Inflammatory Activity of Epithelial Stem Cell Variants from Cystic Fibrosis Lungs Is Not Resolved by CFTR Modulators

Rationale: CFTR (cystic fibrosis transmembrane conductance regulator) modulator drugs restore function to mutant channels in patients with cystic fibrosis (CF) and lead to improvements in body mass index and lung function. Although it is anticipated that early childhood treatment with CFTR modulators will significantly delay or even prevent the onset of advanced lung disease, lung neutrophils and inflammatory cytokines remain high in patients with CF with established lung disease despite modulator therapy, underscoring the need to identify and ultimately target the sources of this inflammation in CF lungs. Objectives: To determine whether CF lungs, like chronic obstructive pulmonary disease (COPD) lungs, harbor potentially pathogenic stem cell "variants" distinct from the normal p63/Krt5 lung stem cells devoted to alveolar fates, to identify specific variants that might contribute to the inflammatory state of CF lungs, and to assess the impact of CFTR genetic complementation or CFTR modulators on the inflammatory variants identified herein. Methods: Stem cell cloning technology developed to resolve pathogenic stem cell heterogeneity in COPD and idiopathic pulmonary fibrosis lungs was applied to end-stage lungs of patients with CF (three homozygous CFTR:F508D, one CFTR F508D/L1254X; FEV1, 14-30%) undergoing therapeutic lung transplantation. Single-cell-derived clones corresponding to the six stem cell clusters resolved by single-cell RNA sequencing of these libraries were assessed by RNA sequencing and xenografting to monitor inflammation, fibrosis, and mucin secretion. The impact of CFTR activity on these variants after CFTR gene complementation or exposure to CFTR modulators was assessed by molecular and functional studies. Measurements and Main Results: End-stage CF lungs display a stem cell heterogeneity marked by five predominant variants in addition to the normal lung stem cell, of which three are proinflammatory both at the level of gene expression and their ability to drive neutrophilic inflammation in xenografts in immunodeficient mice. The proinflammatory functions of these three variants were unallayed by genetic or pharmacological restoration of CFTR activity. Conclusions: The emergence of three proinflammatory stem cell variants in CF lungs may contribute to the persistence of lung inflammation in patients with CF with advanced disease undergoing CFTR modulator therapy.

Cloning a profibrotic stem cell variant in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, irreversible, and rapidly fatal interstitial lung disease marked by the replacement of lung alveoli with dense fibrotic matrices. Although the mechanisms initiating IPF remain unclear, rare and common alleles of genes expressed in lung epithelia, combined with aging, contribute to the risk for this condition. Consistently, single-cell RNA sequencing (scRNA-seq) studies have identified lung basal cell heterogeneity in IPF that might be pathogenic. We used single-cell cloning technologies to generate "libraries" of basal stem cells from the distal lungs of 16 patients with IPF and 10 controls. We identified a major stem cell variant that was distinguished from normal stem cells by its ability to transform normal lung fibroblasts into pathogenic myofibroblasts in vitro and to activate and recruit myofibroblasts in clonal xenografts. This profibrotic stem cell variant, which was shown to preexist in low quantities in normal and even fetal lungs, expressed a broad network of genes implicated in organ fibrosis and showed overlap in gene expression with abnormal epithelial signatures identified in previously published scRNA-seq studies of IPF. Drug screens highlighted specific vulnerabilities of this profibrotic variant to inhibitors of epidermal growth factor and mammalian target of rapamycin signaling as prospective therapeutic targets. This profibrotic stem cell variant in IPF was distinct from recently identified profibrotic stem cell variants in chronic obstructive pulmonary disease and may extend the notion that inappropriate accrual of minor and preexisting stem cell variants contributes to chronic lung conditions.

Regenerative Metaplastic Clones in COPD Lung Drive Inflammation and Fibrosis

Chronic obstructive pulmonary disease (COPD) is a progressive condition of chronic bronchitis, small airway obstruction, and emphysema that represents a leading cause of death worldwide. While inflammation, fibrosis, mucus hypersecretion, and metaplastic epithelial lesions are hallmarks of this disease, their origins and dependent relationships remain unclear. Here we apply single-cell cloning technologies to lung tissue of patients with and without COPD. Unlike control lungs, which were dominated by normal distal airway progenitor cells, COPD lungs were inundated by three variant progenitors epigenetically committed to distinct metaplastic lesions. When transplanted to immunodeficient mice, these variant clones induced pathology akin to the mucous and squamous metaplasia, neutrophilic inflammation, and fibrosis seen in COPD. Remarkably, similar variants pre-exist as minor constituents of control and fetal lung and conceivably act in normal processes of immune surveillance. However, these same variants likely catalyze the pathologic and progressive features of COPD when expanded to high numbers.

Carcinogenic HPV infection in the cervical squamo-columnar junction

Recent studies have suggested the involvement of a unique population of cells at the cervical squamo-columnar junction (SCJ) in the pathogenesis of early (squamous intraepithelial lesion or SIL) and advanced (squamous cell and adeno-carcinomas) cervical neoplasia. However, there is little evidence to date showing that SCJ cells harbour carcinogenic HPV or are instrumental in the initial phases of neoplasia. This study was designed to (1) determine if normal-appearing SCJ cells contained evidence of carcinogenic HPV infection and (2) trace their transition to early SIL. Sections of cervix from high-risk reproductive age women were selected and SCJ cells were analysed by using several techniques which increasingly implicated HPV infection: HPV DNA (genotyping and in situ hybridization)/RNA (PCR), immunostaining for HPV16 E2 (an early marker of HPV infection), p16(ink4), Ki67, and HPV L1 protein. In 22 cases with a history of SIL and no evidence of preneoplastic lesion in the excision specimen, HPV DNA was isolated from eight of ten with visible SCJ cells, six of which were HPV16/18 DNA-positive. In five of these latter cases, the SCJ cells were positive for p16(ink4) and/or HPV E2. Transcriptionally active HPV infection (E6/E7 mRNAs) was also detected in microdissected SCJ cells. Early squamous atypia associated with the SCJ cells demonstrated in addition diffuse p16(ink4) immunoreactivity, elevated proliferative index, and rare L1 antigen positivity. We present for the first time direct evidence that normal-appearing SCJ cells can be infected by carcinogenic HPV. They initially express HPV E2 and their progression to SIL is heralded by an expanding metaplastic progeny with increased proliferation and p16(ink4) expression. Whether certain SCJs are more vulnerable than others to carcinogenic HPV genotypes and what variables determine transition to high-grade SIL remain unresolved, but the common event appears to be a vulnerable cell at the SCJ.

The PAX2-null immunophenotype defines multiple lineages with common expression signatures in benign and neoplastic oviductal epithelium

The oviducts contain high-grade serous cancer (HGSC) precursors (serous tubal intraepithelial neoplasia or STINs), which are γ-H2AX(p) - and TP53 mutation-positive. Although they express wild-type p53, secretory cell outgrowths (SCOUTs) are associated with older age and serous cancer; moreover, both STINs and SCOUTs share a loss of PAX2 expression (PAX2(n) ). We evaluated PAX2 expression in proliferating adult and embryonic oviductal cells, normal mucosa, SCOUTs, Walthard cell nests (WCNs), STINs, and HGSCs, and the expression of genes chosen empirically or from SCOUT expression arrays. Clones generated in vitro from embryonic gynaecological tract and adult Fallopian tube were Krt7(p) /PAX2(n) /EZH2(p) and underwent ciliated (PAX2(n) /EZH2(n) /FOXJ1(p) ) and basal (Krt7(n) /EZH2(n) /Krt5(p) ) differentiation. Similarly, non-ciliated cells in normal mucosa were PAX2(p) but became PAX2(n) in multi-layered epithelium undergoing ciliated or basal (WCN) cell differentiation. PAX2(n) SCOUTs fell into two groups: type 1 were secretory or secretory/ciliated with a 'tubal' phenotype and were ALDH1(n) and β-catenin(mem) (membraneous only). Type 2 displayed a columnar to pseudostratified (endometrioid) phenotype, with an EZH2(p) , ALDH1(p) , β-catenin(nc) (nuclear and cytoplasmic), stathmin(p) , LEF1(p) , RCN1(p) , and RUNX2(p) expression signature. STINs and HGSCs shared the type 1 immunophenotype of PAX2(n) , ALDH1(n) , β-catenin(mem) , but highly expressed EZH2(p) , LEF1(p) , RCN1(p) , and stathmin(p) . This study, for the first time, links PAX2(n) with proliferating fetal and adult oviductal cells undergoing basal and ciliated differentiation and shows that this expression state is maintained in SCOUTs, STINs, and HGSCs. All three entities can demonstrate a consistent perturbation of genes involved in potential tumour suppressor gene silencing (EZH2), transcriptional regulation (LEF1), regulation of differentiation (RUNX2), calcium binding (RCN1), and oncogenesis (stathmin). This shared expression signature between benign and neoplastic entities links normal progenitor cell expansion to abnormal and neoplastic outgrowth in the oviduct and exposes a common pathway that could be a target for early prevention.

Through the glass darkly: intraepithelial neoplasia, top-down differentiation, and the road to ovarian cancer

It is currently hoped that deaths from extra-uterine high-grade serous cancer (HGSC) will be reduced via opportunistic salpingectomy in healthy women. Accumulated data implicate the fimbria as a site of origin and descriptive molecular pathology and experimental evidence strongly support a serous carcinogenic sequence in the Fallopian tube. Both direct and indirect ('surrogate') precursors suggest that the benign tube undergoes important biological changes after menopause, acquiring abnormalities in gene expression that are often shared with malignancy, including PAX2, ALDH1, LEF1, RCN1, RUNX2, beta-catenin, EZH2, and others. However, the tube can be linked to only some HGSCs, recharging arguments that nearby peritoneum/ovarian surface epithelium (POSE) also hosts progenitors to this malignancy. A major sticking point is the difference in immunophenotype between POSE and Müllerian epithelium, essentially requiring mesothelial to Müllerian differentiation prior to or during malignant transformation to HGSC. However, emerging evidence implicates an embryonic or progenitor phenotype in the adult female genital tract with the capacity to differentiate, normally or during neoplastic transformation. Recently, a putative cell of origin for cervical cancer has been identified in the squamo-columnar (SC) junction, projecting a model whereby Krt7+ embryonic progenitors give rise to immunophenotypically distinct progeny under stromal influences via 'top down' differentiation. Similar differentiation can be seen in the endometrium with a parallel in juxtaposed mesothelial and Müllerian differentiation in the ovary. Abrupt mesothelial-Müllerian transitions remain to be proven, but would explain the rapid evolution, short asymptomatic interval, and absence of a defined epithelial starting point in many HGSCs. Resolving this question will require accurately distinguishing progenitor from progeny tumour cells in HGSC and pinpointing where initial transformation and trans-differentiation occur, whether in the tube or POSE. Both will be critical to expectations from prophylactic salpingectomy and future approaches to pelvic serous cancer prevention.

A novel blueprint for 'top down' differentiation defines the cervical squamocolumnar junction during development, reproductive life, and neoplasia

The cervical squamocolumnar (SC) junction is the site of a recently discovered 'embryonic' cell population that was proposed as the cell of origin for cervical cancer and its precursors. How this population participates in cervical remodelling and neoplasia is unclear. In the present study, we analysed the SC junction immunophenotype during pre- and post-natal human and mouse development and in the adult, processes of metaplastic evolution of the SC junction, microglandular change, and early cervical neoplasia. Early in life, embryonic cervical epithelial cells were seen throughout the cervix and subsequently diminished in number to become concentrated at the SC junction in the adult. In all settings, there was a repetitive scenario in which cuboidal embryonic/SC junction cells gave rise to subjacent metaplastic basal/reserve cells with a switch from the SC junction positive to negative immunophenotype. This downward or basal (rather than upward or apical) evolution from progenitor cell to metaplastic progeny was termed reverse or 'top down' differentiation. A similar pattern was noted in high-grade squamous intraepithelial lesions (HSILs), suggesting that HPV infection of the cuboidal SC junction cells initiated outgrowth of basally-oriented neoplastic progeny. The progressive loss of the embryonic/SC junction markers occurred with 'top down' differentiation during development, remodelling, and early neoplasia. Interestingly, most low-grade SILs were SC junction-negative, implying infection of metaplastic progeny rather than the original SC junction cells. This proposed model of 'top down' differentiation resolves the mystery of how SC junction cells both remodel the cervix and participate in neoplasia and provides for a second population of metaplastic progeny (including basal and reserve cells), the infection of which is paradoxically less likely to produce a biologically aggressive precursor. It also provides new targets in animal models to determine why the SC junction is uniquely susceptible to carcinogenic HPV infection.

Abstract 3297: A cell of origin for cervical cancer

Background Squamous cell carcinoma of the cervix and its precursor [cervical intraepithelial neoplasia (CIN)] are thought to develop either within, or in close proximity to, the squamo-columnar (SC) junction of the ecto and endocervix. Despite this assumption, one issue unresolved in cervical cancer research is the identity of the normal cervical cell type in the SC junction in which tumorigenesis begins. Methods Using GeneChip Human Exon Arrays (Affymetrix), we compared the gene expression profiles of the ecto and endocervical epithelia with the SC junctional cells. Fetal and adult cervical specimens were studied in situ to identify, characterize and determine the dynamics of junctional cell development. CINs and cancers were stained with junction-specific antibodies to ascertain their relationship to the SC junctional cell population. Cervices in which the transformation zone had been excised were analyzed for evidence of the SC junctional immunophenotype. Results Human adult cervices displayed a unique monolayer of cuboidal cells at the SC junction that displayed a unique 77 gene expression signature. Analysis of fetal and postnatal mouse and human cervices using biomarkers from this unique gene signature revealed broad expression in the lining cells of the lower genital tract that, over time, become concentrated in the region of the SC junction. Junction-specific biomarkers consistently immunostained high-grade CINs and squamous and glandular cancers associated with both carcinogenic human papillomaviruses (HPV) and strong expression of p16ink4. Non-carcinogenic HPV-associated CINs and low-grade CINs predominated in the ectocervical location and were usually SC junctional-marker negative. Cervices previously subjected to surgical excision of the SC junction did not remanufacture junctional cells at the new SC junction. Conclusions This study shows, for the first time, that a discrete, residual embryonic cell population in the cervix is uniquely susceptible to carcinogenic HPV infection and is lost following surgical excision of the SC junction. The negative association between the junctional immunophenotype and noncarcinogenic HPV-related CIN may signify different affinities for the SC junction between carcinogenic and non-carcinogenic HPVs. Because junction-specific biomarkers highlight CINs and all cancers with carcinogenic HPVs, they may facilitate interpretation of cervical cancer precursors as well as propose a novel cell type for studies of experimental papillomaviral carcinogenesis. The possibility that unique populations of junctional cells are also involved in the pathogenesis of other HPV-related cancers (anogenital and oropharyngeal) merits investigation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3297. doi:1538-7445.AM2012-3297

The p53 family: guardians of maternal reproduction

The p53 family of proteins consists of p53, p63 and p73, which are transcription factors that affect both cancer and development. It is now emerging that these proteins also regulate maternal reproduction. Whereas p63 is important for maturation of the egg, p73 ensures normal mitosis in the developing blastocyst. p53 subsequently regulates implantation of the embryo through transcriptional control of leukaemia inhibitory factor. Elucidating the cell biological basis of how these factors regulate female fertility may lead to new approaches to the control of human maternal reproduction.

Abstract 104: PAX2 dysregulation in the fallopian tube and pelvic serous cancer

High grade ovarian serous cancer in women has been linked to the distal fallopian tube via a carcinogenic sequence of p53 mutations in both a clonally-derived precursor (p53 signature) and an early malignancy (tubal intraepithelial carcinoma)(Lee 2007). Dysregulation of additional genes, including PTEN and PAX2, has been associated with this early carcinogenic sequence and advanced ovarian serous cancers. Dysregulation of PAX2 has not been linked to genetic mutations, and has been recently documented throughout the tube within discrete secretory cell outgrowths (SCOUTs), particularly in fallopian tubes of women with serous cancer (Chen 2010). This study explored the frequency of PAX2-null SCOUTs in the fallopian tube and other potential molecular and cell kinetic correlates of this phenomenon. Fallopian tubes from a wide range of subjects, including (1) pre-adolescents (n=20), women undergoing (2) post-partum tubal ligation (n=25), (3) salpingectomy during surgery for benign disease (n=20), surgery for (4) endometriosis (n=47), (5) low grade endometrioid adenocarcinomas of the ovary (n=42), and (6) high-grade ovarian serous carcinomas (n=12) were immunostained and scored blindly for PAX2-null SCOUTs. Extracted tubal DNA from cancers and controls was analyzed for hypermethylation of the PAX2 promotor by real-time PCR and fallopian tube epithelial cultures were established from cancers and controls to assess clonogenic capacity. Review of over 350 tissue blocks revealed a frequency (%) of PAX2-null SCOUTs of 0, 0.5, 11, 5, 4.5 and 56.2 for groups 1-6 above, respectively, yielding a 5-50-fold increase in the tubes of patients with serous cancer (p < .001). A preliminary analysis of DNA from one cancer-associated fallopian tube revealed a relative increase in PAX2 promotor methylation. A striking increase in cell growth (clonogenic) capacity was observed in tubes from cancer patients versus controls. This study reveals, for the first time, that functional loss of PAX2 expression is linked to a morphologically defined entity (SCOUT) in the fallopian tube that is absent in pre-adolescent fallopian tubes and post-partum tubal ligations, increases with age, and is exquisitely linked to co-existing high grade ovarian serous carcinoma. This unique dysregulation of PAX2 appears to segregate with a markedly higher in vitro clonogenic potential of tubal epithelium in women with serous cancer. The potential that this highly prevalent entity (PAX2-null SCOUT) and its milieu in fallopian tube epithelium of women with serous cancer can be exploited as a predictor of concurrent or future ovarian serous carcinoma is under investigation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 104. doi:10.1158/1538-7445.AM2011-104

STICS, SCOUTs and p53 signatures; a new language for pelvic serous carcinogenesis

The events leading to the most common and most lethal ovarian carcinoma - high grade serous carcinoma - have been poorly understood. However, the detailed pathologic study of asymptomatic women with germ-line BRCA 1 or BRCA2 (BCRA+) mutations has unearthed an early malignancy, serous tubal intraepithelial carcinomas (STIC), which has linked many peritoneal and ovarian serous carcinomas to the fimbria. The distinction between high-grade serous and endometrioid carcinomas continues to narrow, with shared alterations in expression of pTEN, PAX2 and p53. Moreover, the discovery of clonal alterations in p53 in benign tubal epithelium, - p53 signatures - has established a foundation for a serous cancer precursor in the fimbria. We have expanded this concept to include a generic secretory cell outgrowth (SCOUT) in the fallopian tube that is associated with altered PAX2 expression. As the repertoire of gene alterations is expanded and its link to serous carcinogenesis clarified, a cogent pathway to high-grade Mullerian carcinomas will emerge. This will challenge conventional thinking about ovarian carcinogenesis but will provide a new template for studies of ovarian cancer prevention.

Secretory cell outgrowth, PAX2 and serous carcinogenesis in the Fallopian tube

The 'p53 signature' is a benign secretory cell outgrowth in the distal Fallopian tube that shares properties with ovarian serous cancer-including p53 mutations-and is a putative serous cancer precursor. We expanded the precursor definition to all secretory cell outgrowths (SCOUTs) of 30 or more cells and scored normal (N) and altered (A) expression of both p53 and PAX2, a gene down-regulated in ovarian and endometrial cancer. SCOUTs were identified by BCL2/p73 staining in tubes from women with serous carcinoma, inherited mutations in BRCA1 or BRCA2 and controls. SCOUTs were prevalent in both proximal and distal tube and significantly associated with serous carcinoma versus the others (p < 0.001); 89% were PAX2 (A) and 26% were PAX2 (A)/p53 (A) (p53 signatures). PAX2 (A)/p53 (N) SCOUTs were free of p53 mutations; however, 12 of 13 p53 signatures were PAX2 (A). A tubal carcinoma and contiguous SCOUT were p53 (A)/PAX2 (A) and shared the same p53 mutation. SCOUTs are discretely localized alterations commonly containing altered expression of multiple genes within histologically benign tubal epithelium. Geographic distribution in the tube varies by genotype and immunophenotype, from regionally unrestricted (PAX2) to greater likelihood specific area (fimbria) of shared prevalence (PAX2 and p53). This study reveals, for the first time, an entity (SCOUT) that is associated with serous cancer, expands the topography of altered PAX2 expression in the female genital tract mucosa and highlights another potential pathway disturbance involved in early serous carcinogenesis in the Fallopian tube.

p63 in epithelial survival, germ cell surveillance, and neoplasia

The p53homolog p63has emerged as a gene with an enormously complex function that is distinct from that of p53. It encodes two distinct transcript isoforms that have a dramatic impact on replenishment of cutaneous epithelial stem cells and on ovarian germ cell survival. However, although these two fundamental roles of p63 attest to its powerful place in development, its other functions-specifically the apparent capacity of p63, when induced, to supervise the emergence of new cell populations in the breast, prostate, cervix, and upper reproductive tract-are shared by embryo and adult. These observed functions may only scratch the surface of a repertoire that has been postulated to encompass a range of cellular activities, as evidenced by the fact that p63 proteins have been shown to potentially bind to over 5800 target sites. Whether tumorigenic pathways are also involved, and to what extent, is a subject of both promise and controversy that remains to be resolved.

A candidate precursor to serous carcinoma that originates in the distal fallopian tube

The tubal fimbria is a common site of origin for early (tubal intraepithelial carcinoma or TIC) serous carcinomas in women with familial BRCA1 or 2 mutations (BRCA+). Somatic p53 tumour suppressor gene mutations in these tumours suggest a pathogenesis involving DNA damage, p53 mutation, and progressive loss of cell cycle control. We recently identified foci of strong p53 immunostaining-termed 'p53 signatures'-in benign tubal mucosa from BRCA+ women. To examine the relationship between p53 signatures and TIC, we compared location (fimbria vs ampulla), cell type (ciliated vs secretory), evidence of DNA damage, and p53 mutation status between the two entities. p53 signatures were equally common in non-neoplastic tubes from BRCA+ women and controls, but more frequently present (53%) and multifocal (67%) in fallopian tubes also containing TIC. Like prior studies of TIC, p53 signatures predominated in the fimbriae (80-100%) and targeted secretory cells (HMFG2 + /p73-), with evidence of DNA damage by co-localization of gamma-H2AX. Laser-capture microdissected and polymerase chain reaction-amplified DNA revealed reproducible p53 mutations in eight of 14 fully-analysed p53 signatures and all of the 12 TICs; TICs and their associated ovarian carcinomas shared identical mutations. In one case, a contiguous p53 signature and TIC shared the same mutation. Morphological intermediates between the two, with p53 mutations and moderate proliferative activity, were also seen. This is the first report of an early and distinct alteration in non-neoplastic upper genital tract mucosa that fulfils many requirements for a precursor to pelvic serous cancer. The p53 signature and its malignant counterpart (TIC) underline the significance of the fimbria, both as a candidate site for serous carcinogenesis and as a target for future research on the early detection and prevention of this disease.

Microglandular hyperplasia: a model for the de novo emergence and evolution of endocervical reserve cells

BACKGROUND

Microglandular hyperplasia (MGH) of the cervix in human beings is associated early with gland proliferation and terminates in mature squamous metaplasia. Using antibodies to basal cell markers, we analyzed biopsies with MGH to profile the distribution and evolution of reserve cells and their relationship to these epithelial components.

DESIGN

Serial sections of 24 MGHs were subdivided into (1) early MGH with microacinar proliferation, abundant subnuclear vacuoles, and a paucity of supporting stroma and (2) late MGH with more prominent supporting stroma and/or squamous metaplasia. Serial sections were stained with antibodies to p63, bcl-2, and keratin-5.

RESULTS

Three patterns of p63 staining were observed corresponding to the age of the MGH: (1) scattered staining of columnar cells, (2) focal subcolumnar staining in a reserve cell distribution, and (3) linear subcolumnar arrays of p63-positive reserve cells that in some MGHs expanded into a squamous metaplasia. Early acinar proliferations showed weak and focal columnar cell staining followed by focal subcolumnar p63-positive cells. In late lesions, p63 staining was compartmentalized to the extraglandular (or subcolumnar) areas. Stainings of p63, bcl-2, and keratin-5 were concordant. Staining for keratin 14, which localizes to squamous cells, was variable.

CONCLUSIONS

The immunohistochemical profile in MGH indicates that reserve cells are created in adulthood during specialized columnar proliferations. This columnar to reserve cell transition may produce a stable population of reserve cells or a transition to squamous metaplasia. Similar patterns are seen in cervical neoplasia, suggesting a link between benign and neoplastic cervical epithelial differentiation.

p63 and p73 in tumor suppression and promotion

The recent discovery of two genes, termed p63 and p73, encoding transcription factors highly homologous to p53 presents unexpected challenges and opportunities for the understanding and treatment of cancers. The questions raised are many but center on determining whether these new genes possess novel tumor suppressor functions, cooperate with p53, or impart oncogenic effects. At present there is considerable discord in the field concerning these concepts with some favoring a tumor suppressor role for the p53 family members and others an oncogenic influence. In support of a tumor suppressor role is the ability of p73 and p63 isoforms to transactivate p53 target genes and the large body of work linking p73, and to some extent p63, in apoptotic events in response to cellular stresses generally considered the purview of p53. More recently, p73 has been implicated in cell death following T cell activation, the response of cancers to chemotherapy, and finally, along with p63, to the function of p53 itself. Opposing this view is the fact that the p73 and p63 genes are rarely mutated in cancers and the stark absence of tumors in the p73 null mouse. Moreover, the high expression of dominant negative (dn) versions of the p73 and p63 proteins supports an anti-p53 function and therefore possibly an oncogenic effect. Indeed, the p63 gene is located in a region of chromosome three amplified in squamous cell carcinomas and the number of reports of dn-p63 overexpression in these diseases is increasing. This review will examine both sides of these arguments in an attempt to decipher common themes and to identify opportunities these genes represent for understanding tumorigenesis.

Loss of p63 expression is associated with tumor progression in bladder cancer

p63, a member of the p53 gene family, encodes multiple proteins that may either transactivate p53 responsive genes (TAp63) or act as a dominant-negative factor toward p53 and p73 (Delta Np63). p63 is expressed in many epithelial compartments and p63(-/-) mice fail to develop skin, prostate, and mammary glands among other defects. It has been previously shown that p63 is expressed in normal urothelium. This study reports that p63 is regulated in bladder carcinogenesis and that p63 expression is lost in most invasive cancers whereas papillary superficial tumors maintain p63 expression. Examination of bladder carcinoma cell lines reveals that certain lines derived from invasive carcinomas maintain expression of Delta Np63, as demonstrated by both immunoblotting and confirmed by isoform-specific quantitative reverse transcriptase-polymerase chain reaction. Another novel finding reported in this study is the fact that p63(-/-) mice develop a bladder mucosa epithelial layer yet fail to complete uroepithelial differentiation, producing a nontransitional default cuboidal epithelium. These data indicate that in contrast to the skin and prostate, p63 is not required for formation of a bladder epithelium but is indispensable for the specific differentiation of a transitional urothelium.

p63 Coordinates anogenital modeling and epithelial cell differentiation in the developing female urogenital tract

p63 is a p53 homologue required for cutaneous development that is expressed in immature squamous epithelium and reserve cells of the cervix. Humans with p63 mutations exhibit defects in limb, accessory organ (skin appendage, breast, prostate), and genitourinary development. Because p63 expression patterns imply a strong role of the gene in the female genital tract development, newborn female p63-/-, +/-, and +/+ mice were examined in situ, dissected, and compared. Nuclear p63 protein was localized to the skin, vagina, bladder, urethra, and basal columnar cells of the caudal uterus in p63+/+ and +/- animals. p63-/- mice exhibited abnormal genital morphogenesis with hypoplastic genitalia, a single cloacal opening, and persistence of columnar epithelium at lower genital tract sites that normally undergo squamous and urothelial differentiation. The defects observed support p63-dependent pathways of genital tract development that permit externally, ectodermal basal cell replenishment integral to reciprocal epithelial stromal signaling, urorectal septation, and modeling of the external genitalia; and internally, the emergence of basal epithelial cell populations capable of divergent epithelial cell differentiation in the vagina, cervix, and urinary tract. Defects in the first pathway explain imperforate anus, vaginal septum, genital hypoplasia, and micropenis reported in humans with p63 mutations. The second is necessary for the generation of multipotential reserve cells in the cervix and may be operative in other epithelial stromal interactions integral to the emergence of uterine basal cells later in life.

Histologic and immunophenotypic classification of cervical carcinomas by expression of the p53 homologue p63: a study of 250 cases

Recent studies of the p53 homologue p63 indicate that this gene is preferentially expressed in basal and immature cervical squamous epithelium. This study correlated p63 expression with morphologic phenotype and human papillomavirus (HPV) type in a wide range of cervical neoplasms. Two hundred fifty cases of cervical carcinoma, including squamous cell carcinoma (SCCA; n = 178), adenocarcinoma (ADCA; n = 28), adenosquamous carcinoma (ASCA; n = 8), neuroendocrine carcinoma (NECA; n = 15), and other variant or mixed types (n = 21) were studied. Ninety-seven percent of SCCA, 0% of ADCA, and 0% of SCUC showed strong (>75% v <30%) positivity for p63 (P<.001). p63 sharply distinguished SCCA (p63+) from ADCA (p63-), Large-cell, poorly differentiated carcinomas were distinguished as putative glandular (glassy cell) or squamous (lymphoepithelial-like or spindle cell) types based on p63 staining. Eight (73%) of 11 neuroendocrine tumors tested were chromogranin positive; all showed no or low (<30%) levels of p63 immunostaining. Absence of p63 was also associated with a subset of nonneuroendocrine undifferentiated carcinomas. Transitions from squamous to columnar or undifferentiated morphology coincided with loss of p63 expression. A strong association between HPV 16 and p63 positivity was identified because of the colocalization of both within tumors of squamous phenotype. p63 is a powerful marker for squamous differentiation and, when diffusely expressed, excludes a glandular or neuroendocrine differentiation. p63 may be useful for differentiating pure squamous or glandular from adenosquamous carcinomas, tracking shifts in differentiation within tumors, supporting (by its absence) the diagnosis of neuroendocrine carcinomas, and clarifying the spectrum of poorly differentiated carcinomas lacking either squamous or neuroendocrine differentiation.

Expression of the p53 homologue p63 in early cervical neoplasia

BACKGROUND

p63, a homologue of the tumor suppressor gene p53, is expressed in embryonic, adult murine, and human basal squamous epithelium and encodes both transactivating and dominant negative transcript isoforms. Mouse embryos functionally deficient in p63 fail to replenish basal squamous epithelial cells, resulting in multiple defects that include absent genital squamous epithelium. This study investigated the expression of p63 in the human cervical transformation zone and early cervical neoplasia.

METHODS

Tissue localization of p63 was determined by immunohistochemistry in a wide range of epithelia. A correlation was also made between p63 expression and squamous basal cell (keratin 14), endocervical columnar cell (mucicarmine), and cell-cycle specific (Ki-67) markers.

RESULTS

p63 expression by immunostaining delineated basal and parabasal cells of maturing ectocervical squamous mucosa, squamous metaplasia in the cervix, and basal and subcolumnar cells of the cervical transformation zone. In atrophic epithelia immunostaining for p63 was present in all cell strata. In early cervical neoplasia, p63 expression was inversely correlated with both squamous cell maturation and nonsquamous differentiation in CIN. This biomarker also identified basal cells in a subset of preinvasive cervical neoplasms with endocervical cell differentiation that were bcl-2 and keratin 14 negative.

CONCLUSIONS

In the lower female genital tract, p63 is preferentially expressed in immature cells of squamous lineage and is not linked to cell proliferation. The broader range of p63 expression relevant to keratin 14 and bcl-2 indicates that p63 may identify additional subsets of benign and neoplastic epithelial basal cells in the cervical transformation zone and may be useful in studying cell differentiation in the early stages of neoplastic change in this region.

Identification of a basal/reserve cell immunophenotype in benign and neoplastic endometrium: a study with the p53 homologue p63

BACKGROUND

Metaplastic differentiation, including squamous, mucinous, and tubal (ciliated), is common in both benign and neoplastic endometrium, and the cell of origin for this pathway is poorly understood. In this study, expression of a marker for basal and reserve cells in cervical squamous mucosa, designated p63, was investigated in a spectrum of endometrial alterations.

METHODS

One hundred ninety different endometria from 132 patients were examined, including fetal (6), premenarchal (3), benign cyclic (29) and noncyclic (54), hyperplastic (14), and neoplastic (93) endometrial glandular epithelia. The latter included conventional endometrioid carcinomas with and without mucinous, ciliated, and squamous metaplasia, and uterine papillary serous carcinoma (UPSC).

RESULTS

p63 expression was identified in basal/subcolumnar cells in the fetal endometrium in a distribution similar to that in basal/reserve cells of the cervix. Staining was confined to individual scattered basal and suprabasal cells in cycling endometrium. In polyps and postmenopausal endometria, focal clusters of p63-positive cells were identified in inactive glands or surface epithelium. Metaplastic (squamous or mucinous) epithelia, either alone or in conjunction with hyperplasias or carcinomas, exhibited the most intense staining, primarily in basal or subcolumnar cells. In some cases, immediately adjacent nonmetaplastic columnar epithelium also stained positive. UPSCs contained only rare scattered p63-positive cells.

CONCLUSIONS

Cells with a basal or reserve cell phenotype exist in the endometrium during fetal life, are not conspicuous during the reproductive years, but may emerge during shifts in differentiation. Whether these cells signify specialized multipotential endometrial cells is not clear, but the similarity of these cells to basal/reserve cells of the cervix and their association with neoplasia merit further study.

Adenoid basal carcinomas of the cervix: a unique morphological evolution with cell cycle correlates

Adenoid basal carcinoma (ABC) is a rare cervical carcinoma of postmenopausal women composed of small basal-type (basaloid) cells with focal endocervical ("adenoid") differentiation. ABCs are associated with high-grade squamous intraepithelial lesions (HSIL) and contain integrated human papillomavirus type 16 DNA. However, ABCs have a favorable prognosis and do not metastasize. Five (5) ABCs were analyzed histologically for a marker distinguishing basal/ squamous from columnar (adenoid) differentiation (p63) and cell cycle activity (Ki-67), and compared with 20 cervical (CC) carcinomas. In contrast to other CCs, ABCs contained 4 distinct components, including (1) a classic HSIL; (2) a limited invasive component with squamoid maturation, often with a discrete layer of peripheral basal cells; (3) outgrowth of small basal cells from either HSIL or squamoid areas; (4) focal endocervical (adenoid) differentiation. ABCs showed distinct differences in cell cycle activity relative to CCs. Ki-67 positivity was high in associated HSILs but remained high and concentrated in the suprabasal cells of the invasive squamoid component of ABC. Moreover, proliferative index was variable to sharply reduced in areas of basaloid and adenoid differentiation, in contrast to conventional CCs. ABC is a unique neoplasm, not only by its transition through multiple phenotypes during invasion, but also by a proliferative index that is high in more mature neoplastic cells during the infiltrative process and reduced with progressive basal differentiation. The precise mechanism underlying this unique process of tumor evolution is unclear. However, the postmenopausal status of these patients suggests that host factors related to aging may influence tumor evolution and morphology after HPV 16 infection.

Cyclophilin B trafficking through the secretory pathway is altered by binding of cyclosporin A

Cyclophilin B is targeted to the secretory pathway via an endoplasmic reticulum signal sequence. We analyzed the localization and trafficking of endogenous and transfected cyclophilin B in mammalian cells. Cyclophilin B accumulates both in the endoplasmic reticulum and in complexes on the plasma membrane. The immunosuppressant cyclosporin A specifically mobilizes cyclophilin B from the endoplasmic reticulum, and promotes the secretion of cyclophilin B into the medium. We suggest that cyclosporin A competes with endogenous plasma membrane proteins for association with cyclophilin B in the secretory pathway. These findings argue in favor of a role for cyclophilin B as a chaperone to proteins destined for the plasma membrane, rather than solely as a proline isomerase functioning within the endoplasmic reticulum.

Cyclosporin A, the cyclophilin class of peptidylprolyl isomerases, and blockade of T cell signal transduction

Cyclosporin A, the major immunosuppressive drug in transplantation, and the more potent therapeutic drug candidate, FK506, have led to the discovery of two superfamilies of immunosuppressant binding proteins, the cyclophilins and the FK binding proteins. These proteins, enzymes with high kcat values for isomerization of X-Pro bonds in peptides and protein substrates, are distributed in all cell compartments where protein folding normally occurs. It is likely that they play major roles in the protein folding and protein trafficking in the cell. It is also likely that they have been suborned in T cells by the immunosuppressant drugs that are potent pseudosubstrate ligands that selectively block the signal transduction cascade. The discovery of the inhibition of protein phosphatase 2B (calcineurin) by the drug-immunophilin complex (CsA-CyP or FK506-FKBP) provides evidence for a specific downstream target of the drug-immunophilin complexes and may prompt a search for endogenous ligands of cyclophilin and FKBP that may effect signal transduction regulation. The molecular insights gained over a short time in this area have been remarkable; they promise to elucidate the steps in T cell activation and delineate new targets for immunosuppressive therapy.

Nuclear lamin LI of Xenopus laevis: cDNA cloning, amino acid sequence and binding specificity of a member of the lamin B subfamily

Lamins are karyoskeletal proteins associated with the nuclear envelope which can be divided into two groups, i.e. the type A lamins of near neutral pI and the more acidic lamins, including mammalian lamin B. We have isolated cDNA clones encoding a representative of the type B subfamily from Xenopus laevis, and have deduced its amino acid sequence from the coding portion of the approximately 2.9 kb mRNA. The polypeptide (mol. wt 66,433) is identified as a typical lamin by its homology to Xenopus human type A lamins, but detailed sequence comparison shows that LI is less related to Xenopus lamin A than the latter is to human lamin A. The conformation predicted for LI conforms to the general model of lamins and intermediate filament proteins and is characterized by an extended central alpha-helical coiled coil domain, flanked by non-alpha-helical domains, i.e. a relatively short N-terminal head and a long C-terminal tail. As in lamins A and C, the head of lamin LI is positively charged and the tail presents a similar C-terminal pentapeptide, a putative nuclear accumulation signal, a very negatively charged region and a number of short regions that are highly homologous in all lamins. However, LI differs from the type A lamins by the absence of the oligo-histidine stretch and a di-proline motif in the tail region and by a significantly lower number of identical amino acid positions.(ABSTRACT TRUNCATED AT 250 WORDS)

Homologies in both primary and secondary structure between nuclear envelope and intermediate filament proteins

The A, B and C lamins are the major proteins of the nuclear envelope. The complete nucleotide sequence of the coding region of the A and C lamins shows that these proteins are identical except for their carboxy termini. The most prominent structural feature of both lamins is an alpha-helical region of repeating heptads of amino acids that shows striking homology with the entire family of cytoplasmic intermediate filament proteins. These features suggest that the nuclear envelope is made up of a network of coiled-coil polymers.

The redistribution of a conserved nuclear envelope protein during the cell cycle suggests a pathway for chromosome condensation

We describe a human autoantiserum that recognizes specific determinants present both on the nuclear envelope of interphase cells and the periphery of metaphase chromosomes. These determinants are highly conserved through evolution and present on a protein with an apparent molecular weight of 33,000. This 33 kd protein, which we call "perichromin," appears to be directly or indirectly bound to both interphase and metaphase DNA. Studies of the transformation of perichromin from a nuclear envelope association to a perichromosomal position during prophase suggests a pathway for chromosome organization throughout the cell cycle.

Autoimmune response directed against conserved determinants of nuclear envelope proteins in a patient with linear scleroderma

We have studied the autoantibodies in the serum of a patient with linear scleroderma that specifically recognize the nuclear envelope of cultured cells. These antibodies bind to conserved determinants of nuclear lamins, the predominant mammalian nuclear envelope proteins. Of the three mammalian nuclear lamin proteins (970, P68, and P60), only P70 and P60 bind the autoantibodies. In addition, two proteins of the Drosophila embryonic nuclear matrix, P70 and P68, bind these autoantibodies. We have used nuclear matrices to isolate the autoantibodies from the patient's serum that react to the nuclear lamins. At least three different IgG heavy chains were found to be involved in this autoimmune response to nuclear lamins, indicating that this response is not due to the expansion of a single B-cell clone.