Thymosin alpha 1 modulates the expression of high affinity interleukin-2 receptors on normal human lymphocytes

A Randomized Controlled Study for the Evaluation of the Activity of a Triple Combination of Zidovudine, Thymosin-α1 and Interferon-α in HIV-Infected Individuals with CD4 Counts between 200 and 500 cells/mm3

Our objective was to determine the safety and the activity of thymosin-α1 (Tα1) plus interferon-α (IFN-α) and zidovudine in human immunodeficiency virus (HIV)-infected patients with CD4 counts between 200 and 500 cells/mm3. The study was multicentre, Phase II, randomized and open label. Patients were randomized to receive triple therapy, or zidovudine plus IFN-α, or zidovudine alone. Ninety-two patients were enrolled. After 12 months, in the triple combination group there was a median increase from baseline of 69 CD4 cells/mm3; a decrease of 52 cells/mm3 and of 65.5 cells/mm3 was seen in the zidovudine plus IFN-α and in the zidovudine monotherapy groups, respectively. In the triple combination arm the increase in mean CD4 counts was significantly greater than that observed in the other arms, particularly in patients with baseline CD4 counts less than 350 cells/mm3. The plasma HIV RNA load in triple therapy group showed a mean peak decrease from baseline of 16 000 copies/ml after 5 months (versus a decrease of 5000 copies/ml in the zidovudine monotherapy group) that was sustained at 12 months (versus a mean increase of 7000 copies/ml in the zidovudine monotherapy group at 12 months). The triple combination was superior to both the other arms in terms of virological and immunological response. Our study, although based on regimens of clearly sub-optimal antiretroviral potency, addressed the issue of combined therapy directed at two different targets: the HIV replicative cycle and the immune system. The use of immunomodulating agents deserves further investigation in the context of more potent antiretroviral combinations.

A Reappraisal of Thymosin Alpha1 in Cancer Therapy

Thymosin alpha1 (Tα1), an endogenous peptide first isolated from the thymic tissue in the mid-sixties, has gained considerable attention for its immunostimulatory activity that led to its application to diverse pathological conditions, including cancer. Studies in animal models and human patients have shown promising results in different types of malignancies, especially when Tα1 was used in combination with other chemo- and immune therapies. For this reason, the advancements in our knowledge on the adjuvant role of Tα1 have moved in parallel with the development of novel cancer therapies in a way that Tα1 was integrated to changing paradigms and protocols, and tested for increased efficacy and safety. Cancer immunotherapy has recently experienced a tremendous boost following the development and clinical application of immune checkpoint inhibitors. By unleashing the full potential of the adaptive immune response, checkpoint inhibitors were expected to be very effective against tumors, but it soon became clear that a widespread and successful application was not straightforward and shortcomings in efficacy and safety clearly emerged. This scenario led to the development of novel concepts in immunotherapy and the design of combination protocols to overcome these limitations, thus opening up novel opportunities for Tα1 application. Herein, we summarize in a historical perspective the use of Tα1 in cancer, with particular reference to melanoma, hepatocellular carcinoma and lung cancer. We will discuss the current limitations of checkpoint inhibitors in clinical practice and the mechanisms at the basis of a potential application of Tα1 in combination protocols.

Serum thymosin alpha 1 levels in normal and pathological conditions

INTRODUCTION

Thymosin alpha 1 (Ta1) is a natural occurring peptide hormone that is crucial for the maintenance of the organism homeostasis. It has been chemically synthesized and used in diseases where the immune system is hindered or malfunctioning.

AREAS COVERED

Many clinical trials investigate the Ta1 effects in patients with cancer, infectious diseases and as a vaccine enhancer. The number of diseases that could benefit from Ta1 treatment is increasing. To date, questions remain about the physiological basal levels of Ta1 and the most effective dose and schedule of treatment. Evidence is growing that diseases characterized by deregulation of immune and/or inflammatory responses are associated with serum levels of Ta1 significantly lower than those of healthy individuals: to date, B hepatitis, psoriatic arthritis, multiple sclerosis and sepsis. The sputum of cystic fibrosis patients contains lower levels of Ta1 than healthy controls. These data are consistent with the role of Ta1 as a regulator of immunity, tolerance and inflammation.

EXPERT OPINION

Low serum Ta1 levels are predictive and/or associated with different pathological conditions. In case of Ta1 treatment, it is crucial to know the patient's baseline serum Ta1 level to establish effective treatment protocols and monitor their effectiveness over time.

Thymosin α1 Interacts with Hyaluronic Acid Electrostatically by Its Terminal Sequence LKEKK

Thymosin α1 (Tα1), is a peptidic hormone, whose immune regulatory properties have been demonstrated both in vitro and in vivo and approved in different countries for treatment of several viral infections and cancers. Tα1 assumes a conformation in negative membranes upon insertion into the phosphatidylserine exposure as found in several pathologies and in apoptosis. These findings are in agreement with the pleiotropy of Tα1, which targets both normal and tumor cells, interacting with multiple cellular components, and have generated renewed interest in the topic. Hyaluronan (HA) occurs ubiquitously in the extracellular matrix and on cell surfaces and has been related to a variety of diseases, and developmental and physiological processes. Proteins binding HA, among them CD44 and the Receptor for HA-mediated motility (RHAMM) receptors, mediate its biological effects. NMR spectroscopy indicated preliminarily that an interaction of Tα1 with HA occurs specifically around lysine residues of the sequence LKEKK of Tα1 and is suggestive of a possible interference of Tα1 in the binding of HA with CD44 and RHAMM. Further studies are needed to deepen these observations because Tα1 is known to potentiate the T-cell immunity and anti-tumor effect. The binding inhibitory activity of Tα1 on HA-CD44 or HA-RHAMM interactions can suppress both T-cell reactivity and tumor progression.

Thymic Hormones and Cytokines

The discovery and the first studies on thymic hormones (TH) are historically linked with their role on the developmental events of T lymphocytes that occur within the thymus. However, paradoxically, during the most recent years, much more information about the effects of TH on mature effector cells, in relation with those indicating their real functions during the T-cell differentation, have been, in fact, available.

Here we report an update discussion concerning the possible role of the cooperation between TH and cytokines in T-cell development. Moreover we illustrate the results obtained by us and other authors, demonstrating a strict connection between the action of thymosins, a family of peptides first isolated and purified from calf thymus (1), and that of cytokines.

A modified thymosin alpha 1 inhibits the growth of breast cancer both in vitro and in vivo: suppressment of cell proliferation, inducible cell apoptosis and enhancement of targeted anticancer effects

Thymosin alpha 1 (Tα1) is commonly used for treating several diseases; however its usage has been limited because of poor penetration of the target tissue, such as tumor cells. In the present study, Tα1-iRGD, a peptide by conjugating Tα1 with the iRGD fragment, was evaluated its performance in MCF-7 and MDA-MB-231 human breast cancer cells. Compared with the wild-type peptide, Tα1-iRGD was more selective in binding tumor cells in the cell attachment assay. Furthermore, the MTT assay confirmed that Tα1-iRGD proved more effective in significantly inhibiting the growth of MCF-7 cells in contrast to the general inhibition displayed by Tα1. Further, conjugation of Tα1 with iRGD preserved the immunomodulatory activity of the drug by increasing the proliferation of mouse spleen lymphocytes. Further, compared with Tα1 treatment, Tα1-iRGD treatment of MCF-7 cells considerably increased the number of cells undergoing apoptosis, resulting in a dose-dependent inhibition of cancer cell growth, which was associated with a much better effect on up-regulation of the expression of BCL2-associated X protein (Bax), caspase 9, etc. More importantly, treatment with Ta1-iRGD was more efficacious than treatment with Ta1 in vivo. This study highlights the importance of iRGD on enhancement of cell penetration and tumor accumulation. In summary, our findings demonstrate that the novel modified Tα1 developed in this study has the potential to be used for treating breast cancer.

Immune Modulation with Thymosin Alpha 1 Treatment

Thymosin alpha 1 (Ta1) is a peptide originally isolated from thymic tissue as the compound responsible for restoring immune function to thymectomized mice. Ta1 has a pleiotropic mechanism of action, affecting multiple immune cell subsets that are involved in immune suppression. Ta1 acts through Toll-like receptors in both myeloid and plasmacytoid dendritic cells, leading to activation and stimulation of signaling pathways and initiation of production of immune-related cytokines. Due to the immune stimulating effects of Ta1, the compound would be expected to show utility for treatment of immune suppression, whether related to aging or to diseases such as infection or cancer. Extensive studies in both the preclinical and clinical setting will be summarized in the subsequent sections. These studies have demonstrated improvements in immune system cell subsets and the potential of Ta1 for the treatment of a range of diseases.

Historical review of thymosin α 1 in infectious diseases

INTRODUCTION

Thymosin α 1 (Tα1) is a peptidic biological response modifier, which plays a significant role in activating and regulating various cells of the immune system. For the above-mentioned activities it is expected to exert a clinical benefit in the treatment of diseases where the immune system is altered.

AREAS COVERED

Several clinical trials have been carried out with Tα1 for treatment or prevention of many different infectious diseases such as hepatitis B and C, sepsis and Aspergillosis in bone marrow-transplanted patients. Data available on the use of Tα1 in infectious disease as well as a vaccine enhancer will be reviewed to possibly generate new working hypothesis.

EXPERT OPINION

Tα1 has been widely used in thousands of patients. Nevertheless, there are some issues that have not yet been properly addressed (i.e., dose, schedule, combination treatments, end-points to be evaluated in clinical trials). In the most recent clinical trials Tα1 has been used at higher doses than those commonly used in the past showing a direct proportionality between the dose and the effect. The safety profile of Tα1 is excellent and it is virtually devoid of toxicity.

A tumor-penetrating peptide modification enhances the antitumor activity of thymosin alpha 1

A serious limitation of numerous antitumor drugs is the incapacity to penetrate solid tumors. However, addition of an RGD fragment to peptide drugs might solve this problem. In this study, we explored whether the introduction of a permeability-enhancing sequence, such as iRGD (CRGDK/RGPD/EC) fragments, would enhance the activity of thymosin alpha 1 (Tα1). The modified Tα1 (Tα1-iRGD) was successfully expressed and purified, and the in vitro assay showed that Tα1-iRGD presented a similar activity as Tα1 in promoting proliferation of mouse splenocytes. Meanwhile, cell adhesion analysis revealed that Tα1-iRGD exhibited more specific and greater binding with tumor cells compared with Tα1. Furthermore, the iRGD fragment evidently enhanced the basal ability of Tα1 to inhibit proliferation of cancer cells in vitro, particularly of mouse melanoma cell line B16F10 and human lung cancer cell line H460. Our findings indicated that the addition of an iRGD fragment increased the anti-proliferative activity of Tα1 against cancer cells by improving the ability of Tα1 to penetrate the tumor cells. This study highlighted the important roles of an iRGD sequence in the therapeutic strategy of Tα1-iRGD. Thus, Tα1-iRGD could be a novel drug candidate for cancer treatment.

Thymosin α1 continues to show promise as an enhancer for vaccine response

Thymosin α1 (Tα1) is an immune-modulating peptide that can be expected to improve response to vaccinations, as stimulated dendritic cells and T cells can act in concert to increase antibody production along with an improved cytotoxic response from the T cells themselves. Tα1 demonstrated efficacy in preclinical studies; subsequently, it was shown to enhance response to vaccinations in difficult-to-treat populations, including individuals immune suppressed due to age or hemodialysis, and leading to a decrease in later infections. During the 2009 pandemic outbreak of H1N1 influenza, mouse and ferret studies confirmed that the use of higher doses of Tα1 allowed for fewer injections than those used in the previous clinical studies. In addition, a clinical study with Focetria™ MF59-adjuvanted monovalent H1N1 vaccine showed that treatment with Tα1 twice provided an earlier and greater response to the vaccine (P < 0.01).

Thymosin α1 and cancer: action on immune effector and tumor target cells

Since it was first identified, thymosin alpha 1 (Tα1) has been characterized to have pleiotropic effects on several pathological conditions, in particular as a modulator of immune response and inflammation. Several properties exerted by Tα1 may be attributable to a direct action on lymphoid cells. Tα1 has been shown to exert an immune modulatory activity on both T cell and natural killer cell maturation and to have an effect on functions of mature lymphocytes, including stimulating cytokine production and cytotoxic T lymphocyte-mediated cytotoxic responses. In previous studies we have shown that Tα1 increases the expression of major histocompatibility complex class I surface molecules in murine and human tumor cell lines and in primary cultures of human macrophages. In the present paper, we describe preliminary data indicating that Tα1 is also capable of increasing the expression of tumor antigens in both experimental and human tumor cell lines. This effect, which is exerted at the level of the target tumor cells, represents an additional factor increasing the antitumor activity of Tα1.

Molecular characterization, tissue distribution, subcellular localization and actin-sequestering function of a thymosin protein from silkworm

We identified a novel gene encoding a Bombyx mori thymosin (BmTHY) protein from a cDNA library of silkworm pupae, which has an open reading frame (ORF) of 399 bp encoding 132 amino acids. It was found by bioinformatics that BmTHY gene consisted of three exons and two introns and BmTHY was highly homologous to thymosin betas (Tβ). BmTHY has a conserved motif LKHTET with only one amino acid difference from LKKTET, which is involved in Tβ binding to actin. A His-tagged BmTHY fusion protein (rBmTHY) with a molecular weight of approximately 18.4 kDa was expressed and purified to homogeneity. The purified fusion protein was used to produce anti-rBmTHY polyclonal antibodies in a New Zealand rabbit. Subcellular localization revealed that BmTHY can be found in both Bm5 cell (a silkworm ovary cell line) nucleus and cytoplasm but is primarily located in the nucleus. Western blotting and real-time RT-PCR showed that during silkworm developmental stages, BmTHY expression levels are highest in moth, followed by instar larvae, and are lowest in pupa and egg. BmTHY mRNA was universally distributed in most of fifth-instar larvae tissues (except testis). However, BmTHY was expressed in the head, ovary and epidermis during the larvae stage. BmTHY formed complexes with actin monomer, inhibited actin polymerization and cross-linked to actin. All the results indicated BmTHY might be an actin-sequestering protein and participate in silkworm development.

Intracellular and extracellular cytokine-like functions of prothymosin α: implications for the development of immunotherapies

Prothymosin α (ProTα) is a 12.5-kDa, highly acidic protein widely distributed in different cell types expressed intracellularly and extracellularly. ProTα does not contain a secretion-signal sequence and is released by a nonclassical secretory pathway with a cargo protein. New findings on the extracellular function of ProTα have yielded exciting insights into the cytokine-like functions of this host protein that stimulates type I interferon via Toll-like receptor 4. Here, we discuss the intracellular function of ProTα, how new findings of cytokine-like activities of ProTα aid our understanding of mechanisms that direct ProTα functions, and the potential application of these new insights to the development of immunotherapies.

Thymosin alpha 1: biological activities, applications and genetic engineering production

Thymosin alpha 1 (Tα1), a 28-amino acid peptide, was first described and characterized from calf thymuses in 1977. This peptide can enhance T-cell, dendritic cell (DC) and antibody responses, modulate cytokines and chemokines production and block steroid-induced apoptosis of thymocytes. Due to its pleiotropic biological activities, Tα1 has gained increasing interest in recent years and has been used for the treatment of various diseases in clinic. Accordingly, there is an increasing need for the production of this peptide. So far, Tα1 used in clinic is synthesized using solid phase peptide synthesis. Here, we summarize the genetic engineering methods to produce Tα1 using prokaryotic or eukaryotic expression systems. The effectiveness of these biological products in increasing the secretion of cytokines and in promoting lymphocyte proliferation were investigated in vitro studies. This opens the possibility for biotechnological production of Tα1 for the research and clinical applications.

A randomized controlled trial of thymalfasin plus transarterial chemoembolization for unresectable hepatocellular carcinoma

PURPOSE

Patients with advanced hepatocellular carcinoma (HCC) have few treatment options. Thymalfasin (thymosin α-1) is an immunomodulator that may increase response to ablative therapy through direct anti-tumor action or enhanced protection against infections. We compared transarterial chemoembolization (TACE) plus thymalfasin with TACE alone for unresectable HCC.

METHODS

In this phase II, randomized trial, 25 patients received either TACE plus thymalfasin (1.6 mg SC, 5 times weekly; n = 14) or TACE alone (n = 11) for 24 weeks. Response was defined as transition to transplant eligibility or lack of disease progression through week 72. Survival was assessed through 24 months post-treatment.

RESULTS

Eight of fourteen (57.1%) patients in the TACE + thymalfasin group versus 5 of 11 (45.5%) patients in the TACE-only group became responders (P = 1.0). Four of fourteen TACE + thymalfasin patients versus none of 11 TACE-only patients became eligible for transplant. Median overall survival time was 110.3 weeks for the TACE + thymalfasin group versus 57.0 weeks for the TACE-only group (P = 0.45). Seven patients in each group experienced serious adverse events; there were no bacterial infections in the TACE + thymalfasin group versus 4 in the TACE-only group. There were 3 deaths in the TACE + thymalfasin group and 5 in the TACE-only group.

CONCLUSIONS

In patients with unresectable HCC, TACE + thymalfasin resulted in numerically higher rates of survival and tumor response, including transplant candidacy, with fewer bacterial infections, than TACE alone. Treatment regimens for HCC including thymalfasin as an immunomodulator should be evaluated in larger trials.

Expression and hydroxylamine cleavage of thymosin alpha 1 concatemer

Human thymosin alpha 1 (Tα1) is an important peptide in the development and senescence of immunological competence in human, and many studies have reported the expression of this peptide. In this study, we designed and synthesized the Tα1 gene according to the E. coli codon usage preference and constructed a 6×Tα1 concatemer. The latter was inserted into an E. coli expression vector pET-22b (+), and transformed into E. coli BL21 (DE3). After induction with IPTG, the concatemer protein was successfully expressed in E. coli then cleaved by hydroxylamine to release the Tα1 monomer. Gly-SDS-PAGE and mass spectrometry confirmed that the recombinant protein was cleaved as intended. The bioactivity of the Tα1 monomer was analyzed by lymphocyte proliferation and by mitochondrial activity in two different tumor cell lines. This study provides a description of the preparation of a bioactive Tα1, which may prove useful in future biomedical research.

Influence of prothymosin-alpha on HIV-1 target cells

The important role of CD8(+) T cells in controlling HIV-1 infection through the innate as well as the adaptive immune system is well established. In addition to the major histocompatibility complex (MHC)-dependent cytotoxic activity of CD8(+) T cells, they produce soluble factors that suppress HIV-1 replication in an MHC-independent manner. Several of those factors have been identified, including beta-chemokines, Rantes, MIP-1alpha, MIP-1beta, and MDC. We previously identified that prothymosin alpha (ProTalpha) in the conditioned medium of HVS transformed CD8(+) T cells was a potent inhibitor of HIV-1 replication following proviral integration. In this report we further characterize the anti-HIV-1 activity of ProTalpha by demonstrating its target-cell specificity, distinction from additional inhibitors of HIV-1 transcription in CD8(+) T cell supernatants, as well as the differential regulation of host cell antiviral genes that could impact HIV-1 replication. These genes include a number of transcription factors as well IFN-alpha-inducible genes including PKR, IRF1, and Rantes, in the absence of induction of IFN-alpha. These data suggest that the anti-HIV-1 activity of ProTalpha is mediated through the modulation of a number of genes that have been reported to suppress HIV-1 replication including the dysregulation of transcription factors and the induction of PKR and Rantes mRNA.

Immunopharmacology of thymosin alpha1 and cytokine synergy

Thymosin alpha1 (Talpha1) is a 28 amino acid biologically active protein cleaved from positions 2-29 of a precursor protein, prothymosin alpha. Since its discovery, Talpha1 has been administered to animals and humans in a wide variety of settings and its pharmacologic effects are to enhance cellular immunity. Talpha1 administration is highly effective in settings where irradiation, chemotherapy, tumor burden, or immune senescence have caused a reduction of T cell number and/or function. Recent in vitro studies, including the one reported here, suggest that Talpha1 may act via pathways commonly used by various cytokines. This raises the possibility that Talpha1 and cytokines may have synergistic activity through potentiation of cytokine activity by Talpha1. Improved control of tumor growth when tumor-bearing mice were treated with Talpha1 and high doses of IL-2 has been previously reported. We extended those studies with the Lewis lung carcinoma mouse model using IRX-2, a natural well-defined biologic containing multiple cytokines, in combination with Talpha1 (IRX-3). Although IRX-2 was effective alone (using doses that contain significantly less IL-2 than in most typical studies), adding Talpha1 led to significant improvement in survival of the tumor-bearing mice. Based on these observations, the immunopharmacology of Talpha1 predicts an important clinical role for Talpha1 in the restoration of cellular immune activity when used in combination with cytokines. Patients who experience immune suppression due to the presence of tumor, irradiation, and/or chemotherapy or aging of the host would most benefit from this treatment combination.

Thymosin alpha1: a historical overview

Thymosin alpha 1 (Talpha1), initially isolated from thymus, was characterized by Allan Goldstein in 1977. Since the beginning, our studies were aimed at evaluating its immunomodulating effects when used in combination with cytokines and chemotherapy. Combination therapies have now proved to be effective in inhibiting tumoral growth and in controlling infective diseases especially in the immunocompromised host. More recent studies showed that Talpha1 molecule increased major histocompatibility complex (MHC) class-1 and Toll-like receptor expression as well as cytokine production, suggesting its immunoregulatory role. Overall these results led us to start pilot clinical trials on patients with hepatitis C and cancer.

Liposomal plasmid DNA encoding human thymosin alpha and interferon omega potently inhibits liver tumor growth in ICR mice

AIM

To evaluate the potential therapeutic effect of liposomal gene delivery, genes encoding for human thymosin alpha1 (Talpha1) and interferon omega1 were injected via the tail vein into mice bearing a Hep-A-22 liver tumor.

METHODS

The cDNA of human Talpha1 and interferon omega1 were obtained by synthesis or reverse transcription-polymerase chain reaction (RT-PCR), respectively. Eukaryotic expressing vectors pIRES2, encoding Talpha1 and/or interferon omega1, were constructed and injected with liposome via the tail vein into ICR mice bearing a Hep-A-22 tumor. The potency of tumor inhibition was evaluated when three treated groups were compared with the group receiving the empty vector. Apoptosis of tumor cells was investigated by analyzing DNA fragmentation.

RESULTS

Only the group treated with dual-gene plasmid reached an eligible level of tumor inhibition (43%). The difference in tumor weight was statistically significant between the Talpha1 gene or the interferon omega1 gene treated groups and the control (P<0.05), and highly significant between the dual-gene treated group and the control (P<0.01). DNA ladder was observed in the tumor cells from the purpose gene treated groups but not from the control.

CONCLUSION

The dual-gene plasmid-liposome complex showed more potent inhibition than the single gene constructs on the growth of Hep-A-22 tumor cells in mice, which may be attributed to indirect and additive induction of apoptosis in tumor cells by increased expression of Talpha1 and interferon omega1.

Effects of thymosin α1 on immune function in perioperative patients with primary liver cancer

AIM: To investigate the immune state of patients with primary hepatic carcinoma (PHC) liver cancer after treatment with thymosin α1 during perioperative period.

METHODS: One hundred and three patients with PHC were divided into two groups. The patients in group A (n = 35) received hepatectomy plus thymosin α1 treatment and the patients in group B (n = 68) underwent hepatectomy only. Twenty normal blood donors were used as controls. Before and 7, 14, and 21 d after treatment, the changes of serum CD3⁺, CD4⁺CD8⁺, CD8⁺CD28⁺, and CD16⁺CD56⁺ were measured by flow cytometry. MTT colometric assay was performed to detect the activity of interleukin-2 (IL-2).

RESULTS: Before hepatectomy and thymosin α1 treatment, serum CD8⁺, CD4⁺/CD8⁺, CD8⁺CD28⁺, CD16⁺/CD56⁺ and IL-2 were markedly lower in group A than that in the controls (F = 8.2, P = 0.005), while after treatment, serum CD4⁺/CD8⁺, CD16⁺CD56⁺ were significantly increased (F = 8.4, P = 0.004). Seven days after hepatectomy, serum CD4⁺/CD8⁺, CD8⁺CD28⁺, CD16⁺/CD56⁺ were elevated (F = 4.7, P = 0.005 or F= 3.5, P = 0.04), and 14 d after hepatectomy, the level of serum IL-2 was inceased (F = 3.6, P = 0.03). For group B, serum CD4⁺, CD8⁺, CD4⁺/CD8⁺, CD8⁺/CD28⁺, CD16⁺/CD56⁺ were notably reduced 7 d after hepatectomy (F = 5.4, P = 0.006 or F = 3.6, P = 0.02). The levels of serum CD8⁺ and CD8⁺/CD28⁺ were still lower (F = 5.0, P = 0.007) at 14 d than those before operation, but the levels of CD4⁺, CD4⁺/CD8⁺, and CD16⁺/CD56⁺ restored to some extent. At 21 d, serum CD8⁺ level still didn't restore (F = 6.3, P = 0.000). The levels of serum CD3⁺, CD8⁺, CD4⁺/CD8⁺, CD8⁺/CD28⁺, CD16⁺/CD56⁺ were all lower in group B than those in group A (F = 7.2, P = 0.001).

CONCLUSION: The immunosuppression exists in patients with PHC, and it can be aggravated in early stage after hepatectomy. However, the immunosuppression can be alleviated by thymosin α1 treatment during perioperative period.

Roles of thymosins in cancers and other organ systems

Thymosins are small peptides, originally identified from the thymus, but now known to be more widely distributed in many tissues and cells. Thymosins are divided into three main groups, alpha-, beta-, : and gamma-thymosins, based on their isoelectric points. alpha-thymosins (ProTalpha, Talphal) have nuclear localization and are involved in transcription and/or DNA replications; whereas beta-thymosins (Tbeta4, Tbeta10, Tbetal5) have cytoplasmic localization and show high affinity to G-actin for cell mobility. Furthermore, it is well known that both alpha- and beta-thymosins play important roles in modulating immune response, vascular biology, and cancer pathogenesis. More importantly, thymosins may have significant clinical applications. They may serve as molecular markers for the diagnosis and prognosis of certain diseases. In addition, they could be molecular targets of certain diseases or be used as therapeutic agents to treat certain diseases. However, the molecular mechanisms of action of thymosins are largely unknown. This review not only presents recent advances of basic science research of thymosins and their clinical applications but provides thoughtful views for future directions of investigation on thymosins.

Thymosin alpha(1) in combination with cytokines and chemotherapy for the treatment of cancer

Multiple therapeutic approaches have been tested in different experimental tumour models and in human cancers. Most part of them are based on the hypothesis that the inhibition of tumour growth requires a strong immune response in which a main role is played by CTLs. It is known, however, that an efficient CTL response requires expression of tumour antigens, MHC class I surface molecules presentation, expression of different co-stimulatory molecules and a sustained generation and proliferation of specific cytotoxic CD8+ cells with an efficient CD4+ cooperation. In this context, our group has extensively explored a protocol of combined therapy consisting of the use of chemotherapeutic agents associated with thymosin alpha 1 (Talpha 1) and different cytokines, whose efficacy has been demonstrated in experimental models as well as in human cancers. In this manuscript, the main data supporting a pivotal role of Talpha 1 in such combination protocols are reviewed. In particular, a special mention of the molecular mechanisms underlying the effects of Talpha 1 on immune effector cells as well as on target tumour cells is provided. These data contribute to explain the mechanism of action of Talpha 1, when used in combination therapy, for the treatment of cancer and provide new insights in predicting further possible applications of this peptide in other pathological conditions.

Modulatory role of thymosin-alpha-1 in normal bone-marrow haematopoiesis and its effect on myelosuppression in T-cell lymphoma bearing mice

In continuation with the earlier and ongoing studies on Thymosin-alpha-1 (Talpha1) exerting its immunomodulatory effects on various components of the immune system including T-cells, NK-cells, blood lymphocytes and macrophages, the role of Talpha1 in normal bone-marrow haematopoiesis has been investigated in the present study. The haematopoietic alterations associated with the growth of murine T-cell lymphoma, Dalton's Lymphoma (DL) and subsequently its restoration by Talpha1 was also investigated. It is observed that the non-adherent bone-marrow cells from normal mice (N-BMCs) exhibited enhanced proliferation on in vitro treatment with Talpha1 (dose range of 1-100 ng/ml) with maximal response at 100 ng/ml of Talpha1. In vitro stimulation with 100 ng/ml of Talpha1 also resulted in increased myeloid colony formation, as manifested by the rise in total number of colonies, frequency of the individual colony types and their size. This response was further upregulated in the presence of various colony stimulating factors (CSFs) like MCSF, GMCSF, GCSF and IL-3. Similarly, in vivo administration of Talpha1 (a single intraperitoneal injection of 10 microg per mouse) to normal mice also resulted in enhanced proliferation and colony formation by BMCs as compared with BMCs obtained from untreated mice. On the contrary, the progressive growth of T-cell lymphoma in mice led to suppressed myelogenesis, with marked reduction in the total colony numbers and their size. The BMCs from DL-bearing mice (DL-BMCs) displayed a preferential lineage-restricted differentiation towards the granulocytic-type colonies with maximum numbers of CFU-Gs and CFU-GMs, followed by CFU-Ms. However, incubation of DL-BMCs with 100 ng/ml of Talpha1, in vitro restored their suppressed proliferation and colony forming ability (CFA) with significantly enhanced total number of colonies and individual colony types, which further increased in the presence of CSFs. In vivo studies with BMCs from DL-bearing mice treated with single intraperitoneal injection of 10 microg Talpha1/mouse also resulted in significant enhancement in their proliferative as well as colony forming ability in comparison to that of untreated DL-mice. The present observations suggest that Talpha1 can positively modulate the haematopoietic functions of normal murine BMCs, in addition to its myelorestorative role in tumour-bearing mice showing suppressed myelopoiesis.

Treatment of chronic hepatitis D with thymus-derived polypeptide thymic humoral factor-gamma 2: a pilot study

BACKGROUND

Thymic humoral factor-gamma 2 is a thymus-derived synthetic octapeptide, shown to be effective in chronic hepatitis B virus infection; as the latter is needed to support hepatitis D virus, thymic humoral factor-gamma 2 may have a therapeutic role in hepatitis D.

AIM

To evaluate tolerability and efficacy of thymic humoral factor-gamma 2 in chronic hepatitis D.

METHODS

Intramuscular thymic humoral factor-gamma 2, 40 microg, was given for 15 consecutive days and twice weekly for 22 additional weeks to adult patients with chronic hepatitis D virus hepatitis.

RESULTS

A total of 11 patients (male/female 9/2, mean age 45.9 years] completed the treatment period, 10 the 6-month follow-up. At baseline, hepatitis D virus-RNA was positive in 8/11 (73%) patients. During treatment, hepatitis D virus-RNA became undetectable in 3/8 (37%), decreased in 1/8 (13%), remained unchanged in 4/8 (50%) and persisted undetectable in 3 patients, negative at baseline. During follow-up hepatitis D-viraemia relapsed in all patients but 2, one already negative at baseline. No changes in hepatitis B virus markers occurred. Mean serum alanine aminotransferase levels did not change significantly None of the patients reached normal serum alanine aminotransferase levels.

CONCLUSION

At the doses given, thymic humoral factor-gamma 2 has been of limited efficacy A possible role of thymic humoral factor-gamma 2 in the treatment of chronic hepatitis D requires further dose-finding studies and/or combination with other antivirals.

Involvement of mitogen-activated protein kinases in the signal transduction pathway of bone marrow-derived macrophage activation in response to in vitro treatment with thymosin alpha 1

Thymosin alpha 1 (Talpha1), a 28-amino acid, acidic thymic peptide, is a promising natural biological response modifier (BRM), which augments and regulates the immune network and is thought to be immunostimulatory also. Recently, we have reported the ability of Talpha1 to activate macrophages to tumoricidal state. In the present investigation, the activation of the p42/44 MAP kinase (MAPK)/c-Jun NH2 terminal kinase (JNK) pathway in response to in vitro treatment with Talpha1 in murine bone marrow-derived macrophages (BMDMs) has been demonstrated. The activation and expression of phospho-p42/44 MAPK was dose as well as time dependent with maximum expression occurring at 5-15 min following stimulation with 100 ng/ml of Talpha1. The expression of phospho-p42/44 MAPK was inhibited by the MAPK inhibitor, PD98059, pertussis toxin (PTX), tyrosine kinase inhibitor-genistein and P13K inhibitor-wortmannin. Talpha1-induced BMDM tumoricidal functions like the production of NO and TNF-alpha, the key mediator molecules of macrophage cytotoxicity, were also inhibited by the MAPK inhibitor, PD98059, in a dose-dependent manner. These observations suggest that p42/44 MAPK activation is one of the essential signaling events triggered by Talpha1 and may be responsible for the in vitro activation of BMDMs.

In vitro effect of thymosin-alpha1 and interferon-alpha on Th1 and Th2 cytokine synthesis in patients with chronic hepatitis C

Current evidence suggests that increased expression of Th1-associated cytokines is important for immune-mediated eradication of hepatitis C infection, while an increase in Th2-associated cytokines is associated with persistence of infection. In this study we evaluated the effects of thymosin-alpha1 (TA1), a naturally occurring thymic peptide, and interferon-alpha (IFN-alpha) on cytokine production in peripheral blood mononuclear cells from untreated patients with chronic hepatitis C. We examined the effect of incubation with TA1, IFN-alpha, or both, on production of Th1-associated cytokines (IL-2, IFN-gamma), Th2-associated cytokines (IL-4, IL-10), and synthesis of the antiviral protein 2',5'-oligoadenylate synthetase. TA1 treatment induced a significant increase in production of IL-2 and 2',5'-oligoadenylate synthetase. Smaller increases were also seen after treatment with IFN-alpha, while incubation with TA1 and IFN-alpha together led to an additive or synergistic effect. Incubation with TA1 resulted in a decrease in IL-4 and IL-10, whereas IFN-alpha increased these cytokines. The addition of TA1 to IFN-alpha significantly reversed this IFN-alpha-induced increase. Hence, TA1 treatment could benefit patients with hepatitis C infection by increasing the Th1-type response, fundamental for sustained clearance of hepatitis C; and by decreasing the Th2-type response, associated with persistence of viraemia.

Thymosin alpha1 is a time and dose-dependent antagonist of dexamethasone-induced apoptosis of murine thymocytes in vitro

It is well established that glucocorticoid hormones induce apoptosis in immature developing thymocytes. Thymocyte apoptosis can be modulated by growth factors, anti-oxidants and adhesion receptors. We have previously demonstrated that thymosin alpha1 (Talpha1) antagonizes dexamethasone-induced apoptosis of CD4+CD8+ thymocytes. In the present study, we further characterize the dose and time dependence of Talpha1's antagonism of dexamethasone-induced thymocyte apoptosis. Talpha1 is effective at concentrations ranging from 2 to 100 microg/10(6) thymocytes. Talpha1 pre-treatment is necessary to achieve its anti-apoptotic activity. Talpha1 provides temporary protection to thymocytes by slowing dexamethasone's apoptotic activity up to 12 h post dexamethasone treatment. Additionally, Talpha1's activity is not sensitive to cycloheximide treatment, suggesting Talpha1's activity is independent of protein synthesis. Finally, Talpha1 is unable to antagonize apoptosis induced by the reactive oxygen species, H2O2, suggesting Talpha1's antagonism of dexamethasone occurs at the early stages of dexamethasone-induced apoptosis, prior to the production of reactive oxygen species. This evidence suggests that Talpha1 may provide a mechanism to transiently extend the life of a thymocyte during thymic selection.

Thymosin alpha 1 in the treatment of cancer: from basic research to clinical application

Many studies have explored the effects of immunotherapy, alone or in combination with conventional therapies, on both experimental and human cancers. Evidence has been provided that combined treatments with thymosin alpha 1 (T alpha 1) and low doses of interferon (IFN) or interleukin (IL)-2 are highly effective in restoring several immune responses depressed by tumor growth and/or cytostatic drugs. In addition, when combined with specific chemotherapy, they are able to increase the anti-tumor effect of chemotherapy while markedly reducing the general toxicity of the treatment. The advantages of using this combined chemo-immunotherapeutic approach in experimental and human cancers are reviewed in this issue.

Thymosin alpha(1) application augments immune response and down-regulates tumor weight and organ colonization in BALB/c-mice

The immunomodulatory and antimetastatic/antitumor activity of thymosin alpha(1) (Talpha(1)) was evaluated in BALB/c-mice. Daily subcutaneous application (7 consecutive days, 0.01-10 microg of Talpha(1)/injection per mouse) upregulated the number of thymocytes and peripheral blood cells in tumor bearing mice. To check the influence of Talpha(1) treatment on growth of experimental metastases, RAW H10 lymphosarcoma cells or L-1 sarcoma cells were intravenously injected into BALB/c-mice to establish liver or lung metastases. Local tumor growth was induced by subcutaneous injection of L-1 sarcoma cells. Talpha(1) was subcutaneously administered daily for 7 consecutive days starting 24 h after tumor cell challenge. Organ colonization, as well as local tumor growth, were investigated on day 14 after tumor cell inoculation, and demonstrated a statistically significant (P<0.05) reduction of experimental liver and lung metastases and local tumor growth for Talpha(1) treated mice.

Inhibitory effect of natural and environmental estrogens on thymic hormone production in thymus epithelial cell culture

The present study was carried out to assess the direct effect of natural estrogen and environmental estrogens on thymus epithelial cell (TEC) production/secretion of the thymic hormone thymosin-alpha 1 by using the technique of quantitative high-performance liquid chromatography. The presence of estrogen receptors in the TECs was also investigated. Murine TECs were cultured in the experimental DMEM medium containing various concentrations of natural or environmental estrogens, which was followed by determining the production of thymosin-alpha 1. The production of thymosin-alpha 1 by TECs was significantly inhibited by increasing concentrations of 17beta-estradiol (natural estrogen) over 3 x 10(-11) M, genistein (phytoestrogen) over 3 x 10(-9) M, coumestrol (phytoestrogen) over 3 x 10(-9) M, alpha-zearalanol (livestock anabolic) over 3 x 10(-7) and bisphenol-A (plastic) over 3 x 10(-6) M. Small amounts of estrogen receptor were present in the TECs. The above results clearly indicate that natural and environmental estrogens directly modulate TECs to produce thymic hormone probably through an estrogen receptor mechanism. Furthermore, our finding may be useful for evaluating biological effects of chemicals with estrogenic activity.

Evidence that endogenous thymosin alpha-1 is present in the rat central nervous system

We have previously reported that administration of Thymosin alpha 1 (T-alpha1) can enhance the level of the Nerve Growth Factor and the distribution of its receptor in the developing Central Nervous System (CNS) of rat. To further explore the role of T-alpha1 and verify its presence in cells of rat CNS, we carried out an immunohistochemical study using a polyclonal antibody against T-alpha1. T-alpha1 immunoreactivity was found mainly in neurons of the hippocampus and spinal cord and in several small cells, resembling glial cells, of specific regions of the brain. Moreover, to study whether cerebral cells were receptive to T-alpha1, we injected iodinated T-alpha1 (125I-T-alpha1) i.c.v.. 125I-T-alpha1 labelled neurons were observed in the hypothalamus and septal nuclei. Our results indicate that specific neuronal populations in the rat CNS are able to express and respond to T-alpha1.

A role of the thymus and thymosin-alpha1 in brain NGF levels and NGF receptor expression

Using neonatal rats we investigated the role of the thymus and thymosin-alpha1 (T-alpha1) in brain NGF levels, NGF receptor (p75NGFr) expression, as well as the activity of choline acetyl-transferase, a cholinergic enzyme regulated by NGF. It is shown that early postnatal thymectomy causes a decrease in NGF in the hippocampus and cortex and p75NGFr distribution in the basal forebrain cholinergic neurons (FBCN). Intracerebral T-alpha1 injection in thymectomized animals induces a recovery, albeit not complete, of both NGF and p75NGFr. These findings indicate that thymectomy affects both the brain NGF producing and responding cells and that T-alpha1 may be one of the thymic hormones involved in the regulation of cerebral NGF synthesis.

The conformation of peptide thymosin alpha 1 in solution and in a membrane-like environment by circular dichroism and NMR spectroscopy. A possible model for its interaction with the lymphocyte membrane

The 28-residue peptide thymosin alpha1 was studied by circular dichroism and two-dimensional NMR. Circular dichroism indicates that thymosin alpha1 in water solution does not assume a preferred conformation, while in the presence of small unilamellar vesicles of dimiristoylphosphatidylcholine and dimiristoylphosphatidic acid (10:1) and in sodium dodecyl sulphate, it assumes a partly structured conformation. Presence of zinc ions produces similar effects. In a more hydrophobic environment like a solution of a mixed solvent water-2,2,2 trifluoroethanol, it adopts a structured conformation. NMR spectra indicated that in this mixture as solvent, thymosin alpha1 has a structure characterized by two regions. A beta-turn is present between residue 5 and residue 8, while the region between residues 17 and 24 shows an alpha helix conformation. These changes of conformation in different environments may be considered structural requirements in the steps of its interaction with the lymphocyte membrane. In fact, these conformational changes may correspond to the first event of the mechanism of lymphocyte activation in the immune response modulation by thymosin alpha1.

Prothymosin alpha 1 effects, in vitro, on the antitumor activity and cytokine production of blood monocytes from colorectal tumor patients

Recent animal studies demonstrate that prothymosin alpha 1 (ProT alpha) enhances the antitumor response by stimulation of mononuclear phagocyte functions. The present study was aimed at characterizing the in vitro effects by ProT alpha on blood monocytes from human colon cancer patients. Purified peripheral blood monocytes were studied in terms of tumor cytostatic ability and cytokine production after incubation with ProT alpha or interferon (rIFN-gamma) and transforming growth factor-beta (TGF beta), used as reference substances. SW620 colon carcinoma cells were used as tumor target cells in growth inhibition experiments. The level of baseline growth inhibitory activity of unstimulated patient's monocytes was significantly lower than that of normal monocytes. The defective antitumor activity of patient monocytes was associated with a higher production of the inhibitory monokines prostaglandin E2 (PGE2) and TGF beta. The stimulation of monocytes by ProT alpha and/or rIFN-gamma elevated the average antitumor activity in all donor groups. The ProT alpha-induced increase was associated with a significantly higher monocytic secretion of IL-1 beta and TNF-alpha. Moreover, the concentrations of TGF beta and PGE2 in the culture supernatants decreased significantly, when patient's monocytes were treated with ProT alpha and/or rIFN-gamma. Additionally, ProT alpha enhanced the diminished antitumor activity of TGF beta-treated normal monocytes. These results suggest that ProT alpha selectively regulates distinct functions of blood monocytes, the effect of this cytokine varying with the parameter and donor population examined. These data provide a rational and biological endpoint for further studies with ProT alpha as an activator of mononuclear function in colon cancer.

Combination therapy with BRMs in cancer and infectious diseases

In recent years many studies have stressed the importance of using biological response modifiers (BRMs) in the treatment of different conditions of immune-impairment correlated with ageing, cancer and infectious diseases. In particular, the use of different BRMs in conjunction with conventional therapies has been extensively explored. Our studies have demonstrated that treatment with Thymosin alpha-1 and low doses of IFN or IL-2 exert powerful biological effects both in vitro and in vivo. They are highly effective in restoring cytotoxic activities in immunosuppression induced by tumors and/or cytostatic drugs. In addition, when combined with specific chemotherapy, they are able to induce a dramatic inhibition of tumor growth in both experimental models and in humans. Immunotherapeutic treatment also has an application in controlling infectious diseases, especially those occurring in the immuno-compromised host. The advantage of using the combined immunotherapy treatment with antiviral drugs has been recently demonstrated by our group both in a murine experimental influenza model and in patients infected with HBV, HCV and HIV.

Thymosin alpha 1 antagonizes dexamethasone and CD3-induced apoptosis of CD4+ CD8+ thymocytes through the activation of cAMP and protein kinase C dependent second messenger pathways

It is well established that glucocorticoid hormones and anti-CD3 monoclonal antibodies induce apoptosis in immature developing thymocytes. This process can be modulated by soluble factors, anti-oxidants and adhesion receptors. Previously we have demonstrated that thymosin alpha 1 (T alpha 1), a 28-amino acid thymic peptide hormone, is a dose and time dependent antagonist of dexamethasone (DEX) and CD# induced DNA fragmentation of murine thymocytes in vitro. To further investigate the mechanism of T alpha 1 action we determined a T alpha 1 sensitive thymocyte population and examined some of the molecular events associated with T alpha 1 anti-apoptotic activity. Phenotypic analysis of the sub-populations of thymocytes, based on CD4 and CD8 expression, revealed that T alpha 1 exerts its effect on CD4+ CD8+ immature thymocytes. T alpha 1 treatment of thymocytes delays the production of free radicals and the subsequent consumption of glutathione, that is observed during both DEX and CD3 induced apoptosis. We further demonstrate that T alpha 1 stimulates the production of cAMP and activates PKC in thymocytes. These data suggest that T alpha 1 exerts an influence on the development of a population of immature T-cells in the thymus by effecting the sensitivity of thymocytes to apoptosis during the pre-selection stages of thymic development. Our studies also suggest that the mechanism of T alpha 1 action involves the induction of both cAMP and PKC dependent second messenger pathways.

Effects of in vivo thyroid hormone treatment on the expression of interleukin-2 receptors on avian splenocytes

Cornell K strain chickens received a diet supplemented with 0, 0.1 and 1.0 ppm T3 from the day of hatching. At 28 days of age, splenocyte suspensions were prepared and analyzed by flow cytometry for interleukin-2 receptor (IL-2R) and CD3 expression. The low T3 dose increased the percentage of resting small cells expressing IL-2R while the mean fluorescence for this marker was enhanced only after mitogenic activation. This treatment did not alter the number of larger cells positive for IL-2R but did increase their mean fluorescence following mitogenic activation. The high T3 dose depressed the numbers of cells positive for IL-2R and their mean fluorescence amongst all splenocyte preparations. Both levels of T3 enhanced the numbers of CD3-positive cells in all cell preparations. These results suggest that the IL-2R expression can be modulated by in vivo T3 supplementation and that these correlate with the previously demonstrated changes in IL-2-like activity. The regulation of IL-2R expression provides one mechanism through which thyroid status may regulate immune function.

Sequential biochemotherapy for metastatic colorectal cancer using fluorouracil, folinic acid, thymopentin and interleukin-2: clinical and immunological effects

BACKGROUND

A phase II study was performed to evaluate the clinical and immunological effects of a regimen of fluorouracil (5-FU) and folinic acid (FA) combined with thymopentin (TP-5) and interleukin-2 (IL-2) in the treatment of patients with metastatic colorectal cancer.

PATIENTS AND METHODS

Forty-five evaluable patients with measurable colorectal cancer and no prior therapy for metastatic disease were treated with 5-FU 400 mg/m2/d and FA 200 mg/m2/d i.v. on days 1-5, TP-5 50 mg s.c. on days 8-11, and IL-2 9 MU/m2 s.c. twice daily on days 12-16. Cycles were repeated at 4-week intervals if toxicity had resolved. Immunological changes were evaluated in 13 patients and compared with a well matched series of 13 patients treated with the same regimen without TP-5.

RESULTS

Two complete responses and 17 partial responses were seen (42%; 95% confidence interval, 28% to 56%). Fifteen patients (33%) had stable disease. The median time to progression was 8.5 months and the median survival 13 months. Treatment was reasonably well tolerated, and there was no overlapping toxicity or interference between chemotherapy and biotherapy. Hematological and immunological changes during treatment were qualitatively similar to those expected with IL-2 +/- chemotherapy. Quantitatively, significant changes (higher levels of IL-2, CD25 and IFN-gamma, and lower levels of sIL-2R) were observed in patients given TP-5.

CONCLUSION

The combination of 5-FU + FA and TP-5 + IL-2 is effective in advanced colorectal cancer with acceptable toxicity. Immunological data suggest that TP-5 may modulate the action of IL-2 in the clinical setting. However, improved treatment approaches are needed, and the interactions between thymic hormones and cytokines should be further explored.

Binding of human prothymosin alpha to the leucine-motif/activation domains of HTLV-I Rex and HIV-1 Rev

Rex of human T-cell leukemia virus type I (HTLV-I) and Rev of human immunodeficiency virus 1 (HIV-1) are post-transcriptional regulators of viral gene expression. By means of affinity chromatography, we purified an 18-kDa cellular protein that bound to the conserved leucine-motif/activation domain of HTLV-I Rex or HIV-1 Rev. The protein that was purified through a Rev-affinity column was found to bind to Rex immunoprecipitated with anti-Rex IgG from an HTLV-I-producing cell line. We analyzed the purified approximately 18-kDa protein biochemically and identified it as prothymosin alpha. The binding activity of prothymosin alpha to Rev or Rex was completely abolished when the epsilon-amino groups of its lysine residues were chemically modified by N-succinimidyl-3-(4-hydroxy-3,5-diodo- phenyl)propionate. The functional relationship between the nuclear protein prothymosin alpha and Rex-Rev is discussed.

Prothymosin alpha 1 modulates lymphokine-activated killer cell activity and IL-2 production by peripheral blood lymphocytes from melanoma patients in vitro

The effects of prothymosin alpha 1 (Pro alpha 1) on the natural killer (NK), lymphokine (IL-2)-activated killer (LAK) cell activity and the phytohaemagglutinin (PHA)-induced IL-2 secretion of peripheral blood T-lymphocytes (PBL) from 34 malignant melanoma patients of all clinical stages were studied in vitro. On average, melanoma patients showed lower NK and LAK cell activities than healthy donors. In particular, patients with metastases revealed an impaired NK cell activity. However, individuals showed a broad range of LAK cell sensitivity to Pro alpha 1 depending, among other factors, on the disease stage. LAK cell activities were not correlated to tumour stage. Patients' impaired LAK cell activity could be restored by Pro alpha 1. Only patients at stage II (regional metastases) responded to Pro alpha 1. The IL-2 secretion from PBL melanoma and healthy donors did not differ, Pro alpha 1 administration was without any significant effect. However, stage III (distant metastases) PBL expressed significantly lower IL-2 levels, compared to stage I (primary tumours). The highest IL-2 levels was found to be associated with tumour stage II. Pro alpha 1 enhanced the IL-2 secretion from stage I PBL. Therefore Pro alpha 1 administration abrogated the defective LAK cell activity and IL-2 secretion of PBL, mainly from patients at early melanoma stages.

The presence and cytotoxicity of CD16+ CD2- subset from PBL and NK cells in long-term IL-2 cultures enhanced by Prothymosin-alpha

The aim of this study was to characterize the LAK cell subpopulation on which Prothymosin-alpha (ProT alpha) exerts its enhancing effect on cytotoxicity. We investigated the role of ProT alpha on LAK induction from peripheral blood lymphocytes (PBL) and NK-enriched cells, both cultured for 5 weeks with IL-2 and ProT alpha. The different cultures were separated into several subsets throughout the culture time using two color fluorescence activated cell sorting (FACS) and CD56, CD16, CD2 and CD8 monoclonal antibodies. Each cell subset was then tested for cytotoxicity against K562 and Daudi cells. The CD16+ CD2- subset from both, PBL and NK-enriched cells, was the only subset on which ProT alpha had an effect, significantly enhancing this subpopulation. Within the CD16 population, the cells CD16+ CD2+ were the most cytotoxic, although CD16+ CD2- cells were also cytotoxic. ProT alpha only potentiated the cytotoxicity of CD16+ CD2- subset significantly, with 29% and 41% for K562 and Daudi cells, respectively.