Disruption of SUV39H1-Mediated H3K9 Methylation Sustains CAR T-cell Function

Suboptimal functional persistence limits the efficacy of adoptive T-cell therapies. CD28-based chimeric antigen receptors (CAR) impart potent effector function to T cells but with a limited lifespan. We show here that the genetic disruption of SUV39H1, which encodes a histone-3, lysine-9 methyl-transferase, enhances the early expansion, long-term persistence, and overall antitumor efficacy of human CAR T cells in leukemia and prostate cancer models. Persisting SUV39H1-edited CAR T cells demonstrate improved expansion and tumor rejection upon multiple rechallenges. Transcriptional and genome accessibility profiling of repeatedly challenged CAR T cells shows improved expression and accessibility of memory transcription factors in SUV39H1-edited CAR T cells. SUV39H1 editing also reduces expression of inhibitory receptors and limits exhaustion in CAR T cells that have undergone multiple rechallenges. Our findings thus demonstrate the potential of epigenetic programming of CAR T cells to balance their function and persistence for improved adoptive cell therapies.

SIGNIFICANCE

T cells engineered with CD28-based CARs possess robust effector function and antigen sensitivity but are hampered by limited persistence, which may result in tumor relapse. We report an epigenetic strategy involving disruption of the SUV39H1-mediated histone-silencing program that promotes the functional persistence of CD28-based CAR T cells. See related article by López-Cobo et al., p. 120. This article is featured in Selected Articles from This Issue, p. 5.

Abstract 5583: SUV39H1 disruption enhances the persistence and anti-tumor efficacy of CD28-costimulated human CAR T cells

Retrovirally encoded CD19-specific CARs that incorporate CD28 and CD3z signaling motifs (Rv-1928z) have induced remarkable responses in patients with refractory leukemia and lymphoma. These CARs induce a strong effector differentiation program in T cells that can limit their persistence and result in T cell dysfunction. This induction of terminal effector differentiation is accompanied by transcriptional and epigenetic changes resulting in induction of effector transcriptional factors, inhibitory receptors, and suppression of memory associated genes. In this study, we examine the effect of modulating the epigenome of human Rv-1928z CAR T cells by disruption of the histone methyl transferase, SUV39H1, which has been implicated in regulating memory to effector transition in murine T cells (Pace et al. 2018).

To assess the impact of SUV39H1 on human Rv-1928z CAR T cells, we treated immune deficient mice bearing the human ALL cell line, NALM6, with limiting doses of SUV39H1-edited T cells. SUV39H1 editing (SUV39H1etd) significantly enhanced the anti-tumor efficacy of Rv-1928z CAR T cells relative to non-edited counterparts, with 9/10 NALM6 bearing mice treated with SUV39H1etd Rv-1928z surviving over the duration of observation (90 days) as compared to 1/12 mice treated with WT Rv-1928z. This enhanced tumor control in SUV39H1etd Rv-1928z CAR T cells was associated with greater initial CAR T cell proliferation upon tumor encounter and enhanced long-term CAR T cell persistence (> day 50).

To assess whether the persisting SUV39H1etd Rv-1928z CAR T cells can mount an effective effector response upon tumor rechallenge, we modified the stress test model such that post primary tumor clearance (day 17), mice were rechallenged by tumor 5 times over 70 days. SUV39H1etd Rv-1928z CAR T cells outperformed WT Rv-1928z CAR T cells in eliminating NALM6 upon rechallenge. Paired genome accessibility (ATACseq) and transcriptional analysis revealed epigenetic changes associated with SUV39H1 loss in Rv-1928z CAR T cells that promote expression of memory associated transcription factors and receptors while reducing expression of inhibitory receptors and transcriptional factors associated with T cell dysfunction. In summary, we find that loss of SUV39H1 in human Rv-1928z CAR T cells enhances their anti-tumor efficacy by bringing about changes in their epigenome that enhance their functional persistence.

Citation Format: Nayan Jain, Zeguo Zhao, Richard Koche, Yosi Gozlan, David Brocks, Tali Raveh-Sadka, Danny Wells, Anton Dobrin, Yuzhe Shi, Michael Lopez, Gertrude Gunset, Michel Sadelain. SUV39H1 disruption enhances the persistence and anti-tumor efficacy of CD28-costimulated human CAR T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5583.

SUV39H1 disruption imparts functional persistence to CD28-costimulated human CAR T cells

Retrovirally encoded CD19-specific CARs that incorporate CD28 and CD3z signaling motifs (Rv-1928z) have induced remarkable responses in patients with refractory leukemia and lymphoma. These CARs, however, induce a strong effector differentiation program in T cells that can limit their persistence and result in T cell dysfunction. Multiple studies have shown that effector differentiation and eventual dysfunction are associated with transcriptional and epigenetic changes. In this study, we examine the effect of disrupting the histone methyl transferase, SUV39H1 on the functional persistence of human Rv-1928z CAR T cells. SUV39H1 has recently been implicated in regulating memory to effector transition in murine T cells (Pace et al. 2018).

To assess the impact of SUV39H1 in human Rv-1928z CAR T cells, we treated immune deficient mice bearing the human ALL cell line, NALM6, with limiting doses of SUV39H1-edited (SUV39H1etd) T cells. SUV39H1etd Rv-1928z CAR T cells have improved anti-tumor efficacy as compared to WT Rv-1928z CAR T cells, with 9/10 NALM6 bearing mice treated with SUV39H1etd Rv-1928z surviving as compared to 1/12 mice treated with WT Rv-1928z over the duration of observation (90 days). This enhanced tumor control in SUV39H1etd Rv-1928z CAR T cells was associated with improved CAR T cell persistence (> day 50). Paired genome accessibility (ATACseq) and transcriptional analysis on SUV39H1etd and WT Rv-1928z CAR T cells that have undergone multiple rounds of tumor rechallenges in vivo revealed epigenetic changes associated with SUV39H1 loss in Rv-1928z CAR T cells that promote expression of memory associated transcription factors and curtail T cell dysfunction in Rv-1928z CAR T cells.

Mobile genomics: tools and techniques for tackling transposons

Next-generation sequencing approaches have fundamentally changed the types of questions that can be asked about gene function and regulation. With the goal of approaching truly genome-wide quantifications of all the interaction partners and downstream effects of particular genes, these quantitative assays have allowed for an unprecedented level of detail in exploring biological interactions. However, many challenges remain in our ability to accurately describe and quantify the interactions that take place in those hard to reach and extremely repetitive regions of our genome comprised mostly of transposable elements (TEs). Tools dedicated to TE-derived sequences have lagged behind, making the inclusion of these sequences in genome-wide analyses difficult. Recent improvements, both computational and experimental, allow for the better inclusion of TE sequences in genomic assays and a renewed appreciation for the importance of TE biology. This review will discuss the recent improvements that have been made in the computational analysis of TE-derived sequences as well as the areas where such analysis still proves difficult. This article is part of a discussion meeting issue 'Crossroads between transposons and gene regulation'.

Integrative Analysis Defines Distinct Prognostic Subgroups of Intrahepatic Cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA) is the second most common primary liver cancer. It is defined by cholangiocytic differentiation and has poor prognosis. Recently, epigenetic processes have been shown to play an important role in cholangiocarcinogenesis. We performed an integrative analysis on 52 iCCAs using both genetic and epigenetic data with a specific focus on DNA methylation components. We found recurrent isocitrate dehydrogenase 1 (IDH1) and IDH2 (28%) gene mutations, recurrent arm-length copy number alterations (CNAs), and focal alterations such as deletion of 3p21 or amplification of 12q15, which affect BRCA1 Associated Protein 1, polybromo 1, and mouse double minute 2 homolog. DNA methylome analysis revealed excessive hypermethylation of iCCA, affecting primarily the bivalent genomic regions marked with both active and repressive histone modifications. Integrative clustering of genetic and epigenetic data identified four iCCA subgroups with prognostic relevance further designated as IDH, high (H), medium (M), and low (L) alteration groups. The IDH group consisted of all samples with IDH1 or IDH2 mutations and showed, together with the H group, a highly disrupted genome, characterized by frequent deletions of chromosome arms 3p and 6q. Both groups showed excessive hypermethylation with distinct patterns. The M group showed intermediate characteristics regarding both genetic and epigenetic marks, whereas the L group exhibited few methylation changes and mutations and a lack of CNAs. Methylation-based latent component analysis of cell-type composition identified differences among these four groups. Prognosis of the H and M groups was significantly worse than that of the L group. Conclusion: Using an integrative genomic and epigenomic analysis approach, we identified four major iCCA subgroups with widespread genomic and epigenomic differences and prognostic implications. Furthermore, our data suggest differences in the cell-of-origin of the iCCA subtypes.

Reactivation of endogenous retroviral elements via treatment with DNMT- and HDAC-inhibitors

Inhibitors of DNA methyltransferases (DNMTis) or histone deacetylases (HDACis) are epigenetic drugs which are investigated since decades. Several have been approved and are applied in the treatment of hematopoietic and lymphatic malignancies, although their mode of action has not been fully understood. Two recent findings improved mechanistic insights: i) activation of human endogenous retroviral elements (HERVs) with concomitant synthesis of double-stranded RNAs (dsRNAs), and ii) massive activation of promoters from long terminal repeats (LTRs) which originated from past HERV invasions. These dsRNAs activate an antiviral response pathway followed by apoptosis. LTR promoter activation leads to synthesis of non-annotated transcripts potentially encoding novel or cryptic proteins. Here, we discuss the current knowledge of the molecular effects exerted by epigenetic drugs with a focus on DNMTis and HDACis. We highlight the role in LTR activation and provide novel data from both in vitro and in vivo epigenetic drug treatment.

Intratumor heterogeneity in epigenetic patterns

Analogous to life on earth, tumor cells evolve through space and time and adapt to different micro-environmental conditions. As a result, tumors are composed of millions of genetically diversified cells at the time of diagnosis. Profiling these variants contributes to understanding tumors' clonal origins and might help to better understand response to therapy. However, even genetically homogenous cell populations show remarkable diversity in their response to different environmental stimuli, suggesting that genetic heterogeneity does not explain the full spectrum of tumor plasticity. Understanding epigenetic diversity across cancer cells provides important additional information about the functional state of subclones and therefore allows better understanding of tumor evolution and resistance to current therapies.

RAS-pathway mutation patterns define epigenetic subclasses in juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is an aggressive myeloproliferative disorder of early childhood characterized by mutations activating RAS signaling. Established clinical and genetic markers fail to fully recapitulate the clinical and biological heterogeneity of this disease. Here we report DNA methylome analysis and mutation profiling of 167 JMML samples. We identify three JMML subgroups with unique molecular and clinical characteristics. The high methylation group (HM) is characterized by somatic PTPN11 mutations and poor clinical outcome. The low methylation group is enriched for somatic NRAS and CBL mutations, as well as for Noonan patients, and has a good prognosis. The intermediate methylation group (IM) shows enrichment for monosomy 7 and somatic KRAS mutations. Hypermethylation is associated with repressed chromatin, genes regulated by RAS signaling, frequent co-occurrence of RAS pathway mutations and upregulation of DNMT1 and DNMT3B, suggesting a link between activation of the DNA methylation machinery and mutational patterns in JMML.

Erratum: DNMT and HDAC inhibitors induce cryptic transcription start sites encoded in long terminal repeats

This corrects the article DOI: 10.1038/ng.3889.

Identification of DNA methylation changes at cis-regulatory elements during early steps of HSC differentiation using tagmentation-based whole genome bisulfite sequencing

Epigenetic alterations during cellular differentiation are a key molecular mechanism which both instructs and reinforces the process of lineage commitment. Within the haematopoietic system, progressive changes in the DNA methylome of haematopoietic stem cells (HSCs) are essential for the effective production of mature blood cells. Inhibition or loss of function of the cellular DNA methylation machinery has been shown to lead to a severe perturbation in blood production and is also an important driver of malignant transformation. HSCs constitute a very rare cell population in the bone marrow, capable of life-long self-renewal and multi-lineage differentiation. The low abundance of HSCs has been a major technological barrier to the global analysis of the CpG methylation status within both HSCs and their immediate progeny, the multipotent progenitors (MPPs). Within this Extra View article, we review the current understanding of how the DNA methylome regulates normal and malignant hematopoiesis. We also discuss the current methodologies that are available for interrogating the DNA methylation status of HSCs and MPPs and describe a new data set that was generated using tagmentation-based whole genome bisulfite sequencing (TWGBS) in order to comprehensively map methylated cytosines using the limited amount of genomic DNA that can be harvested from rare cell populations. Extended analysis of this data set clearly demonstrates the added value of genome-wide sequencing of methylated cytosines and identifies novel important cis-acting regulatory regions that are dynamically remodeled during the first steps of haematopoietic differentiation.

Musical patterns for comparative epigenomics

Scientific data has been transformed into music in order to raise awareness in the non-scientific community. While the general public is nowadays familiar with the genetic code, there is still a lack of knowledge regarding epigenetic regulation. By making use of the binary nature of the methylome, we here describe a method that transforms methylation patterns into music. The resulting musical pieces show decent complexity and allow the audible recognition between music and underlying methylation state. This approach might therefore facilitate the recognition of complex methylation patterns and increase awareness for epigenetic regulation in the general public.

Abstract B25: Progressive epigenetic programming during B cell maturation yields a continuum of clonal disease phenotypes with distinct etiologies in chronic lymphocytic leukemia

Knowledge of the cell-of-origin is essential for the full understanding of the causes of a malignant disease and for the rational design of targeted therapies. The B cell compartment is composed of a highly complex mixture of subtypes, each with distinct phenotypes and roles within the immune system. In chronic lymphocytic leukemia (CLL), heterogeneity in the biology and clinical course of the disease is thought to be linked to divergent cellular origins. We and others have previously shown that the epigenome of CLL, as measured by the global pattering of DNA methylation, is highly clonal and remarkably stable over time and thus represents a powerful approach to trace founder subtype populations. Here we combine epigenomic and transcriptomic analysis using next-generation sequencing approaches to compare CLL cells to highly purified and specific B cell subpopulations at various stages of maturation. We find that B cell maturation involves substantial unidirectional epigenetic programming that occurs as a continuum throughout the transition between naïve to fully-mature memory B cell subpopulations. Combining 258 CLL cases using Illumina 450K analysis reveals that all CLLs arise from a discrete window within the spectrum of B cell maturation that is more similar to mature B cells, with the majority of cases clustering at two distinct points correlating with unmutated IGHV versus highly mutated (<95% homology) IGHV genes; however, a significant number (~20%) of cases arise at various points between these two clusters. Next we show that using RNA-seq, broad differences in global expression patterns mirror the degree of epigenetic programming achieved by individual CLLs. Progressively further programming is paralleled by a transition from an aggressive to indolent expression pattern, indicated by the decrease in the expression levels of genes with known roles in promoting CLL cell survival, such as ZAP70, BTK, TCL1a, MCL1, miR-155 and others. Using DNA methylation and ChIP-seq data to compare the sequence and chromatin features of genomic regions that are programmed in normal B cell maturation versus CLL, reveals that although a myriad of transcription factors and pathways connected to immune cell function are involved in normal epigenetic programming in B cells, aberrant CLL-specific alterations involve excess activity of NFAT and EGR gene families and, paradoxically, a reduction of AP-1 activity. To further investigate the role of immediate-early genes, RNA-seq analysis of in vitro-activated CLL cells revealed a strong association between the degree of epigenetic programming and the specific inducibility of EGR2 and c-FOS, supporting a functional role of these genes in aberrant DNA methylation programming. Finally, in an independent clinically well-annotated cohort of 349 CLL cases, we demonstrate that the degree of epigenetic programming is significantly associated with time to treatment and overall survival in patients. Collectively, this work demonstrates that instead of a distinct cell(s)-of-origin, CLL is rather derived from a continuum of possible programming states, and that the degree of programming achieved by a particular CLL at the time of transformation dictates its global gene expression pattern and clinical outcome. Furthermore, a parallel assessment of B cell maturation with CLL development permits a refinement of the disease-specific, early molecular events, highlighting the dysregulation of particular transcription factors and pathways in the pathogenesis of aggressive versus indolent disease.

Identification of regulatory networks in HSCs and their immediate progeny via integrated proteome, transcriptome, and DNA methylome analysis

In this study, we present integrated quantitative proteome, transcriptome, and methylome analyses of hematopoietic stem cells (HSCs) and four multipotent progenitor (MPP) populations. From the characterization of more than 6,000 proteins, 27,000 transcripts, and 15,000 differentially methylated regions (DMRs), we identified coordinated changes associated with early differentiation steps. DMRs show continuous gain or loss of methylation during differentiation, and the overall change in DNA methylation correlates inversely with gene expression at key loci. Our data reveal the differential expression landscape of 493 transcription factors and 682 lncRNAs and highlight specific expression clusters operating in HSCs. We also found an unexpectedly dynamic pattern of transcript isoform regulation, suggesting a critical regulatory role during HSC differentiation, and a cell cycle/DNA repair signature associated with multipotency in MPP2 cells. This study provides a comprehensive genome-wide resource for the functional exploration of molecular, cellular, and epigenetic regulation at the top of the hematopoietic hierarchy.

Quiescence-induced LncRNAs trigger H4K20 trimethylation and transcriptional silencing

A complex network of regulatory pathways links transcription to cell growth and proliferation. Here we show that cellular quiescence alters chromatin structure by promoting trimethylation of histone H4 at lysine 20 (H4K20me3). In contrast to pericentric or telomeric regions, recruitment of the H4K20 methyltransferase Suv4-20h2 to rRNA genes and IAP elements requires neither trimethylation of H3K9 nor interaction with HP1 proteins but depends on long noncoding RNAs (lncRNAs) that interact with Suv4-20h2. Growth factor deprivation and terminal differentiation lead to upregulation of these lncRNAs, increase in H4K20me3, and chromatin compaction. The results uncover a lncRNA-mediated mechanism that guides Suv4-20h2 to specific genomic loci to establish a more compact chromatin structure in growth-arrested cells.

Evolution of DNA methylation is linked to genetic aberrations in chronic lymphocytic leukemia

Although clonal selection by genetic driver aberrations in cancer is well documented, the ability of epigenetic alterations to promote tumor evolution is undefined. We used 450k arrays and next-generation sequencing to evaluate intratumor heterogeneity and evolution of DNA methylation and genetic aberrations in chronic lymphocytic leukemia (CLL). CLL cases exhibit vast interpatient differences in intratumor methylation heterogeneity, with genetically clonal cases maintaining low methylation heterogeneity and up to 10% of total CpGs in a monoallelically methylated state. Increasing methylation heterogeneity correlates with advanced genetic subclonal complexity. Selection of novel DNA methylation patterns is observed only in cases that undergo genetic evolution, and independent genetic evolution is uncommon and is restricted to low-risk alterations. These results reveal that although evolution of DNA methylation occurs in high-risk, clinically progressive cases, positive selection of novel methylation patterns entails coevolution of genetic alteration(s) in CLL.

A systematic review of drug absorption following bariatric surgery and its theoretical implications

Demand for bariatric surgery has risen exponentially and bariatric patients often have multiple indications for post-operative pharmacotherapy. The purpose of this study was to systematically review the published literature examining the effect of bariatric surgery on drug absorption. Studies were sought through searches of MEDLINE, EMBASE, the Cochrane Controlled Trials Registry and hand searches of reference lists. Two reviewers independently assessed studies for inclusion. Twenty-six studies (15 case reports/case series evaluating 12 different agents and 11 non-randomized controlled studies examining 15 different agents) were found. Evidence for diminished drug absorption was found in 15/22 studies involving jejunoileal bypass, 1/3 studies of gastric bypass/gastroplasty and 0/1 studies examining biliopancreatic diversion. The effect of bariatric surgery on drug absorption appears drug-specific. Drugs that are intrinsically poorly absorbed, highly lipophilic and/or undergo enterohepatic recirculation exhibited the greatest potential for malabsorption. The most consistent evidence for diminished absorption was found for cyclosporine, thyroxine, phenytoin and rifampin. Reduced drug absorption may occur post-bariatric surgery and this effect appears drug-specific. Individual dose-adjustment and therapeutic monitoring may be required. Rigorously conducted controlled studies are needed to evaluate the effect of modern bariatric procedures on drug absorption.

Gomez-Lopez-Hernandez syndrome: expansion of the phenotype

Gomez-Lopez-Hernandez syndrome (cerebello-trigeminal-dermal dysplasia) is a condition that includes abnormalities of the cerebellum (rhombencephalosynapsis), cranial nerves (trigeminal anesthesia), and scalp (alopecia). Seven patients with this condition have been documented since 1979. We now report a male with Gomez-Lopez-Hernandez syndrome who, at the age of 19 years, is the oldest patient identified to date. He has been followed since birth, allowing us to report on the progression of his physical findings and psychiatric problems including hyperactivity, depression, self-injurious behavior and bipolar disorder. In addition, he has short stature and growth hormone deficiency.

Syncatalytic inactivation of prolyl 4-hydroxylase by synthetic peptides containing the unphysiologic amino acid 5-oxaproline

Peptides containing the unphysiological amino acid 5-oxaproline (Opr) in the sequence R1-Xaa-Opr-Gly-OR2 were found to inactivate prolyl 4-hydroxylase from chick and human origins. Of the substances investigated, compounds with aromatic substituents R1 and R2 were particularly effective when compared with those with an aliphatic group or without a C-terminal blocking group. Both affinity of the individual peptides for the enzyme and partition ratio contributed to the differences in efficiency. Benzylcarbonyl-Phe-Opr-Gly-benzyl ester was the most effective substance tested, its concentration giving 50% inactivation in 1 h being 0.8 microM. Inactivation was only observed in the presence of 2-oxoglutarate and Fe2+. The Opr peptides enhanced the decarboxylation of 2-oxoglutarate by prolyl 4-hydroxylase, the Vmax values obtained with the individual peptides being positively correlated with their inactivating efficiency. Inactivation was prevented by high concentrations of peptide substrate and ascorbate. Lineweaver-Burk kinetics experiments suggested noncompetitive inhibition with respect to peptide substrate and ascorbate. Lysyl hydroxylase was not affected by Opr peptides in concentrations of up to 1.5 mM in either the presence or absence of prolyl 4-hydroxylase. The results suggest that the oxaproline compounds are specific syncatalytic inactivators of prolyl 4-hydroxylase.

Collagen type IV and procollagen type III during granulation tissue formation: a serological, biochemical, immunohistochemical and morphometrical study on the viscose cellulose sponge rat model

The serum concentrations of collagen type IV,7S, collagen type IV,nc1, and aminoterminal type III procollagen peptide immunoreactive components were measured by means of specific radioimmunoassays during development of granulation tissue in rats. The results were compared with tissue deposition of basement membranes and interstitial collagens in the granulation as measured morphometrically. A parallel sequential pattern in tissue deposition of collagen types III and IV, and serum increase of collagen types III- and IV-related fragments, was observed. Serum collagen type IV was less sensitive as a marker for development of granulation tissue than the serum procollagen type III N-peptide. This was in accordance with a low collagen type IV/interstitial collagen ratio in the granulation tissue. However, a cross-sectional study showed that serum collagens types IV,7S and IV,nc1 may be useful as early quantitative indicators of granulation tissue formation. Simultaneously, measurement of collagen type IV- and procollagen type III N-peptide-related antigens in serum provides a differentiated reflection of the dynamic matrix processes in developing granulation tissue.

Levels of type IV collagen and laminin fragments in serum from patients with progressive systemic sclerosis

Sera from patients with progressive systemic sclerosis (PSS) were studied using immuno-assays for laminin P1 fragment and the carboxyterminal NC1 domain from type IV collagen. Compared to healthy controls, patients with PSS showed elevated serum levels of both fragments derived from basement membrane proteins. However, there was no difference when patients with and without Raynaud's phenomenon were compared and no correlation could be established with the activity of the disease or clinically defined types of scleroderma. Our data indicate that the metabolism of basement membrane proteins is involved in the course of scleroderma; however, it remains questionable whether these assays could become useful as diagnostic or prognostic tools.

Serum concentrations of the N-terminal propeptide of type III procollagen and two type IV collagen fragments and gene expression of the respective collagen types in liver in rats with dimethylnitrosamine-induced hepatic fibrosis

Dimethylnitrosamine (DMN)-induced liver fibrosis was used as an experimental model to study the relationship between serum concentrations of the N-terminal propeptide of type III procollagen [S-Pro(III)-N-P] and the N-terminal (S-7S) and C-terminal (S-NC1) domains of type IV collagen and hepatic concentrations of type III and IV collagen mRNAs. Increases in S-Pro(III)-N-P, and especially in the two type IV collagen-related antigens, were found to be early events in the formation of DMN-induced hepatic fibrosis. The mean concentration of S-Pro(III)-N-P was 120% of the control mean on day 7 of DMN treatment, 230% on day 14 and 250% on day 21. The corresponding values for S-7S were 260, 950 and 1100% and, for S-NC1, 310, 820 and 1000%. All these changes were very similar to those found in the hepatic concentrations of the respective mRNAs. These data support a previous suggestion that an enhanced production of basement-membrane (type IV) collagen is an early event in the development of the DMN-induced hepatic fibrosis. The results also indicate that S-7S and S-NC1 are very sensitive indicators of changes in type IV collagen metabolism. Data obtained in gel-filtration experiments for these three serum antigens were consistent with the suggestion that all three antigens are mainly derived from the synthesis of the respective collagens.

Influence of hypertension on serum concentration of type IV collagen antigens in streptozotocin-diabetic and non-diabetic rats

The serum concentration of 7S collagen was measured radioimmunologically as a marker of basement membrane type IV collagen synthesis in diabetic and nondiabetic rats with Goldblatt hypertension. In non-diabetic rats the 7S collagen level was significantly raised after induction of hypertension (51%; p less than 0.001), and showed a positive correlation with relative heart weight as an integral parameter of hypertension (r = 0.63; p less than 0.01). In diabetic rats, which displayed a 7S collagen concentration roughly 2.5 times as high as the metabolically normal animals, the 7S collagen level was 27% higher in the hypertensive animals (p less than 0.01). There was no correlation with blood pressure or heart weight, but only a positive correlation with blood glucose (r = 0.51; p less than 0.05). The results indicate that haemodynamic alterations may alter basement membrane collagen metabolism. However, type IV collagen metabolism in diabetes is influenced to a greater extent by metabolic than by haemodynamic factors.