The relationship between MHC antigen expression and metastasis

CRISPR/Cas-Dependent and Nuclease-Free In Vivo Therapeutic Gene Editing

Precise gene manipulation by gene editing approaches facilitates the potential to cure several debilitating genetic disorders. Gene modification stimulated by engineered nucleases induces a double-stranded break (DSB) in the target genomic locus, thereby activating DNA repair mechanisms. DSBs triggered by nucleases are repaired either by the nonhomologous end-joining or the homology-directed repair pathway, enabling efficient gene editing. While there are several ongoing ex vivo genome editing clinical trials, current research underscores the therapeutic potential of CRISPR/Cas-based (clustered regularly interspaced short palindrome repeats-associated Cas nuclease) in vivo gene editing. In this review, we provide an overview of the CRISPR/Cas-mediated in vivo genome therapy applications and explore their prospective clinical translatability to treat human monogenic disorders. In addition, we discuss the various challenges associated with in vivo genome editing technologies and strategies used to circumvent them. Despite the robust and precise nuclease-mediated gene editing, a promoterless, nuclease-independent gene targeting strategy has been utilized to evade the drawbacks of the nuclease-dependent system, such as off-target effects, immunogenicity, and cytotoxicity. Thus, the rapidly evolving paradigm of gene editing technologies will continue to foster the progress of gene therapy applications.

Escape from IFN-γ-dependent immunosurveillance in tumorigenesis

Immune interferon (IFN), also known as IFN-γ, promotes not only immunomodulation but also antimicrobial and anticancer activity. After IFN-γ binds to the complex of IFN-γ receptor (IFNGR) 1-IFNGR2 and subsequently activates its downstream signaling pathways, IFN-γ immediately causes transcriptional stimulation of a variety of genes that are principally involved in its biological activities. Regarding IFN-γ-dependent immunosurveillance, IFN-γ can directly suppress tumorigenesis and infection and/or can modulate the immunological status in both cancer cells and infected cells. Regarding the anticancer effects of IFN-γ, cancer cells develop strategies to escape from IFN-γ-dependent cancer immunosurveillance. Immune evasion, including the recruitment of immunosuppressive cells, secretion of immunosuppressive factors, and suppression of cytotoxic T lymphocyte responses, is speculated to be elicited by the oncogenic microenvironment. All of these events effectively downregulate IFN-γ-expressing cells and IFN-γ production. In addition to these extrinsic pathways, cancer cells may develop cellular tolerance that manifests as hyporesponsiveness to IFN-γ stimulation. This review discusses the potential escape mechanisms from IFN-γ-dependent immunosurveillance in tumorigenesis.

Co-culture of primary human tumor hepatocytes from patients with hepatocellular carcinoma with autologous peripheral blood mononuclear cells: study of their in vitro immunological interactions

Background

Many studies have suggested that the immune response may play a crucial role in the progression of hepatocellular carcinoma (HCC). Therefore, our aim was to establish a (i) functional culture of primary human tumor hepatocytes and non-tumor from patients with hepatocellular carcinoma (HCC) and (ii) a co-culture system of HCC and non-HCC hepatocytes with autologous peripheral blood mononuclear cells (PBMCs) in order to study in vitro cell-to-cell interactions.

Methods

Tumor (HCC) and non-tumor (non-HCC) hepatocytes were isolated from the liver resection specimens of 11 patients operated for HCC, while PBMCs were retrieved immediately prior to surgery. Four biopsies were obtained from patients with no liver disease who had surgery for non malignant tumor (normal hepatocytes). Hepatocytes were either cultured alone (monoculture) or co-cultured with PBMCs. Flow cytometry measurements for MHC class II expression, apoptosis, necrosis and viability (7AAD) were performed 24 h, 48 h and 72 h in co-culture and monocultures.

Results

HCC and non-HCC hepatocytes exhibited increased MHC-II expression at 48h and 72h in co-culture with PBMCs as compared to monoculture, with MHC II-expressing HCC hepatocytes showing increased viability at 72 h. PBMCs showed increased MHC-II expression (activation) in co-culture with HCC as compared to non-HCC hepatocytes at all time points. Moreover, CD8+ T cells had significantly increased apoptosis and necrosis at 48h in co-culture with HCC hepatocytes as compared to monocultures. Interestingly, MHC-II expression on both HCC and non-HCC hepatocytes in co-culture was positively correlated with the respective activated CD8+ T cells.

Conclusions

We have established an in vitro co-culture model to study interactions between autologous PBMCs and primary HCC and non-HCC hepatocytes. This direct interaction leads to increased antigen presenting ability of HCC hepatocytes, activation of PBMCs with a concomitant apoptosis of activated CD8+ T cells. Although, a partially effective immune response against HCC exists, still tumor hepatocytes manage to escape.

Attenuation of the Fas-L independent b16bL6 melanoma lymphocidic capacity by H-2K class I molecules

We have previously reported that the capacity of highly malignant B16BL6 murine melanoma cells to induce cell death in naive syngeneic lymphocytes stems from the absence of major histocompatibility complex (MHC) class I glycoproteins in these melanoma cells. Our present study provides evidence that the above-mentioned lymphocidic activities of B16BL6 cells are selectively attenuated when the expression of H-2K (but not H-2D or H-2L) MHC class I glycoproteins is reconstituted in these cells. The induction of apoptosis in naive lymphocytes by H-2K-deficient melanoma cells does not involve the Fas ligand (Fas-L)/FAS signaling module, as demonstrated by employing lymphocytes derived from Fas-L(gld)- or Fas(lpr)-deficient mice in co-culture experiments. Furthermore, these tumor cells fail to induce Fas-L-mediated fratricide in co-cultured lymphocytes and do not express Fas-L either when grown alone or co-cultured with lymphocytes. These findings explain the previously widely reported selective down-regulation of certain MHC class I-encoded glycoproteins (H-2K, bur not H-2D or H-2L) during tumor progression. Namely, the initiation of an effective immune response against H-2K-deficient cells could be abrogated at very early steps, as the result of the induction of Fas-L/Fas-independent cell death among naive lymphoid cells.

Alterations in the expression of MHC class I glycoproteins by B16BL6 melanoma cells modulate insulin receptor-regulated signal transduction and augment [correction of augments] resistance to apoptosis

In a variety of malignancies, the immune-escape phenotype is associated, in part, with the inability of tumor cells to properly present their Ags to CTLs due to a deranged expression of MHC class I glycoproteins. However, these molecules were found to possess broader nonimmune functions, including participation in signal transduction and regulation of proliferation, differentiation, and sensitivity to apoptosis-inducing factors; processes, which are characteristically impaired during malignant transformation. We investigated whether the deranged expression of MHC class I expression by tumor cells could affect proper receptor-mediated signal transduction and accentuate their malignant phenotype. The malignant and H-2K murine MHC class I-deficient B16BL6 melanoma cells were characterized by an attenuated capacity to bind insulin due to the retention of corresponding receptor in intracellular stores. The restoration of H-2K expression in these cells, which abrogated their capacity to form tumors in mice, enhanced membrane translocation of the receptor, presumably, by modulating its glycosylation. The addition of insulin to H-2K-expressing melanoma cells cultured in serum-free conditions precluded apoptotic death by up-regulating the activity of protein kinase B (PKB)/Akt. In contrast, the deficiency for H-2K characteristic to the malignant clones was associated with a constitutive high activity of PKB/Akt, which rendered them resistant to apoptosis, induced by deprivation of serum-derived growth factors. The possibility to correct the regulation of PKB/Akt activity by restoration of H-2K expression in B16BL6 melanoma cells may be considered as an attractive approach for cancer therapy, since an aberrant activation of this enzyme is characteristic to resistant malignancies.

Biological properties associated with the enhanced lung-colonizing potential in a B16 murine melanoma line grown in a medium conditioned by syngeneic Corynebacterium parvum-elicited macrophages

A previous study by our laboratory showed that the peritoneal murine Corynebacterium parnum-elicited macrophages released into their growth medium an activity which enhanced the ability of B16-F10 melanoma cells to form experimental metastases in the lung of syngeneic mice. In the present study, we used a clone of B16-F10 line (F10-M3 cells) to investigate whether the increase in lung-colonizing potential due to the pro-clonogenic activity released by C. parvum-elicited macrophages was associated with biological properties characteristic of a metastatic phenotype. We have found that the pulmonary retention, growth rate in lung parenchyma, invasiveness through Matrigel, adhesiveness to IL-1-activated endothelium and MHC class I expression were increased in F10-M3 cells stimulated by the macrophage pro-clonogenic activity. By using an in vitro experimental protocol, the enhancement of lung-colonizing potential in the stimulated melanoma cells turned out to be a transient phenomenon as was the increase of invasiveness through Matrigel and the higher expression of MHC class I antigens. In conclusion, the melanoma cells stimulated by the pro-clonogenic activity released by C. parvum-elicited macrophages showed changes in biological parameters which are relevant to metastatic diffusion. These changes appeared as a temporary phenomenon which sustains the view that the metastatic phenotype represents a transient biological character influenced by host factors.

The role of vascular endothelial growth factor in the tissue specific in vivo growth of prostate cancer cells

Despite the fact that cancer cells can be found in many vascular beds, continued growth of the metastatic tumor focus exhibits a significant degree of 'organ tropism', with only certain organs exhibiting the ravages of metastatic disease. Since a limiting factor to the growth of metastases beyond 2 mm in diameter, may be a lack of angiogenesis, we sought to determine whether tumor overexpression of vascular endothelial growth factor (VEGF), a potent angiogenic factor related to prostate cancer metastasis, is causally related to organ specific tumor growth in a prostate cancer xenograft model. LnCaP-C4-2 is a subline of the human prostate cancer cell line LnCaP which unlike its parent, has a predilection for growth in bone, a common site for human prostate cancer metastasis. LnCaP-C4-2, is tumorigenic when injected intrafemorally in mice but requires co-injection of stromal components (Matrigel) to be tumorigenic in the subcutaneous site. Because of this site-specific tumorigenicity profile and relatively low VEGF mRNA and protein expression, this line was transfected with a full length cDNA encoding the 165 isoform of VEGF. Cells either overexpressing or not expressing the transfected gene were selected for study in vivo and in vitro. Overexpression of VEGF did not seem to affect in vitro cell growth. Such overexpression did affect tumorigenicity and in vivo tumor growth rates when cells were inoculated in the subcutaneus site. Interestingly, the dependency of subcutaneous tumorigenicity on Matrigel co-inoculation was still observed in cells overexpressing VEGF. In contrast to the impact that VEGF overexpression has on subcutaneous tumorigenicity, no such effect was observed when cells were inoculated in orthotopic/prostate (primary) or intrafemoral (metastatic) sites. In view of the importance of tumor-stromal interactions in growth of xenografts, we sought to determine if the host strain is important to the observed tumorigenicity effects of VEGF overexpression. No differences in subcutaneous tumorigenicity as a function of either Matrigel use or VEGF expression levels were observed when SCID/bg and RAG/pfp mouse strains were compared. In conclusion, our data indicate that the biological impact of prostate tumor VEGF overexpression is organ/site specific, leading to the speculation that it may play a part in the observed organ tropism of metastatic spread. In addition, these results highlight the importance of the tumor microenvironment in determining the biological impact of transfected and overexpressed genes in the study of tumor biology.

Methylcholanthrene-induced sarcomas in nude mice have short induction times and relatively low levels of surface MHC class I expression

In order to study the role of the T-cell-mediated immune defense in tumor development, a total of 93 sarcomas were induced using different doses (8 micrograms (0.1%), 40 micrograms (0.5%) and 400 micrograms (5%)) of 3-methylcholanthrene in athymic nude Balb/c mice and phenotypically normal immunocompetent Balb/c mice. A shorter tumor induction time and a higher tumor incidence after treatment with low doses of methylcholanthrene were seen in nude mice than in immunocompetent mice, indicating that they have a lower resistance to the carcinogen. Contrary to expectations we found that the MHC class I expression of tumors from nude mice was lower than that of tumors from normal mice. Higher surface expression of MHC class I was demonstrated on high dose tumors from normal mice than on low dose tumors from normal mice. The cellular composition of the individual tumors raised in nude mice was more heterogeneous with respect to MHC class I expression. Since the mice differ genetically only with respect to the nu gene, these results indicate that a lack of T-cell-mediated defense mechanisms may confer upon the bearer a lower resistance to 3-methylcholanthrene and a different MHC profile of the ensuing tumor.

Beta 2-microglobulin expression of AIDS-related and classical Kaposi's sarcoma

The expression of beta 2-microglobulin, the invariable light chain of HLA class I molecules, of Kaposi's sarcoma from 11 AIDS patients and from 11 patients without known immunodeficiency was studied by immunohistochemistry using a polyclonal antibody to beta 2-microglobulin. The staining intensity of spindle cells in these lesions was scored in a semiquantitative system. We found that the spindle cells of Kaposi's sarcomas from AIDS patients showed significantly increased staining intensity for beta 2-microglobulin compared to those of Kaposi's sarcomas from non-AIDS patients. The results may indicate that Kaposi's sarcomas developing in immunocompromised individuals, such as AIDS patients, are not subject to immune selection by T cells eliminating HLA class I high-expressing tumor cells, while this may be the case in non-AIDS patients. Alternatively, the results may be caused by differences in the activity of cytokines, which upregulate the expression of HLA class I molecules on the cell surface.

Expression of MHC class I and class II antigens in primary breast carcinomas and synchronous nodal metastases

Expression of the major histocompatibility (MHC) class I and class II antigens was studied by immunohistochemistry in a series of 70 primary breast carcinomas and in nodal metastases. In particular, the expression of class I (HLA A-B-C) and class II (DP, DQ and DR) molecules was compared in: a) primary breast cancers devoid of nodal metastases (n = 36) and tumors exhibiting metastatic deposits (n = 34) at the time of surgery, and b) primary breast carcinomas and their corresponding synchronous axillary nodal metastases. Reduced or absent HLA A-B-C antigen expression was seen in approximately 54.3% of primary breast carcinomas, whereas a partial or complete induction of class II products was observed in 18.5% (DQ), 30% (DP) or 48.5% (DR) of the same cases. An almost complete overlap of antigen expression was observed in breast tumors in which no metastases were found by histological examination of axillary nodes and in neoplasms showing histologically-diagnosed synchronous metastases. The reactivity for class I and class II antigens in nodal metastases roughly paralleled that exhibited by corresponding primary tumors. A discordant expression was seen in 11 cases (32%) stained for HLA A-B-C and in 8 (24%), 7 (21%) and 6 (18%) cases assayed for DP, DQ and DR products, respectively. When a discordant expression was detected, either decreased or increased staining patterns were observed in metastases. The finding of overlapping MHC antigenic profiles in the majority of primary breast tumors and nodal metastases casts doubts on the hypothesis that loss of MHC antigens can play an important role in the seeding and growth of metastatic breast carcinoma cells.

Adenovirus 12-mediated down-regulation of the major histocompatibility complex (MHC) class I promoter: identification of a negative regulatory element responsive to Ad12 E1A

In highly oncogenic adenovirus (Ad) 12-transformed cells, major histocompatibility complex (MHC) class I gene expression is down-regulated by the products of the viral E1A oncogene at the level of initiation of transcription. However, class I gene expression is unaltered or elevated in non-oncogenic Ad2- or Ad5-transformed cells. These changes in class I expression may permit Ad12-transformed cells to escape host immune surveillance and elicit tumour formation. Here we show that the 2kb of 5' flanking region of the mouse H-2Kb class I gene is sufficient to mediate down-regulation of transcription driven from homologous or heterologous (HSV thymidine kinase) basal promoter elements in cells expressing Ad12 E1A, but not in Ad2 E1A-expressing cells. Deletion analysis of the 2kb region showed that sequences from -1.18 to -1.44kb (relative to the cap site) were a target for Ad12 E1A-mediated transcriptional down-regulation. Deletion of this entire region from the 2kb flanking sequence of the H-2Kb gene abolished Ad12 E1A-mediated down-regulation of transcription. Computer analysis of the -1.18 to -1.44kb sequence identified two 6/7bp matches with the AP-1 transcription factor consensus sequence and two matches with the pig MHC class I PD1 repressor element. Gel retardation analysis using overlapping DNA fragments derived from the -1.18 to -1.44kb sequence revealed several DNA:protein complexes formed using nuclear extract derived from Ad12-, but not from Ad2- or Ad5-transformed cells. Some of these DNA:protein complexes were also present, but at lower levels, in nuclear extracts from untransformed rat cells suggesting the possible involvement of cellular factors in the mechanism of down-regulation mediated by Ad12 E1A. A binding site for the AP-1 factor failed to compete for protein binding to fragments within the -1.18 to -1.44 sequence, while the PD1 site competed for binding only in the -1.15 to -1.23 region. These results indicate that novel factors (as well as a previously identified class I repressor, PD1) may be involved in Ad12 E1A-mediated down-regulation of MHC class I transcription.

Metastasis of mouse T lymphoma cells is controlled by the level of major histocompatibility complex class I H-2Dk antigens

In vivo inoculation of a low metastatic BW 5147 derived T-cell lymphoma variant into syngeneic mice, had led to the generation of a highly metastatic variant. The shift towards a more metastatic phenotype is accompanied by an increase in major histocompatibility class I H-2Dk antigen expression. This suggests that H-2Dk antigens may control the metastatic potential of BW T lymphoma cells. Our present findings indicate that H-2Dk expression is directly correlated with the metastatic potential of BW cells. We have confirmed such correlation by specifically altering the level of H-2Dk expression by: 1) FACS analysis, 2) IFN-gamma treatment, 3) H-2Dk gene transfection. Cells sorted for low H-2Dk expression had a significantly reduced metastatic potential. Induction of H-2Dk expression on these cells by either IFN-gamma treatment or H-2Dk gene transfection concomitantly led to increased metastasis. We also assessed metastatic potential of BW cells in irradiated, immunocompromised recipients. Our results show that the immune system is implicated and we further tested which immune effectors are involved. In vivo depletion of natural killer (NK) and CD8+ T-cells revealed that the difference in metastatic potential of the H-2Dk variants relies upon an NK-dependent mechanism, whereas CD8+ T-cells are not implicated. Our observations suggest that highly metastatic cells, expressing a high level of H-2Dk antigens are more resistant to NK-cell-mediated cytotoxicity in vivo. We have confirmed our in vivo results by in vitro cytotoxicity assays using poly I:C induced NK and IL-2 activated LAK cells. We conclude that a NK-dependent mechanism accounts for the association between differential H-2Dk antigen expression and metastasis.

Tumorigenicity of mouse T lymphoma cells is controlled by the level of major histocompatibility complex class I H-2Kk antigens

We have previously found that an increased tumorigenicity and spontaneous metastatic potential of BW5147-derived T lymphoma cells was associated with a decrease in major histocompatibility complex (MHC) class I H-2Kk antigen expression. This suggested that H-2Kk antigens may control the tumorigenic potential of BW T lymphoma cells. Our current experiments aimed to prove this association by specifically altering H-2Kk expression by gene transfection. Transfected cells expressing a high level of H-2Kk antigens were significantly less tumorigenic and metastatic after subcutaneous inoculation. However, there was selection in vivo for cells expressing a reduced level of H-2Kk antigens, which concomitantly led to an increased tumorigenicity. These data further confirmed the strong association between H-2Kk expression and tumorigenicity. We subsequently tested whether the immune system is implicated in this phenomenon by inoculating the H-2Kk transfectants into irradiated, immunocompromised recipients. Our results indicate that the reduced tumorigenicity of the BW H-2Kk transfectants is due to an immune rejection mechanism, mediated by CD8+ immune effector cells, as revealed by in vivo depletion experiments with anti-CD8 antibodies. Hence, we hereby demonstrated that H-2Kk antigens increased the immunogenicity of BW cells, via a CD8-dependent mechanism, which consequently reduced their tumorigenicity.

The effect of H-ras expression on tumorigenicity and immunogenicity of Balb/c 3T3 fibroblasts

In an attempt to define immunological parameters affected by the H-ras oncogene, we have used Balb/c 3T3 cells transfected with either H-ras (98/6), H-ras+v-myc (98/4v) or plasmid only (98/1). We found that while control and oncogene-transfected Balb/c 3T3 cells exhibit similar low sensitivity to lysis by natural killer (NK) cells, H-ras+v-myc-transfected cells could immunize syngeneic Balb/c mice and induce cytotoxic T cells (CTL) with broad specificity, that lysed all types of Balb/c 3T3 cells tested. Immunization of Balb/c mice with 98/4v cells prevented homologous tumor formation and partially inhibited the formation of tumors derived from H-ras-transfected cells. 98/6 cells were not immunogenic in vivo and did not protect the animals from a challenge of 98/6 cells. The results suggested that CTLs but not NK effector cells were important for eliciting in vivo tumor rejection of H-ras+v-myc-transfected cells. In contrast, antigens eliciting the cytotoxic T-cell response, and possibly also the in vivo tumor cell rejection response, were expressed on all cell types tested but were immunogenic only on the surface of 98/4v cells. We further determined major histocompatibility complex (MHC) class-I molecule expression on the outer cell surface and found that H-2K was down-regulated in H-ras-transfected cells. The results support the observation that oncogenes can down-regulate specific MHC antigens, thereby preventing presentation of tumor antigens and allowing tumor escape from immune recognition.

Decreased adhesion to endothelial cells and matrix proteins of H-2Kb gene transfected tumour cells

Transfection of murine metastatic B78H1 cells (derived from B16 melanoma) with a syngeneic H-2Kb gene was used to study the effect of Major Histocompatibility Complex (MHC) gene products on tumour cell adhesion to endothelial cells and matrix proteins and the involvement in the metastatic process. H-2Kb-expressing transfectants showed a reduced adhesion to endothelial surfaces of different origin (four murine endotheliomas and human umbilical vein endothelial cells) when compared to parental B78H1 cells and to controls transfected with pSV2neo alone. On the average a 50-70% reduction in adhesion to endothelial cells was observed among H-2Kb transfectants. H-2Kb transfectants had a reduced expression of the alpha 4 integrin subunit, moreover the adhesion of Neo-transfected clones to endothelial cells was reduced to the levels of H-2Kb transfectants by antibodies directed against the beta 1 subunit and the endothelial VCAM-1 molecule, thus suggesting an impairment of the VLA-4/VCAM-1 interaction in H-2Kb transfectants. Adhesion to extracellular matrix components was also strongly decreased: in general the adhesion of H-2Kb cells showed a 50-75% inhibition with respect to Neo or parental controls. The highest difference was observed in adhesion to vitronectin and laminin, the lowest in adhesion to fibronectin. Reduction in adhesive properties of H-2Kb-expressing transfectants could be involved in the reduced metastatic ability, evaluated by means of intravenous injection of cells: H-2Kb transfectants yielded less than ten lung colonies, while all controls produced more than 100. Our data indicate that expression of a single class I MHC gene can significantly alter the metastatic phenotype of MHC-negative tumour cells and this could be related to a general alteration of tumour cell adhesive interactions.

Expression of beta 2-microglobulin by premalignant epithelium

Many human tumors express low amounts of HLA class I molecules relative to the normal cells from which they are derived. From experimental work it is clear that the malignant behavior of a tumor cell may depend on its MHC class I expression. Therefore, it is of obvious interest to study the HLA class I expression of human tumors in their various stages. We have studied the HLA class I expression by the cells in premalignant epithelial lesions and invasive carcinoma of the bladder and uterine cervix using immunoperoxidase staining for beta 2-microglobulin of paraffin-embedded tissue. We here assume that beta 2-microglobulin expression by malignant and premalignant cells equals HLA class I expression. Thirty-two of the 36 invasive tumors expressed less overall beta 2-microglobulin than cells from the normal epithelium. In contrast, approximately two-thirds of 34 premalignant bladder epithelia and 47 premalignant cervix epithelia displayed higher overall beta 2-microglobulin expression than the normal epithelium. Thus, a systematic large-scale elimination of HLA class I high-expressing tumor cell variants may take place only after the tumor penetrates the basement membrane.

The H-ras oncogene regulates expression of 70- and 45-kDa cell-surface molecules whose expression correlates with tumor-cell immunogenicity

The effects of the H-ras oncogene on fibroblast cell tumorigenicity and immunogenicity was studied in transfectants of the BALB/c 3T3 clone A31 fibroblastoid cell-line. Cells that were transfected with MC29-LTR-H-ras (98/6) or MC29-LTR-v-myc + H-ras (98/4v) and were inoculated into syngeneic BALB/c mice were tumorigenic in 100% and 60% of animals respectively. By contrast, transfectants containing the pSV2neo plasmid alone (98/1) displayed normal characteristics both in vitro and in vivo. Inoculation of mice with mitomycin-C-treated 98/1 or 98/4v cells induced an effective protective immunity to a challenge of live 98/4v cells, and a partial immunity against 98/6 cells. Mitomycin-C-treated 98/6 cells failed to render immunity against a challenge of either 98/6 or 98/4v cells. To correlate immunogenicity and tumorigenicity of the different cell types with cell-surface-antigen expression, we prepared MAbs against 98/4v cells in syngeneic mice. Immunohistochemical and immunoblot analysis revealed that MAbs 102 and 104 recognized 2 protein band of 70 and 45 kDa respectively, which were expressed predominantly in 98/1 and 98/4v cells. A third immunoreactive protein band of 44 kDa that reacted with MAb 6 was expressed at a similar cell-surface density on all cell types. Cell-differentiation-inducing agents, such as DMSO, retinoic acid or sodium butyrate, were all found to induce 98/6 cell flattening and morphological changes toward a normal phenotype that were followed by up-regulation of the 70- and 45-kDa antigens. The results suggest that regulation of expression of the 70- and 45-kDa molecules is affected by H-ras, and that expression of these cell-surface molecules may be relevant to tumor cell immunogenicity.

Control of H-2 expression in transformed nonhaemopoietic cells by autocrine interferon

The relationship between autocrine interferon (IFN) production and the expression of class I Major Histocompatibility Complex (MHC) membrane glycoproteins in vitro was investigated in a panel of murine transformed cells of nonhaemopoietic origin. The panel included 11 cell lines of H-2Kb haplotype derived from fibrosarcomas, carcinomas and melanoma, and from transformed fibroblasts. IFN activity was detected in the conditioned medium of nine cell lines; fibrosarcomas were among the high IFN producers, while the non-producers were a melanoma clone and a lung carcinoma cell line. A significant correlation was found between IFN production and the expression of H-2K/D glycoproteins, thus suggesting that long-term maintainment of MHC glycoprotein expression in vitro could be mediated by self produced IFN. Two IFN producer cell lines, MN/MCA1 and R80/17, were cultured in the presence of a blocking antiserum against IFN-alpha/beta: a significant decrease in H-2b expression was observed, thus indicating the existence of an autocrine IFN circuit. Taken together these findings suggest that release of IFN is a frequent event among transformed nonhaemopoietic cells, and that self-produced IFN contributes to the regulation of MHC antigen levels in solid tumours.

Possible role of Abb gene in mouse resistance to EL4 metastases

"S" (survivor) mutants were produced in mice for genetic analysis of host resistance to metastatic cancers. S-mutants S-27 and S-31 resist transplantation of lymphoma EL4 of parental C57BL/6J (B6) mice while they accept parental skin grafts. Mutant S-27 also resists formation of spontaneous metastases from intradermally growing EL4 tumor into lymph nodes; mutant S-31 is highly susceptible to EL4 metastases. Another mutant, H-2bm26 (bm26), resists EL4 and rejects B6 skin grafts. Major histocompatibility complex (MHC) class I and class II gene expression was compared in these mutants and normal B6 mice. All three mutants tested, S-27, S-31, and bm26, expressed a low amount of Kb mRNA in organ-specific fashion. Mutants bm26 and S-31 expressed a low amount of Abb mRNA and of Ab antigen on their spleen cells. Some oligonucleotide probes designed to hybridize to the second exon of the class II MHC gene Abb did not hybridize with DNA from all three mutants. These findings suggest extensive sequence alterations in the Abb gene in mutants S-27, S-31, and bm26; they also suggest a major role of MHC in the control of host resistance to spontaneous metastases of the EL4 tumor.

Effect of temperature on the expression of major histocompatibility complex class-I antigens

In the present study we investigated the effect of temperature on MHC class-I gene expression in BALB/C 3T3 cells incubated for 5 days at 34 degrees C, 37 degrees C and 39 degrees C. FACS analysis revealed no significant difference in the cell surface expression of any of the 3 major class-I antigens at 34 degrees C and 37 degrees C. Strikingly, however, when the level of the respective mRNA was determined, only that of the H-2K was comparable at both temperatures, whereas the levels of the H-2D and H-2L mRNA were profoundly higher at 37 degrees C. These data appear to reflect a differential temperature-related transcriptional control of the different class-I genes or a different temperature effect on the stability of their mRNA. The absence of a parallel increase in surface expression of the corresponding H-2D and H-2L antigens may result from some translational or post-translational limiting factors. At 39 degrees C, however, these limiting factors seem to be overcome since the surface expression of all the 3 antigens was remarkably increased although the level of their encoding mRNA was rather lower than in 37 degrees C. This stimulatory effect might be ascribed to heat shock proteins which are known to arise in cells at heat or other stress conditions. They participate in assembly and disassembly of various protein complexes and in transport of certain proteins across intracellular membranes. Such proteins may have arisen in our cells at 39 degrees C and facilitated the intracellular assembly of the class-I molecules and their transport to the cell surface. The possible implication of such heat shock proteins in the anti-tumor effect of hyperthermia is discussed.

Altered binding of regulatory factors to HLA class I enhancer sequence in human tumor cell lines lacking class I antigen expression

Class I antigens encoded in the major histocompatibility complex (MHC) (HLA in man, H-2 in the mouse) play a key role in the recognition of target cells by cytolytic T lymphocytes. Tumor cells frequently do not express class I MHC molecules, which strongly suggests that down-regulation of the latter facilitates escape of tumor cells from immune surveillance. The expression of class I MHC genes is tightly regulated. An enhancer element, conserved in the promoters of mouse and human MHC genes, has been shown to be important for mouse class I MHC gene expression. At least two related regulatory factors (KBF1 and NF-kappa B) bind to this regulatory element. We have analyzed the binding of these factors in cellular extracts of 23 human tumor cell lines displaying various levels of class I mRNA and surface expression. In this panel, combined deficiency of KBF1- and NF-kappa B-like DNA-binding activities was frequent among the class I-negative cell lines and correlated with the absence of class I mRNA. A few cell lines that lack KBF1 binding activity still display NF-kappa B-like activity and express normal levels of MHC class I mRNA. These results suggest (i) that, in the absence of KBF1, NF-kappa B or a related factor promotes MHC class I gene transcription; and (ii) that a combined defect in KBF1/NF-kappa B DNA-binding activity can cause a pleiotropic defect in class I gene expression, which may facilitate tumor progression.

Divergent effects of thyroid HLA-antigens on T and natural killer (NK) cell cytotoxicity

We have used non-autoimmune non-neoplastic human thyroid cells to explore the role of surface class I and DR antigens on these cells' sensitivity towards T and Natural Killer (NK) cell cytotoxicity. Non-treated thyrocytes expressed class I but no DR antigens. Following incubation with gamma-interferon (gamma-IFN) class I antigens were markedly elevated and DR expression was induced. Whereas non-treated thyrocytes were minimally lysed by sensitized T cells, they served as appropriate targets for NK cells. Following incubation with gamma-IFN, the thyroid cells became highly sensitive to T cell lysis, with no significant reduction in their vulnerability to NK cell killing. The addition of monoclonal anti class I or DR antigens, or brief acid treatment which specifically eliminates class I molecules, inhibited T cell cytotoxicity but enhanced the sensitivity to lysis by NK cells. Thus, the presence of HLA antigens on the same thyroid cells have an opposite effect on two major cytotoxi mechanisms. Our findings are relevant within the context of recent suggestions of intervening with target HLA antigens for the management of autoimmune and malignant diseases.

Persistent measles virus infection enhances major histocompatibility complex class I expression and immunogenicity of murine neuroblastoma cells

The effect of persistent measles virus infection on the expression of major histocompatibility complex (MHC) class I antigens was studied. Mouse neuroblastoma cells C1300, clone NS20Y, were persistently infected with the Edmonston strain of measles virus. The persistently infected cell line, NS20Y/MS, expressed augmented levels of both H-2Kk and H-2Dd MHC class I glycoproteins. Activation of two interferon(IFN)-induced enzymes, known to be part of the IFN system: (2'-5')oligoadenylate synthetase and double-stranded-RNA-activated protein kinase, was detected. Measles-virus-infected cells elicited cytotoxic T lymphocytes that recognized and lysed virus-infected and uninfected neuroblastoma cells in an H-2-restricted fashion. Furthermore, immunization of mice with persistently infected cells conferred resistance to tumor growth after challenge with the highly malignant NS20Y cells. The rationale for using measles virus for immunotherapy is that most patients develop lifelong immunity after recovery or vaccination from this infection. Patients developing cancer are likely to have memory cells. A secondary response induced by measles-virus-infected cells may therefore induce an efficient immune response against non-infected tumour cells.

Tumors developing in nude mice express unusually large amounts of MHC class I antigens

Tumors were induced in athymic, T-cell-deficient nude mice and in syngeneic normal haired mice by treatment with low doses of 3-methylcholantrene (MCA). The tumors were studied for tumor cell expression of MHC class I molecules and for immunogenicity by transplantation to syngeneic haired recipients. Ten tumors were obtained by the MCA treatment, six from nude and four from haired mice. They were all fibrosarcomas as judged from their microscopic appearance. Five of the "nude" tumors expressed measurable amounts of MHC class I molecules and two of them expressed high amounts. Both were immunogenic in the sense that they evoked a cytotoxic T-cell response in transplanted haired recipients. Only one of the four "haired" tumors expressed measurable amounts of MHC class I, and none of them were immunogenic. These findings support the concept that some tumors are immunoselected at an early point of time in their existence in a host with a normal immune system and that this results in an elimination of tumor cell variants which are highly immunogenic for the T-cell system, leaving the low or non-immunogenic variants. These take over and grow and kill their host. The results suggest that tumor cell variants expressing high amounts of MHC class I are important targets in the immunoselection in hosts with a normal immune system.

Human tumor spontaneous metastasis in immunosuppressed newborn rats. I. Characterization of the bioassay

We characterize a new model of spontaneous metastasis of human tumor cells using anti-thymocyte serum (ATS) immunosuppressed newborn rats. We analyzed the intrinsic value of the bioassay of measurement of tumorigenicity and metastatic capacity using 17 human tumor cell lines, of which were 9 human malignant melanomas. Most of these cell lines revealed as tumorigenic and metastatic in lungs and/or lymph nodes 3 weeks after s.c. injection in the ventral flank of newborn rats, irrespective of their origin. All the melanoma cell lines that we injected were tumorigenic and 77% were metastatic, whereas the same cell lines grafted in nude mice showed no evidence of metastases after 6 weeks' examination. We were not able to show any relationship between tumorigenicity in nude mice and the malignant behavior of these cells in ATS-treated newborn rats. Likewise, neither chromosome abnormalities, nor antigenic marker expression were found to be related to tumor growth in nude mice or newborn rats. Two intrinsic parameters of the model were studied: number of cells injected vs. dose of ATS injected for one melanoma cell line; and role of the 3rd and 4th injections of ATS in the establishment and development of pulmonary metastases. Moreover, we show that s.c. injection in the ATS-treated newborn rat may represent a suitable method for studying melanoma cell tumor growth and spontaneous dissemination.

Differential transcriptional control of the H-2K and H-2D loci of the major histocompatibility complex in fibrosarcoma cells

In this study we demonstrate a differential transcription of H-2K and H-2D class-I genes in two different tumor cell clones; one is highly metastatic (IE-7) and the other is not metastatic (IC-9), both derived from the same fibrosarcoma, T-10, induced in an (H-2b x H-2k)F1 mouse. The expression of the two parental H-2K alleles is transcriptionally suppressed in both of these clones. In addition the IC-9 clone does not transcribe also the H-2Dk allele. Our data rule out the possibility that this suppression results from enhanced RNA degradation, impaired polyadenylation, DNA rearrangement, or changes in DNA methylation within these genes. Interferons (IFN) are known to enhance MHC expression by acting on a consensus IFN responsive element present in the promoter region of MHC genes. However, IFN-gamma, which is the most potent IFN in this respect, failed to activate the expression of the silent MHC genes in our cells. This finding may reflect a defect within the promoter region of these genes or changes in their chromatin structure.

Immunological and non-immunological influence of H-2Kb gene transfection on the metastatic ability of B16 melanoma cells

The H-2b-negative B78HI clone (derived from B16 melanoma) was transfected with the H-2Kb gene; 4 cell clones expressing membrane H-2Kb antigens and 2 control clones (transfected with pSV2neo alone) were used for studies of metastatic ability, immunogenicity, NK sensitivity and homotypic adhesion. The experimental metastatic capacity of H-2Kb transfectants in syngenic mice was greatly diminished in comparison with control and parent cells. Both immune-mediated and intrinsic properties of transfectants correlated with their lower metastatic ability. A cell-mediated cytotoxic response was induced by repeated in vivo immunizations of syngeneic mice followed by in vitro restimulation of effectors when transfectants (but not controls) were used as immunizers and as targets. Moreover, homotypic adhesion of H-2Kb transfectants was significantly lower than that of controls. Sensitivity to NK cells of transfectants was not decreased in comparison to H-2-negative controls. It is known that in vitro treatment with IFN-gamma of H-2-positive B16 melanoma cells induces a simultaneous increase in H-2 expression and in experimental metastasis; treatment of H-2Kb transfectants with IFN-gamma induced a higher Kb expression, but no increase in metastatic ability, thus suggesting that the IFN-sensitive component that mediates enhancement of metastasis is not H-2Kb.

Tumorigenicity, metastasis and suppression of MHC class-I expression in murine fibroblasts transformed by mutant v-ras deficient in GTP binding

We have introduced point mutations in v-rasH to study their effects on biochemical and biological properties of the ras-encoded protein p21. Several of these mutant proteins do not bind GTP and thus lack GTPase activity, while others were shown to have their GTP binding reduced. We have introduced these ras mutants into NIH 3T3 fibroblastoid cells to study major parameters of clinical importance which are associated with neoplastic transformation, particularly MHC expression in cells, metastasis and tumorigenesis in both nude mice and immune competent mice. Our data show that certain mutations in v-ras differentially affect the expression of the transformed phenotype. Mutant ras molecules deficient in GTP binding fail to generate rapidly progressing tumors in immune competent mice, and not all morphologically transformed cells were capable of experimental metastasis. Cells transformed by certain v-ras mutants form tumors in immunocompetent mice and show reduced expression of MHC class-I antigens. Other cells are morphologically transformed and tumorigenic in athymic nude mice, but fail to form tumors in normal mice and show levels of MHC class-I antigen expression similar to non-transformed 3T3 cells. The inverse relationship between MHC class-I-antigen expression and the degree of transformation in fibroblastoid cells suggests that the ras gene product could be involved in regulating MHC expression.

Heterogeneity of MHC-class-I antigens in clones of methylcholanthrene-induced tumors. Implications for local growth and metastasis

We analyzed the H-2 class-I expression of different clones obtained from 4 different methylcholanthrene-induced tumors in BALB/c (H-2d) mice. The results clearly indicated high intra-tumor heterogeneity in all 4 fibrosarcomas with regard to H-2 K, D and L expression. Clones were found to be H-2-negative, H-2-positive, or to present intermediate expression. Southern blot analysis of class-I genes showed RFLPs equal to those obtained from normal BALB/c DNA, ruling out rearrangements or gross deletions in the class-I genes of different tumors. However, Northern blot studies showed a straightforward relationship between class-I mRNA levels and H-2 expression. In vivo experiments demonstrated an inverse relationship between local growth and spontaneous metastasis, e.g., H-2-positive class-I clones produced high numbers of lung colonies but very poor local growth, and vice-versa. These results paralleled the NK sensitivity or resistance of the different clones. Cross-protection experiments showed that only clones coming from the same tumor were able to protect against challenge with clones of the same neoplasia but not with clones from different chemically induced fibrosarcomas, indicating that a clone of a given tumor probably contained the same TATA. Finally, we compared the H-2, K, D and L expression and class-I mRNA levels of various metastatic colonies. Interestingly, another degree of heterogeneity was found: an H-2-negative clone (GR9.B9) gave rise to H-2-negative (B9MP6) and H-2-positive (B9MP2) metastatic colonies.

DNA binding of regulatory factors interacting with MHC-class-I gene enhancer correlates with MHC-class-I transcriptional level in class-I-defective cell lines

Tumor cells frequently show a lack of surface class-I major histocompatibility complex (MHC) antigen expression. These molecules are key recognition structures for immune rejection of tumor cells and their absence at the surface of tumor cells could favor the progression of tumors. We have analyzed the transcriptional mechanisms that could lead to suppression of MHC-class-I expression in human tumor cell K562. The expression of MHC-class-I genes is highly controlled by regulatory factors interacting with an enhancer sequence upstream of MHC-class-I genes. In this report we show that DNA binding activity of 2 regulatory factors, KBFI and NF-kappa B, known to be essential for constitutive expression of MHC-class-I genes, is deficient in nuclear extracts from K562 cells. Induction of class-I gene expression at the surface of tumor cells by interferon-gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) shows that TNF-alpha can act in synergy with IFN-gamma to induce DNA binding of both factors NF-kappa B and KBFI to the class-I gene enhancer and that this induction of transcriptional factors is correlated with enhancement of MHC-class-I mRNA transcription and cell-surface antigen expression.

Changes in the coding sequence of the H-2Dk gene of metastatic cells that might account for immunogenic abnormality of its encoded antigen

In previous studies we have demonstrated that metastatic cells, derived from T-10 fibrosarcoma, express an immunogenically abnormal H-2Dk glycoprotein which is involved in manifesting their metastatic phenotype. In the present study we show that these cells contain a remarkably high level of H-2Dk specific mRNA. Moreover, by cloning cDNA of this gene and analyzing its nucleotide sequence, we found 4 single nucleotide changes. Two of them did not change the encoded amino acids, whereas the others resulted in two amino acid substitutions in the alpha-2 domain of the protein product that might account for its immunogenic abnormality.

NK sensitivity, H-2 expression and metastatic potential: analysis of H-2Dk gene transfected fibrosarcoma cells

We have used the 3-Methylcholanthrene induced T-10 fibrosarcoma tumour cell system (H-2b xH-2k)F1 to elucidate the possible correlation between metastatic potential, expression of individual H-2 antigens and susceptibility to NK cells. Transfection of the non-metastatic and NK sensitive IC9 cells (Db+, Dk-, Kb-, Kk-) with the H-2Dk gene, altered the metastatic phenotype of the parental cells, yet had no effect on the susceptibility of these tumour cells to lysis by NK and did not elicit a specific CTL response in syngeneic hosts. Variants of the metastatic and NK resistant IE7 clone (Db+, Dk+, Kb-, Kk-), lacking H-2Dk, were selected by treatment with monoclonal anti H-2Dk antibodies and complement. These variants were sensitive to NK and poorly or non metastatic. Retransfection of 'Dk' 'loss' variants with the H-2Dk gene, resulted in the isolation of several clones expressing a wide range of metastatic phenotypes but maintained sensitivity to NK. These results indicate that the H-2D region of the MHC and or closely linked genes may be involved in the complex interrelationship between target susceptibility to NK and metastasis.