**5. Mechanisms of action**

This elemental role of Kv10.1 made us propose the following question: Is Kv10.1 expressed only in some cells all the time, or in all cells but only for some time? If we assume that only a very small fraction of cells will be at G2 at any given time it is possible that we simply missed expression because it occurs for very short periods. So, when analyzing with more detail healthy tissues in their replicative zones, such as the bottom of colon crypts that have stem cells, or testis that contain G2 arrested cells, we were able to demonstrate that Kv10.1 was expressed in those healthy cells together with G2 markers such as Cyclin B [4, 12]. Therefore, tissues do express Kv10.1 for short periods during replication. When looking for its expression during G2, our group showed that when cells lose expression of Kv10.1 using RNA interference, G2 phases last more time compared to controls. This means that

Kv10.1 somehow accelerates G2 phases and therefore, replication. But how exactly is Kv10.1 speeding up cell division? Well, one of the most important processes during cell division is cytoskeleton rearrangement, specifically, microtubule organization. When Kv10.1 is eliminated from cells, the dynamics of microtubule rearrangement is accelerated, with longer growth periods [13]. These changes correlated with changes in calcium oscillations when analyzed by fluorescent calcium sensors. Cells without Kv10.1 have higher calcium oscillation frequencies. Calcium enters the cells in a voltage-dependent manner, so it makes sense that Kv10.1, which hyperpolarizes the cell stabilizes the entry of calcium, making the oscillations less frequent [13].

Other groups have demonstrated that Kv10.1 functionally interacts with Orai1, a calcium channel. So, we looked for physical proximity between Kv10.1 and Orai1 and found a higher amount of interaction in tumoral cells demonstrated by proximity ligation assays. This would mean that Kv10.1 controls calcium entrance by regulating Orai1 and therefore improves the microtubule dynamics during cell division [13, 14].

Even if many mechanisms by which Kv10.1 promotes cell division are still to be explained, we are certain that blocking its conductive function impacts significatively on tumor growth, therefore, approaches towards drugs and strategies to block Kv10.1 in animal models are also a priority of our lab.

### **6. Therapeutic approaches**

In mice models where MDA-MB435S (melanoma) cells are implanted, cells form tumors that can be easily studied. When we compare the effect of Astemizole (a non-specific Kv10.1 blocker, which has antihistaminic properties) vs. Cyclophosphamide, a known chemotherapeutic, we observed that both drugs can diminish tumor size after 40 days of implantation [15]. Moreover, if we analyze the effects of a non-blocking Kv.101 antibody compared to a blocking Kv10.1 antibody and to cyclophosphamide, we observe that the blocking Kv10.1 antibody again can reduce tumor growth at the same rate as cyclophosphamide in some models. If we implant patient-derived cancer cells in those mice, and we test for the antibodies against Kv10.1 we observed a less potent effect, compared to cyclophosphamide [16].

Nowadays chemotherapeutic treatment schemes use the combined effect of synergic drugs. One recent observation in Kv10.1 knock-down cells was the change in mitochondrial structure, generating a more fragmented pattern. Mitochondria are essential organelles for cancer cells due to the high metabolic rate they sustain. Mitochondrial fragmentation sensitizes cells for the additional use of antimetabolic drugs. We could demonstrate that blockage of Kv10.1 increases sensibility for antimetabolic drugs proportionally to their basal Kv10.1 expression, demonstrating that this effect is Kv10.1 expression-dependent [17].

Another approach currently under study by our group is the use of Kv10.1 attached to a more potent cytotoxic molecule such as TRAIL (TNF-related apoptosis-inducing ligand) which can induce apoptosis specifically in cancer cells [18]. We have now an improved design of such molecule using a single domain antibody (nanobody) against Kv10.1 bound to a single-chain TRAIL, which can induce apoptosis in the central region of the tumor in only 24 h at a dose of 3 ng/ml in tumor spheroids.

In conclusion, we believe that Kv10.1 represents one of the best oncological targets ever known, due to their selective expression in normal tissue. Therefore, we hope that in a near future the best anti-cancer strategy can be developed taking advantage of the Kv10.1 expression.

*Targeting the Voltage-Gated Potassium Channel Kv10.1 for Cancer Therapy DOI: http://dx.doi.org/10.5772/intechopen.99973*
