Cytotoxicity and effect on collagen biosynthesis of proline analogue of melphalan as a prolidase-convertible prodrug in cultured human skin fibroblasts.

Proline analogue of melphalan (MEL-PRO) was synthesised as a prodrug susceptible to the action of ubiquitously distributed, cytosolic imidodipeptidase--prolidase [E.C.3.4.13.9]. Conjugation of melphalan (MEL) with proline (PRO) through an imido-bond resulted in formation of a good substrate for prolidase. The susceptibility of MEL-PRO to the action of prolidase was found to be similar, compared to glycyl-proline--the most abundant, endogenous substrate for prolidase and about 6-fold higher compared to its substrate--glycyl-hydroxyproline. We have compared the transport of MEL and its prodrug through cell membrane, their antimitotic activity, cytotoxicity and effect on collagen biosynthesis in cultured, normal human skin fibroblasts. The prodrug was found to be more effectively transported into the cells than the free drug. Moreover, a lower cytotoxicity, antimitotic activity and inhibitory effect on collagen biosynthesis of the prodrug, compared to the free drug were observed after 24 h of incubation. MEL and MEL-PRO at concentrations of 12 microM led to the decrease in cell viability in confluent human skin fibroblasts by about 40 and 20%, respectively, during 24 h of incubation. IC50 of MEL for DNA synthesis (measured by thymidine incorporation assay) was found at about 7 microM, while MEL-PRO used at this concentration produced about 35% reduction in thymidine incorporation. Similarly, MEL and MEL-PRO used at 7 microM concentrations inhibited collagen biosynthesis in fibroblasts cultured for 24 h to about 30 and 80% of control values, respectively. However, when the cells were cultured with the drugs for 72 h, similar effects of both drugs on DNA and collagen biosynthesis were observed. The data suggest that MEL-PRO may serve as a prolidase-convertible prodrug that evokes lower cytotoxicity, antimitotic activity, and lower inhibitory effect on collagen biosynthesis in fibroblast cultures, compared to the free drug.

Decreased cytotoxicity and increased antimitotic activity of a proline analogue of chlorambucil as a prodrug susceptible to the action of fibroblast's prolidase.

We synthesized an proline analogue of chlorambucil (CH-pro) as a prodrug susceptible to the action of ubiquitously distributed, cytosolic imidopeptidase--prolidase [E.C.3.4.13.9]. A conjugation of chlorambucil (CH) with proline through an imido-bond resulted in the formation of a good substrate for prolidase. We have compared several aspects of biological actions of CH and its prodrug in cultured normal human skin fibroblasts. The prodrug was found to be more effectively transported into the cells than the free drug. Moreover, in opposition to CH, CH-pro had no inhibitory effect on fibroblast's prolidase activity against the endogenous substrate, glycyl-L-proline. Lower cytotoxicity and a higher antimitotic activity of the prodrug, compared to the free drug, was observed. CH and CH-pro at concentrations of 25 microM led to a 30% and 10%, decrease in cell viability in confluent human skin fibroblasts. IC50 values of CH and CH-pro for DNA synthesis was found to be 30 microM and 7 microM, suggesting higher antimitotic potency of the pro-drug compared to the free drug. CH-pro also evoked lower ability to inhibit collagen biosynthesis in cultured fibroblasts than the free drug. IC50 values of CH and CH-pro for collagen biosynthesis were found at about 15 microM and 30 microM, respectively. Targeting of prolidase as a prodrug-converting enzyme may serve as a novel strategy in pharmacotherapy of various diseases, leading to the increase in therapeutic efficacy and reduction in untoward side effects of antineoplastic agents.

Proline analogue of melphalan as a prolidase-convertible pro-drug in breast cancer MCF-7 cells.

Prolidase [E.C.3.4.13.9] is ubiquitously distributed cytosolic egzopeptidase that is known to cleave imido-bond of some low molecular weight compounds coupled to L-proline. Previously we have found that conjugation of antineoplastic drug--melphalan (Mel) with proline (pro) through imido-bond resulted in formation of a good substrate for purified prolidase. Cytosolic location of prolidase in neoplastic cells suggests that proline analogue of melphalan (Mel-pro) may serve as a prolidase convertable pro-drug. We have compared several aspects of pharmacologic actions of Mel and Mel-pro in breast cancer MCF-7 cells. It has been found that Mel-pro is more effectively transported into the MCF-7 cells, evokes higher cytotoxicity, lower antimitotic activity and collagen-inhibiting activity, compared to Mel. The results suggest that targeting of prolidase as a pro-drug-converting enzyme may serve as a potential strategy in pharmacotherapy of breast cancer.

Prolidase-activated prodrug for cancer chemotherapy cytotoxic activity of proline analogue of chlorambucil in breast cancer MCF-7 cells.

Although prolidase [EC 3.4.13.9] is found in normal cells, substantially increased levels are found in some neoplastic tissues. Because prolidase possesses the ability to hydrolyse imido bonds of various low molecular weight compounds coupled to L-proline, we hypothesized that coupling of L-proline through an imido bond to anticancer drugs might create prodrugs which would be locally activated by tumour-associated prolidase and consequently would be less toxic to normal cells that evoke lower prolidase activity. To test this concept we have synthesized a conjugate of chlorambucil-proline (CH-pro) as a possible prodrug. Treatment of this prodrug with prolidase generated the L-proline and the free drug, demonstrating its substrate susceptibility to prolidase. We have compared several aspects of biological actions of chlorambucil (CH) and its prodrug in breast cancer MCF-7 cells. IC50 values for chlorambucil and for CH-pro in DNA synthesis were found to be 54 and 16 microM, respectively. CH-pro also exhibited a lesser ability to inhibit collagen biosynthesis in breast cancer MCF-7 cells compared to the free drug. The IC50 values for chlorambucil and for CH-pro in collagen biosynthesis were found to be about 32 and 80 microM, respectively. This suggests that the targeting of prolidase may serve as a potential strategy for converting antineoplastic prodrugs.

Errors of temperature measurement with multiband infrared systems.

A model of the errors of temperature measurement with multiband systems was developed. Calculations of these errors for some measurement conditions and systems were carried out. It was shown that multiband systems are capable of producing accurate results of noncontact temperature measurement only in a limited number of applications and that to have small internal errors, they must be designed and built with much greater care than in the case of typical single-band systems.

Comparison of temperature resolution of single-band, dual-band, and multiband infrared systems.

A new measure of temperature resolution of IR systems called noise-generated error (NGE) was recently proposed. The NGE does not have limitations of the classical noise-equivalent temperature difference and can be used to describe the resolution of single-band, dual-band, and multiband IR measurement systems. The results of theoretical and experimental testing of the temperature resolution NGE of a developed model of single-band, dual-band, and multiband pyrometers are presented.

Measure of the influence of detector noise on temperature-measurement accuracy for multiband infrared systems.

The noise-equivalent temperature difference is a measure of the detector-noise-limited sensitivity of single-band IR systems for noncontact temperature measurement. However, because its definition is based on the signal-to-noise ratio in a single detector channel, the notion of noise-equivalent temperature difference must be generalized in case of dual-band or multiband IR systems. A new measure of temperature-measurement sensitivity is proposed that can be used to describe single-band, dual-band, and multiband IR measurement systems. With this measure a comparison of temperature-measurement accuracy among single-band, dual-band, and multiband systems was carried out.

Experimental verification of a theory of the influence of measurement conditions on temperature measurement accuracy with IR systems.

A theory of the influence of measurement conditions on temperature measurement accuracy with infrared systems has been recently presented. A comparison study of the shortwave (3-5-µm) and longwave (8-12-µm) measuring IR cameras was conducted on the basis of this theory. The results of the simulations show that the shortwave systems in typical measurement conditions generally offer better accuracy in temperature measurement than do the longwave systems. Some experiments that use a commercially available IR camera were carried out to verify the theory. The results of these experiments and a discussion about the theory limitations are presented.

Comparison of shortwave and longwave measuring thermal-imaging systems.

A comparison study of shortwave (3-5-µm) and longwave (8-12-µm) measuring thermal imaging systems has been conducted. The study was limited to systems working in indoor conditions, as is typical in many industrial and scientific applications. A theory of the influence of measurement conditions and system parameters on the accuracy of temperature measurements has been developed. On the basis of the developed formulas an analysis of the influence of signal disturbances (because of incorrectly assumed emissivity, radiation reflected by the object, radiation emitted by system optics, limited transmittance of the atmosphere, and limited temperature resolution of the system) on the accuracy of temperature measurement has been made. It has been found that the shortwave systems in typical measurement conditions offer generally better accuracy in temperature measurement than the longwave ones do.