Systemic T-cell and humoral responses against cancer testis antigens in hepatocellular carcinoma patients

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related deaths worldwide due to high recurrence rates after curative treatment and being frequently diagnosed at an advanced stage. Immune-checkpoint inhibition (ICPI) has yielded impressive clinical successes in a variety of solid cancers, however results in treatment of HCC have been modest. Vaccination could be a promising treatment to synergize with ICPI and enhance response rates. Cancer testis antigens (CTAs) were recently discovered to be widely expressed in HCC and expression in macroscopically tumor-free tissues correlated with recurrence, implying the presence of micro-satellites. To determine whether CTAs are immunogenic in HCC patients, we analyzed systemic T-cell and humoral responses against seven CTAs in 38 HCC patients using a multitude of techniques; flowcytometry, ELISA and whole antigen and peptide stimulation assays. CTA-specific T-cells were detected in all (25/25) analyzed patients, of which most had a memory phenotype but did not exhibit unequivocal signs of chronic stimulation or recent antigen encounter. Proliferative CD4⁺ and CD8⁺ T-cell responses against these CTAs were found in 14/16 analyzed HCC patients. CTA-peptide stimulation-induced granzyme B, IL2, and TNFa in 8/8 analyzed patients, including two MAGEA1 peptides included based on in silico prediction. Finally, IgG responses were observed in 13/32 patients, albeit with low titers. The presence of CD4⁺ and CD8⁺ T-cells and IgG responses shows the immunogenicity of these CTAs in HCC-patients. We hypothesize that vaccines based on these tumor-specific antigens may boost preexisting CTA-specific immunity and could enhance therapeutic efficacy of ICPI in advanced HCC.

TIGIT and PD1 Co-blockade Restores ex vivo Functions of Human Tumor-Infiltrating CD8+ T Cells in Hepatocellular Carcinoma

BACKGROUND & AIMS

TIGIT is a co-inhibitory receptor, and its suitability as a target for cancer immunotherapy in HCC is unknown. PD1 blockade is clinically effective in about 20% of advanced HCC patients. Here we aim to determine whether co-blockade of TIGIT/PD1 has added value to restore functionality of HCC tumor-infiltrating T cells (TILs).

METHODS

Mononuclear leukocytes were isolated from tumors, paired tumor-free liver tissues (TFL) and peripheral blood of HCC patients, and used for flow cytometric phenotyping and functional assays. CD3/CD28 T-cell stimulation and antigen-specific assays were used to study the ex vivo effects of TIGIT/PD1 single or dual blockade on T-cell functions.

RESULTS

TIGIT was enriched, whereas its co-stimulatory counterpart CD226 was down-regulated on PD1^high CD8⁺ TILs. PD1^high TIGIT⁺ CD8⁺ TILs co-expressed exhaustion markers TIM3 and LAG3 and demonstrated higher TOX expression. Furthermore, this subset showed decreased capacity to produce IFN-γ and TNF-α. Expression of TIGIT-ligand CD155 was up-regulated on tumor cells compared with hepatocytes in TFL. Whereas single PD1 blockade preferentially enhanced ex vivo functions of CD8⁺ TILs from tumors with PD1^high CD8⁺ TILs (high PD1 expressers), co-blockade of TIGIT and PD1 improved proliferation and cytokine production of CD8⁺ TILs from tumors enriched for PD1^int CD8⁺ TILs (low PD1 expressers). Importantly, ex vivo co-blockade of TIGIT/PD1 improved proliferation, cytokine production, and cytotoxicity of CD8⁺ TILs compared with single PD1 blockade.

CONCLUSIONS

Ex vivo, co-blockade of TIGIT/PD1 improves functionality of CD8⁺ TILs that do not respond to single PD1 blockade. Therefore co-blockade of TIGIT/PD1 could be a promising immune therapeutic strategy for HCC patients.

Molecular and flow cytometric analysis of the Vbeta repertoire for clonality assessment in mature TCRalphabeta T-cell proliferations

Clonality assessment through Southern blot (SB) analysis of TCRB genes or polymerase chain reaction (PCR) analysis of TCRG genes is important for diagnosing suspect mature T-cell proliferations. Clonality assessment through reverse transcription (RT)-PCR analysis of Vbeta-Cbeta transcripts and flow cytometry with a Vbeta antibody panel covering more than 65% of Vbeta domains was validated using 28 SB-defined clonal T-cell receptor (TCR)alphabeta(+) T-ALL samples and T-cell lines. Next, the diagnostic applicability of the V(beta) RT-PCR and flow cytometric clonality assays was studied in 47 mature T-cell proliferations. Clonal Vbeta-Cbeta RT-PCR products were detected in all 47 samples, whereas single Vbeta domain usage was found in 31 (66%) of 47 patients. The suspect leukemic cell populations in the other 16 patients showed a complete lack of Vbeta monoclonal antibody reactivity that was confirmed by molecular data showing the usage of Vbeta gene segments not covered by the applied Vbeta monoclonal antibodies. Nevertheless, this could be considered indirect evidence for the "clonal" character of these cells. Remarkably, RT-PCR revealed an oligoclonal pattern in addition to dominant Vbeta-Cbeta products and single Vbeta domain expression in many T-LGL proliferations, providing further evidence for the hypothesis raised earlier that T-LGL derive from polyclonal and oligoclonal proliferations of antigen-activated cytotoxic T cells. It is concluded that molecular Vbeta analysis serves to assess clonality in suspect T-cell proliferations. However, the faster and cheaper Vbeta antibody studies can be used as a powerful screening method for the detection of single Vbeta domain expression, followed by molecular studies in patients with more than 20% single Vbeta domain expression or large suspect T-cell populations (more than 50%-60%) without Vbeta reactivity.

Flow cytometric analysis of the Vbeta repertoire in healthy controls

BACKGROUND

Analysis of the T-cell receptor (TCR)-Vbeta repertoire has been used for studying selective T-cell responses in autoimmune disease, alloreactivity in transplantation, and protective immunity against microbial and tumor antigens. For the interpretation of these studies, we need information about the Vbeta repertoire usage in healthy individuals.

METHODS

We analyzed blood T-lymphocyte (sub)populations of 36 healthy controls (age range: from neonates to 86 years) with a carefully selected most complete panel of 22 Vbeta monoclonal antibodies, which together recognized 70-75% of all blood TCRalphabeta(+) T lymphocytes. Subsequently, we developed a six-tube test kit with selected Vbeta antibody combinations for easy and rapid detection of single ("clonal") Vbeta domain usage in large T-cell expansions.

RESULTS

The mean values of the Vbeta repertoire usage were stable during aging in blood TCRalphabeta(+) T lymphocytes as well as in the CD4(+) and CD8(+) T-cell subsets, although the standard deviations increased in the elderly. The increased standard deviations were caused by the occurrence of oligoclonal T-cell expansions in the elderly, mainly consisting of CD8(+) T lymphocytes. The 15 detected T-cell expansions did not reach 40% of total TCRalphabeta(+) T lymphocytes and represented less than 0.4 x 10(9) cells per liter in our study. Vbeta usage of the CD4(+) and CD8(+) subsets was comparable for most tested Vbeta domains, but significant differences (P < 0.01) between the two subsets were found for Vbeta2, Vbeta5.1, Vbeta6.7, Vbeta9.1, and Vbeta22 (higher in CD4(+)), as well as for Vbeta1, Vbeta7.1, Vbeta14, and Vbeta23 (higher in CD8(+)). Finally, single Vbeta domain expression in large T-cell expansions can indeed be detected by the six-tube test kit.

CONCLUSIONS

The results of our study can now be used as reference values in studies on distortions of the Vbeta repertoire in disease states. The six-tube test kit can be used for detection of single Vbeta domain expression in large T-cell expansions (>2.0 x 10(9)/l), which are clinically suspicious of T-cell leukemia.

Novel mutations in the LKB1/STK11 gene in Dutch Peutz-Jeghers families

The Peutz-Jeghers syndrome (PJS) is a rare hereditary disorder in which gastrointestinal hamartomatous polyposis, mucocutaneous pigmentation, and a predisposition for developing cancer are transmitted in an autosomal dominant fashion. The recently identified LKB1/STK11 gene located at chromosome 19p13.3 is mutated in a number of PJS pedigrees. We performed mutation analysis in 19, predominantly Dutch, PJS families. In 12 of these families, we identified LKB1/STK11 mutations, none of which has been described before. These 12 novel LKB1/STK11 mutations consist of one nonsense mutation, three frameshift deletions, three frameshift insertions, two acceptor splice site mutations, and three missense mutations. In addition, we detected four polymorphisms in LKB1/STK11. In the remaining seven PJS families, we found no apparent abnormalities of the LKB1/STK1I gene, which could reflect the existence of locus heterogeneity in PJS. None of the mutations occurred in more than one family, and a number were demonstrated to have arisen de novo. The diverse array of mutations found, the apparent high mutation rate, as well as the existence of a possible second PJS locus, renders diagnostic or predictive genetic testing in individual patients difficult, although future identification of additional mutations or even gene(s) will help in increasing the yield of direct mutation analysis.

Comparison of different polymerase chain reaction-based approaches for clonality assessment of immunoglobulin heavy-chain gene rearrangements in B-cell neoplasia

Several frequently applied polymerase chain reaction strategies for analysis of immunoglobulin heavy-chain gene rearrangements were compared by analyzing 70 B-cell lymphoproliferative disorders and 24 reactive lymphoid lesions. Southern blot analysis was used as the "gold standard" for clonality assessment. For polymerase chain reaction analysis, primers directed against framework (FR) 3 (FR3-A and FR3-B), FR2, and FR1 of the variable gene segments and against joining gene segments of the immunoglobulin heavy-chain gene were used. Polymerase chain reaction products were analyzed by high-resolution fingerprinting analysis using radiolabeled nucleotides, gene scanning using fluorochrome-labeled primers, and heteroduplex analysis. All of the assays generated polyclonal patterns in the reactive tissues. The sensitivity in detecting monoclonality as defined by Southern blotting varied between 60% (heteroduplex analysis with FR3 primers) and 77% (high-resolution fingerprinting analysis with FR2 primers). Comparison of the three FR3 assays revealed that gene scanning had the highest sensitivity (69%), probably because it could detect small aberrant monoclonal amplicons. False-negative results were especially frequent in follicular center lymphoma (n = 20), but also in diffuse large B-cell lymphoma (n = 18), both renowned for having mutated variable gene segments, potentially leading to primer mismatching. For example, in follicular center lymphoma, the FR3, FR2, and FR1 region primer sets detected clonality in only 35 to 40, 65, and 50%, respectively. Combining these techniques, 17 (85%) of 20 follicular center lymphoma samples showed monoclonality. Therefore, especially in follicular center lymphoma, diffuse large B-cell lymphoma, and, to a lesser extent, in other lymphomas, multiple variable gene segment primer sets must be used for a reliable assessment of clonality. Our results also suggest that gene scanning is somewhat more sensitive than other read-out systems. Heteroduplex analysis, however, is a reliable alternative within a diagnostic setting, avoiding the use of radioactivity or expensive automated sequencing equipment and fluorochrome-labeled (oligo)nucleotides.

Peutz-Jeghers syndrome: 78-year follow-up of the original family

BACKGROUND

The association between heredity, gastrointestinal polyposis, and mucocutaneous pigmentation in Peutz-Jeghers syndrome (PJS) was first recognised in 1921 by Peutz in a Dutch family. This original family has now been followed-up for more than 78 years. We did mutation analysis in this family to test whether the recently identified LKB1 gene is indeed the PJS gene in this family.

METHODS

The original family was retraced and the natural history of PJS was studied in six generations of this kindred by interview, physical examination, chart view, and histological review of tissue specimens. DNA-mutation analysis was done in all available descendants.

FINDINGS

Clinical features in this family included gastrointestinal polyposis, mucocutaneous pigmentation, nasal polyposis, and rectal extrusion of polyps. Survival of affected family members was reduced by intestinal obstruction and by the development of malignant disease. A novel germline mutation in the LKB1 gene was found to cosegregate with the disease phenotype in the original family. The mutant LKB1 allele carried a T insertion at codon 66 in exon 1 resulting in frameshift and stop at codon 162 in exon 4.

INTERPRETATION

The morbidity and mortality in this family suggest that PJS is not a benign disease. An inactivating germline mutation in the LKB1 gene is involved in the PJS phenotype in the original and oldest kindred known to be affected by PJS.

Correction of abnormal T-cell receptor repertoire during interferon-alpha therapy in patients with hairy cell leukemia

Patients with the B-cell malignancy hairy cell leukemia (HCL) exhibit a skewed T-cell repertoire with oligoclonal expression or absence of many members of the T-cell receptor (TCR) BV gene families. To evaluate whether interferon-alpha (IFN-alpha) therapy would not only restore normal hematopoiesis, but also the abnormal T-cell repertoire, we studied T lymphocytes from a cohort of HCL patients treated by IFN-alpha in the past, at initiation, and at several intervals up to 6 years of IFN-alpha treatment. The junctional regions from 22 TCRBV gene families were analyzed after polymerase chain reaction amplification of cDNA (RT-PCR) using family specific primers. In all seven patients improvement of the skewed T-cell repertoire was not seen until 2 years of treatment. It consisted of disappearance of oligoclonal subpopulations and (polyclonal) reappearance of absent TCRBV gene families. The RT-PCR results were correlated with the TCRBV protein expression using TCRBV-specific monoclonal antibodies. T lymphocytes from four patients with active HCL contained large expansions of particular TCRBV-expressing cells (up to 25% of the CD3+ cells; 600 to 700/microL whole blood), which decreased during IFN-alpha therapy in both patients tested. Finally, restoration of the TCR repertoire matched normalization of the functional immune repertoire as measured by proliferative, helper, and cytotoxic T-lymphocyte precursor frequencies against major histocompatibility complex-unrelated individuals. In conclusion, oligoclonal bands of TCRBV gene families found by RT-PCR correspond with a dramatic increase in circulating T lymphocytes expressing the same TCRBV family. Moreover, IFN-alpha can restore the skewed T-cell repertoire and suppress persistent T-cell clones upon treatment of the accompanying malignancy.