## 5 Conclusions and Future Perspectives  
Neurotransmitters, including NPs, often exhibit modified expression in several cancers. However, the utility of NPs as therapeutics in cancer treatment remains largely unclear. As knowledge of the nervous system and its implication in tumor development is constantly evolving, the involvement of neuropeptides in the onset and progression of cancer has also undergone significant advances. In the last few decades, NPs have therefore provided new opportunities to examine, identify, and characterize their potential therapeutic exploitation for the diagnosis and treatment of cancer. It is interesting to note that agonists and antagonists of different types of neurotransmitters and NPs have become increasingly \begin{table}
\begin{tabular}{c c c c c} \hline
**Neuropeptide** & **Cancer** & **Drugs/Antagonists** & **Targeted Receptors** & **Refs.** \\ \hline Bombesin (neuromedin & & PD176252, PD166368 & & \\ B/gastrin-releasing peptide) & Small cell lung carcinoma & & & \\  & & & & receptor-NMRB & [169, 170] \\  & & Bantag-1 & Bombesin-receptor subtype-3 & \\  & & Breast & RC-3095, RC-3940-II & & \\  & & & & receptors-GRPR & [92, 171, 127] \\  & & CRC & RC-3095, AN-215 & & \\  & & & & receptors-GRPR & [121, 154] \\  & & Brax 86-7548, & & \\  & Prostate & 64 Cu-CB-TE2A-AR-06, RC-3095 & & \\  & & & & & receptors-GRPR & [149, 173] \\  & & Ovary & PD176252 & receptors-GRPR, neuromedin B & [174] \\  & & Glioma & PD176252, PD166368 & & \\  & & & RC-3095-II, RC-3940-II & & \\  & & and RC-3095-II & & \\ Neurotransin & Breast & **”TC-N1-XL, \({}^{186}\)**-Re-NT-XLX, & & \\  & & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ \end{tabular}
\end{table} 
Table 3: List of neuropeptides, corresponding receptors, and relative drugs/ antagonists useful for preventing cancer progression. available as drugs. For example, serotonin, dopamine, ACh and their receptors, GABA and \(\beta\)-AR antagonists, and dopamine and its agonists have been exploited for diagnostic purposes and as potential drug candidates. Finally, NPs and their receptors regulate several biological processes of the tumor microenvironment; therefore, they may represent a new targetable approach for cancer therapy. Based on the knowledge gained from cited studies, the potential of various neuropeptides and their receptor as novel therapeutic targets for cancer treatment has been demonstrated in several cancers, including colorectal, breast, prostate, glioblastoma, and lung cancer. Nevertheless, despite the promising results reported in the literature, it becomes difficult to determine efficient and specific inhibitors that target neuropeptides due to limited resources, limited efficacy, and a lack of complete understanding of the functional role of various neuropeptides in cancer development and progression. In order to significantly increase the efficacy of various anticancer therapeutic drugs and reduce their side effects in humans, a combined drug therapy system, e.g., including a selective drug delivery approach along with the application of modified neuropeptides, could potentially serve as a promising therapeutic approach for cancer treatment [180,181]. For better clinical application of specific neuropeptide inhibitors, it has become important to determine at which cancer stage the respective neuropeptide receptors respond well. Given these findings and the challenging perspective, it becomes important to address such limitations, and perhaps more advanced research on neuropeptides would help in the better clinical management of cancers, including CRC. As a result of recent advances in this area, the situation may soon change. Further improvements in the area of cancer research are expected to provide an enhanced understanding of drug selectivity and efficacy for better cancer management. Conceptualization, A.S., B.P. and S.S.; methodology, A.S., B.P. and S.S.; validation, A.S., B.P., A.R. and S.S.; formal analysis, M.J.; writing--original draft preparation, A.S., D.R., B.P. and K.K.B.