PubMed Health⌕ Search

Biomedical subjects

J T Parsons

Publications and source records attributed to J T Parsons.

At least 19 recordsLinked to original sources
PubMed1995

Bladder-sparing multimodality treatment of muscle-invasive bladder cancer: a five-year follow-up.

OBJECTIVES: To determine the long-term results of a bladder-sparing approach in the treatment of muscle-invasive bladder cancer. METHODS: Ninety-four patients with invasive transitional cell carcinoma of the bladder were treated by transurethral resection followed by 2 or 3 cycles of cisplatin-based chemotherapy. Patients were then treated with 6480 cGy of radiation in 49 patients, segmental cystectomy in 8, or surveillance only in 7. Patients who failed to respond to chemotherapy or radiation therapy, or who developed recurrent muscle-invasive disease in follow-up, underwent salvage cystectomy. Patients were then carefully followed for a median follow-up of more than 5 years. RESULTS: After initial therapy, 53 patients (56%) were alive with their bladder preserved. Thirty of those 53 (57%) developed a local recurrence in follow-up. After a median follow-up of more than 5 years, the ultimate relapse-free survival is 49% (Stage T2, 84%; T3, 53%; and T4, 11%; P < 0.01). Of all patients enrolled, 53% had bladder preservation; however, of the currently surviving patients, 16 of 39 (41%) have their bladders intact (T2, 50%; T3, 37%; T4, 0%). Only 18% of the initially enrolled population is alive with a preserved bladder. The 5-year survival of patients who had cystectomy at some point during the study, compared with those who have had their bladders preserved, was 65% versus 40%, respectively (P < 0.01). CONCLUSIONS: Our long-term results with multimodality therapy with attempted bladder preservation showed no definitive improvement in survival compared with modern series of cystectomy alone, and a disappointingly low rate of disease-free bladder preservation. We found a high rate of locally recurrent disease in the preserved bladders. We also noted a decrease in survival in our patients with bladder preservation compared with those without preservation. Bladder preservation, although possible, should be limited to a very select group of patients.

Aged↗
PubMed1995

Paxillin, a tyrosine phosphorylated focal adhesion-associated protein binds to the carboxyl terminal domain of focal adhesion kinase.

Focal adhesion kinase (pp125FAK or FAK) and paxillin colocalize with integrins in structures called focal adhesions. pp125FAK plays an important role in the transmission of integrin-induced cytoplasmic signals. Paxillin has also been implicated in cell signaling by virtue of its association with the protein tyrosine kinases pp60src and Csk (C-terminal Src kinase) as well as with the adapter/oncoprotein p47gag-crk. In this report we show that endogenous pp125FAK and paxillin form a stable complex both in vivo and in vitro and that this interaction is direct, requiring only pp125FAK and paxillin. The paxillin binding site on pp125FAK has been localized to the carboxy-terminal 148 residues of pp125FAK, but appears to be distinct from the previously identified focal adhesion-targeting sequence also present in the carboxy-terminal domain of pp125FAK. The interaction of paxillin and pp125FAK is independent of the adhesion of cells to the extracellular matrix, as the association can be detected in suspension cells as well as those attached to fibronectin.

Animals↗
PubMed1995

pp125FAK-dependent tyrosine phosphorylation of paxillin creates a high-affinity binding site for Crk.

Paxillin, a focal-adhesion-associated protein, becomes phosphorylated in response to a number of stimuli which also induce the tyrosine phosphorylation of the focal-adhesion-associated protein tyrosine kinase pp125FAK. On the basis of their colocalization and coordinate phosphorylation, paxillin is a candidate for a substrate of pp125FAK. We describe here conditions under which the phosphorylation of paxillin on tyrosine is pp125FAK dependent, supporting the hypothesis that paxillin phosphorylation is regulated by pp125FAK. pp125FAK must localize to focal adhesions and become autophosphorylated to induce paxillin phosphorylation. Phosphorylation of paxillin on tyrosine creates binding sites for the SH2 domains of Crk, Csk, and Src. We identify two sites of phosphorylation as tyrosine residues 31 and 118, each of which conforms to the Crk SH2 domain binding motif, (P)YXXP. These observations suggest that paxillin serves as an adapter protein, similar to insulin receptor substrate 1, and that pp125FAK may regulate the formation of signaling complexes by directing the phosphorylation of paxillin on tyrosine.

Amino Acid Sequence↗
PubMed1995

Adhesion-induced tyrosine phosphorylation of the p130 src substrate.

Adhesion of cells to the extracellular matrix leads to an increase in the tyrosine phosphorylation of a specific set of proteins, three of which have now been identified as the focal adhesion proteins pp125FAK, paxillin and tensin. In addition, we have previously noted the adhesion-induced tyrosine phosphorylation of a fourth protein, with an apparent molecular mass of 130. As in the case of FAK, paxillin and tensin, a 130 kDa protein is also found to be highly tyrosine phosphorylated in Rous sarcoma virus (RSV)-transformed cells. This protein forms a stable complex with pp60src and is directly phosphorylated by activated forms of c-src. Using a monoclonal antibody (mAb 4F4) specific for the src-associated p130 we show that p130 is also phosphorylated in response to cell adhesion. Immunoprecipitation of p130 followed by an anti-phosphotyrosine immunoblot revealed that adhesion of rat embryo fibroblasts (REF52) to fibronectin (FN) led to a significant increase in the phosphotyrosine content of p130. Furthermore, a comparison of cell lysates before and after immunoprecipitation confirmed the absence of tyrosine phosphorylated p130 from lysates immunoprecipitated with mAb 4F4. Immunofluorescence staining of REF52s revealed that p130 is found in focal adhesions as well as along stress fibers in a pattern reminiscent of that exhibited by alpha-actinin. In addition, in many cells, we found significant staining in the nucleus, but evidence is presented that the nuclear staining is not due to tyrosine phosphorylated p130. Finally, unlike pp125FAK, p130 does not appear to be itself a kinase as evidence by immune-complex kinase assays carried out in the presence or absence of exogenous substrates.

Animals↗
PubMed1994

SH2 domain specificity and activity modified by a single residue.

Many intracellular targets of protein-tyrosine kinases possess Src homology 2 (SH2) domains that directly recognize phosphotyrosine-containing sites on autophosphorylated growth factor receptors and cytoplasmic proteins, and thereby mediate the activation of biochemical signalling pathways. SH2 domains possess relatively well conserved residues that form the phosphotyrosine-binding pocket, and more variable residues that are implicated in determining binding specificity by recognition of the three amino acids carboxy-terminal to phosphotyrosine (the +1 to +3 positions). One such residue, occupying the EF1 position of the +3-binding pocket, is a Thr in the SH2 domain of the Src tyrosine kinase, but is predicted to be a Trp in the SH2 domain of the Sem-5/drk/Grb2 adaptor protein. Here we report that changing this residue in the Src SH2 domain from Thr to Trp switches its selectivity to resemble that of the Sem-5/drk/Grb2 SH2 domain. Furthermore, this mutant Src SH2 domain effectively substitutes for the SH2 domain of the Sem-5 protein in activation of the Ras pathway in vivo. These results identify a residue that can modify SH2 selectivity, and indicate that the biological activity of an SH2 domain correlates with its binding specificity.

Adaptor Proteins, Signal Transducing↗
PubMed1994

CD40 signaling pathway: anti-CD40 monoclonal antibody induces rapid dephosphorylation and phosphorylation of tyrosine-phosphorylated proteins including protein tyrosine kinase Lyn, Fyn, and Syk and the appearance of a 28-kD tyrosine phosphorylated protein.

CD40 plays an important role in B cell activation, proliferation, and Ig class switching. The signal transduction pathway mediated by CD40 was studied using monoclonal antibody (mAb) 626.1 to CD40. Burkitt's lymphoma and Epstein-Barr virus-transformed B cell lines and tonsilar B lymphocytes were treated with the anti-CD40 mAb for various lengths of time. The early events triggered by CD40 were examined by monitoring the changes in tyrosine phosphorylation of cellular proteins with anti-phosphotyrosine mAb. Dephosphorylation of specific proteins ranging between 50-110 kD and the appearance of a 28-kD tyrosine phosphorylated protein were seen within 30 s in human B cell lines. The dephosphorylation was reversed and the 28-kD protein was dephosphorylated in cells stimulated for 1 min. In resting B cells, the appearance of the 28-kD phosphoprotein was observed in 30 s after the addition of the anti-CD40 mAb. The tyrosine phosphorylation of this protein persisted. The patterns of protein tyrosine phosphorylation differed from those induced by an anti-immunoglobulin M mAb. The changes in the state of tyrosine phosphorylation induced by the anti-CD40 mAb were obviated by mAb to CD45, a protein tyrosine phosphatase (PTP) or by the addition of sodium orthovanadate, a broad PTP inhibitor. They were also blocked by protein tyrosine kinase (PTK) inhibitors, herbimycin A and genistein, and PKC and protein serine/threonine kinase inhibitors, H7 and HA1004. In addition, the alteration in the tyrosine phosphorylation of PTKs Lyn, Fyn, and Syk was directly demonstrated. Engagement of CD40 for 30 s induced a transient decrease in tyrosine phosphorylation of these PTKs. These results indicate that the early events in CD40 signaling involve the complex interaction between PTP and protein kinases.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Tyrosine phosphorylation of pp125FAK in platelets requires coordinated signaling through integrin and agonist receptors.

FAK is a focal adhesion kinase that is phosphorylated on tyrosine in activated platelets. Induction of FAK phosphorylation requires both fibrinogen binding to integrin alpha IIb beta 3 and post-occupancy events during agonist-induced platelet aggregation or platelet spreading on a fibrinogen matrix. To identify the signaling pathways necessary for tyrosine phosphorylation of FAK, we have examined the conditions that stimulate or inhibit this phosphorylation in platelets in which fibrinogen binding to alpha IIb beta 3 and platelet aggregation were induced directly with an anti-beta 3 Fab fragment (anti-LIBS6). Apyrase was added to prevent effects of the endogenous platelet agonist, ADP. Under these conditions, neither fibrinogen binding nor primary platelet aggregation was sufficient to induce FAK phosphorylation, suggesting that a second "costimulatory" event was required. Indeed, when epinephrine was added with fibrinogen and anti-LIBS6, large platelet aggregates formed and FAK phosphorylation occurred. This response was prevented by blockade of cyclooxygenase with indomethacin or thromboxane A2 receptors with SQ 30,741. A stable thromboxane A2 analogue (U46619) could substitute for epinephrine as the costimulus. Epinephrine costimulation of FAK phosphorylation was also prevented by chelation of intracellular Ca2+ with BAPTA or selective inhibition of protein kinase C (PKC) with bisindolylmaleimide, indicating that Ca2+ and PKC are necessary for FAK phosphorylation under these conditions. Epinephrine also promoted FAK phosphorylation and adhesive spreading of apyrase-treated platelets on a fibrinogen matrix. Cytochalasin D, an inhibitor of actin polymerization, blocked FAK phosphorylation under all these conditions. Thus, tyrosine phosphorylation of FAK in platelets requires coordinated signaling through occupied integrin and agonist receptors. These separate pathways may converge to increase free Ca2+ and activate PKC and thus promote the cytoskeletal reorganization required for activation of FAK.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1994

Stable association of pp60src and pp59fyn with the focal adhesion-associated protein tyrosine kinase, pp125FAK.

Changes in cellular growth and dramatic alterations in cell morphology and adhesion are common features of cells transformed by oncogenic protein tyrosine kinases, such as pp60src and other members of the Src family. In this report, we present evidence for the stable association of two Src family kinases (pp60src and pp59fyn) with tyrosine-phosphorylated forms of a focal adhesion-associated protein tyrosine kinase, pp125FAK. In Src-transformed chicken embryo cells, most of the pp125FAK was stably complexed with activated pp60src (e.g., pp60(527F). The stable association of pp125FAK with pp60(527F) in vivo required the structural integrity of the Src SH2 domain. The association of pp60(527F) and pp125FAK could be reconstituted in vitro by incubation of normal cell extracts with glutathione S-transferase fusion proteins containing SH2 or SH3/SH2 domains of pp60src. Furthermore, the association of isolated SH2 or SH3/SH2 domains with in vitro 32P-labeled pp125FAK protected the major site of pp125FAK autophosphorylation from digestion with a tyrosine phosphatase, indicating that the autophosphorylation site of pp125FAK participates in binding with Src. Immunoprecipitation of Src family kinases from extracts of normal chicken embryo cells revealed stable complexes of pp59fyn and tyrosine-phosphorylated pp125FAK. These data provide evidence for a direct interaction between two cytoplasmic nonreceptor protein tyrosine kinases and suggest that Src may contribute to changes in pp125FAK regulation in transformed cells. Furthermore, pp125FAK may directly participate in the targeting of pp59fyn or possibly other Src family kinases to focal adhesions in normal cells.

Animals↗
PubMed1994

Autophosphorylation of the focal adhesion kinase, pp125FAK, directs SH2-dependent binding of pp60src.

The phosphorylation of protein tyrosine kinases (PTKs) on tyrosine residues is a critical regulatory event that modulates catalytic activity and triggers the physical association of PTKs with Src homology 2 (SH2)-containing proteins. The integrin-linked focal adhesion kinase, pp125FAK, exhibits extracellular matrix-dependent phosphorylation on tyrosine and physically associates with two nonreceptor PTKs, pp60src and pp59fyn, via their SH2 domains. Herein, we identify Tyr-397 as the major site of tyrosine phosphorylation on pp125FAK both in vivo and in vitro. Tyrosine 397 is located at the juncture of the N-terminal and catalytic domains, a novel site for PTK autophosphorylation. Mutation of Tyr-397 to a nonphosphorylatable residue dramatically impairs the phosphorylation of pp125FAK on tyrosine in vivo and in vitro. The mutation of Tyr-397 to Phe also inhibits the formation of stable complexes with pp60src in cells expressing Src and FAK397F, suggesting that autophosphorylation of pp125FAK may regulate the association of pp125FAK with Src family kinases in vivo. The identification of Tyr-397 as a major site for FAK autophosphorylation provides one of the first examples of a cellular protein containing a high-affinity binding site for a Src family kinase SH2 domain. This finding has implications for models describing the mechanisms of action of pp125FAK, the regulation of the Src family of PTKs, and signal transduction through the integrins.

Amino Acid Sequence↗
PubMed1994

The protein tyrosine kinase substrate cortactin is differentially expressed in murine B lymphoid tumors.

Src family protein tyrosine kinases (PTKs) actively participate in signal transduction during lymphocyte activation. However, little is known about the roles of PTKs and their substrates in lymphocyte differentiation. To identify PTK substrates that may be differentially expressed during B lymphopoiesis, we screened a panel of murine B lymphoid tumor cell lines representing various developmental stages using monoclonal antibodies (MAbs) specific for pp60src substrates. A MAb specific for cortactin, a filamentous-actin binding pp60src substrate, immunoprecipitated proteins from murine plasma-cytoma cell lines but not from pre-B cell lymphoma or B cell lymphoma cell lines. We have cloned a murine cortactin cDNA which encodes a member of a family of proteins distinguished by amino-terminal repeat domains and carboxy-terminal Src Homology 3 domains. Two members of this family (cortactin and HS1) were differentially expressed in murine B lymphoid tumor cell lines; both were detected in plasmacytoma cell lines, however HS1 was additionally detected in pre-B lymphoma and B lymphoma cell lines. Cortactin RNA was detected in most murine tissues, but was not detected in B lymphocytes or plasma cells. We hypothesize that cortactin expression is associated with transformed plasma cells and not with the terminal differentiation of normal B lymphocytes to plasma cells.

3T3 Cells↗
PubMed1992

Cell adhesion or integrin clustering increases phosphorylation of a focal adhesion-associated tyrosine kinase.

We have recently shown that changes in tyrosine phosphorylation of a 130-kDa protein(s) (pp130) may be involved in integrin signaling (Kornberg, L., Earp, H.S., Turner, C., Prokop, and Juliano, R. L. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 8392-8396). One component of the pp130 protein complex reacts with an antibody generated against p125fak, which is a focal contact-associated tyrosine kinase (Schaller, M.D., Borgman, C. A., Cobb, B. S., Vines, R. R., Reynolds, A. B., and Parsons, J. T. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 5192-5196). Both antibody-mediated integrin clustering and adhesion of KB cells to fibronectin leads to increased tyrosine phosphorylation of p125fak. The phosphorylation of p125fak is coincident with adhesion of cells to fibronectin and is maximal prior to cell spreading. Tyrosine phosphorylation of p125fak is induced when KB cells are allowed to adhere to fibronectin, collagen type IV, or laminin, but is not induced on polylysine. When KB cells are subjected to indirect immunofluorescence microscopy, p125fak colocalizes with talin in focal contacts. These data provide additional evidence that tyrosine kinases are involved in integrin signaling.

Animals↗
PubMed1992

pp125FAK a structurally distinctive protein-tyrosine kinase associated with focal adhesions.

Expression of the Rous sarcoma virus-encoded oncoprotein, pp60v-src, subverts the normal regulation of cell growth, which results in oncogenic transformation. This process requires the intrinsic protein-tyrosine kinase activity of pp60v-src and is associated with an increase in tyrosine phosphorylation of a number of cellular proteins, candidate substrates for pp60v-src. We report here the isolation of a cDNA encoding a protein, pp125, that is a major phosphotyrosine-containing protein in untransformed chicken embryo cells and exhibits an increase in phosphotyrosine in pp60v-src-transformed chicken embryo cells. This cDNA encodes a cytoplasmic protein-tyrosine kinase which, based upon its predicted amino acid sequence and structure, is the prototype for an additional family of protein-tyrosine kinases. Immunofluorescence localization experiments show that pp125 is localized to focal adhesions; hence, we suggest the name focal adhesion kinase.

Amino Acid Sequence↗
PubMed1992

The influence of dose and time on wound complications following post-radiation neck dissection.

Data on 205 patients who were treated with a planned unilateral neck dissection following radiation therapy were analyzed with the purpose of understanding how treatment factors affect the incidence of wound complications. There were 27 occurrences of wound complication in the patient series. Logistic regression was used to analyze the data. We found that the surgical technique of flap reconstruction gave a significant increase in wound complications. There was a suggestion, although not statistically significant, that higher total doses increased the complication rate, that lower fraction sizes reduced the complication rate, and that longer overall radiotherapy treatment times were associated with higher complication rates. There was no association between the incidence of complications and the time interval between the end of radiotherapy and surgery.

Carcinoma, Squamous Cell↗
PubMed1992

Stage T3 squamous cell carcinoma of the glottic larynx: a comparison of laryngectomy and irradiation.

One-hundred eighteen patients with previously untreated T3 squamous cell carcinoma of the glottic larynx were treated with curative intent between March 1965 and November 1988 at the University of Florida. All patients were observed for at least 2 years and 83% were observed for 5 or more years. Fifty-three patients were treated with irradiation alone and 65 patients were treated with surgery alone (32) or combined with irradiation (33). Thirty-two patients treated with irradiation alone had twice-daily fractionation and the remainder had once-daily fractionation. The local-regional control rates, including patients successfully salvaged after a local-regional recurrence, were 81% after irradiation alone and 81% after surgery alone or combined with adjuvant irradiation. The local control rates for patients treated with irradiation alone were 53% after once-daily fractionation and 71% after twice-daily fractionation. There was no relationship between vocal cord mobility at 5000 cGy, at the end of radiotherapy, or at 1 month after treatment and subsequent local control. The 5-year cause-specific survival rates were 74% for patients treated with irradiation alone and 63% for patients treated surgically. The incidence of severe complications, including those associated with salvage procedures, was 15% for both treatment groups. The rates of laryngeal voice preservation were 66% after irradiation alone and 2% after surgery. Irradiation alone for selected patients with T3 glottic cancer resulted in similar rates of local-regional control, survival, and severe complications, with a significantly higher likelihood of voice preservation, compared with surgery.

Carcinoma, Squamous Cell↗
PubMed1992

Does neck stage influence local control in squamous cell carcinomas of the head and neck?

Recently, reports have suggested that the probability of local control of head and neck cancers treated with radiotherapy alone is inversely related to the extent of neck node disease at presentation. This has led some to conclude that primary lesions in patients with neck node metastases should be treated more aggressively than lesions of the same T stage in patients presenting with a clinically negative neck. We reviewed the records of 607 patients with squamous cell carcinoma of the head and neck to determine the relationship between the extent of neck node disease at diagnosis and the probability of tumor control at the primary site. All patients were treated with continuous-course irradiation alone to the primary site and have a minimum follow-up of 2 years. Mucosal sites analyzed included the oropharynx (soft palate, tonsillar region, base of tongue), hypopharynx (pharyngeal wall, pyriform sinus), and supraglottic larynx. Patients with simultaneous primary lesions were excluded from the analysis. Parameters tested included T stage, N stage, and fractionation (once daily or twice daily). For statistical analyses, N stage was grouped as N0, N1, N2A-N3A, and N2B-N3B. Local control was analyzed using a multivariate analysis, the forward stepwise long-rank test of association of covariates. Multivariate analyses revealed that the following parameters significantly influenced local control: oropharynx, T stage only (p = .0010); hypopharynx, T stage (p = .001) and twice-daily fractionation (p = .0031); and supraglottic larynx, T stage only (p = .0002). No significant correlation was found between neck stage and primary tumor control on univariate or multivariate analyses. Our data do not support the conclusion that primary lesions are controlled less often in patients with clinically positive neck nodes.

Carcinoma, Squamous Cell↗
PubMed1992

Radiation therapy for skin cancer near the eye: kilovoltage x-rays versus electrons.

When skin cancer near the eye is irradiated, a corneal shield is placed between the lids and globe to protect ocular structures. The effectiveness of the shield was evaluated with 250 kVp x-ray and 6-20 MeV electron beams. To simulate the clinical situation, a face phantom was constructed out of solid pieces of water-equivalent epoxy. In the region of the eye the phantom was milled to the exact contour of a human face. The phantom was used to reconstruct the setup that had been used to treat a patient with a 1-cm basal cell carcinoma of the mid portion of the lower lid. A medium-sized corneal shield (2-mm-thick lead plated with 0.1 mm gold) was placed on the eye portion of the phantom. A contoured lead (6 mm thick) face mask was placed on the surface of the phantom to define a 3-cm diameter radiation field that included only the inferior hemisphere of the shield. The doses that the cornea, lens, and retina would receive beneath the midpoint of the inferior hemisphere of the shield were measured using thermoluminescent and film dosimetry. With 6 to 8 MeV electrons, the corneal dose was 2 to 4 times higher than with 250 kVp x-rays. Corneal and lens doses rose rapidly with increasing electron beam energy such that with greater than 8 MeV the shield would provide relatively poor ocular protection. A scanning ion chamber and film dosimetry were used to determine the isodose profiles of 250 kVp x-ray and 6 MeV electron beams for a 3-cm diameter field collimated on the surface. With 250 kVp x-rays the 95% isodose area was 32% wider than with 6 MeV electrons. The ease of shielding and the ability to minimize field size argue in favor of kilovoltage x-rays for early-stage skin cancer near the eye.

Costs and Cost Analysis↗