Cancer cells have unique characteristics, such as a dysregulated cellular energetic metabolism, the ability to self-sustain via proliferating signals, or the ability to take advantage of tumor-promoting inflammation factors. Their metabolism produces volatile organic compounds (VOCs), which can be used as biomarkers for cancer detection utilising gas chromatography or artificial olfactory systems, for example. The results of GC-MS tests, on the other hand, are exceedingly varied, and most E-nose systems are still in the prototype stage. Animals' finely tuned olfactory systems, which detect minute odorant concentrations and have the computational power to discriminate among complex odorant blends, have evolved over millions of years. Although dogs' noses are well adapted for medical diagnostics and can be utilised to detect cancer-specific VOCs, training them in associative learning paradigms is costly and time intensive. The conditioning phase, in particular, takes months and hundreds of trials before the dog is ready to work. As a result, studies report small sample sizes, both in terms of individual dogs and test numbers. In one study, two dogs, five months of training, and 1531 conditioning trials were used to perform 31 memory tests, resulting in a 90.3 percent correct identification rate.
Insects, unlike dogs, can be easily grown in controlled environments, are inexpensive, have a highly developed olfactory sense, and hundreds of individuals may be conditioned with a small number of trials. Insects have been shown to detect VOCs in cancer cell lines. The scents from various cancer cell lines, for example, elicited specific olfactory receptor activity patterns in the antenna of fruit flies, implying that such insects may be utilised as cancer biodetectors using in vivo calcium imaging, a sophisticated and expensive technology. To produce a powerful, yet economical, bio detection method for cancer VOCs, we integrated the utilisation of insects (the ant Formica fusca) with low-cost, simply transferrable behavioural analysis.Individual worker ants of this species have previously been shown to swiftly learn to correlate an olfactory stimulus with a food reward and to maintain this information for long periods of time (several days). Individual ants were trained to link the odour of a cell sample with food reward, and then had to distinguish between this learned sample and a fresh one in the current study. The principle is classical conditioning, which involves associating an unconditioned stimulus (in our case, a sucrose solution reward) with an initially neutral stimulus (the odour of cancer(A) Schema of the experimental arena utilised during ant training.During three conditioning trials, we placed a reward above a tube containing the conditioned stimulus (CS), and we timed how long it took the ant to find the prize. (B) We employed a somewhat modified arrangement for the memory tests, in which no reward was given and two scents were present (the CS and a novel odor, N). The ant's time spent at each odour area, as well as two unscented control areas, was recorded.
 |
| Behavioral setups of the conditioning experiments |
Ants use olfaction to detect cells.
Individual ants were put through three training trials in a circular arena, where the odour of a human cancer cell sample (IGROV-1, ovarian cancer) cultivated in media (DMEM - Dulbecco modified Eagle's minimum essential medium) was linked to a sugar solution reward. The time it took the ants to find the reward decreased over time, demonstrating that they had learned to recognise the presence of cells based on the volatiles they emitted. This was confirmed by ants who completed two memory tests in a row without receiving a reward. They examined the amount of time the ants spent investigating two distinct scents in a comparable circular arena: the odour of the cells (IGROV-1) (conditioned stimulus) and the odour of the culture medium alone (DMEM) (novel odor). As a control, two empty tubes were also present. Ants spent significantly more time near the conditioned odour (cancer cells) than near the culture media alone during these memory tests, suggesting that they can detect the presence of cells in a sample.
The ability to distinguish between malignant and healthy cells
They next used two breast cell lines to see if ants could tell the difference between cancer and healthy cells: MCF-7, an epithelial cancer cell line derived from adenocarcinoma breast cancer, and MCF-10A, a non-transformed (healthy) breast cell line. Ants were trained to smell either the cancer cell line or the healthy cell line, and then tested in an arena with both odours. MCF-10A served as the novel odour for ants conditioned to MCF-7 odour, and vice versa. Ants spent significantly more time near the conditioned odour, demonstrating that they can distinguish a cancerous cell line from a healthy cell line after only three trials of olfactory learning.
Two cancerous lines are distinguished.
Finally, ants will be tested to see if they can distinguish between two malignant cell lines: MCF-7 and MDA-MD-231, an epithelial cell line generated from an adenocarcinoma breast cancer. MDA-MD-231, unlike MCF-7, is a triple-negative (TN) subtype rather than a luminal-A subtype. Patients with TN malignancies have a harder time getting diagnosed. Ants were conditioned to either the MCF-7 or MDA-MD-231 odours before being tested in an arena with both the conditioned and novel odours. Ants spent significantly more time near the conditioned odour than they did near the novel one, demonstrating that they can distinguish between two cancer cell lines.
Cell differentiation based on VOCs
We employed Solid-Phase Micro-Extraction (SPME) combined with Gas Chromatography and Mass Spectrometry (GC-MS) to examine all of the cell samples and the culture medium alone to investigate the cues used by ants to distinguish the different cell lines from one other. They discovered 25 VOCs in all of the samples. A principal component analysis revealed that various VOC patterns characterised the different cell types as well as the culture media.
The study's limitations
Their research focused on a single F. fusca ant population. Although there is no reason to believe that this population is the only one to have developed refined olfactory abilities capable of detecting human cancer volatiles, it would be interesting to test our protocol with individuals from other F. fusca populations, which can be found throughout the northern hemisphere, as well as other ant species such as Camponotus sp., Linepithema sp., and Lasius sp., which is capable of learning both simple and complicated scents quickly. To yet, no standard procedures for chemical analysis have been established in the literature. Other extraction methods could be tested and the results compared to propose a standard and efficient way to analyse the volatile emissions of cells. We used SPME and GC-MS analyses, as in other studies, but other extraction methods could be tested and the results compared to propose a standard and efficient way to analyse the volatile emissions of cells. It's also worth noting that some of the VOCs found in different investigations could be contaminants from cell culture flasks. Although we did not employ culture flasks in our work, we cannot rule out the possibility that some of the observed VOCs are contaminants.The validity of VOCs as biomarkers should ideally be investigated in behavioural tests in which ants are educated with the entire cell odour and then tested exclusively with a solution containing the putative biomarkers.
Click here to read full article 👉 https://bit.ly/38yb98g
*The information used in this blog referenced by cell press article
0 Comments
Comments here