≤ .001) and those who reported being seen less by their doctor/nurse (60.3% v 11.4%; P ≤ .001) reported more follow-up conversions to virtual visits. In multivariate analyses, patients seen less by their doctors/nurses were 14.3 times more likely to have their routine follow-ups converted to virtual visits than those who did not (odds ratio, 14.33; 95% CI, 8.36 to 24.58). CONCLUSION: COVID-19 caused many patients with cancer in Nigeria to convert visits to a virtual format. These conversions were more common in patients whose surgery, radiotherapy, chemotherapy, and injection chemotherapy treatments were canceled or postponed. Our findings suggest how COVID-19 affects cancer treatment services and the importance of collecting teleoncological care data in Nigeria.

GeneChip profiling of transcriptional responses to soybean cyst nematode, Heterodera glycines, colonization of soybean roots.

Soybean cyst nematode (SCN) is currently the most devastating pathogen of soybean. SCN penetrates the root and migrates toward the central vascular bundle where it establishes a complex multinucleated feeding structure that provides plant-derived nutrients to support the development and growth of the nematode. To identify host genes that play significant roles in SCN development in susceptible roots, RNA from SCN-inoculated and non-inoculated root pieces were hybridized to the Affymetrix soybean genome GeneChips. RNA was collected at 8, 12, and 16 d post-inoculation from root pieces that displayed multiple swollen female SCN and similar root pieces from non-inoculated roots. Branch roots and root tips were trimmed from the root pieces to minimize the amount of RNA contributed by these organs. Of the 35 593 transcripts represented on the GeneChip, approximately 26,500 were expressed in the SCN-colonized root pieces. ANOVA followed by False Discovery Rate analysis indicated that the expression levels of 4616 transcripts changed significantly (Q-value < or =0.05) in response to SCN. In this set of 4616 transcripts, 1404 transcripts increased >2-fold and 739 decreased >2-fold. Of the transcripts to which a function could be assigned, a large proportion was associated with cell wall structure. Other functional categories that included a large number of up-regulated transcripts were defence, metabolism, and histones, and a smaller group of transcripts associated with signal transduction and transcription.

GmEREBP1 is a transcription factor activating defense genes in soybean and Arabidopsis.

Ethylene-responsive element-binding proteins (EREBPs) are plant-specific transcription factors, many of which have been linked to plant defense responses. Conserved EREBP domains bind to the GCC box, a promoter element found in pathogenesis-related (PR) genes. We previously identified an EREBP gene from soybean (GmEREBP1) whose transcript abundance decreased in soybean cyst-nematode-infected roots of a susceptible cultivar, whereas it increased in abundance in infected roots of a resistant cultivar. Here, we report further characterization of this gene. Transient expression analyses showed that GmEREBP1 is localized to the plant nucleus and functions as a transcriptional activator in soybean leaves. Transgenic soybean plants expressing GmEREBP1 activated the expression of the ethylene (ET)-responsive gene PR2 and the ET- and jasmonic acid (JA)-responsive gene PR3, and the salicylic acid (SA)-responsive gene PR1 but not the SA-responsive PR5. Similarly, transgenic Arabidopsis plants expressing GmEREBP1 showed elevated mRNA abundance of the ET-regulated gene PR3 and the ET- and JA-regulated defense-related gene PDF1.2 but not the ET-regulated GST2, and the SA-regulated gene PR1 but not the SA-regulated PR2 and PR5. Transgenic soybean and Arabidopsis plants inoculated with cyst nematodes did not display a significantly altered susceptibility to nematode infection. These results collectively show that GmEREBP1 functions as a transacting inducer of defense gene expression in both soybean and Arabidopsis and mediates the expression of both ET- and JA- and SA-regulated defense-related genes in these plant species.

Insect feeding-induced differential expression of Beta vulgaris root genes and their regulation by defense-associated signals.

Root responses to insect pests are an area of plant defense research that lacks much information. We have identified more than 150 sugar beet root ESTs enriched for genes responding to sugar beet root maggot feeding from both moderately resistant, F1016, and susceptible, F1010, genotypes using suppressive subtractive hybridization. The largest number of identified F1016 genes grouped into the defense/stress response (28%) and secondary metabolism (10%) categories with a polyphenol oxidase gene, from F1016, identified most often from the subtractive libraries. The differential expression of the root ESTs was confirmed with RT-PCR. The ESTs were further characterized using macroarray-generated expression profiles from F1016 sugar beet roots following mechanical wounding and treatment of roots with the signaling molecules methyl jasmonate, salicylic acid and ethylene. Of the examined root ESTs, 20, 17 and 11% were regulated by methyl jasmonate, salicylic acid and ethylene, respectively, suggesting these signaling pathways are involved in sugar beet root defense responses to insects. Identification of these sugar beet root ESTs provides knowledge in the field of plant root defense and will lead to the development of novel control strategies for control of the sugar beet root maggot.

Homologous soybean and Arabidopsis genes share responsiveness to cyst nematode infection.

SUMMARY We previously isolated a partial soybean cDNA clone (D17.1) whose corresponding transcript increases in susceptible roots 1 day post inoculation (dpi) with the soybean cyst nematode, Heterodera glycines. Here we isolated the corresponding full-length cDNA from a soybean cDNA library and designated this gene of unknown function Gm17.1. Time course RNA gel blot analyses revealed that Gm17.1 mRNA steady-state levels were elevated in soybean roots following H. glycines infection up to at least 6 dpi. For further in-depth study we identified a homologous Arabidopsis thaliana gene and designated this gene At17.1. Arabidopsis is successfully infected by the sugar beet cyst nematode (H. schachtii), a close relative of H. glycines. We isolated the At17.1 promoter, fused it to the beta-glucuronidase (GUS) reporter gene, and transformed this construct into Arabidopsis plants as well as soybean hairy roots. Histochemical analysis of plant materials containing the At17.1::GUS construct revealed that the At17.1 promoter is functional in Arabidopsis as well as in soybean and that during normal plant development the At17.1 promoter directs GUS expression predominantly to the vascular tissues and root tips of both plant species. When At17.1::GUS Arabidopsis plants and soybean hairy roots were inoculated with cyst nematodes, strong GUS activity was detected within the cyst nematode-induced feeding structures. Further tests of At17.1 promoter activity in Arabidopsis revealed that this promoter was induced by auxin, jasmonic acid, mannitol and dehydration. Quantitative real-time reverse transcription-polymerase chain reaction assays of At17.1 expression confirmed the observed promoter characteristics. Based on our expression data and the observation that both the soybean and the Arabidopsis homologues behaved in a similar fashion following cyst nematode infection, it is likely that these genes are closely associated with cyst nematode parasitism of plants, potentially with hormone and osmotic changes occurring in the developing nematode feeding cells. Furthermore, these data provide additional insights into the strengths of the Arabidopsis-H. schachtii pathosystem to study cyst nematode-plant interactions in lieu of less tractable pathosystems. This finding is supported by the fact that the Arabidopsis promoter tested here produced similar results in Arabidopsis and soybean.

Arabidopsis gene expression changes during cyst nematode parasitism revealed by statistical analyses of microarray expression profiles.

With the availability of microarray technology, the expression profiles of thousands of genes can be monitored simultaneously to help determine the mechanisms of these biological processes. We conducted Affymetrix GeneChip microarray analyses of the Arabidopsis-cyst nematode interaction and employed a statistical procedure to analyze the resultant data, which allowed us to identify significant gene expression changes. Quantitative real-time RT-PCR assays were used to confirm the microarray analyses. The results of the expression profiling revealed 128 genes with altered steady-state mRNA levels following infection by the sugar beet cyst nematode (Heterodera schachtii; BCN), in contrast to only 12 genes that had altered expression following infection by the soybean cyst nematode (H. glycines; SCN). The expression of these 12 genes also changed following infection by BCN, i.e. we did not identify any genes regulated exclusively by SCN. The identification of 116 genes whose expression changes during successful cyst nematode parasitism by BCN suggests a potential involvement of these genes in the infection events starting with successful syncytium induction. Further characterization of these genes will permit the formulation of testable hypotheses to explain successful cyst nematode parasitism.

Expression of an Arabidopsis phosphoglycerate mutase homologue is localized to apical meristems, regulated by hormones, and induced by sedentary plant-parasitic nematodes.

We previously isolated a partial soybean cDNA clone whose transcript abundance is increased upon infection by the sedentary, endoparasitic soybean cyst nematode Heterodera glycines. We now isolated the corresponding full-length cDNA and determined that the predicted gene product was similar to the group of cofactor-dependent phosphoglycerate mutase/bisphosphoglycerate mutase enzymes (PGM/bPGM; EC 5.4.2.1/5.4.2.4). We designated the corresponding soybean gene GmPGM. PGM and bPGM are key catalysts of glycolysis that have been well characterized in animals but not plants. Using the GmPGM cDNA sequence, we identified a homologous Arabidopsis thaliana gene, which we designated AtPGM. Histochemical GUS analyses of transgenic Arabidopsis plants containing the AtPGM promoter ::GUS construct revealed that the AtPGM promoter directs GUS expression in uninfected plants only to the shoot and root apical meristems. In infected plants, GUS staining also is evident in the nematode feeding structures induced by the cyst nematode Heterodera schachtii and by the root-knot nematode Meloidogyne incognita. Furthermore, we discovered that the AtPGM promoter was down-regulated by abscisic acid and hydroxyurea, whereas it was induced by sucrose, oryzalin, and auxin, thereby revealing expression characteristics typical of genes with roles in meristematic cells. Assessment of the auxin-inducible AUX1 gene promoter (a gene coding for a polar auxin transport protein) similarly revealed feeding cell and meristem expression, suggesting that auxin may be responsible for the observed tissue specificity of the AtPGM promoter. These results provide first insight into the possible roles of PGM/bPGM in plant physiology and in plant-pathogen interactions.

ATP-dependent hexameric assembly of the heat shock protein Hsp101 involves multiple interaction domains and a functional C-proximal nucleotide-binding domain.

Members of the Hsp100 family of heat stress proteins are present in species throughout the bacterial, plant, and fungal kingdoms. Most Hsp100 proteins are composed of five domains that include two nucleotide-binding domains required for their ATP-dependent oligomerization. Mutations within the first but not the second nucleotide-binding site disrupt self-assembly of bacterial Hsp100, whereas the reverse is true for yeast Hsp104. We have examined the functional requirements for oligomerization of plant Hsp101 and have found that Hsp101 resembles Hsp104 in that it assembles into a hexameric complex in an ATP-dependent manner. Self-assembly of Hsp101 involves at least three distinct interaction domains located in the N-proximal domain and in the first and second nucleotide-binding domains. The interaction domain in the second nucleotide-binding domain included the Walker A motif, and mutations within this element disrupted self-assembly of Hsp101. In contrast, mutations affecting conserved residues of the Walker A motif within the first nucleotide-binding site did not affect self-assembly. No interaction between Hsp101 and Hsp104 was observed. These results suggest that plant Hsp101 self-assembly involves multiple evolutionarily diverged interaction domains as well as an evolutionarily conserved requirement for a functional C-proximal nucleotide-binding site.

Identification and characterization of a soybean ethylene-responsive element-binding protein gene whose mRNA expression changes during soybean cyst nematode infection.

Ethylene-responsive element-binding proteins (EREBPs) are members of a family of plant transcription factors. Conserved EREBP domains of these proteins bind to the GCC box, an ethylene-responsive promoter element found in many pathogenesis-related (PR) genes. Using degenerate primers to the EREBP domain from diverse plant species, an EREBP homolog was isolated from a soybean cDNA library. Gel mobility-shift assays revealed that the translation product of this cDNA bound specifically to GCC box sequences. We, therefore, named this gene Glycine max ethylene-responsive element-binding protein 1 (GmEREBP1), i.e., a gene coding for the first confirmed GCC box-binding protein of soybean. GmEREBP1 mRNA abundance was analyzed by RNA blot hybridizations in soybean roots and shoots of cultivars Corsoy 79 and Hartwig, which are susceptible and resistant, respectively, to the soybean cyst nematode (Heterodera glycines). These analyses revealed that GmEREBP1 is expressed in a root-preferential manner and that GmEREBP1 mRNA abundance is changed after H. glycines infection. GmEREBP1 mRNA abundance decreased in infected (susceptible) 'Corsoy 79' roots, whereas it increased in abundance in infected (resistant) 'Hartwig' roots. Furthermore, ethephon treatment repressed GmEREBP1 mRNA accumulation in both cultivars, whereas wounding increased expression in both cultivars. These changes in mRNA steady-state levels suggest that GmEREBP1 plays a role in soybean-H. glycines interactions.