JAK1/2 inhibition with baricitinib in the treatment of autoinflammatory interferonopathies

BACKGROUND

Monogenic IFN-mediated autoinflammatory diseases present in infancy with systemic inflammation, an IFN response gene signature, inflammatory organ damage, and high mortality. We used the JAK inhibitor baricitinib, with IFN-blocking activity in vitro, to ameliorate disease.

METHODS

Between October 2011 and February 2017, 10 patients with CANDLE (chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperatures), 4 patients with SAVI (stimulator of IFN genes-associated [STING-associated] vasculopathy with onset in infancy), and 4 patients with other interferonopathies were enrolled in an expanded access program. The patients underwent dose escalation, and the benefit was assessed by reductions in daily disease symptoms and corticosteroid requirement. Quality of life, organ inflammation, changes in IFN-induced biomarkers, and safety were longitudinally assessed.

RESULTS

Eighteen patients were treated for a mean duration of 3.0 years (1.5-4.9 years). The median daily symptom score decreased from 1.3 (interquartile range [IQR], 0.93-1.78) to 0.25 (IQR, 0.1-0.63) (P < 0.0001). In 14 patients receiving corticosteroids at baseline, daily prednisone doses decreased from 0.44 mg/kg/day (IQR, 0.31-1.09) to 0.11 mg/kg/day (IQR, 0.02-0.24) (P < 0.01), and 5 of 10 patients with CANDLE achieved lasting clinical remission. The patients' quality of life and height and bone mineral density Z-scores significantly improved, and their IFN biomarkers decreased. Three patients, two of whom had genetically undefined conditions, discontinued treatment because of lack of efficacy, and one CANDLE patient discontinued treatment because of BK viremia and azotemia. The most common adverse events were upper respiratory infections, gastroenteritis, and BK viruria and viremia.

CONCLUSION

Upon baricitinib treatment, clinical manifestations and inflammatory and IFN biomarkers improved in patients with the monogenic interferonopathies CANDLE, SAVI, and other interferonopathies. Monitoring safety and efficacy is important in benefit-risk assessment.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01724580 and NCT02974595.

FUNDING

This research was supported by the Intramural Research Program of the NIH, NIAID, and NIAMS. Baricitinib was provided by Eli Lilly and Company, which is the sponsor of the expanded access program for this drug.

JAK1/2 inhibition with baricitinib in the treatment of autoinflammatory interferonopathies

BACKGROUND. Monogenic IFN–mediated autoinflammatory diseases present in infancy with systemic inflammation, an IFN response gene signature, inflammatory organ damage, and high mortality. We used the JAK inhibitor baricitinib, with IFN-blocking activity in vitro, to ameliorate disease.

METHODS. Between October 2011 and February 2017, 10 patients with CANDLE (chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperatures), 4 patients with SAVI (stimulator of IFN genes–associated [STING-associated] vasculopathy with onset in infancy), and 4 patients with other interferonopathies were enrolled in an expanded access program. The patients underwent dose escalation, and the benefit was assessed by reductions in daily disease symptoms and corticosteroid requirement. Quality of life, organ inflammation, changes in IFN-induced biomarkers, and safety were longitudinally assessed.

RESULTS. Eighteen patients were treated for a mean duration of 3.0 years (1.5–4.9 years). The median daily symptom score decreased from 1.3 (interquartile range [IQR], 0.93–1.78) to 0.25 (IQR, 0.1–0.63) (P < 0.0001). In 14 patients receiving corticosteroids at baseline, daily prednisone doses decreased from 0.44 mg/kg/day (IQR, 0.31–1.09) to 0.11 mg/kg/day (IQR, 0.02–0.24) (P < 0.01), and 5 of 10 patients with CANDLE achieved lasting clinical remission. The patients’ quality of life and height and bone mineral density Z-scores significantly improved, and their IFN biomarkers decreased. Three patients, two of whom had genetically undefined conditions, discontinued treatment because of lack of efficacy, and one CANDLE patient discontinued treatment because of BK viremia and azotemia. The most common adverse events were upper respiratory infections, gastroenteritis, and BK viruria and viremia.

CONCLUSION. Upon baricitinib treatment, clinical manifestations and inflammatory and IFN biomarkers improved in patients with the monogenic interferonopathies CANDLE, SAVI, and other interferonopathies. Monitoring safety and efficacy is important in benefit-risk assessment.

TRIAL REGISTRATION. ClinicalTrials.gov NCT01724580 and NCT02974595.

FUNDING. This research was supported by the Intramural Research Program of the NIH, NIAID, and NIAMS. Baricitinib was provided by Eli Lilly and Company, which is the sponsor of the expanded access program for this drug.

GTF2E2 Mutations Destabilize the General Transcription Factor Complex TFIIE in Individuals with DNA Repair-Proficient Trichothiodystrophy

The general transcription factor IIE (TFIIE) is essential for transcription initiation by RNA polymerase II (RNA pol II) via direct interaction with the basal transcription/DNA repair factor IIH (TFIIH). TFIIH harbors mutations in two rare genetic disorders, the cancer-prone xeroderma pigmentosum (XP) and the cancer-free, multisystem developmental disorder trichothiodystrophy (TTD). The phenotypic complexity resulting from mutations affecting TFIIH has been attributed to the nucleotide excision repair (NER) defect as well as to impaired transcription. Here, we report two unrelated children showing clinical features typical of TTD who harbor different homozygous missense mutations in GTF2E2 (c.448G>C [p.Ala150Pro] and c.559G>T [p.Asp187Tyr]) encoding the beta subunit of transcription factor IIE (TFIIEβ). Repair of ultraviolet-induced DNA damage was normal in the GTF2E2 mutated cells, indicating that TFIIE was not involved in NER. We found decreased protein levels of the two TFIIE subunits (TFIIEα and TFIIEβ) as well as decreased phosphorylation of TFIIEα in cells from both children. Interestingly, decreased phosphorylation of TFIIEα was also seen in TTD cells with mutations in ERCC2, which encodes the XPD subunit of TFIIH, but not in XP cells with ERCC2 mutations. Our findings support the theory that TTD is caused by transcriptional impairments that are distinct from the NER disorder XP.

Systemic retinoids in the management of ichthyoses and related skin types

The term retinoid includes both natural and synthetic derivatives of vitamin A. Retinoid-containing treatments have been used since ~1550BC by the early Egyptians. Treatment of ichthyosiform disorders with retinoids dates back at least to the 1930s. Early use of high-dose vitamin A demonstrated efficacy, but because vitamin A is stored in the liver, toxicity limited usefulness. Interest turned to synthetic retinoids in an effort to enhance efficacy and limit toxicity. Acetretin, isotretinoin and, in the past etretinate, have provided the most effective therapy for ichthyosiform conditions. They have been used for a variety of ages, including in newborns with severe ichthyosis and for decades in some patients. Careful surveillance and management of mucous membrane, laboratory, skeletal, and teratogenic side effects has made systemic retinoids the mainstay of therapy for ichthyosis and related skin types.

Chimeric negative regulation of p14ARF and TBX1 by a t(9;22) translocation associated with melanoma, deafness, and DNA repair deficiency

Melanoma is the most deadly form of skin cancer and DiGeorge syndrome (DGS) is the most frequent interstitial deletion syndrome. We characterized a novel balanced t(9;22)(p21;q11.2) translocation in a patient with melanoma, DNA repair deficiency, and features of DGS including deafness and malformed inner ears. Using chromosome sorting, we located the 9p21 breakpoint in CDKN2A intron 1. This resulted in underexpression of the tumor suppressor p14 alternate reading frame (p14ARF); the reduced DNA repair was corrected by transfection with p14ARF. Ultraviolet radiation-type p14ARF mutations in his melanoma implicated p14ARF in its pathogenesis. The 22q11.2 breakpoint was located in a palindromic AT-rich repeat (PATRR22). We identified a new gene, FAM230A, that contains PATRR22 within an intron. The 22q11.2 breakpoint was located 800 kb centromeric to TBX1, which is required for inner ear development. TBX1 expression was greatly reduced. The translocation resulted in a chimeric transcript encoding portions of p14ARF and FAM230A. Inhibition of chimeric p14ARF-FAM230A expression increased p14ARF and TBX1 expression and improved DNA repair. Expression of the chimera in normal cells produced dominant negative inhibition of p14ARF. Similar chimeric mRNAs may mediate haploinsufficiency in DGS or dominant negative inhibition of other genes such as those involved in melanoma.

Ocular manifestations of xeroderma pigmentosum: long-term follow-up highlights the role of DNA repair in protection from sun damage

OBJECTIVE

Xeroderma pigmentosum (XP) is a rare autosomal recessive disease caused by mutations in DNA repair genes. Clinical manifestations of XP include mild to extreme sensitivity to ultraviolet radiation resulting in inflammation and neoplasia in sun-exposed areas of the skin, mucous membranes, and ocular surfaces. This report describes the ocular manifestations of XP in patients systematically evaluated in the Clinical Center at the National Institutes of Health.

DESIGN

Retrospective observational case series.

PARTICIPANTS

Eighty-seven participants, aged 1.3 to 63.4 years, referred to the National Eye Institute (NEI) for examination from 1964 to 2011. Eighty-three patients had XP, 3 patients had XP/Cockayne syndrome complex, and 1 patient had XP/trichothiodystrophy complex.

METHODS

Complete age- and developmental stage-appropriate ophthalmic examination.

MAIN OUTCOME MEASURES

Visual acuity; eyelid, ocular surface, and lens pathology; tear film and tear production measures; and cytologic analysis of conjunctival surface swabs.

RESULTS

Of the 87 patients, 91% had at least 1 ocular abnormality. The most common abnormalities were conjunctivitis (51%), corneal neovascularization (44%), dry eye (38%), corneal scarring (26%), ectropion (25%), blepharitis (23%), conjunctival melanosis (20%), and cataracts (14%). Thirteen percent of patients had some degree of visual axis impingement, and 5% of patients had no light perception in 1 or both eyes. Ocular surface cancer or a history of ocular surface cancer was present in 10% of patients. Patients with an acute sunburning skin phenotype were less likely to develop conjunctival melanosis and ectropion but more likely to develop neoplastic ocular surface lesions than nonburning patients. Some patients also showed signs of limbal stem cell deficiency.

CONCLUSIONS

Our longitudinal study reports the ocular status of the largest group of patients with XP systematically examined at 1 facility over an extended period of time. Structural eyelid abnormalities, neoplasms of the ocular surface and eyelids, tear film and tear production abnormalities, ocular surface disease and inflammation, and corneal abnormalities were present in this population. Burning and nonburning patients with XP exhibit different rates of important ophthalmologic findings, including neoplasia. In addition, ophthalmic characteristics can help refine diagnoses in the case of XP complex phenotypes. DNA repair plays a major role in protection of the eye from sunlight-induced damage.

Clinical and radiological features in young individuals with nevoid basal cell carcinoma syndrome

PURPOSE

Nevoid basal cell carcinoma syndrome is an autosomal dominant disorder characterized by multiple basal cell carcinomas, jaw cysts, palmar/plantar pits, spine and rib anomalies, and falx cerebri calcification. Current diagnostic criteria are suboptimal when applied to pediatric populations, as most common symptoms often do not begin to appear until teenage years.

METHODS

We studied minor and major clinical features in 30 children/teenagers and compared the findings with 75 adults from 26 families with nevoid basal cell carcinoma syndrome.

RESULTS

Fifty percent of children/teenagers and 82% of adults had at least one basal cell carcinoma. Jaw cysts occurred in 60% of children/teenagers and 81% of adults. Palmar/plantar pits were the most frequent feature seen in affected individuals at all ages. Macrocephaly was seen in 50% of affected and 8% of unaffected children/teenagers. Frontal bossing, hypertelorism, Sprengel deformity, pectus deformity, and cleft lip/palate were seen among affected children/teenagers but not among their unaffected siblings. Falx calcification, the most frequent radiological feature, was present in 37% of individuals <20 and 79% of those >20 years.

CONCLUSION

We report clinical and radiological manifestations of nevoid basal cell carcinoma syndrome in children/teenagers, many of whom lacked major features such as basal cell carcinomas, jaw cysts, and falx calcification. Evaluations for palmar/plantar pits, craniofacial features, and radiological manifestations permit early diagnosis and optimum surveillance.

Adverse effects of trichothiodystrophy DNA repair and transcription gene disorder on human fetal development

The effects of DNA repair and transcription gene abnormalities in human pre-natal life have never been studied. Trichothiodystrophy (TTD) is a rare (affected frequency of 10(-6)) recessive disorder caused by mutations in genes involved in nucleotide excision repair (NER) pathway and in transcription. Based on our novel clinical observations, we conducted a genetic epidemiologic study to investigate gestational outcomes associated with TTD. We compared pregnancies resulting in TTD-affected offspring (n = 24) with respect to abnormalities during their antenatal and neonatal periods to pregnancies resulting in their unaffected siblings (n = 18), accounting for correlation, and to population reference values. Significantly higher incidence of several severe gestational complications was noted in TTD-affected pregnancies. Small for gestational age (SGA) <10th percentile [Relative risk (RR ) = 9.3, 95% CI = 1.4-60.5, p = 0.02], SGA <3rd percentile (RR = 7.2, 95% CI = 1.1-48.1, p = 0.04), and neonatal intensive care unit (NICU) hospitalization (RR = 6.4, 95% CI = 1.4-29.5, p = 0.02) occurred more frequently among TTD-affected neonates compared with their unaffected siblings. Compared with reference values from general obstetrical population, pregnancies that resulted in TTD-affected infants were significantly more likely to be complicated by hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome (RR = 35.7, 95% CI = 7.6-92.5, p = 0.0002), elevated mid-trimester maternal serum human chorionic gonadotropin (hCG) levels (RR = 14.3, 95% CI = 7.0-16.6, p < 0.0001), SGA <3rd percentile (RR = 13.9, 95% CI = 7.4-21.1, p < 0.0001), pre-term delivery (<32 weeks) (RR = 12.0, 95% CI = 4.9-21.6, p < 0.0001), pre-eclampsia (RR = 4.0, 95% CI = 1.6-7.4, p = 0.006), and decreased fetal movement (RR = 3.3, 95% CI = 1.6-5.2, p = 0.0018). Abnormal placental development is an underlying mechanism that may explain the constellation of observed complications in our study. Thus, we hypothesize that TTD DNA repair and transcription genes play an important role in normal human placental development.

Unexpected occurrence of xeroderma pigmentosum in an uncle and nephew

BACKGROUND

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder characterized by a decreased ability to repair DNA damaged by UV radiation and the early development of cutaneous and ocular malignant neoplasms. Approximately 20% of patients with XP also develop progressive neurologic degeneration.

OBSERVATIONS

We describe a boy who was found to have XP after a severe burn following minimal sun exposure. His maternal uncle, now age 20 years, had been diagnosed with XP after a similar sunburn in infancy. The uncle has the typical skin pigmentary findings of XP along with severe progressive neurologic involvement. Although the infant's parents were not known to be blood relatives, the infant and his affected uncle proved to be compound heterozygotes for the same 2 frameshift mutations in the XPA DNA repair gene (c.288delT and c.349_353del). After the diagnosis of XP in the infant, genealogic investigation identified a common Dutch ancestor for both of his grandfathers 5 generations back.

CONCLUSIONS

Counseling families at risk for a rare inherited disease is not always straightforward. The sociocultural and demographic backgrounds of the families must be considered for evaluation of risk assessment.

Persistence of repair proteins at unrepaired DNA damage distinguishes diseases with ERCC2 (XPD) mutations: cancer-prone xeroderma pigmentosum vs. non-cancer-prone trichothiodystrophy

Patients with xeroderma pigmentosum (XP) have a 1,000-fold increase in ultraviolet (UV)-induced skin cancers while trichothiodystrophy (TTD) patients, despite mutations in the same genes, ERCC2 (XPD) or ERCC3 (XPB), are cancer-free. Unlike XP cells, TTD cells have a nearly normal rate of removal of UV-induced 6-4 photoproducts (6-4PP) in their DNA and low levels of the basal transcription factor, TFIIH. We examined seven XP, TTD, and XP/TTD complex patients and identified mutations in the XPD gene. We discovered large differences in nucleotide excision repair (NER) protein recruitment to sites of localized UV damage in TTD cells compared to XP or normal cells. XPC protein was rapidly localized in all cells. XPC was redistributed in TTD, and normal cells by 3 hr postirradiation, but remained localized in XP cells at 24-hr postirradiation. In XP cells recruitment of other NER proteins (XPB, XPD, XPG, XPA, and XPF) was also delayed and persisted at 24 hr (p<0.001). In TTD cells with defects in the XPD, XPB, or GTF2H5 (TTDA) genes, in contrast, recruitment of these NER proteins was reduced compared to normals at early time points (p<0.001) and remained low at 24 hr postirradiation. These data indicate that in XP persistence of NER proteins at sites of unrepaired DNA damage is associated with greatly increased skin cancer risk possibly by blockage of translesion DNA synthesis. In contrast, in TTD, low levels of unstable TFIIH proteins do not accumulate at sites of unrepaired photoproducts and may permit normal translesion DNA synthesis without increased skin cancer.

KRT14 haploinsufficiency results in increased susceptibility of keratinocytes to TNF-alpha-induced apoptosis and causes Naegeli-Franceschetti-Jadassohn syndrome

Naegeli-Franceschetti-Jadassohn syndrome (NFJS) is a rare autosomal dominant disorder characterized by loss of dermatoglyphics, reticulate hyperpigmentation of the skin, palmoplantar keratoderma, abnormal sweating, and other developmental anomalies of the teeth, hair, and skin. We recently demonstrated that NFJS is caused by heterozygous nonsense or frameshift mutations in the E1/V1-encoding region of KRT14, but the mechanisms for their deleterious effects in NFJS remain elusive. In this study, we further expand the spectrum of NFJS-causing mutations and demonstrate that these mutations result in haploinsufficiency for keratin 14 (K14). As increased apoptotic activity was observed in the epidermal basal cell layer in NFJS patients and as previous data suggested that type I keratins may confer resistance to tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis in epithelial tissues, we assessed the effect of down-regulation of KRT14 expression on apoptotic activity in keratinocytes. Using a HaCaT cell-based assay, we found that decreased KRT14 expression is associated with increased susceptibility to TNF-alpha-induced apoptosis. This phenomenon was not observed when cells were cultured in the presence of doxycycline, a known negative regulator of TNF-alpha-dependant pro-apoptotic signaling. Collectively, our results indicate that NFJS results from haploinsufficiency for K14 and suggest that increased susceptibility of keratinocytes to pro-apoptotic signals may be involved in the pathogenesis of this ectodermal dysplasia syndrome.

Radiological features in 82 patients with nevoid basal cell carcinoma (NBCC or Gorlin) syndrome

PURPOSE

Nevoid Basal Cell Carcinoma Syndrome (NBCCS) is an autosomal-dominant disorder characterized by multiple basal cell carcinomas, jaw cysts, palmar/plantar pits, calcification of the falx cerebri, and spine and rib anomalies. NBCCS is due to mutations in PTCH1, the human homologue of the Drosophila segment polarity gene patched. Mutations are detected in approximately 60% to 85% of individuals tested by sequencing of PTCH1; therefore, clinical examination and x-rays remain important in diagnosis of NBCCS.

METHODS

We studied 82 NBCCS patients and 38 of their unaffected siblings at the NIH between 1985 and 1994. Chest, rib, spine, skull, hand and foot x-rays, brain MRI or CT, and pelvic ultrasound (in females) were obtained in the affected individuals and compared to their unaffected relatives.

RESULTS

The following features were significantly more frequent in those with NBCCS: calcification of the falx cerebri, the most frequent radiological feature, was present in 79% of patients > 20 years and in 37% <20 years, calcification of the tentorium cerebellum was present in 20%, bridging of the sella in 68%, and abnormal frontal sinus aeration in 18% of affected individuals. Bifid ribs most often involving the third, fourth, and fifth ribs were seen in 26%; splayed, fused, and misshapen ribs in a further 16%, and widened ends of clavicles in 12%. Spine X-rays revealed calcification of the nuchal ligament in 18%, fusion of vertebrae in 10%, and hemivertebrae in 15%. Flame-shaped lucencies of the metacarpals and/or phalanges were present in 30%, modeling deformities of the phalanges in 14%, and polydactyly of the feet in 4%. The frequency of scoliosis, cervical ribs, absent or rudimentary ribs, spina bifida occulta, or short 4th metacarpal was not higher in the affected individuals as compared to their unaffected relatives. Except for falx calcification, the frequency of radiological manifestations was similar in different age groups. Cranial CT or MRI in 42 affected individuals revealed asymmetric or dilated ventricles in 24%, cerebral atrophy in 10%, cavum septum pellucidum in 19%, dysgenesis or agenesis of the corpus callosum in 10%, and meningioma in 5%. Ovarian fibromas were detected in 17% of females.

CONCLUSIONS

This study reports the varied radiological manifestations of NBCCS. In the absence of major features such as basal cell carcinomas, jaw cysts, or falx calcification, which is often not evident until the teen years, other radiological manifestations of the disorder can permit early diagnosis of NBCCS in childhood. This will allow optimum surveillance for medulloblastoma and other neoplasms (cardiac fibromas and basal cell carcinomas) associated with NBCCS.

Changing paradigms in dermatology: information technology

Medicine and specifically, dermatology, is undergoing enormous changes in the way in which it is practiced. Much of this is a result of a fundamental change in the manner in which information is exchanged through information technology. With the advent of more advanced telecommunications, imaging capabilities and information transfer, the very ways in which we examine patients, develop diagnoses and plan treatments as dermatologists have changed dramatically. This chapter will briefly review the development of personal computers and the Internet, as well as changes in telecommunications capabilities and how these changes have already altered how we see patients and care for them, as well as how new advances may continue to change the world of medicine and dermatology in the near future.

A highly conserved lysine residue on the head domain of type II keratins is essential for the attachment of keratin intermediate filaments to the cornified cell envelope through isopeptide crosslinking by transglutaminases

We have addressed the question of how keratin intermediate filaments are associated with the cell envelope at the periphery of cornified epidermal cells. Many peptides from human epidermal cell envelopes containing isopeptide crosslinks inserted by transglutaminases in vivo have been characterized. A major subset involves the type II keratin chains keratin 1, 2e, 5, or 6 crosslinked to several protein partners through a lysine residue located in a conserved region of the V1 subdomain of their head domains. This sequence specificity was confirmed in in vitro crosslinking experiments. Previously the causative mutation in a family with diffuse nonepidermolytic palmar-plantar keratoderma was shown to be the loss in one allele of the same lysine residue of the keratin 1 chain. Ultrastructural studies of affected palm epidermis have revealed abnormalities in the organization of keratin filaments subjacent to the cell envelope and in the shape of the cornified cells. Together, these data suggest a mechanism for the coordination of cornified cell structure by permanent covalent attachment of the keratin intermediate filament cytoskeleton to the cell envelope by transglutaminase crosslinking. Furthermore, these studies identify the essential role of a conserved lysine residue on the head domains of type II keratins in the supramolecular organization of keratin filaments in cells.

Arthritis in patients with psoriasis treated with gamma-interferon

We observed 3 patients with psoriasis who developed arthritis during treatment of psoriatic skin disease with intramuscular recombinant human gamma-interferon (IFN-gamma). Symptoms primarily involved the hands, feet, shoulders, and neck. One patient had acute plantar fasciitis. Routine laboratory studies were unrevealing. Patients presented with symptoms initially between the 10th and 12th weeks of treatment and the arthritis resolved after cessation of IFN-gamma. One patient was subsequently retreated with IFN-gamma for 4 weeks and had a temporary recurrence of arthritis with an associated rise and fall of his articular index.

Protein tyrosine kinase and protein phosphotyrosine phosphatase in normal and psoriatic skin

Protein tyrosine kinase and protein phosphotyrosine phosphatase activities were measured in extracts of skin samples from patients with psoriasis. Both kinase and phosphatase activities were significantly greater in samples taken from an involved area, characterized by epidermal hyperproliferation, than from adjacent skin of normal appearance. Samples from skin of non-psoriatic individuals were indistinguishable from the normal-appearing skin of psoriatic patients. There was no detectable change in the apparent Km for either ATP or casein of the protein tyrosine activity in plaques compared with controls. Phosphorylation of endogenous proteins was also increased about 2-fold in plaque extracts compared with controls. Both epidermal growth factor and platelet-derived growth factor stimulated endogenous protein tyrosine phosphorylation in particulate fractions of plaque biopsies but not in solubilized extracts nor in any control fractions. Our data suggest that increased protein tyrosine phosphorylation and dephosphorylation activity and growth factor sensitivity are important factors in non-malignant hyperplastic cell growth.