Prognostic and predictive impact of consensus molecular subtypes and CRCAssigner classifications in metastatic colorectal cancer: a translational analysis of the TRIBE2 study.

INTRODUCTION: The consensus molecular subtypes (CMS) demonstrated prognostic value in metastatic colorectal cancer (mCRC). Similarly, a prognostic impact was suggested for the pre-consensus CRCAssigner (CRCA) classifier in early stages. The potential predictive role of these classifiers with regard to the choice of the first-line therapy has not been established. We investigated the prognostic and predictive impact of CMS and CRCA subtypes among mCRC patients treated in the TRIBE2 study. METHODS: Among 679 randomized patients, 426 and 428 (63%) samples were profiled according to CMS and CRCA classifications, respectively. The prognostic and predictive impact of both CMS and CRCA subtypes was investigated with univariate and multivariate analyses for progression-free survival (PFS), PFS 2 (PFS2), and overall survival (OS). RESULTS: Significant associations of CMS and CRCA subtypes with PFS, PFS2, and OS were demonstrated; the CMS classifier confirmed its independent prognostic value in the multivariable model (P value for PFS/PFS2/OS = 0.01/0.07/0.08). The effect of treatment intensification was independent of CMS subtypes (P value for interaction for PFS/PFS2/OS = 0.88/0.75/0.55). A significant interaction effect between CRCA subtypes and treatment arm was demonstrated in PFS (P = 0.02), PFS2 (P = 0.01), and OS (P = 0.008). The benefit of FOLFOXIRI seemed more relevant in the stem-like (PFS, hazard ratio = 0.60; P = 0.03) and mixed subtypes (hazard ratio = 0.44; P = 0.002). These findings were confirmed in a subgroup of patients of the previous TRIBE study. CONCLUSIONS: We confirmed the independent prognostic role of CMS classification in mCRC independently of RAS/BRAF status. CRCA classification may help identifying subgroups of patients who may derive more benefit from FOLFOXIRI/bevacizumab.

Overall survival with 3 or 6 months of adjuvant chemotherapy in Italian TOSCA phase 3 randomised trial.

BACKGROUND: Oxaliplatin-based adjuvant chemotherapy is the standard treatment of high-risk colon cancer (CC). A shorter duration (3 months) can achieve a similar outcome [in terms of relapse-free survival (RFS)] to a longer duration. This study reports the overall survival (OS) analysis of the three or six colon adjuvant (TOSCA) phase III study. It assessed different adjuvant chemotherapy durations in patients with resected high-risk stage II and stage III CC. MATERIAL AND METHODS: TOSCA was an open-label, phase III, multicentre, non-inferiority trial conducted in 130 Italian centres. Patients were randomly assigned, in a 1 : 1 ratio, to receive 3 months of standard doses of FOLFOX/CAPOX, or 6 months of FOLFOX/CAPOX. Patients with histologically confirmed high-risk stage II and III CC were included, with RFS being the primary end point. OS was a secondary end point. RESULTS: From June 2007 to March 2013, 3759 patients were accrued. At a median follow-up of 7 years, the hazard ratio (HR) for RFS of the 3-month versus 6-month arms was 1.13; 95% confidence interval (CI) 0.99-1.29, P for non-inferiority = 0.380, P for superiority = 0.068, crossing the non-inferiority limit of 1.20. This result did not allow us to reject the null hypothesis of the inferiority of the 3-month arm. The HR for OS of the 3-month versus 6-month arms was 1.09 (95% CI 0.93-1.26, P for superiority = 0.288). At the last follow-up analysis, the absolute OS difference between arms was <1%. CONCLUSIONS: The present analysis of the TOSCA trial does not indicate any significant difference in OS between the treatment groups. The extra benefit provided by the longer treatment should be balanced against the extra toxicity of more prolonged therapy. The trial is registered with ClinicalTrials.gov, registration number: NCT0064660.

Impact of age and gender on the safety and efficacy of chemotherapy plus bevacizumab in metastatic colorectal cancer: a pooled analysis of TRIBE and TRIBE2 studies.

BACKGROUND: The phase III TRIBE and TRIBE2 studies randomized metastatic colorectal cancer patients to first-line FOLFOXIRI/bevacizumab or a doublet (FOLFIRI or FOLFOX)/bevacizumab. The studies demonstrated a significant benefit from the triplet at the price of an increased incidence of chemotherapy-related adverse events (AEs). In both trials, males and females aged between 18 and 70 years with ECOG PS ≤2 and between 71 and 75 years with ECOG PS = 0 were eligible. We investigated the effect of FOLFOXIRI/bevacizumab versus doublets/bevacizumab according to age and gender. PATIENTS AND METHODS: Subgroup analyses according to age (<70 versus 70-75 years) and gender were carried out for overall response rate (ORR), progression-free survival (PFS), and AE rates. RESULTS: Of 1187 patients, 1005 (85%) were aged <70 years and 182 (15%) 70-75 years; 693 (58%) were males and 494 (42%) females. There was no evidence of interaction between age or gender and the benefit provided by the intensification of the upfront chemotherapy in terms of ORR and PFS, or the increased risk of experiencing G3/4 AEs. Elderly patients and females experienced higher rates of overall G3/4 AEs (73% versus 60%, P < 0.01 and 69% versus 57%, P < 0.01, respectively). Notably, in the FOLFOXIRI/bevacizumab subgroup, G3/4 diarrhea and febrile neutropenia occurred in 27% and 16% of elderly patients, respectively, while females reported high incidences of any grade nausea (67%) and vomiting (50%). CONCLUSIONS: The improvements in terms of ORR and PFS of FOLFOXIRI/bevacizumab versus doublets/bevacizumab are independent of gender and age, with a similar relative increase in AEs among elderly patients and females. Initial dose reductions and possibly primary G-CSF prophylaxis should be recommended for patients between 70 and 75 years old treated with FOLFOXIRI/bevacizumab, and a careful management of antiemetic prophylaxis should be considered among females.

The prognostic impact of primary tumour location in patients with stage II and stage III colon cancer receiving adjuvant therapy. A GISCAD analysis from three large randomised trials.

PURPOSE: Because the role of the primary tumour location in the adjuvant setting has not been clearly established in colon cancer, we analysed the clinical outcome according to the primary tumour location from three Italian trials assessing adjuvant therapy in colon cancer. PATIENTS AND METHODS: Overall survival (OS) and disease-free survival (DFS) were assessed globally and in each trial, according to right-sided, transverse and left-sided primary colon cancer. Analysis was planned to provide overall and stage-specific results. RESULTS: Individual data of 5239 patients were included in this analysis. The right-sided tumours were 1540 (29%), tumours originating in the transverse were 815 (16%) and left-sided tumours were 2884 (55%). At the multivariate analysis, DFS findings from the comparison of the right-sided versus left-sided tumours (hazard ratio [HR] = 1.00; 95% confidence interval [CI] = 0.89-1.14) were not statistically associated with clinical outcomes in the overall population. On the contrary, OS findings, from the comparison of the right-sided versus left-sided tumours, were significantly associated with outcomes (HR = 1.20; 95% CI = 1.04-1.39). In stage II patients, there was no difference in terms of DFS and OS among the three different tumour locations, whereas in stage III patients, the left-sided tumours showed an improved prognosis in terms of OS (HR: 1.36 95% CI = 1.14-1.62, p < 0.001). CONCLUSION: This is the largest analysis demonstrating a prognostic effect of the tumour location on patients with colon cancer receiving adjuvant chemotherapy. Nevertheless, the effect is limited to OS in stage III colon cancer. In stage II tumours, the primary location has a lesser impact. The transverse tumours should be prognostically considered in between the right-sided and left-sided tumours.

Dihydropyrimidine dehydrogenase pharmacogenetics for predicting fluoropyrimidine-related toxicity in the randomised, phase III adjuvant TOSCA trial in high-risk colon cancer patients.

BACKGROUND: Dihydropyrimidine dehydrogenase (DPD) catabolises ∼85% of the administered dose of fluoropyrimidines. Functional DPYD gene variants cause reduced/abrogated DPD activity. DPYD variants analysis may help for defining individual patients' risk of fluoropyrimidine-related severe toxicity. METHODS: The TOSCA Italian randomised trial enrolled colon cancer patients for 3 or 6 months of either FOLFOX-4 or XELOX adjuvant chemotherapy. In an ancillary pharmacogenetic study, 10 DPYD variants (*2A rs3918290 G>A, *13 rs55886062 T>G, rs67376798 A>T, *4 rs1801158 G>A, *5 rs1801159 A>G, *6 rs1801160 G>A, *9A rs1801265 T>C, rs2297595 A>G, rs17376848 T>C, and rs75017182 C>G), were retrospectively tested for associations with ⩾grade 3 fluoropyrimidine-related adverse events (FAEs). An association analysis and a time-to-toxicity (TTT) analysis were planned. To adjust for multiple testing, the Benjamini and Hochberg's False Discovery Rate (FDR) procedure was used. RESULTS: FAEs occurred in 194 out of 508 assessable patients (38.2%). In the association analysis, FAEs occurred more frequently in *6 rs1801160 A allele carriers (FDR=0.0083). At multivariate TTT analysis, significant associations were found for *6 rs1801160 A allele carriers (FDR<0.0001), *2A rs3918290 A allele carriers (FDR<0.0001), and rs2297595 GG genotype carriers (FDR=0.0014). Neutropenia was the most common FAEs (28.5%). *6 rs1801160 (FDR<0.0001), and *2A rs3918290 (FDR=0.0004) variant alleles were significantly associated with time to neutropenia. CONCLUSIONS: This study adds evidence on the role of DPYD pharmacogenetics for safety of patients undergoing fluoropyrimidine-based chemotherapy.

MTHFR-1298 A>C (rs1801131) is a predictor of survival in two cohorts of stage II/III colorectal cancer patients treated with adjuvant fluoropyrimidine chemotherapy with or without oxaliplatin.

Adjuvant treatment based on fluoropyrimidines (FL) improves the prognosis of stage II/III colorectal cancer (CRC). Validated predictive/prognostic biomarkers would spare therapy-related morbidity in patients with a good prognosis. We compared the impact of a set of 22 FL-related polymorphisms with the prognosis of two cohorts of CRC patients treated with adjuvant FL with or without OXA, including a total of 262 cases. 5,10-Methylentetrahydrofolate reductase (MTHFR) MTHFR-1298 A>C (rs1801131) polymorphism had a concordant effect: MTHFR-rs1801131-1298CC genotype carriers had a worse disease free survival (DFS) in both the cohorts. In the pooled population MTHFR-rs1801131-1298CC carriers had also a worse overall survival. We computed a clinical score related to DFS including MTHFR-rs1801131, tumor stage, sex and tumor location, where rs1801131 is the most detrimental factor (hazard ratio=5.3, 95% confidence interval=2.2-12.9; P-value=0.0006). MTHFR-rs1801131 is a prognostic factor that could be used as an additional criteria for the choice of the proper adjuvant regimen in stage II/III colorectal cancer patients.

A prospective validation pharmacogenomic study in the adjuvant setting of colorectal cancer patients treated with the 5-fluorouracil/leucovorin/oxaliplatin (FOLFOX4) regimen.

The discovery of pharmacogenomic markers in colorectal cancer (CRC) could be setting-specific. FOLFOX4 is employed in the adjuvant and metastatic setting in CRC. This prospective study is aimed to validate in the adjuvant setting the pharmacogenomic markers of toxicity reported in the metastatic setting (that is, GSTP1-rs947894, and -rs1138272; GSTM1-null genotype; AGXT-rs4426527, -rs34116584 and del-74 bp), and to discover additional markers. CRC patients (n=144) treated with adjuvant FOLFOX4 were genotyped for 57 polymorphisms in 29 genes. Grade ≥ 2 neurotoxicity was associated (false discovery rate-adjusted q-value <0.1) with single-nucleotide polymorphisms in ABCC1 (rs2074087: odds ratio=0.43(0.22-0.86)), and ABCC2 (rs3740066: 2.99(1.16-7.70); rs1885301: 3.06(1.35-6.92); rs4148396: 4.69(1.60-13.74); rs717620: 14.39(1.63-127.02)). hMSH6-rs3136228 was associated with grade 3-4 neutropenia (3.23(1.38-7.57), q-value=0.0937). XRCC3-rs1799794 was associated with grade 3-4 non-hematological toxicity (8.90(2.48-31.97), q-value=0.0150). The markers previously identified in metastatic CRC were not validated. We have identified new markers of toxicity in genes of transport and DNA repair. If validated in other studies, they could help to identify patients at risk of toxicity.

Phase II study of a triplet regimen in advanced colorectal cancer using methotrexate, oxaliplatin and 5-fluorouracil.

Building upon the concept of schedule-specific biochemical modulation of 5-fluorouracil (FU), which alternates bolus and continuous infusion (CI) FU, we have incorporated oxaliplatin (l-OHP) following the bolus part of the regimen to explore the activity of this new combination. Patients with advanced, untreated, measurable colorectal cancer received sequential methotrexate (MTX) (days 1 and 15)-->l-OHP+FU (days 2 and 16) (200, 85 and 600 mg m(-2), respectively) followed by 3 weeks of CI FU (200 mg m(-2) day(-1)) given from day 29 to 50, modulated by weekly leucovorin (LV) (20 mg m(-2)). After 1 week of rest, the second cycle was started. The treatment was continued until progression or patient's refusal. According to the intention-to-treat analysis on all 46 patients accrued, the response rate was 42% (95% CL=28-55%), with three complete responses and 16 partial responses. The median overall survival was 15.9 months and the median progression-free survival 6.9 months. Toxicity was very mild, with the bolus part of the regimen more toxic than the infusional part (24 vs 7% of grade III-IV, respectively). This new combination of MTX -->l-OHP-FU followed by FU CI is well tolerated, feasible and produces activity results similar to other more simple, but more toxic, regimens. Pros and cons of the different fluoropyrimidines-l-OHP combinations are discussed.

Dose finding of ifosfamide administered with a chronic two-week continuous infusion.

PURPOSE: Ifosfamide (IFO) is an active drug in several malignancies. A short-term 3- to 7-day (A) continuous infusion (c.i.) has been used in different tumor types. The 14-day c.i. (B) has been investigated in advanced breast cancer and in soft tissue sarcoma patients at a fixed daily dose. The tolerance and response rate (RR) of therapies A and B has been considered encouraging. AIM: To study the 14-day c.i. IFO schedule, every 28 days, with a dose-finding approach. METHODS: From January 1998 to December 2001, 34 pretreated patients with advanced malignancy and disease progression were treated with c.i. IFO (and the same dose of mesna) from 400 to 1,000 mg/m(2)/24 h for 2 consecutive weeks every 28 days. An elastomeric pumping device via an Infuse-a-Port((R)) or a Groshong((R)) catheter was used. RESULTS: A total of 159 cycles were evaluable for toxicity and results. No toxic deaths occurred. Three patients (8.8%) had a severe acute allergic cutaneous reaction with various grade 3-4 toxicities requiring hospitalization and therapy was stopped at day 6 of the first cycle, 7 and 12 of the second cycle respectively. In the other 31 patients, grade 4 neutropenia occurred in 6 (19.3%) and it represented the main toxicity. There was a positive relationship between the IFO dose step and neutropenia (p = 0.001). A positive relationship was observed between the RR and the received total IFO dose (g) (p < 0.004). Twelve patients out of 31 had progressive disease (PD) (38.7%), 8 had partial remission (PR) (25.8%), and 11 maintained a steady state (35.5%). Six of the 12 patients (50%) with PD and 2 of the 8 PRs (25%) had bone metastases. CONCLUSIONS: IFO c.i. is generally well tolerated, but acute untoward allergic reactions can occur. In chemotherapy-pretreated patients the recommended daily dose of continuously infused IFO for 14 days every 4 weeks is 900 mg/m(2)/day, together with mesna at the same dose schedule.

Cisplatin and gemcitabine in non-small-cell lung cancer.

The nucleoside analogue, gemcitabine, has shown activity as a single agent in the treatment of metastatic non-small-cell lung cancer (NSCLC), producing consistent response rates of 20% and above. Because of its unique mechanism of action and its non-overlapping toxicity with other active agents, gemcitabine is an attractive candidate for trials in combination with other cytotoxic agents. In preclinical models, the cisplatin-gemcitabine combination suggested synergy between the two drugs. In phase I-II studies, response rates are as high as 54% when gemcitabine is combined with cisplatin, both in stage III and IV NSCLC. The gemcitabine-containing regimens showed a favourable safety-efficacy profile and compared well with standard regimens used in NSCLC. These preliminary results must be validated by large randomised trials comparing gemcitabine-containing regimens with NSCLC reference chemotherapy regimens.

Physical and functional association of CD45 and CD3-TCR complex on CD1+ human thymocytes. Evidence that the engagement of CD45 molecules can prevent CD1+ thymocytes from apoptosis.

In this study the effects of CD45 engagement on CD3-TCR-driven stimulation of CD1+ human immature thymocytes have been analyzed. Simultaneous cross-linking of CD45 and CD3 antigens on highly purified CD1+ thymocytes reduced the number of cells undergoing apoptosis after 16 h of in vitro culture. This cell population might represent immature thymocytes committed in vivo to die by programmed cell death (PCD). CD45 engagement could also increase the number of cycling CD1+ thymocytes; of note, the large majority (> 95%) of dividing cells expressed the CD1 molecule at the cell surface, indicating that proliferating cells were actually represented by immature thymocytes. These data suggest that the CD45 molecule might play a role in the rescue of immature thymocytes from PCD during differentiation. Along this line, we found that activation of CD1+ thymocytes via the CD3-TCR complex could be enhanced by CD45, both in terms of transcription and surface expression of IL-2R. These effects might be explained by the finding that the CD45 molecule (but not its isoforms CD45RO and RA) was physically associated with the CD3-TCR complex at the cell surface of CD1+ human thymocytes, as shown by co-precipitation and co-capping experiments. Finally, cross-linking of CD45 and CD3 antigens led to the expansion of CD3+ thymocytes co-expressing CD4 and CD8, indicating that simultaneous engagement of CD45 and CD3 molecules can block CD1+ cells at the double-positive (CD3+CD4+CD8+) differentiation stage. On the other hand, stimulation through CD3 resulted in the expansion of thymocytes showing a mature phenotype (CD3+CD4+ or CD3+CD8+). Altogether, these findings suggest that the CD45 molecule is involved both in early activation and in the regulation of CD1+ thymocyte differentiation.

Expression of human NKRP1A by CD34+ immature thymocytes: NKRP1A-mediated regulation of proliferation and cytolytic activity.

In this study, we show that NKRP1A is expressed and functions on a subset of immature human thymocytes. We took advantage of the monoclonal antibody (mAb) 191B8 that was obtained by immunizing mice with cultured human thymocytes characterized by an immature surface phenotype [CD2- CD3- CD4- CD8- stem cell factor receptor (SCFR)+] and expressing cytoplasmic CD3 epsilon chain. The 191B8 antibody homogeneously reacted with the immunizing population but not with most unfractionated thymocytes. It stained a minor population of resting immature thymocytes co-expressing CD34, SCFR, or both. Following culture of the CD34+ or CD34- fractions of CD2- CD3- CD4- CD8- purified immature thymocytes with recombinant interleukin-2 (rIL-2), the 191B8-defined antigen was expressed on virtually all cells even when 191B8+ cells were removed from the starting population. On the other hand, no 191B8+ cells were detected in fresh or cultured thymocytes expressing a more mature phenotype. Biochemical analysis of 191B8 mAb-reactive molecules revealed, under non-reducing conditions, two bands displaying apparent molecular masses of 80 and 44 kDa and a single band of 44 kDa under reducing conditions. Digestion with proteases indicated that the 80-kDa form represented a homodimeric form of two 44-kDa molecules, while deglycosylation with N-glycanase suggested the existence of four N-glycosylation sites. Transfection of COS7 or NIH3T3 cells with hNKRP1A cDNA showed that the 191B8 mAb recognized NKRP1A as shown by both immunofluorescence analysis and immunoprecipitation experiments. Functional studies showed that the 191B8/NKRP1A molecule mediated strong inhibition of the cytolytic activity of cultured CD2- CD3- immature thymocytes against a panel of tumor target cells. More importantly, 191B8 mAb induced proliferation of CD2- CD3- fresh thymocytes which was not increased by rIL-2. Thus, we propose that NKRP1A molecules, which are expressed in highly immature thymocytes, may play a regulatory role in their growth and function.

Dissection of lymphocyte function-associated antigen 1-dependent adhesion and signal transduction in human natural killer cells shown by the use of cholera or pertussis toxin.

The effect of the guanosine triphosphate-binding protein (G-protein) inhibitors cholera toxin (Ctx) and pertussis toxin (Ptx) has been analyzed on lymphocyte function-associated antigen 1 (LFA-1)-dependent adhesion and signal transduction in human natural killer (NK) cells. Ctx, but not Ptx, inhibited the LFA-1-dependent adhesion of NK cells to tumor target cells which constitutively express the intercellular cell adhesion molecule-1 (ICAM-1) and to NIH/3T3 mouse fibroblasts stably transfected with human ICAM-1. This effect was detectable only by the use of the entire Ctx but not of the Ctx B subunit. In addition, Ctx could inhibit both NK cell binding and spreading to purified ICAM-1 protein. NK cell treatment with Ctx modified neither the surface expression of LFA-1 nor its Mg2+ binding site. These findings, together with the absence of any detectable effect of Ctx on the constitutive phosphorylation of LFA-1 alpha, suggests that this toxin modifies the avidity of LFA-1 for ICAM-1 by acting on LFA-1-cytoskeletal protein association. Unlike Ctx, Ptx did not affect NK cell adhesion. The effects of Ctx and Ptx are unlikely to depend on intracellular levels of cyclic adenosine 3',5'-monophosphate (cAMP), since a strong increase of cAMP was induced by both toxins. Moreover, this was confirmed by the observation that the LFA-1-dependent adhesion was not inhibited by the adenylate cyclase activator forskolin (FSK), the phosphodiesterase inhibitor isobutyl-1-methylxanthine (IBMX), or both, which increase intracellular cAMP levels. Unlike the differential effect on cell adhesion, both the intracellular calcium [Ca2+]i increase and phosphoinositide breakdown mediated via LFA-1 were consistently inhibited in a dose-dependent manner by both Ctx and Ptx. Also in this case, the inhibitory effect did not depend on an increase of intracellular cAMP as indicated by NK cell treatment with FSK, IBMX, or both. Further evidence of the involvement of G-proteins in LFA-1-mediated signal transduction was the inhibitory effect of the GDP analog guanosine-5'-O-2-thiodiphosphate (GDP beta S) on LFA-1-mediated calcium mobilization. Taken together, our data provide evidence that the LFA-1-mediated NK cell adhesion and signal transduction are partially independent phenomena which may be regulated by different G-proteins.

p40, a novel surface molecule involved in the regulation of the non-major histocompatibility complex-restricted cytolytic activity in humans.

Four monoclonal antibodies (mAb) termed NKTA255, NKTA72, 1F1 and 1B1 were selected on the basis of their ability to inhibit the cytolytic activity of natural killer (NK) cell clones against P815 target cells. These mAb selectively reacted with normal or tumor cells of hematopoietic origin and displayed a cellular distribution similar to that of CD45 or CD11a/CD18 antigens. Immunoprecipitation experiments showed that they reacted with molecules with an apparent molecular mass of 40 kDa under both reducing and nonreducing conditions ("p40" molecules), thus differing from CD45 or CD11a/CD18 antigens as well as from the "inhibitory" receptors for HLA class I molecules (i.e. p58, CD94 and NKB1 molecules). Double-immunofluorescence analysis of peripheral blood mononuclear cells allowed the identification of three distinct populations on the basis of the fluorescence intensity of cells stained with anti-p40 mAb. p40bright cells were homogeneously HLA-DR-positive, p40medium cells were HLA-DR-negative but co-expressed CD56 antigens, while p40dull cells were all CD3+. Anti-p40 mAb strongly inhibited the lysis of K562 target cells, mediated by fresh NK cells, as well as the lysis of P815 target cells by NK or T cell clones. In addition, in redirected killing assays, anti-p40 mAb strongly reduced the anti-CD16 mAb-induced cytolytic activity of NK cell clones. On the contrary, they did not inhibit either the anti-CD3 or anti-T cell receptor mAb-mediated cytolytic activity of T cell clones or the lysis of allogeneic phytohemagglutinin blasts mediated by specific cytolytic T cell clones. The p40-induced inhibition of the NK cytotoxicity required optimal cross-linking, as anti-p40 mAb could inhibit the lysis of Fc gamma receptor (Fc gamma R)-positive but not of Fc gamma R-negative target cells. In addition, (Fab')2 fragments of anti-p40 mAb failed to inhibit the lysis of Fc gamma R-positive target cells. In conclusion, p40 molecules represent a new type of inhibitory surface molecule that appears to play a general regulatory role in the NK-mediated cytolysis.

Expression of a wide T cell receptor V beta repertoire in human T lymphocytes derived in vitro from embryonic liver cell precursors.

As shown recently, CD3+/TcR+ functional T lymphocytes can be derived in culture from embryonic liver cell precursors at a gestational age (6-8 weeks) preceding the colonization of the epithelial thymus. In this report, we analyzed the V beta repertoire of T lymphocytes derived from embryonic liver by applying a quantitative reverse transcriptase-polymerase chain reaction technique. To this end, oligonucleotide primers for C alpha or the various human V beta have been used to study both freshly derived embryonic liver cell suspensions and CD3+/TcR+ populations derived after approximately 6 weeks upon stimulation with 1% phytohemagglutinin and culture in 100 units/ml recombinant interleukin-2. In order to exclude possible contaminations with mother-derived T lymphocytes, only T cells displaying both X and Y chromosomal sequences (i.e. derived from male embryos) were further analyzed. While neither C alpha nor the various V beta could be detected in fresh liver cells, C alpha and the large majority of V beta were detected in in vitro cultured populations. The levels of the various V beta expressed by embryo-derived T cells was similar to that detected in adult peripheral blood-derived T lymphocytes. These experiments indicate that the immature liver precursors can potentially give rise in vitro to T cells which express a wide V beta repertoire and may provide a suitable in vitro system for the analysis of the selection processes mediated by either major histocompatibility complex antigen or superantigens.

CD45-mediated regulation of LFA1 function in human natural killer cells. Anti-CD45 monoclonal antibodies inhibit the calcium mobilization induced via LFA1 molecules.

The TA218 and T205 monoclonal antibodies (mAb) were selected on the basis of their ability to inhibit the non-major histocompatibility complex-restricted lysis of the murine mastocytoma P815 cell line mediated by CD3-CD16+ natural killer (NK) cells. Both mAb were found to react with CD45 molecules, as demonstrated by immunoprecipitation after surface iodination and western blot analysis. A panel of tumor target cells susceptible to lysis by polyclonal or clonal CD3-CD16+ NK cells was used to study the mAb-mediated inhibitory effect. The inhibition of cytolysis mediated by TA218 and T205 mAb was found to consistently parallel the inhibition mediated (with the same tumor target cells) by the anti-LFA1 alpha mAb TS.1.22 or by the anti-LFA1 beta mAb TS.1.18. However, different from the anti-LFA1 mAb, T205 or TA218 mAb did not inhibit the binding of activated CD3-CD16+ effector NK cells to the same tumor target cells. This finding supported the concept that the anti-CD45 mAb-mediated inhibition could occur at a post-binding stage. In polyclonal or clonal CD3-CD16+ NK cells T205 or TA218 mAb were found to reduce by 50-70% the intracellular Ca++ ([Ca++]i) mobilization induced by anti-LFA1 alpha or anti-LFA1 beta mAb. On the other hand, TA218 and T205 mAb did not inhibit the Ca++ mobilization induced by anti-CD16 mAb or phytohemagglutinin, thus suggesting that, in NK cells, CD45 molecules may exert a selective inhibitory effect on the signal transduction mediated by LFA1 molecules. In line with this hypothesis, the cytolytic activity of human NK clones was triggered in the presence of the hybridoma cells secreting either anti-CD16 or anti-LFA1 alpha mAb (as "triggering targets"). This effect of anti-LFA1 alpha, but not of anti-CD16 hybridoma was susceptible to inhibition by the anti-CD45 mAb T205 or TA218. Further, experiments on cloned NK cells indicated that T205 or TA218 mAb induced a strong decrease in the constitutive phosphorylation of the LFA1 alpha chain (but not of HLA class I antigens). Taken together, these studies suggest that in human NK lymphocytes, CD45 molecule may regulate both the activation state and the function of the LFA1 molecule.

Extrathymic differentiation of T lymphocytes and natural killer cells from human embryonic liver precursors.

Liver cells were isolated on Ficoll/Hypaque gradients from embryos or fetuses at 6-10 weeks of gestation; 2-20% of the cells expressed CD45 or HLA class I surface antigens and 2-6% expressed CD7. Other T- or natural-killer (NK)-cell-lineage-specific markers were undetectable. Liver-cell suspensions cultured in the presence of phytohemagglutinin and recombinant interleukin 2 gave rise to large proportions of CD3+ lymphocytes expressing either alpha/beta or gamma/delta T-cell receptors. This occurred not only in bulk cultures but also when cells were cloned under limiting dilution conditions. Importantly, these figures were obtained also in embryos at 6-8 weeks of gestation, which is before colonization of the thymic rudiment by T-cell precursors. When the same liver-cell suspensions were cultured in the presence of irradiated H9 cells and recombinant interleukin 2 (either in bulk cultures or under cloning conditions), large proportions of cells (or clones) expressed surface CD16 and CD56 antigens and displayed a strong cytolytic activity against both NK-sensitive (K562) and NK-resistant (M14) target cells. In addition, liver-derived T or NK cells expressed functional receptor molecules since they could be activated via either CD3/T-cell receptor or CD16 surface antigens, respectively. Further fractionation of liver cells on the basis of CD45 antigen expression indicated that only CD45+ cells could give rise to T or NK cells in culture. Thus, CD45 can be used as a marker for identification of an early liver-cell population containing T- and NK-cell precursors. That T or NK cells were derived from male embryos and not from the mother was shown by PCR amplification of X and Y chromosomal sequences. Our present data may offer an in vitro model for extrathymic embryonic T-cell maturation that can be used to examine fundamental aspects of human T-cell development and function.

CD69-mediated pathway of lymphocyte activation: anti-CD69 monoclonal antibodies trigger the cytolytic activity of different lymphoid effector cells with the exception of cytolytic T lymphocytes expressing T cell receptor alpha/beta.

The effect of anti-CD69 monoclonal antibodies (mAbs) on the induction of the cytolytic activity in different types of lymphoid effector cells has been investigated. Three anti-CD69 mAbs, including the reference mAb MLR3 and two new mAbs (c227 and 31C4), have been used. All cloned CD3-CD16+ natural killer (NK) cells belonging to different subsets (as defined by the surface expression of GL183 and/or EB6 antigens) were efficiently triggered by anti-CD69 mAbs and lysed P815 mastocytoma cells in a redirected killing assay. Triggering of the cytolytic activity could also be induced in CD3-CD16- NK clones, which fail to respond to other stimuli (including anti-CD16, anti-CD2 mAbs, or phytohemagglutinin). A similar triggering effect was detected in T cell receptor (TCR) gamma/delta+ clones belonging to different subsets. On the other hand, anti-CD69 mAbs could not induce triggering of the cytolytic activity in TCR alpha/beta+ cytolytic clones. Since all thymocytes are known to express CD69 antigen after cell activation, we analyzed a series of phenotypically different cytolytic thymocyte populations and clones for their responsiveness to anti-CD69 mAb in a redirected killing assay. Again, anti-CD69 mAb triggered TCR gamma/delta+ but not TCR alpha/beta+ thymocytes. Anti-CD69 mAb efficiently triggered the cytolytic activity of "early" thymocytes lines or clones (CD3-4-8-7+), which lack all other known pathways of cell activation. Thus, it appears that CD69 molecules may initiate a pathway of activation of cytolytic functions common to a number of activated effector lymphocytes with the remarkable exception of TCR alpha/beta+ cytolytic cells.