Acquirement of resistance to rituximab has been observed in lymphoma patients. To define mechanisms associated with rituximab resistance, we developed various rituximab-resistant cell lines (RRCL) and studied changes in CD20 expression/structure, lipid raft domain (LRD) reorganization, calcium mobilization, antibody-dependent cellular cytotoxicity, and complementmediated cytotoxicity (CMC) between parental and RRCL. Significant changes in surface CD20 antigen expression were shown in RRCL. Decreased calcium mobilization and redistribution of CD20 into LRD were found in RRCL. Western blotting identified a unique 35 kDa protein band in RRCL, which was not seen in parental cells and was secondary to an increase in surface and cytoplasmic expression of IgM light chains. CD20 gene expression was decreased in RRCL. In vitro exposure to PS341 increased CD20 expression in RRCL and minimally improved the sensitivity to rituximab-associated CMC. Our data strongly suggest that the acquisition of rituximab resistance is associated with global gene and protein down-regulation of the CD20 antigen affecting LRD organization and downstream signaling. CD20 expression seems to be regulated at the pretranscriptional and posttranscriptional levels. Proteasome inhibition partially reversed rituximab resistance, suggesting the existence of additional mediators of rituximab resistance. Future research is geared to identify drugs and/or biological agents that are effective against RRCL.

CD37 is a lineage-specific B-cell antigen that to date has been neglected as an attractive therapeutic target. To exploit this, novel CD37-specific small modular immunopharmaceuticals ( IntroductionImmunotherapy using monoclonal antibodies (MAbs) is emerging as a safe and selective method for the treatment of cancer. 1 The role of monoclonal antibodies in B-cell malignancies has expanded since the introduction of rituximab (Rituxan) targeted against the CD20 antigen on the B-cell surface in 1997. Numerous studies have confirmed the efficacy of rituximab as a single agent and in combination therapy in low-grade non-Hodgkin lymphoma (NHL), 2-6 mantle-cell lymphoma, 7-11 diffuse large-cell lymphoma, 12,13 and Burkitt leukemia/lymphoma. 14 However, only a subset of patients respond to therapy and the majority of those eventually relapse after rituximab treatment. Therefore, identification of new therapeutic targets on B cells that are potentially more effective than CD20 represents a novel strategy for therapy of B-cell malignancies.The CD37 antigen is one potential target that has not been adequately evaluated. CD37 is a heavily glycosylated 40-to 52-kDa glycoprotein and a member of the tetraspan transmembrane family of proteins. 15,16 CD37 is expressed strongly on the surface of B cells and transformed mature B-cell leukemia and lymphoma cells [17][18][19][20]22,23,25,26 but is either absent or minimally expressed on normal T cells. 21 The CD37 antigen is expressed on monocytes and granulocytes at very low density and is absent on natural killer (NK) cells, platelets, and erythrocytes. 15,22 During B-cell development, CD37 is expressed in cells progressing from pre-B to peripheral mature B-cell stages and is absent on terminal differentiation to plasma cells. 23 Although the precise function of CD37 remains unknown, it has been found to form complexes with CD53, CD81, CD82, and class II glycoprotein on B-cell surface that may represent an ion channel or a transporter. 24 CD37 has modest internalization and shedding in transformed B cells expressing the antigen. 25,26 It is highly expressed in endosomes and exosomes in B lymphocytes, reflecting possible involvement in intracellular trafficking and antigen presentation. 15 Targeted inactivation of CD37 in mice revealed no changes in the development of lymphoid organs but a reduced IgG1 level in the sera and an alteration of response to T-cell-dependent antigens, indicating a possible role of CD37 in T cell-B cell interaction. 27 Given the relative B-cell selectivity, CD37 thus represents a valuable therapeutic target for malignancies derived from peripheral mature B cells, such as B-cell chronic lymphocytic leukemia (CLL), hairy-cell leukemia (HCL), and B-cell NHL. 25,26 In particular, CLL may be a good target of CD37-based immunotherapy, because the expression of CD37 is relatively high, even compared with CD20, in this type of leukemia. 17 Efforts to target CD37 clinically have been limited. One reported preclinical trial performed in the late 1980s examined the ...

Interleukin-21 (IL-21

PURPOSE Hereditary cancer syndromes infer high cancer risks and require intensive surveillance. Identification of high-risk individuals among patients with colorectal cancer (CRC) needs improvement. METHODS Three thousand three hundred ten unselected adults who underwent surgical resection for primary invasive CRC were prospectively accrued from 51 hospitals across Ohio between January 1, 2013, and December 31, 2016. Universal Tumor screening (UTS) for mismatch repair (MMR) deficiency was performed for all, and pathogenic germline variants (PGVs) were identified using multigene panel testing (MGPT) in those who met at least one inclusion criterion: MMR deficiency, diagnosed < 50 years, multiple primary tumors (CRC or endometrial cancer), or with a first-degree relative with CRC or endometrial cancer. RESULTS Five hundred twenty-five patients (15.9%) had MMR deficiency. Two hundred thirty-four of 3,310 (7.1%; 16% of the 1,462 who received MGPT) had 248 PGVs in cancer susceptibility genes. One hundred forty-two (4.3%) had a PGV in an MMR gene, and 101 (3.1%) had a PGV in a non-MMR gene. Ten with Lynch syndrome (LS) also had a non-MMR PGV and were included in both groups. Two (0.06%) had constitutional MLH1 hypermethylation. Of unexplained MMR-deficient patients, 88.4% (76 of 86) had double somatic MMR mutations. Testing for only MMR genes in MMR-deficient patients would have missed 18 non-MMR gene PGVs (7.3% of total PGVs identified). Had UTS been the only method used to screen for hereditary cancer syndromes, 38.6% (91 of 236) would have been missed, including 6.3% (9 of 144) of those with LS. These results have treatment implications as 5.3% (175 of 3,310) had PGVs in genes with therapeutic targets. CONCLUSION UTS alone is insufficient for identifying a large proportion of CRC patients with hereditary syndromes, including some with LS. At a minimum, 7.1% of individuals with CRC have a PGV and pan-cancer MGPT should be considered for all patients with CRC.

SummaryAntibody-based therapies, such as rituximab and alemtuzumab, have contributed significantly to the treatment of Chronic Lymphocytic leukaemia (CLL). The CD40 antigen is expressed predominantly on B-cells and represents a potential target for immune-based therapies. SGN-40 is a humanized IgG1 monoclonal antibody currently in Phase I/II clinical trials for indolent lymphomas, diffuse large B cell lymphomas and Multiple Myeloma. Its biological effect on CLL cells has not been studied. The present study demonstrated that SGN-40 mediated modest apoptosis in a subset of patients with secondary cross-linking but did not mediate complementdependent cytotoxicity. SGN-40 also mediated antibody-dependent cellular cytotoxicity (ADCC) predominantly through natural killer (NK) cells. Previous studies by our group and others have demonstrated that lenalidomide upregulates CD40 expression on primary B CLL cells and activates NK-cells. We therefore examined for the combinatorial effect of lenalidomide and SGN-40 and demonstrated that both enhanced direct apoptosis and ADCC against primary CLL B cells. These data together provide justification for clinical trials of SGN-40 and lenalidomide in combination for CLL therapy.

+ Foxp3+ T regulatory cells with redundant roles in natural killer cell mediated antibody dependent cellular cytotoxicity in chronic lymphocytic leukemia, mAbs, 2:1, 35-41,

Recent advances in risk stratification provide clinicians with tools to better predict outcome of chronic lymphocytic leukemia at the time of treatment and response to treatment at the time of developing symptomatic disease.

9024 Background: While prior studies have shown robust efficacy leading to FDA approval of PARP inhibitors (PARPi) in BRCA-associated cancers, data in NSCLC are much less clear. S1900A, a LUNG-MAP substudy, evaluated the PARPi rucaparib in advanced stage NSCLC harboring BRCA1/2 mutations or genomic loss of heterozygosity (LOH) as a phenotypic marker of homologous recombination deficiency (HRD). Methods: Eligible patients (pts) were required to have a deleterious mutation in BRCA1/BRCA2 and/or high (≥21%) genomic LOH. Key eligibility criteria: advanced NSCLC patients (pts) with progression on or after platinum based chemotherapy and/or PD-(L)1 antibody and progressed on most recent line of systemic therapy, a Zubrod performance status of 0-1, adequate organ function, no ≥ grade 3 hypercholesterolemia, no previous PARPi exposure and no systemic therapy within 21 days of registration. Pts stratified by histology into two cohorts (squamous [sq] and non-squamous/mixed histology [nsq]). With 40 eligible pts per cohort, the design had 91% power to rule out an ORR of 15% if the true ORR was at least 35% at the 1-sided 5% level. A planned interim analysis on the first 20 pts evaluable for response per cohort required ≥ 3 responses to proceed to full enrollment. Results: 64 pts enrolled (27 sq cohort; 37 nsq cohort) of whom 59 are eligible. Median age 65.7 yrs; M/F 33/26 (56/44%); 98% of the pts received at least 1 prior line of treatment for stage IV disease. Biomarker selection included 36 pts (61%) LOH only, 4 pts (7%) BRCA1 only, 11 pts (19%) BRCA2 only, 4 pts (7%) BRCA1 + LOH high and 4 pts (7%) BRCA2 + LOH high. Both cohorts were closed for futility with insufficient responses in the interim analysis populations. In the full study, 4 responses (3 nsq/1 sq) were reported. ORR was 7% (95% CI: 0-13) (9% nsq/4% sq) and DCR was 62% (95% CI: 50-75) (62% nsq/64% sq); 3 of the 4 responders harbored BRCA1/2 mutations and 1 of 4 high LOH; ORR in BRCA1/2+ pts 3/23 (13%). Median PFS was 3.2 months (95% CI: 1.6-4.6) in nsq cohort and 2.9 months (95% CI 1.6-6.2) in sq cohort. Median OS was 7.8 months in nsq cohort and 7.9 months in sq cohort. The most frequent grade ≥3 adverse events were anemia (22%), lymphopenia (8%), fatigue (8%) and transaminitis (5%). Conclusions: S1900A failed to show the requisite level of efficacy for rucaparib in advanced NSCLC pts with high genomic LOH and/or a BRCA1/2 mutation. There were no new safety signals and hematologic toxicities were the most frequent adverse events. Genomic LOH as a phenotypic marker of HRD does not predict sufficient activity of rucaparib in NSCLC. These results stand in contrast to the high level of efficacy of PARPi in patients with BRCA-associated or high LOH cancers of other tumor types. Underlying biologic differences in the genomic characteristics of these cancers vs. NSCLC may be responsible. Studies examining this premise are ongoing. (NCT03845296). Clinical trial information: NCT03845296.