L1 pseudogenes of the erythrocyte blood fraction in patients with malignant tumors

Abstract

Introduction. Unfortunately, malignant tumors continue to lead the world in the structure of morbidity and mortality, along with the pathology of the cardiovascular system. There is a clear correlation between discoveries in the field of molecular biology and the emergence of new drugs. Therefore, the new criteria for chemosensitivity and resistance will make it possible to individualize the treatment of patients.

The aim of the work is to search for molecular genetic criteria for the immediate effectiveness of chemotherapy and parameters that influence the spectrum of circulating nucleic acids of a regulatory nature in the patient’s body.

Materials and methods. We examined 31 patients with malignant tumors of different localizations, separated the nucleic acids from the erythrocyte fraction on fine glass, and used primers for the 5’ and 3’ regions of L1 to do PCR.

Results and discussion. We present data on the registration of 3’ fragments of L1 pseudogenes in the peripheral blood erythrocyte fraction of all cancer patients who responded to chemotherapy with either complete or partial regression. For the first time, we put forward a hypothesis regarding the molecular mechanism of differentiation of somatic cells, including tumor cells (therapeutic pathomorphosis), through the RNA excretion of L1 pseudogenes by lymphocytes precommitted to the tissue, post-transcriptional modification in erythrocytes, horizontal transmission to the target tissue, and silencing of abnormally activated reporter genes. It’s possible that L1 pseudogenes function in erythrocytes as an endonuclease that cuts circulating extracellular RNA into smaller fragments that are less immunogenic and capable of carrying out targeted silencing of a reporter gene when they enter a target cell, using a mechanism similar to small endogenous RNAs. Endonuclease-active erythrocyte L1 fragments can provide the immune system with fragments of circulating tumor nucleic acids that can trigger both innate and adaptive immune responses.

Conclusions. For the first time, 3–4 fragments of the 3’ sequence L1 with molecular weight from 500 to 2000 bp were found in all patients who responded to chemotherapy with complete or partial regression, as well as in patients who received adjuvant chemotherapy without the disease continuing during an actual follow-up period of 5–6 years.

We classify these sequences as L1 pseudogenes due to their lack of amplification to the 5’ fragment and their size, which is less than a third of the full L1.

Since the leukocyte fraction of chemosensitive patients contains exactly the same fragments of the 3’ sequence, lymphocytes are the most likely source of L1 pseudogenes. It is possible that the intravital excretion of these sequences by lymphocytes controls differentiation and the balance between proliferation and apoptosis in the target tissue.

It has been suggested that it is possible to conduct “replacement therapy” of lymphocytes of chemoresistant patients with molecular structures identified in chemosensitive patients by vector transfection of lymphocytes with sequences synthesized in vitro. If successful, this approach could solve the problem of drug resistance.