Indocyanine green fluorescence applied to gynecologic oncology: beyond sentinel lymph node.

Indocyanine green (ICG), a well-known molecule employed in medicine for over five decades, has emerged as a versatile dye widely embraced across various surgical disciplines. In gynecologic oncology, its prevalent use revolves around the detection of sentinel lymph nodes. However, the true potential of ICG extends beyond this singular application, owing to its pragmatic utility, cost-effectiveness, and safety profile. Furthermore, ICG has been introduced in the theranostic landscape, marking a significant juncture in the evolution of its clinical utility. This narrative review aims to describe the expanding horizons of ICG fluorescence in gynecologic oncology, beyond the sentinel lymph node biopsy. The manifold applications reported within this manuscript include: 1) lymphography; 2) angiography; 3) nerve visualization; 4) ICG-driven resections; and 5) theranostic. The extensive exploration across these numerous applications, some of which are still in the pre-clinical phase, serves as a hypothesis generator, aiming to stimulate the development of clinical studies capable of expanding the use of this drug in our field, enhancing the care of gynecological cancer patients.

The new surgical robot Hugo™ RAS for total hysterectomy: a pilot study.

Background: With the rising popularity of robotic surgery, Hugo™ RAS is one of the newest surgical robotic platforms. Investigating the reliability of this tool is the first step toward validating its use in clinical practice; and presently there arelimited data available regarding this. The literature is constantly enriched with initial experiences, however no study has demonstrated the safety of this platform yet. Objectives: This study aimed to investigate its reliability during total hysterectomy. Materials and Methods: A series of 20 consecutive patients scheduled for minimally invasive total hysterectomy with or without salpingo-oophorectomy for benign disease or prophylactic surgery were selected to undergo surgery with Hugo™ RAS. Data regarding any malfunction or breakdown of the robotic system as well as intra- and post-operative complications were prospectively recorded. Results: Fifteen of the twenty patients (75.0%) underwent surgery for benign uterine diseases, and five (25.0%) underwent prophylactic surgery. Among the entire series, an instrument fault occurred in one case (5.0%). The problem was solved in 4.8 minutes and without complications for the patient. The median total operative time was 127 min (range, 98-255 min). The median estimated blood loss was 50 mL (range:30-125 mL). No intraoperative complications were observed. One patient (5.0%) developed Clavien-Dindo grade 2 post-operative complication. Conclusions: In this pilot study, Hugo™ RAS showed high reliability, similar to other robotic devices. What is new?: Present findings suggest that Hugo™ RAS is a viable option for major surgical procedures and deserves further investigation in clinical practice.

Carbonic anhydrase XII expression is linked to suppression of Sonic hedgehog ligand expression in triple negative breast cancer cells.

Aberrant activity of the hedgehog (Hh) pathway is prevalent in pathologies such as cancer. Improved understanding of Hh activity in the aggressive tumor cell phenotype is being pursued for development of targeted therapies. Recently, we described a link between Hh activity and carbonic anhydrase XII (CAXII) expression. Extracellular facing CAs (IX/XII) are highly expressed in hypoxia, contribute to tumor pH regulation and are thus of clinical interest. Here we have extended the investigation of potential interactions between Hh activity and CAXII utilizing genomic disruption/knockout of either GLI1 (the main transcriptional factor induced with Hh activity) or CAXII in the triple negative breast cancer cell lines MDA-MB-231 and BT-549. Knockout of GLI1 and CAXII significantly decreased hallmarks of tumor aggressiveness including proliferation and migration. Most intriguingly, CAXII knockout caused a massive induction of the Sonic hedgehog (Shh) ligand expression (gene and protein). This novel finding indicates that CAXII plays a potential role in suppression of Shh and may act in a feedback loop to regulate overall Hh activity. Enhanced knowledge of these CA-Hh interactions in future studies may be of value in understanding this currently 'incurable' subclass of breast cancer.

Role of different approaches to the abdominal retroperitoneum for aortic lymphadenectomy in patients with gynecological cancers.

BACKGROUND: Paraaortic lymphadenectomy (PALN) is a standard part of many interventions, but currently there are no established care protocols effective in preventing gastro-intestinal (GI) symptoms. The aim of our study was to retrospectively evaluate patients with gynecologic cancers submitted to PALN, in order to evaluate if different approaches to the retroperitoneum could influence the radicality of the procedure and the onset of GI complications. METHODS: We divided 121 patients with gynecologic tumors submitted to PALN into 3 groups according the used right, left or combined left-right approach to the retroperitoneum, comparing the groups according the main surgical-pathological parameters, such as the number of nodes removed and the incidence and severity of GI complications. RESULTS: The mean number of nodes removed did not significantly differ between the groups, while the mean number of positive nodes was significantly higher in combined approach. 39.8% of our patients experienced GI side effects, but those submitted to the combined approach had a significantly higher incidence of GI symptoms. CONCLUSIONS: Our data demonstrate that the choice of the retroperitoneal approach could be the most important feature for the appearance of post-operative GI side effects, even if there is no significant difference on the radicality of PALN performed retroperitoneal approach.

Role of the hypoxic microenvironment in the antitumor activity of tyrosine kinase inhibitors.

The tumor microenvironment is characterized, not only by marked gradients in drug concentration, but also by gradients in the rate of cell proliferation and by regions of hypoxia and acidity, all of which can influence tumor cell sensitivity to drug treatment. Hypoxia is also an important environmental factor in chronic myeloid leukemia (CML), because bone marrow is intrinsically hypoxic in nature. Systems-wide analyses of tumors have recently identified receptor tyrosine kinase coactivation as an important mechanism by which cancer cells achieve chemoresistance. Recent work suggests that Src activation might play a prominent role in the response to hypoxia to promote cell survival, progression, and metastasis of a variety of human cancer. Other studies also established a functional link between Bcr-Abl and the Src family tyrosine kinases. It is well known that mutations can also cause some tyrosine kinases to become constitutively active, a nonstop functional state that may contribute to initiation or progression of cancer as in CML. Leukemic cells carrying chromosomal alteration, are sensitive to imatinib that induces complete remission in most patients. This inhibitor is a highly selective Bcr-Abl tyrosine kinase inhibitor (TKI). There is a considerable interest in understanding how activated signaling pathways enhance tumor cell survival under hypoxia, because this might lead to the introduction of more effective treatments to target these resistant subpopulations. For all these reasons it is important to identify new TKIs which are also active in hypoxia, the real tumor microenvironment, as possible alternative therapy.

Secondary cytoreduction plus oxaliplatin-based HIPEC in platinum-sensitive recurrent ovarian cancer patients: a pilot study.

OBJECTIVES: To assess feasibility, complications and efficacy of secondary surgical cytoreduction (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) in a selected group of platinum-sensitive recurrent ovarian cancer patients. METHODS: Recurrent ovarian cancer patients with a platinum-free interval of at least 6 months were prospectively enrolled. After complete CRS they were submitted to intraperitoneal perfusion of oxaplatinum (460 mg/m(2)) heated to 41.5 degrees C for 30 min. Then they received systemic chemotherapy with taxotere 75 mg/m(2) and oxaliplatin 100 mg/m(2) for 6 cycles. Patients were followed up routinely until recurrence or death. RESULTS: Twenty-five recurrent ovarian cancer patients were valuable for the study. The median Platinum Free Interval (PFI) was 25 months (range 7-67). The majority of the patients (76%) had diffuse carcinosis. Nobody had ascites. An optimal residual disease was obtained in all patients. The median duration of CRS+HIPEC was 312 min (range 138-619). Median intensive care unit (ICU) stay was 2 days (1-6), median hospital stay was 13 days (7-30). Post-operative major complications were observed in 7 patients (28%). Post-operative mortality was 0%. With a median follow-up time of 18 months (range 3-38), 24 patients (96%) are alive, but seven women (28%) have relapsed. CONCLUSIONS: Adequate pre-operative selection can improve feasibility of CRS and HIPEC. Morbidity rate is comparable to aggressive cytoreduction without HIPEC. Although associated with some post-operative morbidity, long-term results are encouraging, waiting for larger series and longer follow-up data.

Analysis of protease-activated receptor-1 and -2 in human scar formation.

Protease-activated receptor (PAR)-1 and PAR-2 are reported to contribute to the fibrotic process in a number of organs, including lung, liver, pancreas, and kidney. The aim of this study was to localize expression and biological activity of PAR-1 and PAR-2 in normal and pathological cutaneous scars. First, we investigated the immunohistochemical expression of PAR-1 and PAR-2 proteins in a series of human normal scars (NS, n = 10), hypertrophic scars (HS, n = 10), and keloids (K, n = 10). Expression of PAR-1 and PAR-2 was observed in all types of scar. Specifically, in HS and K, diffuse PAR-1 and PAR-2 positivity was found in dermal cellular areas composed of myofibroblasts, while no or minor staining was observed in the scattered fibroblasts embedded in abundant extracellular matrix in the context of the more collagenous nodules, irrespective of the type of scar. The hyperplastic epidermis overlying K was also found to be strongly PAR-1 and PAR-2 positive, whilst in most NS and HS the epidermis was faintly to moderately stained. Second, ribonuclease protection assay on paraffin-embedded specimens showed overexpression of PAR-1 and PAR-2 mRNA in K compared to NS and HS. Third, cultured human fibroblasts exposed to TGF-beta1 expressed a myofibroblast phenotype associated with overexpression of PAR-2, while PAR-1 expression was unaffected. Intracellular Ca(2+) mobilization by PAR-2 agonists in myofibroblasts was increased as compared to fibroblasts, whereas the effect of PAR-1 agonists was unchanged. Our in vivo study indicates that PAR-1 and PAR-2 are expressed in cells involved in physiological and pathological scar formation and suggests that in vitro overexpression and exaggerated functional response of PAR-2 may play a role in the function of myofibroblasts in scar evolution from a physiological repair process to a pathological tissue response.

Endometrioid adenocarcinoma with squamous differentiation arising from ureteral endometriosis in a patient with no history of gonadal endometriosis.

BACKGROUND: Malignant transformation may occur in up to 1% of women with endometriosis and only 20% of these cases occur at extragonadal pelvic sites. Similarly, urinary tract endometriosis is rare and occurs in only 1% of all endometriotic lesions. CASE: An endometrioid carcinoma with squamous differentiation arising from periureteral endometriosis presented as a pelvic mass encasing the right ureter. The patient had a history of total hysterectomy and bilateral salpingo-oopherectomy 8 years earlier because of bilateral serous benign cysts with right hemorrhagic corpus luteum and uterine fibroids, and has since been under unopposed estrogen replacement therapy for 5 years. CONCLUSION: This is the second case of a malignancy arising in endometriosis presenting as an obstructive ureteral mass and the first case of a patient with this condition whose endometriosis is not consistent with a gonadal origin. An analysis of the case and related literature is presented together with the discussion of possible pathogenetic mechanisms.

Phase II study of pegylated liposomal doxorubicin in heavily pretreated epithelial ovarian cancer patients. May a new treatment schedule improve toxicity profile?

OBJECTIVE: Pegylated liposomal doxorubicin (PLD) has shown promising activity in the treatment of recurrent ovarian cancer but skin toxicity remains the dose-limiting toxicity of the drug. The aim of this study was to investigate whether a different treatment schedule may improve the toxicity profile, especially in terms of dermatological and mucosal toxicity. METHODS: It is an open-label phase II study in a population of heavily pretreated ovarian cancer patients. PLD was administered at the dose of 35 mg/m2 q21 until disease progression or unacceptable toxicity. RESULTS: Thirty-seven heavily pretreated (median number of previous chemotherapy regimens 2, range 1-6) ovarian cancer patients were enrolled. All patients received at least two courses of chemotherapy and all were evaluated for response. No one showed complete response, while five partial responses (13.5%), 16 stabilizations of disease (48.6%) and 14 progressions of disease (37.8%) were observed. The median time to response was 12 weeks (range 8-16). The median duration of response was 22.8 weeks (range 4-68), the median duration of stabilization of disease was 17.6 weeks (range 4-28). Palmar plantar erythrodysesthesia (PPE) occurred in 8 patients (21.6%) and was of grade 3 in one patient (2.8%). Grade 1 stomatitis occurred in 3 patients (8.1%). Grade 3-4 neutropenia occurred in only 4 patients (10.8%). CONCLUSIONS: PLD at the dose of 35 mg/m2 q21 seems to translate into an acceptable skin toxicity profile with a response rate comparable to others obtained with a standard schedule.

New pyrazolo[3,4-d]pyrimidines endowed with A431 antiproliferative activity and inhibitory properties of Src phosphorylation.

New 4-aminopyrazolo[3,4-d]pyrimidines bearing various substituents at the position 1 and 6, were synthesized. The new compounds showed antiproliferative activity toward A431 cells, were found to be inhibitors of Src phosphorylation, and induced apoptotic cell death. In particular, 2h was a better inhibitor of Src phosphorylation than the reference compound PP2.

Inhibition of interleukin-12 expression by alpha-thrombin in human peripheral blood mononuclear cells: a potential mechanism for modulating Th1/Th2 responses.

In addition to its central role in blood coagulation and hemostasis, human alpha-thrombin is a powerful regulator of inflammatory responses and is known to affect cell-mediated immunity. Interleukin (IL)-12 is a strong promoter of the development of Th1-type lymphocytes and its downregulation implies a positive feedback mechanism for development of Th2 responses. We have previously shown that thrombin enhances the release of IL-6, a Th2-related cytokine, in human peripheral blood mononuclear cells (PBMC). Here we show that thrombin downregulates IL-12 production at both protein and mRNA levels in human PBMC. The inhibition of IL-12 production was accompanied by an enhanced release of IL-10, which inhibits Th1-related processes and promotes Th2-type responses. The use of proteolytically inactive thrombin and of the specific thrombin receptor agonist peptide, SFLLRN, reveals that this downregulation is thrombin-specific and requires thrombin proteolytic activity. In addition, activation of coagulation inhibits IL-12 production in whole blood cultures, confirming the tight relationship between the coagulation pathway, where thrombin is a key enzyme, and inflammation. Decreased IL-12 production appears to be related also to IL-10 production, since the addition of an anti-IL-10 monoclonal antibody to thrombin-treated PBMC resulted in a partial restoration of IL-12 production. In conclusion, the observation that thrombin significantly affects the production of IL-12, as well as of IL-10, implies a concerted role orchestrated by thrombin in PBMC that could be crucial to effective immunity and inflammation.

Regulation of angiogenesis by Th1- and Th2-type cytokines.

Angiogenesis is a complex process, where several cell types and mediators interact to establish a specific microenvironment suitable for the formation of new capillaries from pre-existing vessels. Such biological processes occur in several physiological conditions, such as embryo development and wound healing, as well as in pathological conditions, including tumours and diabetic retinopathy. T lymphocytes, neutrophils and monocytes fully participate in the angiogenic process by secreting cytokines that may control endothelial cell (EC) proliferation, their survival and apoptosis, as well as their migration and activation. Angiogenesis is the result of a net balance between the activities exerted by positive and negative regulators. This balance is conceptually very similar to that of the Th1/Th2 cells that modulate an appropriate and specific immune response. Th1 or Th2 cytokines may control angiogenesis directly, by acting on cell growth and differentiation, indirectly by inducing the release of other cytokines in the microenvironment, and by modulating the expression of specific receptors, involved in the control of angiogenic processes, such as EC proliferation and migration. In this review we will mainly discuss the role of Th1- and Th2-type cytokines in the angiogenic process, emphasizing the complexity of the cytokine and leukocyte/EC network, and highlighting the care that needs to be taken when designing new therapeutic interventions involving Th1 and Th2 cytokines.

Hypoxia induces the expression and release of interleukin 1 receptor antagonist in mitogen-activated mononuclear cells.

Hypoxia modulates the expression of inflammatory mediators in a variety of cell types. Since interleukin (IL-)1 receptor antagonist (Ra) is a cytokine widely associated with an inflammatory state and is expressed by activated mononuclear cells, we investigated whether hypoxia induces IL-1Ra expression in human peripheral blood mononuclear cells (PBMC) activated by phytohaemagglutinin (PHA). RNase protection assay, conducted on PHA-activated PBMC cultured under hypoxic conditions (2% O(2)) for 16-40 h, revealed that hypoxia enhances IL-1Ra mRNA expression. Further, IL-1Ra release was significantly affected by hypoxia, as determined by ELISA. Concomitantly, hypoxia enhanced, even though at a lesser extent, both IL-1alpha and IL-1beta mRNA expression and release, as determined by RPA and ELISA. However, at 40 h of treatment, hypoxia did not affect cell viability and DNA fragmentation, but caused an inhibition of the proliferation index after PHA stimulation, obtained by MTT assay. These results suggest that activated mononuclear cells tend to respond to hypoxic stress by modulating the expression of IL-1Ra and IL-1-related molecules and their release in the surrounding microenvironment.

Heparin coating of extracorporeal circuits inhibits cytokine release from mononuclear cells during cardiac operations.

PURPOSE: To evaluate whether the production of interleukin 2 (IL 2), interleukin 6 (IL 6) and interleukin 10 (IL 10) from stimulated peripheral blood mononuclear cells (PBMC) was affected by coating extracorporeal circuits in patients undergoing cardiopulmonary bypass (CPB). In addition, postoperative clinical parameters were compared between patients with heparin-coated and uncoated CPB. DESIGN: Prospective, controlled in vivo/ex vivo study. PROCEDURE: Blood samples were drawn immediately before, at the end and 24 hours after the end of CPB using either a conventional circuit (n=10) or a heparin-coated circuit (n=10) in patients undergoing CPB. Cytokine release on the supernatants of activated PBMC was detected. Cardiopulmonary parameters were measured before CPB, at ICU admission, 3 hours and 24 hours after ICU admission in both groups of patients. Statistical difference intragroups and between groups were investigated with the analysis of variance for repeated measures. RESULTS: IL 6 and IL 10 release was significantly less (p<0.05) in the heparin-coated group. No differences in clinical parameters were observed between the two groups. CONCLUSIONS: These results suggest that with the use of heparin-coated circuits there is a lower production of IL 6 and IL 10 from isolated PBMC than with uncoated circuits.

Thrombin regulates the expression of proangiogenic cytokines via proteolytic activation of protease-activated receptor-1.

In addition to its central role in blood coagulation and hemostasis, human alpha-thrombin is a growth factor for a variety of cell types, including monocytes and endothelial cells, involved in the control of angiogenesis. Different cytokines produced by mononuclear cells have been implicated in angiogenic processes associated with tissue repair and certain human malignancies. We have previously shown that thrombin enhances proliferative responses in T lymphocytes. More recently, we reported that interferon-gamma-differentiated monocytes have increased expression of protease-activated receptor-1 (PAR-1) and increased thrombin binding. Since cytokines may be involved directly and indirectly in angiogenesis, we initiated studies to determine thrombin effects on the induction of cytokines, such as interleukin (IL)-1 and IL-6, in human mononuclear cells. IL-1 and IL-6 protein expression was significantly enhanced by thrombin (P<.05), as determined by enzyme-linked immunosorbent assay (ELISA). Treating mononuclear cells with the PAR-1 peptide, SFLLRN, has effects similar to those of thrombin. Thus, it appears that these thrombin effects are mediated through activation of PAR-1. These results confirm that thrombin is a strong activator of monocytes and could be involved in angiogenesis by inducing cytokines that could enhance the angiogenic process in tissue repair.

Hypoxia modulates cyclin and cytokine expression and inhibits peripheral mononuclear cell proliferation.

Previously, we found that hypoxia can deeply affect the production of cytokines in human peripheral mononuclear cells (PBMC). Here, we demonstrated that the cycle progression of hypoxic PBMC, cultured in the presence or not of a specific T cell activator such as phytohaemagglutinin (PHA), was delayed when compared with aerobic cultures. This delay was accompanied by a decrease of the expression of specific cyclins associated to cell cycle progression phases. Ribonuclease Protection Assay (RPA) studies reveal a decrease in the expression of cyclin A and B in PHA-stimulated PBMC kept for 40 hr under hypoxic condition (2% O(2)), when compared with aerobic cultures (20% O(2)). In concomitance, a decrease of cyclin D2 expression was present after 16 hr of hypoxic treatment. However, the decrease was transient and disappeared after 40 hr of hypoxic treatment. Furthermore, cyclin C expression was not affected by hypoxia. Hypoxia-induced cyclin modulation was accompanied by an increased synthesis of interleukin (IL)-2 and IL-4, analyzed by ELISA. By evaluating these results, it appears that hypoxia induces a growth suppressive state in mitogen-activated PBMC by inhibiting the synthesis of mitotic cyclins A and B. However hypoxic PBMC maintain their viability and capability of producing stimulatory cytokines, after mitogen treatment. This should be important in local hypoxia, usually associated with necrotic areas, in inflammation, and infections, where T lymphocyte capability of producing stimulatory cytokines is desirable.

Interleukin 10 production in patients undergoing cardiopulmonary bypass: evidence of inhibition of Th-1-type responses.

The cardiopulmonary bypass (CPB) procedure has long been associated with a generalized immunosuppression. To understand further the cytokine-mediated regulation of the complex physiological and immunological changes induced by CPB, the authors decided to investigate whether CPB affects the release of interleukin (IL)-10, as well as other cytokines, in correlation to the inhibition of T cell responses. Using phytohaemagglutinin (PHA) as mitogen and peripheral blood mononuclear cells (PBMC) isolated from patients undergoing CPB, we investigated whether this procedure has an effect on the secretion of different patterns of cytokines (Th1- and Th2-type) and PBMC proliferation. In all patients, CPB significantly enhances IL-10 and IL-6 production in resting and PHA-stimulated PBMC. On the other hand, IL-2 production, in response to PHA, was significantly diminished. Reduced IL-2 and enhanced IL-10 production were associated with a significant decrease in PBMC proliferation. Immunosuppression was also associated to lymphopenia, while neutrophil counts were significantly enhanced. These results show that after CPB there is a transient but clear unbalanced immune response demonstrated by a differentiated production of Th1- and Th2-type cytokines. The release of different patterns of cytokines observed after CPB may be helpful in understanding and preventing the development of infectious and immune complications in surgical procedure employing CPB.

Thrombin receptor expression and responsiveness of human monocytic cells to thrombin is linked to interferon-induced cellular differentiation.

Human thrombin has been shown to stimulate monocyte chemotaxis, phagocytosis, and interleukin (IL8) production, but the mechanisms responsible for stimulation are not well defined. In some cells, thrombin stimulation of proliferation appears to require both cleavage of the proteolytically activated receptor for thrombin (PAR1) and activation of a nonproteolytically activated thrombin receptor (N-PAR), while in others activation of either receptor alone may be sufficient for stimulation. We, therefore, have initiated studies to address thrombin receptor expression and cell responsiveness to thrombin in interferon gamma (IFNgamma)-differentiated and nondifferentiated U937 monocytic cells. Northern blot analysis shows that PAR1 expression is upregulated upon differentiation. Experiments with biotinylated and 125I-thrombin show that specific thrombin binding is dramatically increased by differentiation although it is not clear if this binding is to PAR1 or to a separate binding component such as N-PAR which is present on fibroblasts and other cells. Addition of thrombin at concentrations of 1-10 microg/ml (30-300 nM, concentrations where specific thrombin binding is observed) stimulates proliferation of IFNgamma-differentiated U937 cells but not of undifferentiated U937 cells. Thrombin also stimulates interleukin-6 (IL6) production in IFNgamma-differentiated U937 cells. Moreover, thrombin induces high levels of IL6, interleukin-1beta (IL1beta), and tumor necrosis factor-alpha (TNF alpha) production by peripheral blood mononuclear cells (PBMC) and monocytes. These results show that differentiated U937 cells and mature PBMC are responsive to thrombin whereas nondifferentiated U937 are not. Further, this responsiveness appears to correlate with expression of PAR1 and to a dramatic increase in specific thrombin binding. That thrombin stimulates cytokine production and proliferation in populations of differentiated monocytes suggests that thrombin may be an important regulator of inflammation and wound healing.

Hypoxia affects cytokine production and proliferative responses by human peripheral mononuclear cells.

We have shown that hypoxia (2% O2 approximately pO2 14 mmHg) as opposed to O2 atmospheric pressure (20.9% O2 approximately pO2 140 mmHg) can deeply affect the production of cytokines in human peripheral mononuclear cells (PBMC) in the presence or absence of a specific T-cell activator such as phytohemagglutinin (PHA). In hypoxia, interleukin (IL)-2, IL-4, and interferon (IFN)-gamma production increased by 110, 70, and 50% over that of controls, respectively, in PHA-stimulated PBMC (P < 0.05). Moreover, in hypoxia, IL-6 production was significantly enhanced in both resting and PHA-stimulated PBMC by 36 and 37%, respectively (P < 0.05). However, in hypoxia, IL-10 production decreased in both resting and stimulated PBMC, being 80 and 67% of controls, respectively (P < 0.05). PBMC proliferation was not significantly affected by hypoxia, although PBMC susceptibility to PHA was about 80% of that of the control (P < 0.05) after 40 hr of treatment, whereas the cycle progression of hypoxic PBMC was delayed. From an evaluation of these results, hypoxia apparently modifies the production of cytokines by PBMC. These results have both theoretical and practical interest because local hypoxia is very common in several conditions, such as inflammation and local ischemia, and is a host-nonspecific defense against infection. Furthermore, these results suggest a differential pattern of cytokine production in vivo in hypoxic tissues.