Effect of human immunodeficiency virus infection on serum beta2-microglobulin levels in pregnant women

Factors influencing blood tumor marker concentrations in the absence of neoplasia

BACKGROUND

Tumor markers (TMs) are a heterogeneous group of molecules used in the diagnosis, prognosis and follow-up of cancer patients. During neoplastic differentiation, cells can either directly synthesize or induce the synthesis of TMs, and the release of these molecules into the bloodstream allows their quantification in biological fluids. Although very small concentrations of TMs are usually present in the serum or plasma of healthy subjects, increased concentrations may also be found in the presence of benign diseases or due to technical interference, producing false positive results.

MATERIAL AND METHODS AND RESULTS

Our review analyses the causes of false positives described between January 1970 to February 2023 for the TMs most frequently used in clinical practice: α-fetoprotein (AFP), β2-microglobulin (β2-M), cancer antigen 15-3 (CA 15-3), cancer antigen CA 19-9 (CA 19-9), cancer antigen CA 72-4 (CA 72-4), cancer antigen 125 (CA 125), carcinoembryonic antigen (CEA), chromogranin A (CgA), choriogonadotropin (hCG), cytokeratin 19 fragment (CYFRA 21-1), neuron-specific enolase (NSE), human epididymis protein 4 (HE4), serum HER2 (sHER2), squamous cell carcinoma antigen (SCCA), protein induced by vitamin K absence-II (PIVKA-II), Pro-gastrin-releasing peptide (Pro-GRP), prostate-specific antigen (PSA), Protein S-100 (S-100) and thyroglobulin (Tg). A total of 247 references were included.

CONCLUSIONS

A better understanding of pathophysiological processes and other conditions that affect the concentration of TMs might improve the interpretation of results and their clinical application.

Increased plasma concentrations of tumour markers in the absence of neoplasia

Tumour markers are a very heterogeneous group of molecules that are generally found in very small concentrations in the plasma and serum of healthy individuals. In the process of neoplastic differentiation the cell can synthesize, release, or induce synthesis of other cells, thus increasing their concentration in plasma and serum. These substances may also increase their plasma concentration in patients without cancer due to processes that increase the release or reduce catabolism, and so give rise to false positives. An understanding of the main physiopathological processes that increase the concentrations of these substances could improve our interpretation of tumour markers and their clinical application. In this study we review the physiopathological processes that may increase the plasma concentrations of tumour markers. We performed a bibliography review in PubMed, searching for causes of false positives for the following tumour markers: α-Fetoprotein, CA 125, CA 15-3, CA 19-9, CA 72-4, carcinoembryonic antigen, CYFRA 21-1, squamous cell carcinoma, prostatic specific antigen, β(2)-microglobulin, choriogonadotropin (β chain), chromogranin A, neuron specific enolase, HER2-neu, progastrin releasing peptide, S-100, and thyroglobulin. The results favour the use of tests which can identify pathological processes that may increase tumour marker concentrations.

Increased expression of MDR1 mRNAs and P-glycoprotein in placentas from HIV-1 infected women

P-glycoprotein transports several compounds including protease inhibitors, actually used in the clinical management of HIV-1 infection. Since P-glycoprotein is expressed in placental trophoblasts, its efflux activity could interfere with placental transfer of antiretrovirals. The purpose of this study was to investigate the expression of P-gp-encoding MDR1 gene and P-gp itself in full-term placentas from uninfected (n=35) and HIV-1 infected women (n=24). MDR1 transcripts were quantified by real-time PCR using relative (MDR1 normalized upon 28S levels) and absolute (copy number) determinations. P-glycoprotein localization and expression were evaluated by immunohistochemistry and western blot analysis, respectively. Relative or absolute PCR quantification showed a significant 3.3-fold (p<0.0009) or 3.7-fold (p<0.0002) mean increase in MDR1 placental transcription in HIV-infected compared to non-infected women, respectively. Ratios of individual HIV-positive values to HIV-negative mean ranged from 0.1 to 21.8. Moreover a significant 2.5-fold increased expression of immunoreactive P-glycoprotein was evidenced in placentas from HIV-infected women (p<0.0001). This MDR1 overexpression was observed in a similar extent in placentas from pregnant women treated with Zidovudine alone or in combination with Nelfinavir and/or Lamivudine. Our findings suggest that P-glycoprotein in placentas from HIV-infected women would contribute to modulate the materno-fetal transport of antiretrovirals across the placental barrier and consequently diminish fetal exposure to these compounds.