Here we report up-regulation of COX-2and p53 protein expression in SLL and DLBCL indicating their interactive involvement in the pathogenesis of lymphoma.
MYD88/CD79B, DNMT3A, and TP53 were chosen as genes of interest, representing each of the following categories: lymphoma driver genes, CHIP-related genes, and genes shared between lymphoma and CHIP.
Mechanistically, the reactivation response was dependent on Cdkn2a/p19Arf, which is commonly silenced in p53 wild-type lymphomas, but became reexpressed upon late-stage p53 inactivation.
We identified 122 patients diagnosed as having large B-cell lymphoma (44, MYC-negative; 29, MYC-EC; 23, MYC rearrangement; 22, MYC and BCL2 rearrangements; 4, MYC, BCL2, and BCL6 rearrangements). p53 expression significantly correlated with DLBCL with abnormal MYC status (MYC-EC, MYC rearrangement, and MYC overexpression), but adverse p53 prognostic effect was only seen with MYC-rearranged lymphoma.
Based on our recommendations, we systematically characterized all new cell lines that we generated by a standardized approach that included (1) determination of human origin, (2) exclusion of lymphoma, (3) DNA fingerprinting and histological comparisons to establish linkage to presumed tissue of origin, (4) examining thyroid differentiation by screening two to three thyroid markers, (5) examination of biological behavior (growth rate, tumorigenicity), and (6) presence of common thyroid cancer genetic changes (TP53, BRAF, PTEN, PIK3CA, RAS, TERT promoter, RET/PTC, PAX8/PPARγ, NF1, and EIF1AX).
TRRAP silencing attenuated p53 accumulation in lymphoma and colon cancer models, whereas TRRAP overexpression increased mutp53 levels, suggesting a role for TRRAP across cancer entities and p53 mutations.
In particular, patients with high TP53 expression (>50% positive lymphoma cells) had a shorter TTF and poor OS independent of both MIPI score and Ki-67 index.
Further examination of direct p53 target genes implicated in DNA repair showed that knockdown of Mlh1, Msh2, Rnf144b, Cav1 and Ddit4 accelerated MYC-driven lymphoma development to a similar extent as knockdown of p53.
Interestingly, experiments in mouse models have proven that conditional T-cell specific deletion of Cdkn1c gene may induce a differentiation block at the DN3 to DN4 transition, and that the loss of this gene in the absence of Tp53 led to aggressive thymic lymphomas.
The subsequent accumulation of genetic mutations and/or epigenetic modifications in driver genes, such as DDX3X and TP53, may lead to overt lymphoma and leukemia.
Patients with lymphoma showing concurrent P53 expression and MYC-R had a worse prognosis compared with patients with either P53 expression or MYC-R alone (P<0.0001).
Mutations and deletions of the tumor suppressor TP53 gene are the most frequent genetic alterations detected in human tumors, though they are rather less frequent in lymphomas.
In mouse models, the Runx genes appear to act as conditional oncogenes, as ectopic expression is growth suppressive in normal cells but drives lymphoma development potently when combined with over-expressed Myc or loss of p53.
Analysis of other B cell markers revealed a lack of paired box 5 (PAX5) in CD19 positive lymphomas with mutant TP53 (50%), which was more frequent compared to tumors with wild-type TP53 (15%, p = 0.002).
We previously showed that the HSP90 inhibitor ganetespib potently suppresses T-lymphoma initiation and progression and extends overall survival (OS) in hotspot knockin mice expressing the p53 gain-of-function mutants R175H and R248Q (mutp53) by 30-59%.
Analysis of mRNA levels for p53 transcriptional targets showed that a subset of p53 targets in the p53-null lymphomas and HCT116 cells were activated despite the absence of functional p53.
Here we show that somatic heterozygous deletion of mouse chromosome 11B3, a 4-megabase region syntenic to human 17p13.1, produces a greater effect on lymphoma and leukaemia development than Trp53 deletion.
Notably, despite their continued growth and tumorigenic potential, Runx1null lymphoma cells displayed impaired proliferation and markedly increased sensitivity to DNA damage and dexamethasone-induced apoptosis, validating Runx1 function as a potential therapeutic target in Myc-driven lymphomas regardless of their p53 status.