Thymidine salvage changes with differentiation in human keratinocytes in vitro

Capecitabine-Induced Hand and Foot Syndrome and the Reproducibility of Friction Skin

In 2008 a sixty-two year old male was detained by United States Customs and Immigration officials when attempting to enter the United States because his fingerprints were not detectable thus preventing his identify from being verified. It was later reported by his physician in Singapore that the individual suffered from Hand and Foot Syndrome (palmar-plantar erythrodysaesthesia) as a result of his cancer treatment of capecitabine (N4-pentyloxycarbonyl-5-deoxy-5-fluorocytidine) which causes interruptions to the normal growth of keratinocytes in the friction skin. Capecitabine is a recently developed, orally administered fluoropyrimidine prodrug designed to generate 5-fluorouracil through a three step enzymatic process giving it antineoplastic properties to combat cancerous tumor growth in a number of different cancers, including adjuvant colon cancer, metastatic colorectal cancer, and metastatic breast cancer. This study consisted of a 253 day evaluation of the physiological effects to the friction ridge skin from an individual undergoing capecitabine chemotherapy treatment. The results indicate the quality of the friction ridge skin impressions decreased by 32% and to a degree which may impair the ability to positively identify individuals using friction skin impressions alone while undergoing this type of treatment and experiencing hand and foot syndrome. Following cessation of capecitabine treatment, normal growth of keratinocytes resumed returning the skin to a normal state with no indication of damage thus demonstrating the persistency of the friction ridge skin despite the temporary toxicity of capecitabine.

Decreased expression of thymidine phosphorylase/platelet-derived endothelial cell growth factor in basal cell carcinomas

Thymidine phosphorylase (TP)/platelet-derived endothelial cell growth factor is associated with tumor angiogenesis. We evaluated the TP mRNA and protein expression in basal cell carcinomas (BCC) and in various skin tumors including numerous BCC histological simulants. Immunohistochemistry was performed on 99 paraffin sections of formalin-fixed skin tumors using monoclonal antibodies (mAb) against TP. TP mRNA levels were measured by real time RT-PCR in whole BCCs (wBCC) and laser capture microdissected (LCM) BCC tumor cells. TP immunostaining was negative in all BCC variants and in most of the benign trichogeneic tumors studied. By contrast, TP was constantly immunodetected in actinic keratosis (AK), squamous cell carcinomas (SCC), syringomatous carcinomas (SC), basosquamous carcinomas (BSC) and melanomas. TP mRNA levels were low and statistically not different in wBCC and normal skin but were strongly downregulated in LCM-BCC as compared with LCM-normal epidermis. We concluded that (i) anti-TP mAb is an useful marker to differentiate BCC from AK, SCC, BSC and SC but not from trichoblastic tumors, (ii) the lack of TP protein expression in BCC tumoral cells is linked to transcriptional regulatory mechanisms, (iii) the low TP mRNA levels in whole BCC may be related to the low intra-tumoral microvessel density, the slow growth and the very low metastatic potential of these tumors.

Lack of contribution of dihydrofluorouracil and alpha-fluoro-beta-alanine to the cytotoxicity of 5'-deoxy-5-fluorouridine on human keratinocytes

Capecitabine (Xeloda) is a very active oral fluoropyrimidine (colon and breast cancers) whose clinical use is complicated by the presence of hand-foot syndrome (HFS). This cutaneous toxicity is less frequently encountered with other oral fluoropyrimidines containing a dihydropyrimidine dehydrogenase (DPD) inhibitor. The HFS is thus attributed to the presence of the main 5-fluorouracil (5-FU) metabolites, dihydrofluorouracil (5-FUH2) and alpha-fluoro-beta-alanine (FBAL), but without strong pharmacological arguments. The aim of the present study was to closely examine this latter hypothesis. Capecitabine generates 5'-deoxyflourouridine (5'-DFUR) which is transformed into 5-FU at the cellular target site through the intermediary of thymidine phosphorylase (TP). The cytotoxic effects (MTT test, 4-day exposure) of 5'-DFUR, 5-FU, 5-FUH2 and FBAL were tested against the spontaneously immortalized human keratinocyte cell line (HaCaT) and the human cancer colon cell line WiDr as a control. Mean IC50s on HaCaT and WiDr were, respectively, 1.3 and 10 microM for 5'-DFUR, 0.2 and 3.3 microM for 5-FU, 13.4 and 560 microM for 5-FUH2, and greater than 650 and 6500 microM for FBAL. The respective 5'-DFUR IC50s values were not different when cells were exposed to 5'-DFUR alone or in combination with 5-FU, 5-FUH2 and FBAL in both cell lines, the relative proportion of each drug reflecting known pharmacokinetic data for capecitabine (5'-DFUR 12.4%, 5-FUH2 6.4%, 5-FU 1.2% and FBAL 80%). This latter finding demonstrates the relative lack of significant cytotoxic activity of 5-FUH2 and FBAL on human keratinocytes. TP activity was particularly high in HaCaT cells and DPD activity was very low in both cell lines. These data strongly suggest that the presence of 5-FU metabolites does not play a major role in the HFS generated by capecitabine and that it can probably be attributed to particularly high TP activity in keratinocytes. This observation may have important clinical consequences such as a possible local pharmacological inhibition of TP for controlling HFS.

Role of antimetabolites of purine and pyrimidine nucleotide metabolism in tumor cell differentiation

Transformed cells are characterized by imbalances in metabolic routes. In particular, different key enzymes of nucleotide metabolism and DNA biosynthesis, such as CTP synthetase, thymidylate synthase, dihydrofolate reductase, IMP dehydrogenase, ribonucleotide reductase, DNA polymerase, and DNA methyltransferase, are markedly up-regulated in certain tumor cells. Together with the concomitant down-modulation of the purine and pyrimidine degradation enzymes, the increased anabolic propensity supports the excessive proliferation of transformed cells. However, many types of cancer cells have maintained the ability to differentiate terminally into mature, non-proliferating cells not only in response to physiological receptor ligands, such as retinoic acid, vitamin D metabolites, and cytokines, but also following exposure to a wide variety of non-physiological agents such as antimetabolites. Interestingly, induction of tumor cell differentiation is often associated with reversal of the transformation-related enzyme deregulations. An important class of differentiating compounds comprises the antimetabolites of purine and pyrimidine nucleotide metabolism and nucleic acid synthesis, the majority being structural analogs of natural nucleosides. The CTP synthetase inhibitors cyclopentenylcytosine and 3-deazauridine, the thymidylate synthase inhibitor 5-fluoro-2'-deoxyuridine, the dihydrofolate reductase inhibitor methotrexate, the IMP dehydrogenase inhibitors tiazofurin, ribavirin, 5-ethynyl-1-beta-D-ribofuranosylimidazole-4-carboxamide (EICAR) and mycophenolic acid, the ribonucleotide reductase inhibitors hydroxyurea and deferoxamine, and the DNA polymerase inhibitors ara-C, 9-(2-phosphonylmethoxyethyl)adenine (PMEA), and aphidicolin, as well as several nucleoside analogs perturbing the DNA methylation pattern, have been found to induce tumor cell differentiation through impairment of DNA synthesis and/or function. Thus, by selectively targeting those anabolic enzymes that contribute to the neoplastic behavior of cancer cells, the normal cellular differentiation program may be reactivated and the malignant phenotype suppressed.

Expression and localization of thymidine phosphorylase/platelet-derived endothelial cell growth factor in skin and cutaneous tumors

Thymidine phosphorylase/platelet-derived endothelial cell growth factor (TPase/PD-ECGF) is a catabolic enzyme that has been shown to be chemotactic for endothelial cells in vitro and angiogenic in vivo. TPase/PD-ECGF expression is increased in a variety of tumors. In the skin, TPase is active in normal keratinocytes in vitro and in vivo. Our objective was to study the expression and localization of TPase/PD-ECGF by immunohistochemical analysis in normal skin and cutaneous tumors and to correlate this information with enzymatic activity of TPase. TPase/PD-ECGF expression was observed in keratinocytes with intense staining of the infundibulum of hair follicles but no staining of hair bulbs. Expression localized primarily to the nucleus of keratinocytes in the basal layer but was more intense and cytoplasrmic in suprabasal keratinocytes. Increased expression of TPase/PD-ECGF in differentiated cells was confirmed by in vitro studies of TPase activity. In cutaneous tumors, there was positive staining for TPase/ PD-ECGF in squamous cell carcinomas (10/10), eccrine poromas (3/4), eccrine syringomas (4/4), trichoepitheliomas (1/3), and tumors of the follicular infundibulum (2/3) and melanomas (5/8). There was no staining of any intradermal nevi (0/2), basal cell carcinomas (0/10) or Merkel cell carcinoma (0/1). We conclude TPase/PD-ECGF is found throughout the epidermis and its expression increases with differentiation of keratinocytes. In cutaneous tumors, expression of TPase/PD-ECGF may be linked to the cell of origin of the tumor as well as the tumor's degree of differentiation.

Thymidine phosphorylase expression in Kaposi sarcoma

AIMS

To examine the immunohistochemical distribution of thymidine phosphorylase (TP) in all clinicopathological subtypes of Kaposi sarcoma.

METHODS

Thirty two biopsy specimens of Kaposi sarcoma (29 patients) were studied. Six of these patients represented classic, six endemic, eight HIV associated, seven post-immunosuppression/transplant related, and two unclassified variants of Kaposi sarcoma. The average age was 49 years (range 22-83 years) and the male: female ratio 24:5. Four samples of angiosarcoma and one of spindle cell haemangio-endothelioma were stained in parallel. All specimens were fixed in formalin, embedded in paraffin wax and processed routinely. Immunohistochemistry was carried out using an antibody directed against CD31 (JC70) and the monoclonal antibody P-GF.44C against TP.

RESULTS

All biopsy specimens showed immunoexpression for TP. The spindle cell component stained more strongly than newly formed endothelium lined vessels and normal, resident vessels at a distance from the lesions.

CONCLUSIONS

The strong immunoexpression of TP suggests up-regulation of TP and a role for TP in angiogensis in Kaposi sarcoma. The mechanism for the up-regulation of TP remains unknown, but viral infections may trigger it. The differential staining of the various cell components of Kaposi sarcoma also suggest that TP either plays a role in the differentiation and maturation of Kaposi sarcoma or is a reflection of such changes.

Neurons of the peripheral nervous system express thymidine phosphorylase

Platelet-derived endothelial cell growth factor (PD-ECGF) is an angiogenic factor which recently has been shown to be identical to thymidine phosphorylase. We describe here, high levels of expression of PD-ECGF/thymidine phosphorylase in neurons of the peripheral nervous system (PNS) but very little in the central nervous system (CNS). Monoclonal and polyclonal antibodies were used for the staining of sections of dorsal root ganglia, sympathetic cervical ganglia and the enteric plexus as well as the brain and spinal cord. In addition, in situ hybridisation confirmed the results of immunohistochemistry. The possible role of thymidine phosphorylase in the PNS is discussed.

Platelet-derived endothelial cell growth factor/thymidine phosphorylase expression in normal tissues: an immunohistochemical study

Angiogenesis is the formation of new blood vessels from the existing vascular bed. It is a complex multi-step process controlled by a number of angiogenic factors. One such factor is platelet-derived endothelial cell growth factor (PD-ECGF), recently shown to be thymidine phosphorylase (TP), which is angiogenic in several in vivo assays and tumour systems. PD-ECGF/TP catalyses the reversible phosphorylation of thymidine to deoxyribose-1-phosphate and thymine. Since PD-ECGF/TP has an important role in cellular metabolism and in angiogenesis and its expression has been only partially characterized, we raised a monoclonal antibody against recombinant PD-ECGF/TP and used an immunohistochemical approach to examine the expression of PD-ECGF/TP in a comprehensive range of normal human tissues. The clone P-GF44.C, which recognizes recombinant PD-ECGF/TP and cell lysates transfected with a plasmid expressing PD-ECGF/TP cDNA on Western blotting, was selected for its ability to stain routinely processed tissue. Staining was observed in both the cytoplasm and/or the nucleus. Immunoreactivity was strongly expressed by macrophages, stromal cells, glial cells, and some epithelia. Gastrointestinal epithelium, smooth muscle, adrenal, lung, and testis were negative. Although endothelial cell expression was observed, there was no correlation with sites of new vessel growth. This pattern of expression suggests tight PD-ECGF/TP regulation and that cellular thymidine pools may serve to control its different functions. Thus, in the nucleus it might modulate the pool for DNA synthesis, whilst in the cytoplasm it could control other effects through different enzyme systems. The high expression present in macrophages and skin might be important for total body thymidine homeostasis.

Keratinocytes differentiate in response to inhibitors of deoxyribonucleotide synthesis

We previously reported that methotrexate (MTX) caused an irreversible inhibition of growth and induced terminal differentiation of human keratinocytes. These effects of methotrexate were prevented by thymidine and thus, were attributed to depletion of thymine deoxyribonucleotides. The purpose of the research reported in this paper was to determine whether differentiation was induced by the general class of agents which are known to interfere with synthesis or utilization of deoxyribonucleotides. Agents examined included 5-fluorouracil, 5-bromodeoxyuridine, hydroxyurea, high-dose thymidine, aphidicolin, and AG#85, a newly reported thymidylate synthase inhibitor. All these agents increased the expression of involucrin and increased the amount of cornified envelope protein at doses that inhibited proliferation by > 75%. We demonstrated, however, that in our cell culture system not all conditions producing inhibition of proliferation induced differentiation; withdrawal of growth factors and supplemental amino acids inhibited proliferation but did not increase involucrin expression or production of cornified envelope protein.

Quantification of cellular proliferation in acne using the monoclonal antibody Ki-67

The mechanism by which ductal hypercornification occurs in acne is uncertain. We investigated proliferation in normal and acne follicles and in the interfollicular epidermis using the monoclonal antibody Ki-67, which reacts with a nuclear antigen expressed by cells in the G1, S, M, and G2 phases of the cell cycle. Cryostat sections of biopsies from the interscapular region from acne patients and from normal volunteers were stained with Ki-67 antibody and counterstained with 2% methyl green. The number of Ki-67-positive nuclei in the basal layer were counted and expressed as a percentage of the total number of basal nuclei in the ductal or interfollicular epithelia. The data was expressed as mean percent +/- SD. In normal follicles from acne-affected sites 17.40% +/- 1.86% (n = 8) of the nuclei were Ki-67 positive. This was significantly higher (p < 0.01) than follicles from an area of skin unaffected by acne (11.01% +/- 6.16%, n = 8). In the follicular epithelia of non-inflamed lesions, the percentage of Ki-67 positive nuclei was 23.44% +/- 8.36% (n = 15). It was impossible to count the nuclei of follicular epithelium of inflamed lesions because little of this remained intact. In normal interfollicular epidermis, Ki-67-positive nuclei represented 5.33% +/- 3.36% (n = 8) of the total. This value was not significantly different from the value obtained for interfollicular epidermis near non-inflamed lesions (10.46% +/- 4.45%, n = 15). However, the number of Ki-67-positive nuclei in the interfollicular epidermis near inflamed lesions was significantly higher than either of these two values: 25.26% +/- 6.83%, n = 13, p < 0.05. Our results with Ki-67 confirm that ductal hyperproliferation occurs in acne and shows that normal follicles from acne skin may be "acne-prone."

A novel in vitro model for the study of human keratinocyte/leucocyte interactions under autologous conditions

Keratinocyte/leucocyte interactions have become an area of intense investigations in the last decade. However, few convenient in vitro models are available at present. We have therefore designed a novel in vitro system for autologous human keratinocyte/leucocyte co-culture. Non-invasive epidermal cell sampling was achieved by using outer root sheath cells from hair follicles. After one passage, pure keratinocyte cultures (no Langerhans cells or melanocytes) were obtained. Co-culture experiments were performed on a Transwell system: keratinocytes were grown on the porous cupula, and then laid on to wells containing leucocytes. Alternatively, leucocytes can be added to the cupula when contact interactions between the two cell types are to be investigated. Using this system, we demonstrated that Phaesolus vulgaris phytohaemagglutinin-activated T lymphocytes (with 10% monocytes) in the lower compartment induced intercellular adhesion molecule 1 (ICAM-1) and HLA-DR expression, and inhibited methyl-3H-thymidine incorporation in normal human autologous keratinocytes cultured on the cupula. These changes were mediated by soluble factors (no cell contacts between keratinocytes and leucocytes), and required lymphocyte activation. This is the first direct in vitro evidence for leucocyte-induced ICAM-1 and HLA-DR expression on keratinocytes. This system is a potential tool for the study of keratinocyte/leucocyte interactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Flow cytometric identification of proliferative subpopulations within normal human epidermis and the localization of the primary hyperproliferative population in psoriasis

In this study we define the proliferative compartments of in vivo human epidermis, using specific antibodies related to cell differentiation (beta 1 and beta 4 integrins and K1/K10 differentiation keratins) and cell cycle (proliferating cell nuclear antigen [PCNA]) in combination with flow cytometric quantitation of the DNA content and optical characteristics of the cells. The beta 1 integrin (CD29) marked both of the potentially proliferative subsets in normal epidermis. One subset of normal epidermis is CD29+ K1/K10-, which was predominantly basal, and found to be comprised of slow cycling, small cells with primitive cytoplasmic organization. The vast majority (95.5%) of these cells were in a quiescent state (G0/early G1) as indicated by their lack of the cyclin, PCNA. The other proliferative subset of normal epidermis was CD29+ K1/K10+, which was suprabasal and occasional basal, highly proliferative, larger in size, and which exhibited a more complex cytoplasmic structure. Because early differentiation (K1/K10 expression) has begun in the CD29+ K1/K10+ subset, it is highly likely that they represent the proliferative population which is capable of transiently amplifying itself before terminal differentiation. Within lesional psoriatic epidermis, similar proliferative cell populations were present as in normal epidermis, and the hyperproliferative defect was localized to the beta 1 and beta 4 integrin+, K1/K10- populations, which in normal epidermis is basally located and quiescent with regard to cell cycle. In psoriatic epidermis, a six- to sevenfold increase in the number of cells in the S/G2+M phase of cell cycle was found among CD29+ K1/K10- cells (p < 0.05). Furthermore, all lesional K1/K10- cells showed high PCNA positivity, indicating that all these cells had been recently induced into cell cycle. By contrast, the proportion of cycling cells among lesional psoriatic CD29+ K1/K10+ keratinocytes was similar to normals. Anti-HLA-DR, CD45, and vimentin antibodies were used to concomitantly track the proliferative states of Langerhans cell, melanocyte, and infiltrating leukocyte populations. In normal epidermis, the cycling fractions (cells in S/G2/M phase) of these cells were similar to the CD29+K1/K10- keratinocytes, whereas in lesional epidermis their cycling pools were increased relative to normal, but not so much as the proliferative fractions of psoriatic CD29+ K1/K10- keratinocytes. These data demonstrate the use of simultaneous analysis of integrin expression, differentiation keratins, cyclin, cell cycle status, and optical characteristics of freshly isolated human epidermal cells. Such analysis allowed the physical identification and quantification of cy cling populations in normal human skin, and has enabled the precise location of the primary epidermal proliferative defect in psoriasis.