Gene expression profiling with corresponding clinical data
Gene LY2784544 profiling with corresponding clinical data supported the notion that increased expression of S1PR1 in DLBCL was associated with poor outcome , , . These studies also identified increased expression of the GPCRs GPR183, CCR7, ADRB2 and CNR2 as risk factors for poor outcome . However, a conflicting study found that CNR2 protein expression was not associated with outcome or related to ABC/GCB subtype . While the significance of cannabinoid receptor expression in DLBCL remains to be elucidated, it has been shown that CNR1 and CNR2 mRNA were both upregulated in DLBCL compared to reactive lymph node tissue  and that 45/79 (57%) patients were CNR2 immunopositive . Chemokine receptor expression in DLBCL is shown in Table 1. Consistent with its role in NHL, CXCR4 plays an important role in enabling cell migration in DLBCL. Increased CXCR4 expression was associated with worse survival in both ABC and GCB subtypes for 468 patients treated with the standard therapy R-CHOP  and a separate study of 94 patients found that those positive for CXCR4 has reduced survival and increased recurrence of disease . However, a smaller cohort of 70 Korean patients did not identify an association between CXCR4 expression and survival . At the cellular level, strong nuclear CXCR4 staining was correlated with systemic DLBCL whereas strong cytoplasmic CXCR5 staining was correlated with CNS involvement . Furthermore, hypoxia was associated with upregulation of CXCR4 protein  and such an increase in CXCR4 expression is believed to increase cell dissemination . IHC revealed that 80% of patients had CXCR4 coexpressed with NF-κB , which is often mutated in DLBCL, while CXCR4 itself contains an AIDCA somatic hypermutation hotspot that is suspect to mutation . Various therapeutics targeting CXCR4 in DLBCL have been studied including the CXCR4 antagonist plerixafor which enhanced rituximab treatment , BTK140 which inhibited growth in cell lines , PIM inhibitors which impaired proliferation and CXCR4-mediated migration , and in vivo blocking of CXCR4 which was critical for regulatory T cell attraction to lymphoma . CCR1 expression was IHC positive in 77/209 (37%) of DLBCL cases and associated with the ABC subtype of DLBCL but did not correlate with survival . At least 75% of gastric extranodal DLBCL cases had positive mRNA expression for CCR1 along with the chemokine receptors CCR5, CCR7, CCR8, CCR9, CXCR3, CXCR5, CXCR6, CXCR7 and XCR1 , . IHC was also positive in the majority of extranodal cases for CCR8, CCR9, CXCR4, CXCR6 and CXCR7 . Multiple reports have highlighted the difference in chemokine receptor expression based on anatomical location of DLBCL. Similar to FL, IHC staining of CCR9 was stronger in gastrointestinal DLCBL compared to nodal DLBCL . XCR1 surface protein was found to be significantly elevated in DLBCL cases manifesting in the bone marrow  and also present in the majority of extranodal DLBCL cases . CXCR3 protein expression was higher in thyroid DLBCL than stomach DLBCL  and has also been observed in case reports of epidermotropic B cell lymphoma  and intravascular large B cell lymphoma . Closely related primary mediastinal large B-cell lymphomas (PMBCLs or MLBCLs) have been characterized by increased CCR9 and decreased CCR6, CCR7 and CXCR5 immunoreactivity compared to nonmediastinal DLBCL , . Finally, although not a chemokine receptor, analysis of 57 NHL biopsies found that 9/10 (90%) PMBCL and 1/9 (11%) DLBCL cases were positive for the leukotriene receptor CYSLT1 but no positive samples were found in other NHL subtypes . Other chemokine receptors that have been observed in DLBCL include CX3CR1, which was found to be present in up to 43% of cases and enriched in the GCB subtype . IHC of 80 DLBCL cases found that 10 (12.5%) were positive for CCR4 expression but this had no correlation with patient outcome . CCR4 expression may be subtype specific as DLBCL originating from the thyroid and stomach had very few cells positive for CCR4 protein expression  but multiple case reports of CCR4 in other DLBCL subgroups have been reported , , .