CD19-Chimeric Antigen Receptor T Cells for Treatment of Chronic Lymphocytic Leukaemia and Acute Lymphoblastic Leukaemia

Adoptive cell therapy (ACT) for cancer represents a promising new treatment modality. ACT based on the administration of cytotoxic T cells genetically engineered to express a chimeric antigen receptor (CAR) recognizing CD19 expressed by B cell malignancies has been shown to induce complete lasting responses in patients with chronic lymphocytic leukaemia (CLL) and acute lymphoblastic leukaemia (ALL). So far, eleven clinical trials including 99 CLL and ALL patients treated with CAR T cells targeting CD19 have been published, and the results from these trials are promising with impressive clinical responses in heavily pretreated patients. Thus, CAR T cell therapy has induced complete responses in both CLL and ALL, and surprisingly, current results indicate that patients with ALL are more prone to respond than are CLL patients. Importantly, the majority of CAR cell studies have observed severe therapy-associated toxicities, which needs attention. Herein we review current data and discuss key aspects of this powerful approach to treat and potentially cure B cell malignancies.

Characterization and comparison of 'standard' and 'young' tumour-infiltrating lymphocytes for adoptive cell therapy at a Danish translational research institution

Adoptive cell therapy (ACT) with ex vivo expanded tumour-infiltrating lymphocytes (TILs) in combination with IL-2 is an effective treatment for metastatic melanoma. Modified protocols of cell expansion may allow the treatment of most enrolled patients and improve the efficacy of adoptively transferred cells. The aims of this study were to establish and validate the novel 'Young TIL' method at our institution and perform a head-to-head comparison of clinical-grade products generated with this protocol opposed to the conventional 'Standard TIL', which we are currently using in a pilot ACT trial for patients with melanoma. Our results confirm that 'Young TILs' display an earlier differentiation state, with higher CD27 and lower CD56 expression. In addition, CD8(+) TILs expressing CD27 had longer telomeres compared with the CD27(-). A recently described subset of NK cells, endowed with a high expression of CD56 (CD56(bright)), was detected for the first time in both types of cultures but at a higher frequency on Young TILs. Young and Standard TILs' reactivity against autologous tumours was similar, with significant expression of TNF-α/IFN-γ/CD107a by CD8(+) TILs detected in all cultures analysed. However, either slow expansion with high-dose IL-2 only or large numerical expansion with a rapid expansion protocol, which is required for current therapeutic protocols, significantly modified TIL phenotype by reducing the frequency of less differentiated, cancer-specific TILs. These studies further support the adoption of the Young TIL method in our current ACT trial and highlight the importance of continuous quality control of expansion protocols.

The CIMT-monitoring panel: a two-step approach to harmonize the enumeration of antigen-specific CD8+ T lymphocytes by structural and functional assays

The interpretation of the results obtained from immunomonitoring of clinical trials is a difficult task due to the variety of methods and protocols available to detect vaccine-specific T-cell responses. This heterogeneity as well as the lack of standards has led to significant scepticism towards published results. In February 2005, a working group was therefore founded under the aegis of the Association for Immunotherapy of Cancer ("CIMT") in order to compare techniques and protocols applied for the enumeration of antigen-specific T-cell responses. Here we present the results from two consecutive phases of an international inter-laboratory testing project referred to as the "CIMT monitoring panel". A total of 13 centers from six European countries participated in the study in which pre-tested PBMC samples, synthetic peptides and PE-conjugated HLA-tetramers were prepared centrally and distributed to participants. All were asked to determine the number of antigen-specific T-cells in each sample using tetramer staining and one functional assay. The results of the first testing round revealed that the total number of cells analyzed was the most important determinant for the sensitive detection of antigen-specific CD8(+) T-cells by tetramer staining. Analysis by ELISPOT was influenced by a combination of cell number and a resting phase after thawing of peripheral blood mononuclear cells. Therefore, the experiments were repeated in a second phase but now the participants were asked to change their protocols according to the new guidelines distilled from the results of the first phase. The recommendations improved the number of antigen-specific T-cell responses that were detected and decreased the variability between the laboratories. We conclude that a two-step approach in inter-laboratory testing allows the identification of distinct variables that influence the sensitivity of different T-cell assays and to formally show that a defined correction to the protocols successfully increases the sensitivity and reduces the inter-center variability. Such "two-step" inter-laboratory projects could define rational bases for accepted international guidelines and thereby lead to the harmonization of the techniques used for immune monitoring.

Evidence for involvement of clonally expanded CD8+ T cells in anticancer immune responses in CLL patients following nonmyeloablative conditioning and hematopoietic cell transplantation

We have analyzed the clonotype composition of CD8+ T cells following nonmyeloablative (NMA) conditioning and hematopoietic cell transplantation (HCT), of patients with chronic lymphocytic leukemia (CLL). Consecutive analyses of blood samples taken up to 2 years following HCT, demonstrated that CD8+ T-cell clonality was highly dynamic in the early phases after HCT, but became more stable after 4-5 months. Moreover, donor lymphocyte infusion (DLI) given for disease progression in one of the patients led to establishment of recurrent as well as new T-cell clonotypes. This coincided with disease remission, strongly suggesting that these T cells were engaged with anti-CLL cytotoxicity. To examine the functional capacity of stable clonally expanded T cells after HCT, CD8+ T cells isolated post-transplant from the recipients were stimulated ex vivo with CLL cells and subsequently analyzed by FACS for surface expression of the marker for cytotoxic activity, CD107a. Stimulation with CLL cells indeed led to surface expression of CD107a, and clonotype analyses of sorted cells demonstrated that CD107a positive T cells were stably expanded following HCT. Our data suggest that clonally expanded CD8+ T-cell clones participate in the ongoing T-cell response against CLL cells following HCT with NMA conditioning.

Longitudinal analysis of MART-1/HLA-A2-reactive T cells over the course of melanoma progression

An HLA-A2-positive patient with advanced stage IV melanoma was vaccinated with dendritic cells (DCs) pulsed with melanoma antigens, whereby the rapid progression of disease stalled for a period of 10 months. Monitoring of the cellular immune response against one of the vaccinated HLA-A2-restricted epitopes demonstrated both induction and subsequent decline in the number of interferon-gamma (IFN-gamma)-producing MART-1-reactive cells present in the blood. Enumeration of reactive T cells by MART-126-35/HLA-A2 tetramer staining revealed an induction of such cells after three vaccinations and a subsequent decline that most prominent at times of rapid disease progression. However, a substantial number of reactive cells were present even when no MART-1 reactivity was detectable by functional assays. Isolation of such MART-126-35-reactive T cells by means of peptide/HLA-A2-coated magnetic beads demonstrated the persistence of a TCRVbeta14+ T-cell clone in this population over the whole observation period. Intracellular fluorescence-activated cell sorter staining of such TCRVbeta14+ T cells for IFN-gamma and interleukin-2 after maximal stimulation with phorbol 12-myristate 13-acetate/ionomycin revealed an impairment in their capacity to produce cytokines at the end of the observation period. Thus, functional changes of individual T-cell clones, e.g. clonal exhaustion, seem to be responsible for the known discrepancy between functional and phenotype assays for immune monitoring of tumour patients.

A case of lymphoblastoid natural killer (NK)-cell lymphoma: association with the NK-cell receptor complex CD94/NKG2 and TP53 intragenic deletion

The clinical, histological, phenotypic and genotypic features of a lymphoblastoid natural killer (NK)-cell lymphoma presenting in the skin in a young caucasian woman are described. The disease behaved aggressively, but long-lasting remission was obtained by combination chemotherapy followed by autologous bone marrow transplantation. The blastoid cells were positive for terminal deoxynucleotidyl transferase, CD34, CD56 and CD4. Furthermore, the NK-cell receptor complex CD94/NKG2 was strongly expressed, as shown by examination with reverse transcription-polymerase chain reaction. The T-cell receptor (TCR)-gamma genes were in germline, and with the exception of CD4 all T-cell antigens were negative, including CD3, TCR-beta, TCR-delta, TIA-1, granzyme B and perforin. Epstein-Barr virus was negative, and no expression was seen of myeloid cell-associated markers. Molecular analysis showed no abnormalities of the CDKN2A (p16), CDKN2B (p15) or TNFRSF6 (Fas) genes. By contrast, a 34-bp deletion in exon 7 of the TP53 (p53) gene was detected. It is suggested that lymphoblastoid NK-cell lymphoma, which is a rare but distinctive disease, originates from NK cell precursors and may be associated with and possibly caused by alterations in the TP53 gene. Experience is too limited to warrant therapeutic suggestions. However, stem cell transplantation may be a useful option in younger patients.

Induction of systemic CTL responses in melanoma patients by dendritic cell vaccination: cessation of CTL responses is associated with disease progression

Two HLA-A2-positive patients with advanced stage IV melanoma were treated with monocyte-derived dendritic cells (DC) pulsed with either tumor peptide antigens from gp100, MART-1 and MAGE-3 alone or in combination with autologous oncolysates. Clinically, the rapid progression of disease was substantially stalled and both patients were alive for more than 15 months after initiation of therapy. Specific CTL reactivity against several tumor antigens was detectable in peripheral blood, which declined just before reactivation of disease progression. Furthermore, CD3 zeta-chain expression detected by Western lotting was decreased in PBL at this time. In summary, our data confirm that DC-based vaccinations induce peptide-specific T cells in the peripheral blood of advanced-stage melanoma patients. Although successful induction of systemic tumor antigen-specific CTL may not lead to objective clinical tumor regression, their presence are indicative of a prolonged survival.

Spontaneous cytotoxic T-cell responses against survivin-derived MHC class I-restricted T-cell epitopes in situ as well as ex vivo in cancer patients

Recent advances in therapeutic tumor vaccinations necessitate the identification of broadly expressed, immunogenic tumor antigens that are not prone to immune selection. To this end, the human inhibitor of apoptosis, survivin, is a prime candidate because it is expressed in most human neoplasms but not in normal, differentiated tissues. Here, we demonstrate spontaneous cytotoxic T-cell responses against survivin-derived MHC class I-restricted T-cell epitopes in breast cancer, leukemia, and melanoma patients both in situ as well as ex vivo. Moreover, survivin-reactive T cells isolated by magnetic beads coated with MHC/peptide complexes were cytotoxic against HLA-matched tumors of different tissue types. Being a universal tumor antigen, survivin may serve as a widely applicable target for anticancer immunotherapy.

Targeting of lymphotoxin-alpha to the tumor elicits an efficient immune response associated with induction of peripheral lymphoid-like tissue

A recombinant antibody-lymphotoxin-alpha fusion protein induced an adaptive immune response protecting mice from melanoma. Importantly, this fusion protein elicited the formation of a lymphoid-like tissue in the tumor microenvironment containing L-selectin+ T cells and MHC class II+ antigen-presenting cells, as well as B and T cell aggregates. Furthermore, PNAd+/TCA4+ high endothelial venules were observed within the tumor, suggesting entry channels for naive T cell infiltrates. Over the course of therapy, a marked clonal expansion of certain TCR specificities occurred among tumor-infiltrating lymphocytes that displayed reactivity against melanoma cells and the TRP-2(180-188) peptide. Consequently, naive T cells may have been recruited to as well as primed and expanded in the lymphoid-like tissue induced by the lymphotoxin-alpha fusion protein at the tumor site.

Identification of a cytotoxic T lymphocyte response to the apoptosis inhibitor protein survivin in cancer patients

During the last decade, a large number of human tumor-associated antigens have been identified that are recognized by CTLs in a MHC-restricted fashion. The apoptosis inhibitor protein survivin is overexpressed in most human cancers, and inhibition of its function results in increased apoptosis. Therefore, this protein may serve as a target for therapeutic CTL responses. Here, using CTL epitopes deduced from survivin, we describe specific T-cell reactivity against this antigen in peripheral blood from chronic lymphatic leukemia patients and in tumor-infiltrated lymph nodes from melanoma patients by ELISPOT analysis. CTL responses against two survivin-deduced peptide epitopes were detected in three of six melanoma patients and three of four chronic lymphatic leukemia patients. No T-cell reactivity was detected in peripheral blood lymphocytes from six healthy controls. Thus, survivin may serve as an important and widely applicable target for anticancer immunotherapeutic strategies.

Oligoclonal T-cell receptor usage of melanocyte differentiation antigen-reactive T cells in stage IV melanoma patients

Ex vivo ELISPOT analysis of peripheral blood lymphocytes obtained from stage IV melanoma patients demonstrated reactivity against peptides derived from MART-1 and gp100. However, the number of reactive T cells was < 1% that of total lymphocytes as detected by flow cytometry using tetrameric MHC/peptide complexes. Despite this low frequency, we were able to directly isolate these populations ex vivo by means of magnetic beads coated with MHC/peptide complexes and to subject these cells to T-cell receptor clonotype mapping. This analysis revealed that the MART-1/A*0201- and gp100/A*0201-reactive T-cell populations are composed of oligoclonal T cells that engage several T-cell receptor beta chain families. Longitudinal studies using this approach may result in a better correlation between T-cell reactivity and the course of neoplastic disease.

In situ cytokine therapy: redistribution of clonally expanded T cells

Immunity to tumors relies on recirculating antigen-specific T cells. Whilst induction of antigen-specific T cells by immunotherapy has been convincingly proven, direct evidence for recirculation of such cells is still lacking. Here, employing a recently established in situ immunotherapy model for murine melanoma we directly demonstrate the redistribution of clonally expanded T cells. In this model IL-2 is targeted to the tumor microenvironment by means of specific antibody-IL-2 fusion proteins resulting in the expansion of T cells. The therapeutic effect of the fusion protein is not restricted to tumors expressing the targeted antigen, but extends to antigen negative variants of the tumor if present in the same animal. Analysis of the T cell infiltrate by quantitative reverse transcription-PCR revealed the presence of highly expressed TCR BV regions in both tumor variants. TCR clonotype mapping revealed that the high expressions of these regions were caused by clonal expansions and, notably, that these specific clonotypic TCR transcripts were identical in both tumors. Thus, T cell clones activated locally by targeted IL-2 therapy recirculate and mediate eradication of distant tumor sites not subjected to in situ cytokine therapy.

T-cell receptor clonotype mapping using denaturing gradient gel electrophoresis : analysis of clonal T-cell responses in melanoma

Melanoma cells are considered to be immunogenic because they express melanoma-associated antigens that are recognized by autologous T-cells. The role of T-lymphocytes in the host's immune response to cancer in general and to melanoma in particular has been studied intensively during the past decade, and an immense amount of data have strengthened the notion that a functional and specific antimelanoma T-cell response operates in melanoma patients (1,2). This assumption has been strongly reinforced by the demonstration of clonotypic T-cells in both primary and metastatic melanoma (3,4). Nevertheless, the prognosis of metastatic melanoma is one of the most unfavorable in medicine. The coexistence of tumor-specific immunity with a progressing tumor remains a major paradox of tumor immunology and highlights the urgency to reveal new insights into the biology of antitumor T-cells.

Differential expression of CD28 and CD94/NKG2 on T cells with identical TCR beta variable regions in primary melanoma and sentinel lymph node

NK cell tolerance is maintained by the interaction of killer inhibitory receptors with self MHC class I gene products. A subset of T cells also express killer inhibitory receptors, but the functional significance of this is unclear. Here we demonstrate that the expression of the C-lectin-like killer inhibitory receptor CD94 / NKG2 on T cells depends on the state of differentiation during the immune response to solid tumors. To this end we identified clonally expanded T cells which were present both in the sentinel lymph node of primary melanoma, as well as in the tumor itself. In situ characterization of such T cell clonotypes revealed that within the early stages of T cell activation, i. e. priming in the lymph node, T cells did not express CD94 / NKG2 whereas the same T cell clones expressed high levels of CD94 / NKG2 having reached the effector state at the tumor site. Moreover, while the phenotype of these T cell clones was CD28high in the lymph node only CD28low or CD28- T cells were found within the tumor. Double staining for CD94 and CD28 conformed that CD94 / NKG2-expressing cells were preferentially CD28-. Thus, T cells may down-regulate CD28 and up-regulate NK receptors as consequence of prolonged activation for cytolytic effector function. It is likely that NK receptors are involved in peripheral regulatory mechanisms avoiding overwhelming immune responses and immunopathology, particularly in situations of long-lasting immune activation.

Quantification of melanoma cell-specific MART-1 mRNA in peripheral blood by a calibrated competitive reverse transcription-PCR

BACKGROUND

Reverse transcription-PCR (RT-PCR) amplification of melanoma cell-specific mRNA can detect melanoma cells in the peripheral blood of patients with malignant melanoma. We present a method to quantify mRNA coding for the melanoma-specific melanoma antigen recognized by T cells #1 (MART-1) in RNA isolated from peripheral blood.

METHODS

To establish a calibration curve, we measured the concentration of MART-1 mRNA in SK-MEL-28 melanoma cells grown in vitro by competitive RT-PCR. Serial dilutions of these cells were used as calibrators in the assay. The assay was conducted by adding a fixed amount of a RNA internal standard to RNA isolated from either peripheral blood or the calibrators before RT-PCR amplification with MART-1 primers in a nested PCR design. The amount of MART-1 mRNA in blood samples was calculated from the calibration curve.

RESULTS

Addition of melanoma cells grown in vitro to blood from healthy donors demonstrated that the method can detect a single SK-MEL-28 melanoma cell in 1 mL of blood (1.5 x 10(-21) mol MART-1 mRNA/mL). MART-1 mRNA was observed in 4 of 12 blood samples from patients with malignant melanoma, at concentrations of 3-18 x 10(-21) mol MART-1 mRNA/mL of blood. No MART-1 mRNA was detected in blood samples from 25 controls without malignant melanoma. Intra- and interassay CVs were 15% (n = 12; mean = 44 x 10(-21) mol MART-1 mRNA/mL) and 33% (15 samples analyzed in two different analytical runs; mean = 30 x 10(-21) mol MART-1 mRNA/mL), respectively.

CONCLUSIONS

Our method is the first competitive RT-PCR assay for quantification of melanoma cells in blood samples that compensates for the variation of both the reverse transcription and PCR reactions. The method allows the inclusion of control samples for continuous quality assessment.

Tumor infiltrating lymphocytes in melanoma comprise high numbers of T-cell clonotypes that are lost during in vitro culture

Melanoma is generally accepted as being an antigenic tumor capable of eliciting T-cell responses that, however, in most cases are inadequate to control tumor growth. Tumor-infiltrating lymphocytes (TIL) in melanoma lesions comprise clonotypic T cells, indicating the in situ recognition of melanoma-associated peptide epitopes. Cultured TIL have been studied in order to unveil characteristics of TIL and the interactions of TIL and melanoma cells. Whether in vitro cultured TIL mirrors the in situ situation has, however, been questioned. In the present study we have taken advantage of T-cell receptor clonotype mapping methodology to conduct a full and detailed analysis of the T-cell clonotypes in melanoma lesions and in corresponding lines of TIL established in vitro. All melanoma lesions and the corresponding TIL cultures comprised high numbers of T-cell clonotypes, typically in the range of 40 to more than 60. The subsequent comparison of T-cell clonotypes present in the original lesions and in the corresponding T-cell lines established in vitro demonstrated that a very limited number of the T-cell clonotypes established in vitro are identical to the T-cell clonotypes expanded in situ. These results demonstrate that in situ T-cell clonotypes in melanoma are not readily expanded in vitro and that the majority of T-cell clonotypes present in cultured TIL are not present in situ.

Expression of CD94/NKG2 subtypes on tumor-infiltrating lymphocytes in primary and metastatic melanoma

Natural killer receptors are expressed both on natural killer populations and subpopulations of T cells, mainly alpha/beta TCR+CD8+ T cells. We have characterized the expression of the C-type lectin natural killer receptor CD94/NKG2 on tumor-infiltrating lymphocytes in primary and metastatic melanoma lesions. By immunohistochemistry, 5-10% of the tumor-infiltrating lymphocytes, both in primary and metastatic lesions, expressed CD94. More than 95% of these CD94+ cells coexpressed CD8 and the percentage of CD94 expression within the CD8+ cell population ranged from 5 to 20% with a higher expression in metastatic lesions. CD94/NKG2 exists both in an inhibitory and an activating form; thus, it was necessary to determine whether the inhibitory CD94/NKG2-A/B, the activating CD94/NKG2-C/E, or both were expressed on tumor-infiltrating lymphocytes. Reverse transcription-polymerase chain reaction using specific primers for NKG2-A/B and C/E mRNA revealed the presence of NKG2-C/E in all primary and metastatic lesions. In contrast, the inhibitory NKG2-A/B was only present in 50% of primary tumors whereas 80% of tumor-infiltrating lymphocytes in metastatic lesions expressed these transcripts. In healthy humans, the mean number of inhibitory natural killer receptors is higher than that of activating receptors, but the opposite was true for tumor-infiltrating lymphocytes in melanoma. The reversal of the ratio of inhibitory to activating natural killer receptors among tumor-infiltrating lymphocytes suggests a regulated event due to either specific factors within the tumor microenvironment, preferential homing of T cell subsets, or certain stages of T cell activation.

Accumulation of identical T cells in melanoma and vitiligo-like leukoderma

The cloning of genes encoding melanoma antigens has opened new possibilities for the treatment of patients with cancer; however, most tumor rejection antigens recognized by tumor infiltrating lymphocytes are the products of genes that are also expressed by normal melanocytes. Hence, a large set of antigenic determinants of the self have not induced self-tolerance and these peptide determinants furnish target structures for immune responses directed against tumors. The notion that the immunotherapeutic targets involved in cancer regression comprise normal differentiation antigens is stressed by the association between vitiligo-like leukoderma, due to destruction of normal melanocytes, and melanoma regression, due to destruction of cancer cells. Nevertheless, this is the first report to demonstrate by means of a new technique based on reverse transcription polymerase chain reaction and denaturing gradient gel electrophoresis, the presence of clonally expanded T cells with identical BV regions in areas of destruction of both normal and neoplastic cells.

In situ T cells in melanoma

During the past decade new insights have been gained into the role of T lymphocytes in the host's immune response to cancer in general and to melanoma in particular. Several melanoma-associated antigens (MAA) recognized by T cells have been characterized, and a number of HLA class I- and class II-restricted peptides have been identified. These antigens can be divided into three different groups: tumor-associated testis-specific antigens, melanocyte differentiation antigens, and mutated or aberrantly expressed antigens. These proteins give rise to several antigenic peptides. The number of known melanoma-associated peptides that can induce killing by cytotoxic T-lymphocytes (CTL) exceeds 30 and is still increasing. In line with these findings, clinical data indicate that the immune system is essential in the control of tumor growth. A brisk infiltration of lymphocytes is associated with a favorable prognosis, and complete or partial regression of primary melanoma occurs quite frequently. Furthermore, immunomodulatory therapies have accomplished complete or partial tumor regression in a number of patients. However, the immune response is in most cases inadequate to control tumor growth as tumor progression often occurs. Hence, the coexistence of a cellular immune response in melanoma lesions, demonstrated by the presence of clonally expanded T cells, remains a major paradox of tumor immunology. In the present paper we review current knowledge regarding tumor infiltrating lymphocytes (TIL) in melanoma and discuss possible mechanisms of escape from immune surveillance.

In situ T cell responses against melanoma comprise high numbers of locally expanded T cell clonotypes

It is well established that melanoma cells express Ags that are recognized by autologous T cells in vitro. Tumor-infiltrating lymphocytes in situ comprise clonotypic T cells, suggesting that their expansion is driven by Ag stimulation. Still, little is known about the detailed characteristics of the in situ T cell response. In the present study, we scrutinized this response by analyzing multiple metastatic lesions for the presence of clonotypic T cells. This approach was chosen to distinguish whether the clonal T cell expansion occurs as a systemic or localized phenomenon. TCR clonotype mapping of six s.c. metastases from two patients revealed the presence of multiple (from 40 to >60) clonotypic T cells in all lesions. Clonotypic T cells were present in TCR beta-variable regions expressed both at high and low levels. Comparison of the T cell clonotypes present in different lesions from individual patients demonstrated that, in general, clonotypes were exclusively detected in a single lesion. Hence, anti-melanoma T cell responses are much more heterogeneous than previously anticipated and accommodate a predominance of strictly localized T cell clonotypes.

Somatic mutation of the Peutz-Jeghers syndrome gene, LKB1/STK11, in malignant melanoma

Mutations in LKB1/STK11, a gene mapping to chromosome 19p13.3 and encoding a widely expressed serine/threonine kinase, were recently identified as the cause of Peutz-Jeghers syndrome. Despite the hamartomatous polyps and increased cancer risk associated with this syndrome, somatic alterations in LKB1/STK11 have not been identified in human tumours. Prompted by another feature of the syndrome, lentigines of the lips and oral mucosa, we evaluated the status of LKB1/STK11 expression, deletion, and mutation in cell lines and tumour samples from 35 patients with sporadic malignant melanoma. Two somatic mutations were identified, a nonsense mutation (Glu170Stop) causing exon skipping and intron retention, and a missense mutation (Asp194Tyr) affecting an invariant residue in the catalytic subunit of LKB1/STK11. Our data suggest that LKB1/STK11 may contribute to tumorigenesis in a small fraction of malignant melanomas.

Somatic Fas mutations in non-Hodgkin's lymphoma: association with extranodal disease and autoimmunity

Fas (APO-1/CD95) is a cell-surface receptor involved in cell death signaling. Germline mutations in the Fas gene have been associated with autoimmune lymphoproliferative syndrome, and somatic Fas mutations have been found in multiple myeloma. We have examined the entire coding region and all splice sites of the Fas gene in 150 cases of non-Hodgkin's lymphoma. Overall, mutations were identified in 16 of the tumors (11%). Missense mutations within the death domain of the receptor were associated with retention of the wild-type allele, indicating a dominant-negative mechanism, whereas missense mutations outside the death domain were associated with allelic loss. Fas mutations were identified in 3 (60%) MALT-type lymphomas, 9 (21%) diffuse large B-cell lymphomas, 2 (6%) follicle center cell lymphomas, 1 (50%) anaplastic large cell lymphoma, and 1 unusual case of B-cell chronic lymphocytic leukemia with a marked tropism for skin. Among the 16 patients with somatic Fas mutations, 15 showed extranodal disease at presentation, and 6 relapsed in extranodal areas. Ten of 13 evaluable patients showed features suggestive of autoreactive disease. Our data indicate that somatic disruption of Fas may play a role in the pathogenesis of some lymphomas, and suggest a link between Fas mutation, cancer and autoimmunity.

Detection and characterization of alpha-beta-T-cell clonality by denaturing gradient gel electrophoresis (DGGE)

Accumulation of T cells carrying identical T-cell receptors (TCR) is associated with a number of immunological and non-immunological diseases. Therefore, it is of interest to be able to analyze complex T-cell populations for the presence of clonally expanded subpopulations. Here, we describe a simple method combining reverse transcription (RT)-PCR and denaturing gradient gel electrophoresis (DGGE) for rapid detection and characterization of T-cell clonality. The detection of clonally expanded T cells by DGGE relies on the fact that clonal transcripts have no junctional diversity and therefore resolve at a fixed position in the gel, which is determined by their melting properties. For polyclonal populations with a high degree of junctional diversity, the different DNA molecules will resolve at different positions in the gel and together will be revealed as a smear. For each of the TCR beta-variable gene (BV) 1-24 families, cloned transcripts were amplified and shown to resolve as distinct bands in the denaturing gradient gel, whereas the analysis of polyclonal T-cell populations resulted in a smear in the gel. The present method might prove useful to test for clonotypic T-cells in a variety of pathological and physiological conditions and for monitoring T-cell responses in diagnostic and therapeutic settings.

Concurrent disruption of cell cycle associated genes in mantle cell lymphoma: a genotypic and phenotypic study of cyclin D1, p16, p15, p53 and pRb

Mantle cell lymphomas (MCL) are morphologically and immunophenotypically distinctive lymphoid neoplasms characterised by overexpression of cyclin D1. Recent studies have suggested that co-operating aberrations of cell cycle associated genes may provide a growth advantage to a tumour. To address this issue further, we investigated five typical and three aggressive (blastoid) MCL for alterations in the cell cycle regulating genes p15, p16, CDK4, Rb and p53. In 3/3 aggressive cases with cyclin D1 overexpression we found aberration of at least one additional gene. One case showed diminished expression of the retinoblastoma protein (pRb); one case harboured deletion of both p15 and p16; and one case exhibited both deletion of p16 and point mutation of p53. However, we also identified two typical cases which in addition to cyclin D1 overexpression exhibited diminished pRb expression and p15 and p16 hypermethylation, respectively. Our findings confirm and extend other recent investigations and indicate that co-operating genetic alterations of cell cycle-associated genes may contribute to the pathogenesis of MCL.

Activation of preexisting T cell clones by targeted interleukin 2 therapy

The induction of an immunological antitumor response capable of eradicating metastatic tumors is the ultimate goal of immunotherapy. We have recently shown that this can be achieved by interleukin 2 (IL-2) therapy directed to the tumor microenvironment by a recombinant antibody-IL-2 fusion protein. It is not known, however, whether this curative treatment is associated with a predominance of T cells carrying specific T cell receptor variable beta regions (TCRBV) or the presence of clonally expanded T cells. To address this question, we have used a quantitative reverse transcriptase-coupled PCR method to analyze the TCRBV region repertoire in tumor-infiltrating lymphocytes of treated and untreated animals. As controls the TCRBV region repertoire was analyzed in blood and skin from disease-free animals. The results indicate an overexpression of TCRBV5 in the tumors of all treated mice and an additional overexpression of individual regions in each tumor. Direct sequencing of these TCRBV regions did not reveal any evidence of clonal expansions. However, since clonal expansions could exist as subpopulations in highly expressed regions, not detectable by direct sequencing, a denaturing gradient gel electrophoresis assay was used for clonal analysis of TCRBV PCR products. Denaturing gradient gel electrophoresis analysis of selected TCRBV regions revealed the presence of clonotypic T cells in tumors from both treated and untreated animals. These data indicate that targeted IL-2 therapy in this model does not induce clonal T cell responses de novo, rather it acts as an activator for an already existing population of clonotypic T cells.

Ecto-ATP diphosphohydrolase/CD39 is overexpressed in differentiated human melanomas

Ecto-ATPase activities of melanocytes and human melanoma cell lines differing in the stage of progression were compared. A dramatic increase in ecto-ATPase activity above the level of normal melanocytes was demonstrated in the differentiated melanomas and was followed by a gradual decrease with tumor progression. The characteristics of this enzymatic activity were consistent with CD39/ecto-ATP diphosphohydrolase (ATPDase) which was found to be the major ecto-ATP-hydrolysing enzyme in melanomas. Indeed, the expression of CD39 and the level of CD39 mRNA followed a similar pattern. Since CD39 is known to regulate homotypic adhesion and, supposedly, affects the disaggregation step, we suggest that overexpression of CD39 may enable tumor cells to reduce contacts with T-lymphocytes and escape from immunological recognition.

Detection of mutations in GC-rich DNA by bisulphite denaturing gradient gel electrophoresis

Denaturing gradient gel electrophoresis (DGGE) in combination with PCR and 'GC-clamping' has proven highly efficient as a method for detection of DNA sequence differences. Due to strand dissociation phenomena, however, its use has been limited to the analysis of sequences with a relatively low content of GC pairs. This paper describes how treatment of template DNA with sodium bisulphite drastically lowers the melting temperature of very GC-rich sequences and renders them amenable to DGGE analysis. We demonstrate the use of bisulphite DGGE for rapid and efficient detection of mutations in the p16(INK4/CDKN2) tumour suppressor gene.

Generation and characterization of gp100 peptide-specific NK-T cell clones

MHC-restricted cytotoxic T lymphocytes (CTLs) specific for antigens expressed by malignant cells are important components of immune responses against human cancer. Peripheral blood monocytes of HLA-A2+ healthy donors were used to induce dendritic cells (DCs) by granulocyte-macrophage colony-stimulating factor and interleukin-4 and loaded with a gp100 peptide (YLEPGPVTA). By applying these peptide-loaded DCs, a CTL line that displayed high cytotoxic reactivity with peptide-loaded target cells was generated. A total of 11 gp100 peptide-specific CTL clones were generated from this cell line. Several of these CTL clones were studied in detail. Of particular interest was clone CTL-45, which, contrary to the parental cell line, displayed strong NK activity and, by flow-cytometric analysis, revealed a CD3+, TCR BV17, CD8+ and CD56+ phenotype. This clone was strictly peptide-specific and effectively killed a panel of melanoma cells expressing HLA-A2 and gp100. Tumor-specific T cells with this kind of dual function are potentially of great clinical importance as they have a backup mechanism that may go into action when tumor cells escape specific killing by losing their HLA-class I molecules.

Complete scanning of the CDK4 gene by denaturing gradient gel electrophoresis: a novel missense mutation but low overall frequency of mutations in sporadic metastatic malignant melanoma

The cyclin-dependent kinase 4 (CDK4) is a key component in regulation of the mammalian cell cycle. The recent discovery of a common missense mutation (Arg24Cys) in both sporadic and familial forms of malignant melanoma strongly supports the candidacy of CDK4 as a proto-oncogene. To study further the role of CDK4 in melanoma pathogenesis, we have established a method based on polymerase chain reaction (PCR) in combination with denaturing gradient gel electrophoresis (DGGE) to scan the CDK4 gene for point mutations. By analyzing the entire coding sequence of the CDK4 gene in 56 sporadic metastatic malignant melanomas, we identified a novel missense mutation, Asn41Ser. This mutation was also found in the germline of the patient who had no family history of melanoma. Analysis of a tumor-derived cell line demonstrated equal expression of the mutant and wild-type CDK4 alleles, together with lack of functional p16. Our findings suggest that an oncogenic mechanism of the CDK4-Asn41Ser variant would be different from the CDK4-Arg24Cys variant. Altogether, our data demonstrate that point mutation of CDK4 is a rare event in melanoma pathogenesis.

Disruption of the MMAC1/PTEN gene by deletion or mutation is a frequent event in malignant melanoma

The MMAC1/PTEN gene, located at 10q23.3, is a candidate tumor suppressor commonly mutated in glioma. We have studied the pattern of deletion, mutation, and expression of MMAC1/PTEN in 35 unrelated melanoma cell lines. Nine (26%) of the cell lines showed partial or complete homozygous deletion of the MMAC1/PTEN gene, and another six (17%) harbored a mutation in combination with loss of the second allele. Mutations could also be demonstrated in uncultured tumor specimens from which the cell lines had been established, and cell lines derived from two different metastases from one individual carried the same missense mutation. Collectively, these findings suggest that disruption of MMAC1/PTEN by allelic loss or mutation may contribute to the pathogenesis or neoplastic evolution in a large proportion of malignant melanomas.

Analysis of T cell receptor AV and BV chain gene expression by infiltrating lymphocytes in Spitz naevi and in halo naevi

Spitz naevi and halo naevi are benign melanocytic lesions that share many histological features with malignant melanoma. All lesions are characterized by a brisk infiltration of lymphocytes, mainly of the T cell subtype, and halo naevi are known to undergo spontaneous regression. Since the benign nature of Spitz naevi and halo naevi might therefore be caused by specific T cell responses against tumour-associated antigens, it was found of interest to characterize this T cell response in detail. A reverse transcriptase-polymerase chain reaction (RT-PCR)-based method adapted for analysis of paraffin-embedded material combined with Southern blot analysis has been used to analyse the T cell receptor (TCR) AV and BV repertoires of infiltrating lymphocytes in 14 different melanocytic lesions. The results have shown that only a few particular TCRAV and TCRBV regions are expressed in each lesion. To evaluate the T cell response, it is of interest to know the HLA-type of the analysed lesions, since most melanoma-specific effector lymphocytes are CD8+ cytotoxic T cells and therefore HLA class I-restricted. As blood samples were not available from any of these patients, an RT-PCR method using HLA-A2-specific primers was used to analyse for the presence of this allele. The preferentially expressed TCRAV genes were sequenced, and this analysis showed that the high expression of these TCRAV genes was due to a clonal or oligocional expansion of T cells. In summary, the expression of relatively few TCR variable regions indicates a clonal expansion of T cells.

Clonal T cell responses in tumor infiltrating lymphocytes from both regressive and progressive regions of primary human malignant melanoma

The T cell receptor (TCR) BV variable (V) gene repertoire of tumor infiltrating lymphocytes (TIL) found in progressive and regressive regions of the same primary human melanomas were characterized by reverse transcription coupled polymerase chain reaction (RT-PCR). After surgery, the tumors were divided into different parts which were judged as regressive or progressive regions by visual inspection. Subsequently this diagnosis was confirmed by histology. From a total of four primary melanomas analyzed, 2 were drawn to be HLA-A2+. Only relatively few BV-gene families were expressed at significant levels in each of the samples. Comparison of the BV-expression in regressive versus progressive regions of the same tumor revealed major differences in all cases examined. Direct sequencing of RT-PCR products indicated that highly expressed BV-gene families were of clonal origin in both the regressive and progressive regions. Together, these data strongly suggest the occurrence of clonal T cell responses in both regressive and progressive areas of the same primary tumor. The differences in expression of certain BV-genes may correlate with the functional activity of certain populations of tumor-infiltrating T cells.

Differential modulation by interferon gamma of the sensitivity of human melanoma cells to cytolytic T cell clones that recognize differentiation or progression antigens

Human melanoma is a highly immunogenic tumor capable of inducing a specific immune response. A number of melanoma-associated antigens have been characterized during the past several years and can be classified into two groups: differentiation antigens-present also in normal melanocytes-and tumor-specific antigens, which, with the exception of testis, are present only in tumor cells. In a previous publication [Kirkin A. F., Petersen T. R., Olsen A. C., Li L., thor Straten P., Zeuthen J. (1995) Cancer Immunol Immunother 41:71] we have described the production of clones of cytotoxic T lymphocytes (CTL) against the highly immunogenic human melanoma cell line FM3. Using these clones we have defined four previously unknown melanoma-associated antigens, which could be subdivided into differentiation and progression antigens. In the experiments reported in this paper, we have further compared CTL clones from different groups and shown that the sensitivity of melanoma cells to CTL that recognize differentiation or progression antigens is differentially modulated during tumor progression as well as by the lymphokines interferon gamma (IFN gamma) and interleukin-10 (IL-10). The interaction of CTL clones recognizing progression antigens was strongly increased after treatment of melanoma cells with IFN gamma, while the recognition by CTL clones specific for differentiation antigens either was unchanged or significantly decreased. IL-10 treatment of melanoma cells induced up-regulation with respect to recognition by CTL clones specific for differentiation antigens without affecting the recognition of melanoma cells by CTL clones specific for progression antigens. Using cellular systems at different stages of tumor progression, we demonstrated that the progressed state of melanoma cells is associated with increased sensitivity to recognition by CTL clones detecting progression antigens, and with decreased sensitivity to CTL clones recognizing differentiation antigens. Mimicking tumor progression, treatment with IFN-gamma induced apparent down-regulation of differentiation antigens. A hypothesis is suggested in which IFN-gamma plays different roles in the immune response against poorly immunogenic and highly immunogenic melanoma cells, increasing the progression of poorly immunogenic tumor cells or promoting a strong immune response and regression of highly immunogenic melanoma cells.

Generation of human-melanoma-specific T lymphocyte clones defining novel cytolytic targets with panels of newly established melanoma cell lines

Melanoma is a cancer where the immune system is believed to play an important role in the control of malignant cell growth. To study the variability of the immune response in melanoma patients, we derived melanoma cell lines from several HLA-A2+ and HLA-A2- patients. The melanoma cell lines studied were designated FM3, FM6, FM9, FM28, FM37, FM45, FM55p, FM55M1 and FM55M2 and were established from eight metastatic tumors as well as from one primary tumor from a total of seven different patients. On the basis of the ability of tumor cells to induce specific cytotoxic T lymphocytes (CTL) from peripheral blood lymphocytes (PBL) in mixed lymphocyte/tumor culture with HLA-A2+ melanoma cells, the FM3 cell line was characterized as highly immunogenic. To investigate the expression of different melanoma-associated antigens recognized by CTL on different melanoma cell lines, we selected the cell line FM3 for restimulation and further T cell cloning experiments. The lytic activity of CTL clones with good proliferative activity was examined using a panel of HLA-A2+ and HLA-A2- melanoma cell lines. None of the tested HLA-A2- melanoma cell lines were susceptible to lysis by the CTL clones, whereas allogeneic HLA-A2+ melanoma cell lines were lysed only by a few CTL clones. On the basis of their reactivity with different melanoma cell lines, it was possible to divide the present CTL clones into at least four groups suggesting the recognition of at least four different antigens. Three of these target structures probably are different from already-described HLA-A2-restricted melanoma-associated antigens, because their expression in the different melanoma cell lines do not correlate with the recognition of melanoma cells by these CTL. The results first indicate that poorly immunogenic melanoma cells may express melanoma-associated antigens, and also suggest that, by using CTL clones obtained against different HLA-class-I-matched melanoma cells, it is possible to define such antigens.