Molecular profiling of pediatric and young adult colorectal cancer reveals a distinct genomic landscapes and potential therapeutic avenues.

Colorectal cancer (CRC) is a global health concern, and the incidence of early onset (EO) CRC, has an upward trend. This study delves into the genomic landscape of EO-CRC, specifically focusing on pediatric (PED) and young adult (YA) patients, comparing them with adult (AD) CRC. In this retrospective monocentric investigation, we performed targeted next-generation sequencing to compare the mutational profile of 38 EO-CRCs patients (eight PED and 30 YA) to those of a 'control group' consisting of 56 AD-CRCs. Our findings reveal distinct molecular profiles in EO-CRC, notably in the WNT and PI3K-AKT pathways. In pediatrics, we observed a significantly higher frequency of RNF43 mutations, whereas APC mutations were more prevalent in adult cases. These observations suggest age-related differences in the activation of the WNT pathway. Pathway and copy number variation analysis reveal that AD-CRC and YA-CRC have more similarities than the pediatric patients. PED shows a peculiar profile with CDK6 amplification and the enrichment of lysine degradation pathway. These findings may open doors for personalized therapies, such as PI3K-AKT pathway inhibitors or CDK6 inhibitors for pediatric patients. Additionally, the distinct molecular signatures of EO-CRC underscore the need for age-specific treatment strategies and precision medicine. This study emphasizes the importance of comprehensive molecular investigations in EO-CRCs, which can potentially improve diagnostic accuracy, prognosis, and therapeutic decisions for these patients. Collaboration between the pediatric and adult oncology community is fundamental to improve oncological outcomes for this rare and challenging pediatric tumor.

Evidence for dimer/tetramer equilibrium in Trypanosoma brucei 6-phosphogluconate dehydrogenase.

6-Phosphogluconate dehydrogenase (6PGDH), the third enzyme of the pentose phosphate pathway (PPP), is essential for biosyntheses and oxidative stress defence. It also has the function of depleting 6PG, whose accumulation induces cell senescence. 6PGDH is a proposed drug target for African trypanosomiasis caused by Trypanosoma brucei and for other microbial infections and cancer. Gel filtration, density gradient sedimentation, cross-linking and dynamic light scattering were used to assay the oligomerization state of T. brucei 6PGDH in the absence and presence of several ligands. The enzyme displays a dimer-tetramer equilibrium and NADPH (but not NADP) reduces the rate of approach to equilibrium, while 6PG is able to antagonize the NADPH effect. The different behaviour of the two forms of coenzyme appears to be related to the differences in ΔCp, with NADP binding ΔCp closer to what is expected of crystallographic structures, while NADPH ΔCp is three times larger. The estimated dimer-tetramer association constant is 1.5·10(6)M(-1), and the specific activity of the tetramer is about 3 fold higher than the specific activity of the dimer. Thus, cellular conditions promoting tetramer formation could allow an efficient clearing of 6PG. Experiments carried out on sheep liver 6PGDH indicate that tetramerization is a specificity of the parasite enzyme.

A rolB regulatory factor belongs to a new class of single zinc finger plant proteins.

A protein which binds to the regulatory domain B necessary for expression of the plant oncogene rolB in (root) meristems contains a single zinc finger of a novel type conserved in dicots and monocots. Band shift analysis revealed the presence in tobacco nuclei of a protein selectively binding to domain B, a tetramer of which was used to isolate a cDNA (NtBBF1, Nicotiana tabacum rolB domain B Factor 1) from a tobacco expression library. The corresponding genomic clone was also isolated. The protein encoded by NtBBF1 contains a single C2C2 zinc finger, and its target sequence in domain B was identified by means of mutagenized oligonucleotides. The DNA-binding capability of the zinc finger was assessed by means of a fusion of this latter with the glutathione-S-transferase protein, that was shown to bind the same target sequence as NtBBF1. A number of other tobacco cDNAs encoding different proteins with a domain (BBF domain) encompassing the zinc finger identical to NtBBF1 were also isolated. Furthermore, a cDNA encoding a protein with an almost identical single zinc finger was isolated from Arabidopsis. A very closely related zinc finger has very recently been identified in maize transcription factors and termed the Dof domain. It is proposed that the tobacco, Arabidopsis and maize BBF/Dof domain proteins are members of a new broad family of plant transcription factors acting through a single zinc finger widely utilized in the plant kingdom.

Expression in different populations of cells of the root meristem is controlled by different domains of the rolB promoter.

Selective gene expression in different populations of cells of the root apex of transgenic tobacco could be evidenced by means of GUS constructs with deletions of the rolB promoter and fusions with the CaMV 35S minimal promoter. Five regulatory regions have been broadly identified in the rolB 5' non-coding region. The presence of all five domains (A to E) directs gene expression in the root cap, in the protoderm and in the different tissues within the root meristematic region: the dermatocalyptrogen, the cortex and the vascular cylinder. Deletion of domain A (-623 to -471) selectively suppresses expression in non-meristematic cells, i.e. the root cap and the protoderm. Deletion of either domain B (-341 to -306) or E (80 bp around the TATA box) causes loss of expression in all cells of the root apex: constructs C + D + E, B + C + D, B + C are inactive. Domain D (70 bp around the CAAT box) is necessary for gene expression in the dermatogen and in meristematic cells of the cortex but not in the innermost meristematic layer: construct B + C + E is active only in vascular meristematic cells. Domain C (-216 to -158) seems to have a double regulatory role as construct B + E is no longer expressed in meristematic cells of the vascular cylinder but is very active in the protoderm. Constructs allowing gene expression in meristematic cells are also inducible by auxin in leaf protoplasts, while activation of the regulatory elements necessary for gene expression in the non-meristematic cells of the root apex do not seem to depend upon the hormone. The connection between auxin induction and meristematic expression is discussed.

Bacterial plant oncogenes: the rol genes' saga.

The rol genes are part of the T-DNA which is transferred by Agrobacterium rhizogenes in plant cells, causing neoplastic growth and differentiation. Each of these bacterial oncogenes deeply influences plant development and is finely regulated once transferred into the plant host. Both from the study of the effects and biochemical function of the rol genes and from the analysis of their regulation, important insight in plant development can be derived. Some of the most intriguing aspects of past, current and future research on this gene system are highlighted and discussed.

Different promoter regions control level and tissue specificity of expression of Agrobacterium rhizogenes rolB gene in plants.

Expression of the rolB gene of A. rhizogenes T-DNA triggers root differentiation in transformed plant cells. In order to study the regulation of this morphogenetic gene, the GUS reporter gene was placed under the control of several deleted fragments of the rolB 5' non-coding region: carrot disc transformations and the analysis of transgenic tobacco plants containing these constructions identified the presence of distinct regulatory domains in the rolB promoter. Two regions (located from positions -623 to -471 and from -471 to -341, from the translation start codon) control the level but not the tissue specificity of rolB expression: progressive deletions of the rolB promoter starting from position -1185 to -341, although at different levels, maintained the same pattern of GUS expression-maximal in root meristems and less pronounced in the vascular tissue of aerial organs. Further deletion of 35 bp, from -341 to -306, drastically affected tissue specificity: GUS activity was still clearly detectable in the vascular tissue of the aerial organs while expression in the root meristem was totally suppressed. Analysis of transgenic embryos and seedlings confirmed that distinct promoter domains are responsible for meristematic (root) and differentiated (vascular) expression of rolB. Finally, we present data concerning the effects of plant hormones on the expression of rolB-GUS constructions.

Agrobacterium rhizogenes T-DNA genes capable of inducing hairy root phenotype.

Segments of the TL-DNA of the agropine type Ri plasmid pRi 1855 encompassing single and groups of open-reading frames were cloned in the Ti plasmid-derived binary vector system Bin 19. Leaf disc infections on Nicotiana tabacum led to transformed plants, some of which showed typical hairy root phenotypes, such as the wrinkled leaf morphology, excessive and partially non geotropic root systems and the ability of leaf explants to differentiate roots in a hormone-free culture medium. Particularly interestingly, most of these traits were shown by plants transformed with a TL-DNA segment encompassing the single ORF 11, corresponding to the rolB locus. Hairy root can be induced by this latter T-DNA segment on wounded stems of tobacco plants; hairy root induction on carrot discs requires, on the contrary, a more complex complement of TL-DNA genes.