Relative distribution of actin, myosin I, and myosin II during the wound healing response of fibroblasts

Myosin I is present in Swiss 3T3 fibroblasts and its localization reflects a possible involvement in the extension and/or retraction of protrusions at the leading edge of locomoting cells and the transport of vesicles, but not in the contraction of stress fibers or transverse fibers. An affinity-purified polyclonal antibody to brush border myosin I colocalizes with a polypeptide of 120 kD in fibroblast extracts. Within initial protrusions of polarized, migrating fibroblasts, myosin I exhibits a punctate distribution, whereas actin is diffuse and myosin II is absent. Myosin I also exists in linear arrays parallel to the direction of migration in filopodia and microspikes, established protrusions, and within the leading lamellae of migrating cells. Myosin II and actin colocalize along transverse fibers in the lamellae of migrating cells, while myosin I displays no definitive organization along these fibers. During contractions of actin-based fibers, myosin II is concentrated in the center of the cell, while the distribution of myosin I does not change. Thus, myosin I is found at the correct location and time to be involved in the extension and/or retraction of protrusions and the transport of vesicles. Myosin II-based contractions in more posterior cellular regions could generate forces to separate cells, maintain a polarized cell shape, maintain the direction of locomotion, maximize the rate of locomotion, and/or aid in the delivery of cytoskeletal/contractile subunits to the leading edge.

Serum and acute phase protein modulation of the effector phase of lymphokine-activated killer cells

An understanding of the role that immunomodulatory factors play in the effector phase of lymphokine-activated killer (LAK) activity is essential for the development of biologic response modifiers for use in the treatment of advanced carcinoma. Fifteen head and neck cancer patients were studied. Single-donor killer cells activated by recombinant interleukin-2 (10 U/mL) and induced in either a complete medium or complete medium plus a 10% autologous serum solution were used. Effector phase solutions of 25% autologous serum were used in chromium 51 release assays to determine sera immunomodulation of LAK cell cytotoxicity. Both K562 and squamous carcinoma (MDA686-Ln) tumor cell lines were tested. Significant effector phase inhibition (EPI) of cytotoxicity occurred in 40% of studied patients. Seventy percent of patients with stage III or IV or recurrent disease exhibited EPI, whereas only 20% of patients with stage I or II disease and 30% of controls did so. EPI of cancer patient serum correlated directly with alpha 1-antitrypsin, alpha 1-acid glycoprotein, and C-reactive protein (CRP) levels (MDA686-Ln targets) (r = 0.6, 0.7, and 0.6, respectively) (P < .02). Neither EPI against K562 targets nor EPI in control patients correlated with acute phase protein levels. These findings suggest that advances in in vivo immunomodulatory therapy will be dependent upon further elucidation of serologic inhibition of the effector phase of the LAK cell phenomenon. The relationship between LAK cell recognition and EPI requires further investigation.

Detection of regulatory factors of lymphokine-activated killer cell activity in head and neck cancer patients treated with interleukin-2 and interferon alpha

Interleukin-2 (IL-2) and interferon-alpha (INF-alpha) are biologic modifiers that have met with limited clinical success in the treatment of human malignancies. We conducted a phase 2 trial of IL-2-IFN-alpha in patients with advanced or unresectable squamous cell carcinoma of the upper aerodigestive tract. Two patients were analyzed sequentially for serum induction phase-blocking factors of lymphokine-activated killer (LAK) cell activity in their therapy. Serum also modulated LAK activity independent of autologous or allogeneic effector cells. Significantly inhibitory serum samples were stable in multiple freezings and thawings. Heat-treating the inhibitory serum, at 56 degrees C for 30 minutes, only partially removed the serum inhibitory capacity. Sequential analysis of p55 and p75, subunits of IL-2 receptors, showed that absence of effector cell lytic activity was associated with markedly decreased fluorescence of the IL-2Rp75 subunit only. No significant alteration of the IL-2Rp55 subunit occurred with therapy. These studies support the theory that lymphocyte and multiple serum factors, developing during IL-2-IFN-alpha therapy, regulate the induction of in vitro LAK activity. Further understanding of these factors may lead to improvements in biologic modifier therapy.

Patterns of elevated free calcium and calmodulin activation in living cells

The temporal and spatial dynamics of intracellular signals and protein effectors are being defined as a result of imaging using fluorescent reagents within living cells. We have described a new class of fluorescent analogues termed optical biosensors, which sense chemical or molecular events through their effects on protein transducers. One example of this new class of indicators is MeroCaM, an environmentally sensitive fluorophore which when it is attached to calmodulin reflects the activation of calmodulin by calcium in vitro. We report here that the rise in free calcium and MeroCaM activation occur in the same period during serum stimulation of quiescent fibroblasts. MeroCaM activation also correlates with the spatial pattern of increased free calcium and the contraction of transverse fibres during wound healing. Finally, migrating fibroblasts in the later stages of wound-healing exhibit an increasing gradient of free calcium and MeroCaM activation from the front to the rear.

Myosin II phosphorylation and the dynamics of stress fibers in serum-deprived and stimulated fibroblasts

The actin-based cytomatrix generates stress fibers containing a host of proteins including actin and myosin II and whose dynamics are easily observable in living cells. We developed a dual-radioisotope-based assay of myosin II phosphorylation and applied it to serum-deprived fibroblasts treated with agents that modified the dynamic distribution of stress fibers and/or altered the phosphorylation state of myosin II. Serum-stimulation induced an immediate and sustained increase in the level of myosin II heavy chain (MHC) and 20-kDa light chain (LC20) phosphorylation over the same time course that it caused stress fiber contraction. Cytochalasin D, shown to cause stress fiber fragmentation and contraction, had little effect on myosin II phosphorylation. Okadaic acid, a protein phosphatase inhibitor, induced a delayed but massive cell shortening preceded by a large increase in MHC and LC20 phosphorylation. Staurosporine, a kinase inhibitor known to effect dissolution but not contraction of stress fibers, immediately caused an increase in MHC and LC20 phosphorylation followed within minutes by the dephosphorylation of LC20 to a level below that of untreated cells. We therefore propose that the contractility of the actin-based cytomatrix is regulated by both modulating the activity of molecular motors such as myosin II and by altering the gel structure in such a manner as to either resist or yield to the tension applied by the motors.

2-Deoxyglucose and cytochalasin D modulate aldolase mobility in living 3T3 cells

Approximately 23% of the glycolytic enzyme aldolase in the perinuclear region of Swiss 3T3 cells is immobile as measured by FRAP. Previous studies suggest that the immobile fraction may be associated with the actin cytoskeleton (Pagliaro, L. and D. L. Taylor. 1988. J. Cell Biol. 107:981-991), and it has been proposed that the association of some glycolytic enzymes with the cytoskeleton could have functional significance, perhaps involving a fundamental relationship between glycolysis, cytoplasmic organization, and cell motility. We have tested the effect of a key glycolytic inhibitor and an actin cytoskeletal modulator on the mobility of aldolase in living cells directly, using fluorescent analog cytochemistry and FRAP. We report here that the competitive hexokinase inhibitor 2-deoxyglucose releases the bound fraction of aldolase in 3T3 cells within 10 min, and that this process is reversible upon washout of the inhibitor. A similar result is produced with the actin-binding agent, cytochalasin D. These results are consistent with models in which glycolytic enzymes are not exclusively diffusion-limited, soluble proteins, but may exist partially in the solid phase of cytoplasm. Such organization has significant implications for both the modulation of cytoplasmic structure and for cellular metabolism.

Detection of human cytomegalovirus in peripheral mononuclear cells and urine samples using PCR

Samples of peripheral blood lymphocytes from 105 different blood donors were investigated for the presence of human cytomegalovirus (HCMV) DNA using the polymerase chain reaction (PCR) with primers specific for the Pst I w fragment (IE region). Viral DNA sequences were detected in 53 samples, a fifth of which had been previously serotyped as HCMV negative. In the latter cases, Western blot analysis re-determined two out of three individuals that were resampled as seropositive. PCR could therefore be used to extend existing methods employed for the identification of HCMV infected blood samples prior to transfusion to individuals in high risk groups. In addition, the value of PCR as a diagnostic test was evaluated in a small pilot study by comparing the results obtained with urine samples from babies suffering congenital infection and from other high risk patients, with data obtained by isolation of infectious virus or through the detection of immediate early antigens in infected cultures. Data from this study indicated that PCR is at least as sensitive as the other methods used in HCMV diagnosis.

Acute-Phase Proteins in Patients With Head and Neck Cancer Treated With Interleukin 2/Interferon Alfa

Circulating acute-phase proteins may mediate adverse reactions in patients receiving biologic response modifiers, including inhibition of immune responsiveness and clinical toxic effects. Nine patients with unresectable head and neck squamous cell carcinoma were prospectively examined for levels of acute-phase proteins during interleukin 2/interferon alfa immunotherapy and for clinical toxic effects. Simultaneous determination of the in vitro immunomodulatory capacity of autologous serum on the induction of lymphokine-activated killer cells was assessed in 4-hour chromium release assays. Of the seven acute-phase proteins analyzed, haptoglobin and C-reactive protein levels were elevated before therapy was started. Toxic events leading to cessation of interleukin 2/interferon alfa therapy had a high correlation with elevated C-reactive protein and lowered C3 component of complement levels. No relationship was noted between serum levels of acute-phase proteins and induction inhibition of lymphokine-activated killer cell cytotoxicity. The role of C-reactive protein and complement degradation products in mediating interleukin 2/interferon alfa toxicity requires further investigation.

Actin-binding proteins regulate the work performed by myosin II motors on single actin filaments

Regulation of actin/myosin II force generation by calcium [Kamm and Stull, Annu. Rev. Physiol. 51:299-313, 1989] and phosphorylation of myosin II light chains [Sellers and Adelstein, "The Enzymes," Vol. 18, Orlando, FL: Academic Pres, 1987, pp. 381-418] is well established. However, additional regulation of actin/myosin II force generation/contraction may result from actin-binding proteins [Stossel et al., Ann. Rev. Cell Biol. 1:353-402, 1985; Pollard and Cooper, Ann. Rev. Biochem. 55:987-1035, 1986] as they affect the gel state of the actin cytomatrix [reviewed in Taylor and Condeelis, Int. Rev. Cytol., 56:57-143, 1979]. Regulation of the gel state of actin may determine whether an isotonic or isometric contraction results from the interaction between myosin and actin. We have extended the single actin filament motility assay of Kron and Spudich [Proc. Natl. Acad. Sci. U.S.A. 83:6272-6276, 1986] by including filamin or alpha-actinin on the substrate with myosin II to examine how actin-crosslinking proteins regulate the movements of single actin filaments. Increasing amounts of actin-crosslinking proteins inhibit filament velocity and decrease the number of filaments moving. Reversal of crosslinking yields increased velocities and numbers of moving filaments. These results support the solation-contraction coupling hypothesis [see Taylor and Fechheimer, Phil. Trans. Soc. London B 299:185-197, 1982] which proposes that increased crosslinking of actin inhibits myosin-based contraction. This study also illustrates the potentially varied roles of different actin-crosslinking proteins and offers a novel method to examine actin-binding protein activity and their regulation of motility at the single molecule level.

The role of solation-contraction coupling in regulating stress fiber dynamics in nonmuscle cells

Serum-deprived Swiss 3T3 fibroblasts constitutively form stress fibers at their edges. These fibers move centripetally towards the perinuclear region where they disassemble. Serum stimulation causes shortening of fibers in a manner suggesting active actin-myosin-based contraction (Giuliano, K.A. and D.L. Taylor. 1990. Cell Motil. and Cytoskeleton. 16:14-21). To elucidated the role of actin-based gel structure in these movements, we examined the effects of disrupting actin organization with cytochalasin. Serum-deprived fibroblasts were microinjected with rhodamine analogs of actin or myosin II and fiber dynamics were monitored with a multimode light microscope workstation using video-enhanced contrast and fluorescence modes. When cells were perfused with greater than or equal to 3 microM cytochalasin B or 0.5 microM cytochalasin D, formation and transport of stress fibers were reversibly inhibited, and rapid and immediate shortening of existing fibers was induced. Quantification of actin and myosin II fluorescence associated with individual shortening fibers demonstrated that fluorescence per length of fiber increased for both components, suggesting sliding filament contraction. However, there was also a net loss of both actin and myosin II from fibers as they shortened, indicating a self-destructive process. Loss of material from fibers coupled with increased overlap of actin and myosin II remaining in the fibers suggested that contraction could be induced not only by increasing the force exerted by contractile motors, but also by decreasing gel structure through partial solation. Finally, cytochalasin accelerated contraction of actin-myosin-based gels reconstituted from purified proteins in the absence of myosin-based regulation, further supporting solation-contraction coupling as a possible mechanism for modulating cytoplasmic contractility (Taylor, D.L. and M. Fechheimer. 1982. Philos. Trans. R. Soc. Lond. B. Biol. Sci. 299:185-197).

Modulation of contraction by gelation/solation in a reconstituted motile model

The actin-based cytoskeleton is a dynamic component of living cells with major structural and contractile properties involved in fundamental cellular processes. The action of actin-binding proteins can decrease or increase the gel structure. Changes in the actin-based cytoskeleton have long been thought to modulate the myosin II-based contractions involved in these cellular processes, but there has been some debate concerning whether maximal gelation increases or decreases contractile activity. To address this question, we have examined how contractile activity is modulated by the extent of actin gelation. The model system consists of physiologically relevant concentrations and molar ratios of actin filaments (whose lengths are controlled by gelsolin), the actin-cross-linking protein filamin, and smooth muscle myosin II. This system has been studied at the macroscopic and light microscopic levels to relate the gel structure to the rate of contraction. We present results which show that while a minimal amount of structure is necessary to transmit the contractile force, increasing the gel structure inhibits the rate of contraction, despite an increase in the actin-activated Mg(2+)-ATPase activity of myosin. Decreasing the total myosin concentration also inhibits the rate of contraction. Application of cytochalasin D to one side of the contractile network increases the rate of contraction and also induces movement comparable to flare streaming observed in isolated amoeba cytoplasm. These results are interpreted relative to current models of the relationship between the state of gelation and contraction and to the potential effects of such a relationship in the living cell.

Stilbene disulfonic acids. CD4 antagonists that block human immunodeficiency virus type-1 growth at multiple stages of the virus life cycle

The stilbene disulfonic acids 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonic acid and, 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid bound the variable-1 immunoglobulin-like domain of CD4 on JM cells. The interaction blocked the binding of the anti-CD4 monoclonal antibody OKT4A and the envelope glycoprotein gp120 of the human immunodeficiency virus type-1 (HIV-1). DIDS inhibited the acute infection of CD4+ cells by HIV-1 with a potency (IC50 approximately 30 microM) similar to that which blocked gp120 binding (IC50 approximately 20 microM) to the cellular antigen. Pretreating uninfected CD4+ C8166 cells with DIDS blocked their fusion with chronically infected gp120+ cells. DIDS covalently and selectively modified lysine 90 of soluble CD4 and abolished the gp120-binding and antiviral properties of the recombinant protein. When added to cells productively infected with HIV-1, DIDS blocked virus growth and cleared cultures of syncytia without inhibiting cellular proliferation. The stilbene disulfonic acids are a novel class of site-specific CD4 antagonists that block multiple CD4-dependent events associated with acute and established HIV-1 infections.

Immunomodulation of the induction phase of lymphokine-activated killer activity by acute phase proteins

Effective treatment of head and neck cancer with biologic response modifiers may be benefitted by an understanding of in vivo factors capable of modulating the lymphokine-activated killer (LAK) cell phenomenon. Eighteen patients with squamous cell carcinoma of the head and neck were studied. Killer cells from each patient, activated by recombinant interleukin-2 (10 U/ml), were induced in either complete medium alone or complete medium plus 10% autologous serum solution and analyzed. Cytotoxicity against both K562 and squamous cell carcinoma (MDA686-Ln) cell lines was determined by use of standard chromium-release assays. The immunomodulatory capacity of serum was correlated with levels of various acute phase proteins. Autologous serum significantly inhibited the induction phase of the LAK phenomenon in 61% of patients and stimulated it in 22%. No patients with early stage I or II disease had significant inhibition of induction. No direct correlation between inhibition and serum acute phase protein levels were seen. An inverse relationship was seen between the C3 component of complement and induction inhibition (r = -0.6). These findings suggest that advances of in vivo immunomodulatory therapy will require elucidation of mechanisms of serologic inhibition of the induction phase of the LAK phenomenon. Such studies may lead to serologic modification to enhance treatment efficacy of biologic response modifiers.

6-0-butanoylcastanospermine (MDL 28,574) inhibits glycoprotein processing and the growth of HIVs

The antiviral activity of 6-0-butanoylcastanospermine (MDL 28,574) [50% inhibitory concentration (IC50: 1.1 microM)] in JM cells infected with a recent isolate of HIV-1 (GB8), was compared with other inhibitors of glycoprotein-processing enzymes. N-butyldeoxynojirimycin (BuDNJ), deoxynojirimycin (DNJ), castanospermine (CAST) or the reverse transcriptase inhibitor 2'3'-dideoxycytidine (ddC) had activities of 56, 560, 29 and 0.1 microM, respectively. MDL 28,574 was at least 50 times more active than BuDNJ and less active but better tolerated in cell culture than ddC, two compounds currently undergoing clinical trials. The CAST derivative showed good protection in H9 cells infected with HIV-1 (RF; IIIB; U455), and HIV-2 (ROD), although the potency was less than that seen in the JM/GB8 system. HIV-1 glycoproteins, gp160 and gp120, synthesized in H9 cells chronically infected with HIV-1 (RF) and treated with MDL 28,574, were characterized by an increase in relative molecular weight of approximately 7-8000 kD. The ratio of gp120 to gp160 was markedly reduced in treated cells and provided further evidence that cleavage of the gp160 precursor molecule is a major consequence of the inhibition of glycoprotein processing. The intracellular target for MDL 28,574 was verified as alpha-glucosidase-I of the processing enzymes by the analysis of high-glucose glycopeptides recovered from treated mouse cells. This activity correlated with the antiviral effect observed against the growth of a mouse retrovirus, Moloney murine leukemia virus (MOLV), in mouse cells.

Quaternary salts of 2-[(hydroxyimino)methyl]imidazole. 4. Effect of various side-chain substituents on therapeutic activity against anticholinesterase intoxication

A series of quaternary salt derivatives of 2-[(hydroxyimino)methyl]-1-methylimidazole incorporating various side chains bearing ether, silyl, nitrile, ester, halogen, nitro, sulfone, amino, or aminosulfonyl substituents was prepared and evaluated in vivo for the treatment of anticholinesterase intoxication. Test results in the mouse revealed that the type and location of the side-chain substituent both have a significant influence on the toxicity and antidotal effectiveness of the compounds. Some of the more active examples represent the most potent therapeutics to date against intoxication by the powerful cholinesterase inhibitors soman and tabun. Significantly, the antidotal effectiveness of the compounds was not dependent on the inhibiting agent nor was there any correlation between in vivo efficacy and in vitro reactivation of ethyl (4-nitrophenyl)methylphosphonate inhibited human acetylcholinesterase. These observation suggested that the main mode of antidotal protection by the compounds is something other than enzyme reactivation.

Imaging cytometry by multiparameter fluorescence

A system is described for performing multicolor fluorescence image cytometry of cell preparations. After the setting up stage, the operation is automatic: the microscope fields are found and focused; then images are acquired for each fluorophore, corrected and analyzed, without any operator interaction. Human peripheral blood lymphocytes on microscope slides were used as a test system. In these experiments, three fluorescent antibodies were used to identify lymphocyte sub-populations, and a DNA content probe was used to identify all nucleated cells. The cell subset percentages determined by image cytometry were comparable to percentages obtained when cells from the same preparation were analyzed by flow cytometry. Multicolor fluorescence imaging cytometry can potentially be extended to the analysis of cells in smears, fine needle biopsies, imprints, and tissue sections.

A calcium-sensitive fluorescent analog of calmodulin based on a novel calmodulin-binding fluorophore

Structure-activity studies of tetramethinemerocyanine fluorophores enabled the synthesis of novel dyes which showed spectral changes during reversible, calcium-dependent association with calmodulin. These spectral changes were greatly enhanced in dyes with a quaternary nitrogen and specifically placed hydrophobic chains. One such dye was covalently attached to calmodulin, producing a calmodulin analog with calcium-sensitive fluorescence. The analog, MeroCaM, showed a calcium-induced 3.4-fold increase in excitation ratio (608/532 nm excitation, 623 nm emission), which was fully reversed by lowering free calcium levels. MeroCaM's excitation ratio showed a half-maximal change at 300-400 nM calcium, below calcium concentrations reported to produce half-maximal saturation of calcium-calmodulin binding. However, the calcium dependence of MeroCaM's phosphodiesterase activation paralleled that of calmodulin. MeroCaM's fluorescence changes therefore appear to reflect primarily calcium binding to high affinity sites. MeroCaM's maximal phosphodiesterase activation was 30-40% that of calmodulin. In myosin light chain kinase activation, MeroCaM and calmodulin displayed indistinguishable maximal activation levels and concentration dependence of activation. Changes in MeroCaM's calcium affinity induced by magnesium, phosphodiesterase, and melittin were similar to those reported for calmodulin. Experiments with melittin revealed that target protein interaction could alter the fluorescence changes produced by calcium binding. MeroCaM showed promising brightness and photostability when imaged in individual living fibroblasts. The long excitation and emission wavelengths of MeroCaM, and the strong dependence of its excitation ratio on calcium concentrations, suit it well for use as a probe of calmodulin-dependent calcium signaling in living cells, as well as for experiments in vitro.

Continuous or interrupted fascial closure: a prospective evaluation of No. 1 Maxon suture in 402 gynecologic procedures

During a 14-month period of using a long-term absorbable suture (No. 1 Maxon), 402 patients were entered into a prospective, randomized trial of fascial closure. Patients were randomized between a continuous closure (201 patients) and an interrupted en bloc (201 patients) technique. Each patient was subjected to a preoperative and intraoperative protocol for wound management. There were no acute wound failures. Wound infection rates and risk of hernia were not apparently affected by closure technique.

The analysis of natural killer cell activity by flow cytometry

A flow cytometric assay was used to detect the lytic and binding capacities of both fresh peripheral blood lymphocytes and purified Leu-19+ natural killer cells against head and neck cancer cell lines. Results demonstrated that natural killer cell-mediated cytotoxicity and effector-target conjugate formation evaluated by flow cytometry was significantly correlated with the standard chromium 51 release assay and the single-cell microscopic assay, respectively. The sorted Leu-19+ natural killer cells demonstrated higher lytic capacity with a corresponding higher binding rate compared with the unsorted peripheral blood lymphocytes and sorted Leu-19- cells. Flow cytometric analysis of natural killer cell activity (a rapid, simple, and quantifiable procedure) is an alternative to the standard chromium 51 release assay.

Single-dose antibiotic prophylaxis for patients undergoing extended pelvic surgery for gynecologic malignancy

The comparative efficacy of single-dose antibiotic prophylaxis was retrospectively evaluated in 116 patients undergoing extended pelvic surgical procedures with curative intent. During the 24-month period, other important variables such as surgeon's experience, duration of preoperative hospitalization, preoperative preparation, method of hair removal, suture type, suture size, use of drains, use of cautery, and abdominal closure were controlled. The overall surgical site infection rate was 4.3% after radical hysterectomy with lymphadenectomy and 4.5% after total hysterectomy with lymphadenectomy. In this clinical situation the use of a single dose of antibiotic prophylaxis theoretically decreases cost and patient exposure and appears to be as efficacious as a multiple-dose regimen.

Differential sensitivity of head and neck cancers to non-major histocompatibility-restricted killer cell activity

Cell lines derived from squamous cell carcinoma of the upper aerodigestive tract (head and neck cancer) were phenotypically characterized with regard to differential sensitivity to nonmajor histocompatibility restricted (non-MHCr) killer cell activity. Requirements for detectable lysis of the cell lines in a standard chromium release assay included either isolation of fresh enriched Leu 19+ large granular lymphocytes (both Leu 19+CD3+ and Leu 19+CD3- populations) or interleukin-2 (IL-2) stimulation of peripheral blood lymphocytes (PBL). In neither circumstance could lytic activity be identified among Leu 19- populations. With PBL IL-2 stimulation significant differential sensitivity to lysis expressed by the head and neck cancer cell lines (P less than 0.001 by analysis of variance) was identified and maintained regardless of PBL source, i.e., PBL from healthy controls and three differing populations of head and neck cancer patients categorized by disease status and treatment. One factor associated with a cell line's increased sensitivity was degree of tumor differentiation, poorly differentiated tumors (as defined by intermediate filament cytochemical staining [decreased keratin and increased vimentin]) being more sensitive. Furthermore, as tumor cell lytic sensitivity increased, major histocompatibility complex (MHC)-class I antigen expression diminished concurrently. In 1 of 4 cell lines tested, however, pretreatment of tumor cells with interferon-gamma induced diminished lytic sensitivity independent of changes in MHC-class I expression, indicating factors not related to MHC-class I expression are likewise relevant. In previous studies we defined the in vivo prognostic significance of non-MHCr killer cell cytotoxicity activity against K562 targets, diminished activity being principally predictive of metastatic disease development in persons with poorly differentiated head and neck cancers. This report extends these observations by demonstrating in vitro that poorly differentiated head and neck cancer target cells are highly sensitive to changes in lytic function expressed by Leu 19+ non-MHCr effector cells.

Formation, transport, contraction, and disassembly of stress fibers in fibroblasts

Swiss mouse 3T3 fibroblasts grown on a solid substrate in the presence of 10% serum exhibit cell movement, organelle transport, and cytokinesis. When the serum concentration in the culture medium is decreased to 0.2% for 48 h the serum-deprived cells virtually stop locomoting, spread, decreased organelle transport, and exhibit extensive arrays of stress fibers that are visible with video-enhanced differential interference contrast microscopy and that also incorporate fluorescent analogs of actin and conventional myosin (myosin II). The stress fibers form in a constitutive manner at the cytoplasm-membrane interface, transport toward the nucleus, and then disappear. The rate of transport of these fibers is quite heterogeneous with average rates in the range of 10-20 microns/h. When serum-deprived cells are stimulated with mitogens such as 10% serum or 10 nM thrombin, many of the stress fibers immediately begin to shorten, suggesting a contraction. The rate of shortening is approximately two orders of magnitude slower than that of unloaded smooth muscle cells. The fiber shortening is often accompanied by retraction of the edges of the cell and continues for at least the 1st hour post-stimulation.

A multicellular tumor spheroid model of cellular immunity against head and neck cancer

A multicellular tumor spheroid (MTS) model for head and neck cancers has been used to examine the immune function of fresh and 6-day interleukin-2(IL-2)-activated peripheral blood lymphocytes (PBL). MTS are individually cultured in the presence of effector cells, and the spheroids' growth is monitored by sizing them under an inverted microscope. Dose/response studies for IL-2 (0-100 U/ml) alone and for fresh unstimulated PBL (0-10(5) cells/MTS) showed no effects on MTS growth. IL-2-activated PBL (0-10(5) cells/MTS), in contrast, modulated MTS growth in a multiphasic pattern: MTS growth was unperturbed for the first 3 days and then growth inhibition occurred, followed by MTS disintegration. Histological analysis showed that intact MTS histoarchitecture correlated with unperturbed growth, and increasing cell sloughing and MTS dissolution and replacement by activated PBL correlated with growth inhibition and disintegration. Flow-cytometric sorting of lymphocyte subset populations indicated that it was the Leu19+CD3- cells that produced these growth-modulatory effects. In contrast to the initial LAK cell resistance of MTS, single-cell suspensions demonstrated significant lysis in standard 4-h chromium-release assays. Differences between single cells and MTS suggest a potential for tissue-like organization as a factor in lymphokine-activated killing.

Natural killer cell lysis of head and neck cancer

This study analyzed the capacity of both fresh unseparated peripheral blood lymphocytes and enriched natural killer (NK) cells to lyse head and neck cancer cell lines. In a 6-hour chromium-release assay, only Leu-19+ NK cells mediated significant lysis. Furthermore, cell lines established from poorly differentiated cancers were more sensitive to lysis than were cell lines established from well-differentiated cancers. Cell lines from well-differentiated cancers also less readily inhibited K562 lysis in a cold-target inhibition assay, were not recognized by NK cells in a monolayer absorption assay (unlike poorly differentiated cancers), and failed to form conjugates with NK cells in a single-cell assay. These results indicated that deficient killing of a well-differentiated cancer cell vs a poorly differentiated cancer cell is partly a function of diminished NK cell recognition and tumor binding necessary to initiate lysis. As in previous studies regarding the prognostic implication of quantitated measures of NK cell activity within head and neck cancer patients, the results support the biologic relevance of the NK cell as a defense mechanism against metastatic disease, especially in patients with poorly differentiated, low major histocompatibility complex class I-expressing head and neck cancers.