High-throughput mutagenesis identifies mutations and RNA-binding proteins controlling CD19 splicing and CART-19 therapy resistance

Following CART-19 immunotherapy for B-cell acute lymphoblastic leukaemia (B-ALL), many patients relapse due to loss of the cognate CD19 epitope. Since epitope loss can be caused by aberrant CD19 exon 2 processing, we herein investigate the regulatory code that controls CD19 splicing. We combine high-throughput mutagenesis with mathematical modelling to quantitatively disentangle the effects of all mutations in the region comprising CD19 exons 1-3. Thereupon, we identify ~200 single point mutations that alter CD19 splicing and thus could predispose B-ALL patients to developing CART-19 resistance. Furthermore, we report almost 100 previously unknown splice isoforms that emerge from cryptic splice sites and likely encode non-functional CD19 proteins. We further identify cis-regulatory elements and trans-acting RNA-binding proteins that control CD19 splicing (e.g., PTBP1 and SF3B4) and validate that loss of these factors leads to pervasive CD19 mis-splicing. Our dataset represents a comprehensive resource for identifying predictive biomarkers for CART-19 therapy.

Multiple alternative splicing events in CD19 mRNA have been associated with resistance/relapse to CD19 CAR-T therapy in patients with B cell malignancies. Here, by combining patient data and a high-throughput mutagenesis screen, the authors identify single point mutations and RNA-binding proteins that can control CD19 splicing and be associated with CD19 CAR-T therapy resistance.

Estrogen-dependent control and cell-to-cell variability of transcriptional bursting

Cellular decision-making and environmental adaptation are dependent upon a heterogeneous response of gene expression to external cues. Heterogeneity arises in transcription from random switching between transcriptionally active and inactive states, resulting in bursts of RNA synthesis. Furthermore, the cellular state influences the competency of transcription, thereby globally affecting gene expression in a cell-specific manner. We determined how external stimuli interplay with cellular state to modulate the kinetics of bursting. To this end, single-cell dynamics of nascent transcripts were monitored at the endogenous estrogen-responsive GREB1 locus. Stochastic modeling of gene expression implicated a two-state promoter model in which the estrogen stimulus modulates the frequency of transcriptional bursting. The cellular state affects transcriptional dynamics by altering initiation and elongation kinetics and acts globally, as GREB1 alleles in the same cell correlate in their transcriptional output. Our results suggest that cellular state strongly affects the first step of the central dogma of gene expression, to promote heterogeneity in the transcriptional output of isogenic cells.

PET of HER2-positive pulmonary metastases with 18F-ZHER2:342 affibody in a murine model of breast cancer: comparison with 18F-FDG

Targeted therapies often depend on the expression of the target present in the tumor. This expression can be difficult to ascertain in widespread metastases. (18)F-FDG PET/CT, although sensitive, is nonspecific for particular tumor markers. Here, we compare the use of a human epidermal growth factor receptor 2 (HER2)-specific (18)F-Z(HER2)(:342)-Affibody and (18)F-FDG in HER2-expressing pulmonary metastases in a murine model of breast cancer.

METHODS

The lung metastasis model was established by intravenous injection of MDA-MB-231(HER2)-Luc human breast cancer cells into the tail vein. Bioluminescence imaging was used to evaluate metastasis progression. Uptake of (18)F-Z(HER2)(:342)-Affibody and (18)F-FDG was confirmed by coregistration of the PET images with MR and CT images. At the end of the study, the presence of neoplastic cells and HER2 expression in lung tissues, and distribution of the tracer, were assessed ex vivo by immunohistochemistry and autoradiography.

RESULTS

(18)F-Z(HER2)(:342)-Affibody successfully targeted HER2-positive lesions in the lung and allowed detection of metastases as early as 9 wk after injection of cells. In contrast, (18)F-FDG uptake was often masked by surrounding inflammatory changes and was nonspecific for HER2 expression. HER2 expression at a cellular level correlated well with tracer uptake on autoradiography.

CONCLUSION

(18)F-Z(HER2)(:342)-Affibody is a promising tracer for evaluation of HER2 status of breast cancer metastases and is more specific for detecting HER2-positive lesions than (18)F-FDG.

HER2-affitoxin: a potent therapeutic agent for the treatment of HER2-overexpressing tumors

PURPOSE

Cancers overexpressing the HER2/neu gene are usually more aggressive and are associated with poor prognosis. Although trastuzumab has significantly improved the outcome, many tumors do not respond or acquire resistance to current therapies. To provide an alternative HER2-targeted therapy, we have developed and characterized a novel recombinant protein combining an HER2-specific Affibody and modified Pseudomonas aeruginosa exotoxin A (PE 38), which, after binding to HER2, is internalized and delivered to the cytosol of the tumor cell, where it blocks protein synthesis by ADP ribosylation of eEF-2.

EXPERIMENTAL DESIGN

The effect of the Affitoxin on cell viability was assessed using CellTiter-Glo (Promega). To assess HER2-specific efficacy, athymic nude mice bearing BT-474 breast cancer, SK-OV-3 ovarian cancer, and NCI-N87 gastric carcinoma xenografts were treated with the Affitoxin (HER2- or Tag-specific), which was injected every third day. Affitoxin immunogenicity in female BALB/c mice was investigated using standard antibody production and splenocyte proliferation assays.

RESULTS

In vitro experiments proved that HER2-Affitoxin is a potent agent that eliminates HER2-overexpressing cells at low picomolar concentrations. Therapeutic efficacy studies showed complete eradication of relatively large BT-474 tumors and significant effects on SK-OV-3 and NCI-N87 tumors. HER2-Affitoxin cleared quickly from circulation (T(1/2) < 10 minutes) and was well tolerated by mice at doses of 0.5 mg/kg and below. Immunogenicity studies indicated that HER2-Affitoxin induced antibody development after the third injected dose.

CONCLUSIONS

Our findings showed that HER2-Affitoxin is an effective anticancer agent and a potential candidate for clinical studies.

Abstract 1151: HER2- and EGFR-specific Affiprobes - Novel recombinant optical probes for cell imaging

The human epidermal growth factor receptors EGFR (Her1, ErbB1) and HER2 (HER2/neu, ErbB2, or c-erb-b2) are members of EGFR (ErbB) family of cell-surface receptors/tyrosine kinases: EGFR, HER2, HER3, and HER4. There are several identified ligands for these receptors (except HER2), including EGF and TGF-alpha, that induce receptor dimerization followed by tyrosine autophosphorylation, which leads to cell proliferation. EGFR and HER2 are found overexpressed in a number of cancer types, such as breast, ovarian, salivary gland, stomach, kidney, colon, prostate, and non-small cell lung cancer. Research has shown that EGFR- or HER2-positive cancers represent a more aggressive disease with greater likelihood of recurrence, poorer prognosis, and decreased survival rate compared to EGFR- or HER2-negative cancers. The details of HER2 proto-oncogenic function, its internalization mechanism, and subcellular trafficking are not fully understood, partially because the availability of imaging reagents and tools for detection of EGFR and HER2 is still restricted to medium/low affinity antibody conjugated to small-molecule dyes. We have created photo-stable and relatively simple-to-prepare imaging probes for in vitro staining of EGFR and HER2. These new reagents, called Affiprobes, consist of the targeting moiety, a HER2- or EGFR-specific Affibody® molecule, and a fluorescent detection moiety mCherry (Red), or EGFP (Green). These fluorescent proteins were chosen due to their high stability and solubility and low toxicity for eukaryotic cells. Furthermore, HER2 and EGFR receptors can be detected simultaneously using corresponding optical filter sets. Our flow cytometry and confocal microscopy experiments demonstrated high specificity and signal/background ratio for the Affiprobes. This type of optical probe can be easily extended to targeting other cell-surface antigens/receptors using different Affibody® molecules and fluorescent proteins.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1151.

Abstract 2588: Affitoxin - A novel approach to HER2-targeted therapy

Expression of the human epidermal growth factor receptor 2 (HER2) is amplified in 25 −30% of breast cancers and has been associated with unfavorable prognosis. In spite of the development of new HER2-targeted therapies, such as trastuzumab (Herceptin®; Genentech, Inc., South San Francisco, CA), which has revolutionized the treatment of HER2-overexpressing breast cancers, there is a significant number of patients with HER2-positive tumors who do not respond or acquire resistance to these therapies. An alternative treatment maybe constituted by immunotoxins. Immunotoxins are hybrid proteins composed of a targeting moiety such as an antibody, antibody fragment or ligand directed to an antigen or a receptor on the surface of tumor cells, and a toxic domain derived form plant (ricin) or bacteria (diphtheria toxin or Pseudomonas aeruginosa exotoxin A). The targeting moiety directs the toxin moiety to the tumor cell and, then, the active domain induces apoptosis by inhibition of protein synthesis. The PE38, which is a truncated version of Pseudomonas exotoxin A (PE), is preferred for construction of immunotoxin because its high toxic potential has been well documented and cytotoxic pathways described and understood.

Affitoxins are immunotoxin derivatives containing Affibody molecule as a targeting moiety instead of antibodies or antibodies fragments. Affibody molecules are a new class of relatively small (∼7-kDa) affinity proteins. Structurally, they are based on a 58-amino-acid scaffold, derived from the Z domain of the Staphylococcus aureus protein, and were obtained by combinatorial protein engineering.

Previously we reported construction, overxpression and characterization of Affitoxin targeting tumors with HER2 overexpression. Receptor-dependent binding and tumorocidal activity was confirmed on cell lines varying with receptor number. Both binding and toxicity was reverted when excess of Affibody molecules (acting as a competitor) was applied.

Here we report in vivo characterization of HER2 -Affitoxin. First we show that Affitoxin is well tolerated in athymic mice. Pharmacokinetic analysis indicates relatively short half-life of Affitoxin in the circulation most probably due to rapid renal clearance which seems to be compatible with fast binding of Affitoxin to HER2. Finally we show that HER2-Affitoxin is potent agent that leads to elimination of breast and ovarian xenografts (BT474 and SKOV3 s.c. tumors), while no such an effect was observed for off-target Affitoxin applied in the same concentration. Immunogenic potential of HER2 Affitoxin was also evaluated.

We conclude that our HER2-Affitoxin has potential to become an attractive alternative in treatment of tumors associated with expression of HER2 receptors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2588.

HER2- and EGFR-specific affiprobes: novel recombinant optical probes for cell imaging

The human epidermal growth factor receptors, EGFR and HER2, are members of the EGFR family of cell-surface receptors/tyrosine kinases. EGFR- and HER2-positive cancers represent a more aggressive disease with greater likelihood of recurrence, poorer prognosis, and decreased survival rate, compared to EGFR- or HER2-negative cancers. The details of HER2 proto-oncogenic functions are not deeply understood, partially because of a restricted availability of tools for EGFR and HER2 detection (A. Sorkin and L. K. Goh, Exp. Cell Res. 2009, 315, 683-696). We have created photostable and relatively simple-to-produce imaging probes for in vitro staining of EGFR and HER2. These new reagents, called affiprobes, consist of a targeting moiety, a HER2- or EGFR-specific Affibody molecule, and a fluorescent moiety, mCherry (red) or EGFP (green). Our flow cytometry and confocal microscopy experiments demonstrated high specificity and signal/background ratio of affiprobes. Affiprobes are able to stain both live cells and frozen tumor xenograph sections. This type of optical probe can easily be extended for targeting other cell-surface antigens/ receptors.

A comparison of volume and circumference phallometry: response magnitude and method agreement

Penile circumference and penile volume phallometry are laboratory methods of assessing sexual arousal. Volume phallometry is reportedly more sensitive to responses, but comparative studies have been inconclusive and beset with methodological problems. In this study, 42 self-professed heterosexual volunteers were assessed with both methods simultaneously, employing a standard test for erotic partner preference. Pearson correlations between test outcome profiles were very high (r > .80) for subjects whose circumferential increase was > 2.5 mm [10% of a full erection (FE)]. However, among lower responders the agreement dropped precipitously (mean r = -.15). Moreover, as a group higher responders differentiated adult and pubescent age female stimuli from each other and all other categories with either method, but lower responders made this differentiation only with the volume method. We conclude that (l) at high levels of response both methods are equally good, (2) at low levels of response volumetric phallometry is a more accurate measure of arousal, and (3) 10% FE, or a 2.5-mm circumference increase, should be the minimum response criterion for the circumferential measure.

The sexual preferences of incest offenders

Inclusive fitness theory suggests that discriminative solicitude and inbreeding avoidance are important mechanisms regulating parent-children interactions. From an inclusive fitness perspective, sex with one's biological children is paradoxical. The authors hypothesized that incest can occur when these mechanisms are not activated (e.g., if a father is uninvolved in child rearing) or are overwhelmed by another factor, such as pedophilic interest. They predicted that biological fathers, who presumably have been the most involved in the rearing of their victims, would show greater phallometrically measured pedophilic interest than would other incest offenders against children (e.g., grandfathers, uncles, stepfathers). The prediction was not supported. A testable alternative hypothesis to explain biological father incest is presented and the importance of assessing pedophilic interest among incest offenders is discussed.

Pedophiles: mental retardation, maternal age, and sexual orientation

Intellectual functioning, parental age, and sexual orientation in 991 male sexual offenders were investigated. Sources of data included semistructured interviews, clinical charts, phallometric tests, and self-administered questionnaires. The results suggest two main conclusions: (i) Among pedophiles in general, erotic preference moves away from adult women along two dimensions: age and sex. The extent of this movement is greater, along both dimensions, for pedophiles with lower levels of intellectual functioning. (ii) High maternal age (or some factor it represents) increases the likelihood of exclusive sexual interest in boys. Intellectual deficiency (or some factor it represents) decreases the likelihood of exclusive sexual interest in girls. These two factors summate, so that a pedophile with both factors is more likely to be sexually interested in boys than a pedophile with only one.

Pedophilia, sexual orientation, and birth order

This study extended research on birth order and erotic preferences by examining birth order in a sample of pedophiles. Charts of 338 pedophiles, assessed from 1980-1994 in the Behavioural Sexology Department of the Clarke Institute of Psychiatry in Toronto, were reviewed for family-demographic information. In total, 170 (57 heterosexual pedophiles, 68 homosexual pedophiles, and 45 bisexual pedophiles) of these men had sufficient sibling information to be included in the analyses. The results indicated that homosexual-bisexual pedophiles had a later birth order than heterosexual pedophiles and that this effect was primarily the result of the homosexual-bisexual group being born later among their brothers. The results extend previous findings that homosexual men, regardless of sample composition, have a later birth order than comparable groups of heterosexual men. The results also challenge some existing theories on the nature and origins of pedophilia.

Two types of fetishism

This study attempted to differentiate two clinical types of fetishism-fetishism proper and tranvestism-and to determine if tranvestites are truly fetishistic. The transvestites were further divided into gender-conforming and gender-noncomforming groups according to their score on a gender identity scale. These groups were compared using a self-report scale measuring fetishistic interests, and a set of questionnaire items regarding their childhood history, parental characteristics, and their emotional closeness with their parents. In addition, the penile responses of a subset of fetishists and tranvestites were recorded while they were presented with visual depictions of female and male public regions and potentially fetishistic objects (nylon stockings, female and male shoes, panties, male underwear, female and male feet). The fetishists proper and the transvestite subgroups did not differ from each other in terms of self-reported fetishistic interest or childhood and family histories. Moreover, there were no differences between these groups in their penile response to the potentially fetishistic stimulus they were most aroused by, relative to the depictions of the pubic region of their preferred gender. These results suggest that transvestites are in fact fetishistic, and that they are difficult to distinguish from fetishists proper.

Criterion-related validity of a phallometric test for paraphilic rape and sadism

Eight men admitting to sadistic fantasies or urges (fantasizers), 7 sadistic rapists (sadists), 14 nonsadistic rapists, 31 courtship-disordered men (men displaying exhibitionism, voyeurism, frotteurism, or a combination of these paraphilias), and 20 community controls were compared on their relative phallometric responses to stimuli depicting rape, violent rape, and nonsexual violence. This study extended previous research by including a group of men who admitted to having sadistic fantasies or urges, in contrast to rapists who are likely to deny any such interests because of possible legal or social sanctions, and by including a large comparison group of men with a paraphilia other than sadism. Criterion-related validity was greater after combining the sadistic and nonsadistic rapists: fantasizers, sadists, and rapists did not differ from each other; fantasizers differed from community controls in their relative responses to rape, violent rape, and nonsexual violence; rapists differed from community controls in their relative responses to violent rape and nonsexual violence; and courtship-disordered men differed from community controls in their relative responses to nonsexual violence.

The basis of the abused abuser theory of pedophilia: a further elaboration on an earlier study

The connection between the retrospective self-report of sexual abuse in childhood by an adult person, and (i) erotically preferred age bracket and (ii) type of offense, was investigated in 303 heterosexual males. This group consisted of 83 pedophilic sex offenders against female children, 52 sex offenders against female children who erotically preferred adult women, 34 sex offenders against adult women, and 134 volunteer controls. An earlier exploratory investigation with somewhat smaller numbers of individuals had rendered only ambiguous results. After regrouping of individuals and more precise analysis of results, the present study demonstrated that the self-report of having been sexually abused in childhood is mainly connected with pedophilia. Status as a sex offender in general was not related to childhood abuse.

Deficient erotic gender differentiation in pedophilia: a follow-up

Divided 262 phallometrically diagnosed pedophiles into heterosexual, homosexual, and bisexual groups, according to the sex of their victims. Each group was then divided into 3 subgroups according to degree of admitting to an erotic preference for children. They were compared among each other and with 47 self-professed heterosexual and 20 self-professed homosexual male volunteers phallometrically diagnosed as having an erotic preference for physically mature partners. The comparison was in regard to phallometrically assessed "erotic gender differentiation." Results demonstrate that gender differentiation of even the fully admitting heterosexual pedophiles was significantly weaker than that of the heterosexual controls, and the gender differentiation of the fully admitting homosexual pedophiles was significantly weaker than that of both groups of controls. Gender differentiation of the nonadmitting heterosexual pedophiles was significantly weaker than that of the heterosexual pedophiles who fully admitted to their paraphilia. This was demonstrated to be caused by the nonadmitters suppression of responses.

Toward a testable developmental model of pedophilia: the development of erotic age preference

Retrospective self-reports about childhood curiosity to see persons in the nude were used to compare the development of erotic sex and age preferences among four groups of males; 46 heterosexual pedophiles, 30 homosexual pedophiles, 462 gynephiles (who erotically prefer physically mature females), and 51 androphiles (who erotically prefer physically mature males). The results suggest (a) throughout this erotic developmental process among males, the establishment of erotic sex preference precedes that of erotic age preference, and (b) a greater proportion of pedophiles than of individuals who prefer physically mature partners remembers curiosity in their own childhood to see nude children without remembering such curiosity in regard to adults. This suggests that in a substantial proportion of pedophiles the occurrence of this paraphilia is predetermined at a very early developmental phase. A further set of retrospective self-reports, obtained from a group of 78 gynephilic university students suggests that at least in gynephiles the erotic appeal of children of the preferred sex ceases by about the time of puberty. This may be an indication that there exists a process of active devaluation of the nonpreferred age bracket, culminating at puberty.